platinum metals review - Johnson Matthey Technology Review

Transcription

UK ISSN 0032-1400
PLATINUM METALS REVIEW
A quarterly survey of research on the platinum metals and of
developments in their application in industry
VOL. 36
JANUARY 1992
NO. 1
Contents
Catalysts for Nitrogen Oxides Control under Lean Burn Conditions
2
Rhodium-Iron Resistance Thermometer
11
111-V Semiconductor Vapour Growth
12
Tungsten-Iridium Alloys at High Temperatures
13
Reduction of Platinum Corrosion in Molten Glass
14
Platinum Group Organometallics
26
Osmium-Ruthenium Coatings
33
An Important Work of Reference
34
Efficient Ruthenium Dye-Sensitised Solar Cell
38
Versatility of Palladium Compounds
39
Platinum in the Eighteenth Century
40
Abstracts
48
New Patents
60
Communications should be addressed to
The Editor, Platinum Metals Review
Johnson Matthey Public Limited Company, Hatton Garden, London ECl N 8EE
Catalysts for Nitrogen Oxides
Control under Lean Burn Conditions
THE OPPORTUNITY FOR NEW TECHNOLOGY TO
COMPLEMENT PLATINUM GROUP METAL AUTOCATALYSTS
By T. J. Truex
Johnson Matthey Technology Centre
R. A. Searles
Johnson Matthey Catalytic Systems Division, Royston
and D. C. Sun
Johnson Matthey Catalytic Systems Division, Wayne
Regulations to control the exhaust emissions from motor vehicles are being adopted by more and more countries around the world, and in future
more stringent regulations will be introduced, particularly in the U.S.A.
and Europe. This, together with the need to show good pollution control
under real-world driving conditions, has led to the widespread introduction of closed-loop, three-way catalysts based on the use of platinum
group metal technology. “he increasing concern about emissions of carbon dioxide, as well as the three traditional pollutants, offers an opportunity f o r catalyst technology to control nitrogen oxides from both fuel
eficient lean burn petrol engines and from diesel engines, thus complementing the use of platinum group metals catalysts to control nitrogen
oxides and other emissions. This paper reviews the development of “leanNOx” technology based on the use of zeolite supported catalysts; it
highlights the promise shown and the shortcomings still to be overcome.
Over the last 25 years the motor vehicle has
increasingly become a cause for concern on environmental issues. This initially led to the control of carbon monoxide, because of the
potential build-up of this toxic gas in congested
city centres, and of hydrocarbons and nitrogen
oxides, both precursors of the photochemical
smog and low level ozone prevalent in some
regions, particularly in the Los Angeles basin.
Now the motor vehicle is identified as the
contributor of around 15 per cent of carbon
dioxide emissions. Carbon dioxide is the main
“greenhouse” gas contributing to perhaps 50
per cent of the predicted global warming and is
of course the inevitable product of burning
carbon-containing fossil fuels.
Platinum Metals Rev., 1992, 36, (l), 2-11
The twin goals of low and efficient fuel use
and minimum emissions are increasingly being
addressed by research in both the motor and
the catalyst industries of the world.
The Lean Burn Engine
In various prototype forms the lean burn
engine has been around for nearly 25 years.
However, successful and widespread usage of
this engine has been restricted by increasingly
strict control on the level of pollutants emitted
under the full range of engine operating conditions (1). Recent developments have included
the evolution of lean operating two-stroke
engines (Figure 1).
Lean burn operation involves the burning of
2
Fig. 1 Among lean burn engines
under development that would
benefit from using lean-nitrogen
oxides catalysts is the Orbital
2-stroke engine, shown here
fuel with an excess of air, in ratios up to 24
parts of air to one part of fuel. Under these conditions nitrogen oxides and carbon monoxide
emissions are at a minimum, but hydrocarbons
can rise at the onset of unstable combustion, as
can be seen in Figure 2. Engine design to increase the swirl of the aidfuel charge can increase the air:fuel ratio at which misfire starts
and minimise, but not prevent, hydrocarbon
emissions.
The main reason that lean burn engines have
not so far had widespread acceptance has been
that the power output from an engine falls as
the fuelling moves to leaner operation. This
means that to meet driver expectations of performance and drivability a rich fuel setting is
LEAN
\\
1
ENGINE
1
Hydrocarbons
I
10.1
1i:l
.
.
14:l (4.7.1
16:l
ie:i
20:l
22:l
24:l
A I R : FUEL RATIO, by weight
Fig. 2 These four curves indicate trends which apply to all petrol engines. Under lean burn
operation fuel is burnt with an excess of air at ratios of up to 24 parts of air to 1 part of
fuel, and it can be seen that nitrogen oxides and carbon oxides emissions are at a minimum,
but that hydrocarbon emissions can rise at the start of unstable combustion. When there
is excess fuel, the engine power is high but high levels of hydrocarbons and carbon monoxide are emitted. Peak combustion temperatures occur just on the lean side of the
stoichiometric composition and result in the highest emissions of nitrogen oxides
Platinum Metals Rev., 1992, 36, (1)
3
Table I
European Regulations
I
I
II
1 9 9 2 Standards in gramslkm
I
Pollutants
Carbon monoxide
nitrogen oxides
Hydrocarbons
Particulates/diesel
+
Type approval
2.72
0.97
0.14
I
Production
3.16
1.13
0.18
On 1/7/92 applies to new models; on 31/12/92 applies to all new registrations
provided for acceleration, high speed cruising
and hill climbing, thus causing nitrogen oxides
emissions to increase.
The Diesel Engine
The only true lean burn engine in widespread
use is the diesel engine. The diesel engine stays
in the lean operating region under all engine
conditions. The petrol engine is throttled on
the air intake, and ultimate power from a given
engine is limited by the amount of air that the
engine can “breathe”. Conversely the diesel
engine is unthrottled and its power output is
determined by the amount of fuel that is injected into the combustion chamber. The maximum fuel input level is controlled by the onset
of unacceptable levels of smoke or particulate
formation. To limit particulate emissions to acceptable or legislated levels it is necessary for
the diesel engine always to operate in the lean
region (2). This means that the diesel engine
has a significantly lower power output than a
petrol engine of the same capacity.
Three-Way Catalyst Operation
Conventional three-way catalysts, based on
the use of combinations of platinum group
metals - platinum, palladium and rhodium - can
convert over 90 per cent of the three main
pollutants carbon monoxide, hydrocarbons and
nitrogen oxides (3). They do this by the exhaust
gas being controlled by an airfuel ratio (or
lambda) sensor around the so-called
stoichiometric point at which neither air nor
fuel is in excess at the intake to the engine; for
a typical petrol composition this is at a ratio of
14.7 parts of air to 1 part of petrol.
Under lean conditions the three-way catalyst
will act as an oxidation catalyst controlling carbon monoxide and hydrocarbon emissions, but
the conversion of the nitrogen oxides emissions
falls to very low levels.
Limitations to Lean Operation
as Legislation Tightens
The introduction of lean bum engines is
limited by a number of key factors. The European driving cycle, during which the emissions
from motor cars are measured against the
legislated levels, has been changed. The
original City Test Cycle was based on inner city
driving in congested traffic with a top speed of
50 k.p.h. (31 m.p.h.) and an average speed of
18.8 k.p.h. (11.7 m.p.h.). Under these conditions a typical car might need to use only 15 per
cent of its maximum available power, so that
lean operation would be possible throughout
the cycle. However, the realisation that a major
contribution to regional and global pollution is
made by motor vehicles operating at high
speeds on highways led to the addition of the
Extra Urban Driving Cycle (EUDC), which includes speeds up to 120 k.p.h. (75 m.p.h.) and
needs more power than the City Test Cycle.
This causes greater nitrogen oxides emissions.
The new European Community directive,
4
Fig. 3 The U.S. Federal Standards include a timetable for
the progressive reduction of
pollutant emissions in exhaust
gas:
hydrocarbon reduction
from 0.41 glmile in 1991, to
0.125 glmile in 2004
carbon
monoxide
reduction from 3.4 glmile in
1991 to 1.7 glmile in 2004
nitrogen oxides reduction from 1.O glmile in 1991
to 0.2 glmile in 2004
4
2
E3
E
9c
5
VI
L"
5
1
1991
1994 to 1996
(40%)
llW%)
2004
YEARS
published on 30th August 1991 (4), sets maximum pollution levels for all sizes of motor cars
(Table I) and is based on the combined City and
EUDC cycles. The standards will necessitate
the use of closed loop, three-way catalysts on all
new models sold from 1st July 1992 and on all
new cars registered for sale after 31st December
1992.
In the U.S. new, more demanding Federal
and Californian standards have been set. The
former will reduce the allowed hydrocarbon
emissions by 40 per cent and nitrogen oxides
emissions by 60 per cent, by 1996 (Figure 3).
Californian standards call for increasingly lower
and lower emissions, culminating in a requirement for all motor vehicle manufacturers to include 10 per cent of zero emissions vehicles in
their fleets by 2003 (Figure 4 and Table 11).
The Californian standards are also expected to
be adopted by 13 states in north eastern
U.S.A., which together account for nearly 40
per cent of U.S. car sales.
100
80
1
c
8 60
P)
L
c
'
40
LL
1
20
1994
1995
1996
1997
1998
1999
YEARS
2000
2001
2002
2003
Fig. 4 Californian standards give a timetable for lower emissions and call for motor vehicle
manufacturers to include 10 per cent of zero emission vehicles in their fleets by 2003
a
zero emission vehieles
ultra low emission vehicles
low emission vehicles
0
transitional low emission vehicles
1993 standards
1991 standards
5
Table II
Californian Standards
Emission limits, gramshile
Year and standard
I
Hydrocarbons
Carbon monoxide
Nitrogen oxides
0.39
0.25
0.125
0.075
0.04
0
7.0
3.4
3.4
3.4
1.7
0
0.4
0.4
0.4
0.2
0.2
0
1991
1993
1994 (TLEV)
1997 (LEV)
1997 (ULEV)
1998 (ZEV)
The European Commission will propose
tougher standards for the European Community by the end of 1992, for agreement during
1993 and with implementation expected in
1996. It is anticipated that these will be similar
to the new U.S.Federal standards.
These increasing restrictions on nitrogen oxides emissions and the inclusion of real-world
driving conditions mitigates against the use of
lean burn engines, unless the emissions of
nitrogen oxides can be limited in the engine or
controlled externally.
Removal of Nitric Oxide under
Lean Operation
Nitric oxide is thermodynamically unstable
relative to nitrogen and oxygen under the full
range of exhaust gas stoichiometries and
temperatures encountered in internal combustion engines (5). A number of catalysts were
studied during the 1970s, including platinum
group metals and metal oxides (6) and some
were found to decompose nitric oxide, but none
of these had sufficiently high activity to be of
practical importance. In their reduced states,
these catalysts are rapidly oxidised by nitric oxide, with release of nitrogen. Oxygen is retained
on the catalyst surface, however, inhibiting further nitric oxide adsorption and decomposition.
Reducing agents are required to remove this
surface oxygen and regenerate catalyst activity.
Selective catalytic reduction using ammonia as
the reducing agent has been utilised for the
removal of nitric oxide from industrial boilers
and gas turbines under conditions of excess oxygen (7). Careful stoichiometric control of the
ammonia must be maintained to assure efficient
nitric oxide removal without emission of
surplus ammonia. For transportation applications this process is not practical because of the
problems associated with the storage of ammonia, and controlling ammonia injection
under transient conditions. An active and
durable nitric oxide decomposition catalyst, or
a selective reduction catalyst utilising reducing
species present in the engine exhaust stream
would be a major breakthrough for the control
of nitric oxide in transportation applications.
Recent literature reports and work conducted
by Johnson Matthey now indicate that progress
is being made towards developing these catalyst
technologies employing platinum group metals.
New Nitric Oxide Decomposition
Catalysts
Copper-exchangedzeolites have high activity
for the catalytic decomposition of nitric oxides
according to Iwamoto and co-workers (8). A
number of zeolite systems were investigated including Mordenite, Ferrierite, L-type and
ZSM-5, with the Cu-ZSM-5 system showing
the highest activities (9, 10). Using gas mixtures of 0.5-2.1 per cent nitric oxide in helium,
with gas hourly space velocities of 10-80,000
6
per hour, nitric oxide conversions of 13 to 60
per cent were reported. Maximum conversions
to nitrogen were observed at about 5OO0C,
with the degree of decomposition decreasing at
higher temperatures. This is apparently due to
a change in mechanism, as opposed to catalyst
degradation, as the same conversions were
observed with decreasing catalyst temperature
after high temperature operation. Water and
carbon monoxide additions to the gas mixture
did not greatly influence activity. The addition
of oxygen resulted in a decrease in nitric oxide
decomposition activity, although it is claimed
that this effect is dependent upon the level of
copper exchange in the zeolite, with high levels
of exchange resulting in less oxygen inhibition.
The addition of sulphur dioxide was found to
poison catalyst activity completely in the 400 to
6OOOC temperature range, with restoration of
activity being achieved after the high
temperature desorption of sulphur.
Detailed kinetic studies of nitric oxide
decomposition over the Cu-ZSM-5 system have
been reported by Li and Hall (11, 12). Their
work has shown that the reaction is first order
in nitric oxide pressure and inhibited by oxygen. The kinetics can be described in the
Langmuir-Hinshelwood form with the inhibition being half-order in oxygen pressure. As
with Iwamoto and co-workers, they observed
that the nitrogen formed was significantly less
than the equivalent nitric oxide which disappeared. This discrepancy was accounted for by
nitrogen dioxide which appears in the products
as a result of homogeneous reaction of product
oxygen with undecomposed nitric oxide
downstream of the catalyst. The redox capacity
of Cu-ZSM-5 was found to be near 0.5 O:Cu,
that is le-. In particular, it was shown that oxygen could be desorbed isothermally from the
catalyst surface upon reducing the oxygen partial pressure in the gas stream and that Cu' *
was reduced to Cu+I during the desorption of
oxygen. Since it is generally believed that the
rate of removal of strongly adsorbed product
oxygen from the surface limits the nitric oxide
decomposition on most catalysts, the continuous desorption of oxygen from the active
sites of the Cu-ZSM-5 catalyst during steadystate reaction is felt to be the key to their high
sustained activity.
Although the above results represent a
significant advancement in the development of
catalysts for nitric oxide decomposition, major
improvements will be required before such
systems can be used to control nitric oxide
emissions from combustion sources. Nitric oxide concentrations in exhausts of internal combustion engines are generally <3000 ppm,
significantly lower than those used in the work
reported above. Tests in our laboratories at
these concentrations with 5 per cent oxygen
present and gas hourly space velocities of
20,000 per hour show little nitric oxide conversion. In addition, the almost complete poisoning of activity by sulphur dioxide in the
reaction gas mixture would preclude use with
present petroleum-derived fuels.
Selective Catalytic Reduction of
Nitric Oxide by Hydrocarbons
Another significant, and potentially more
practical, breakthrough has been the reports by
Iwamoto (10, 13, 14), Hamada (15, 16, 17) and
Held (18) and co-workers demonstrating the
selective catalytic reduction of nitric oxide by
hydrocarbons in the presence of excess oxygen.
Hamada and co-workers have studied nitric oxide reduction over solid acid (19, transition
metal promoted alumina and silica (17), and Hform zeolites (16). Some of their results using
C,H, as the selective reducing agent are summarked in Table 111. Alumina, titania and zirconia all showed modest activity for the
selective reduction of nitric oxide with C, H , .
The addition of transition metals to alumina
resulted in substantially higher activity, with
cobalt and iron presenting the highest conversions. Interestingly, the observation was made
that a correlation exists between cobalt
aluminate formation and nitric oxide reduction
activity. Of the platinum group metals,
platinum exhibited the highest activity. As the
results presented in Table 111show, the H-form
zeolites were the most active catalysts tested by
these workers. In all these studies nitric oxide
7
Table 111
Selective Reduction of Nitric Oxide over Solid Acid (15),
Transition Metal Promoted Alumina (17) and Zeolite (16) Catalysts
Nitric oxide conversion to nitrogen, per cent
Catalyst
at 3OOOC
<
SiO,
4
~
0
3
TiO,
TiO,
ZrO,
ZrO,
2% Co/AI,O, (blue)
2% Cu/AI,O, (green)
2% Fe/AI,O, (orange)
2% Ni/AI,O, (green)
2% Mn/AI,O, (brown)
0.5% Pt/AI,O,
0.5% Pd/AI,O,
0.5% Rh/AI,O,
H-ZSM-5
H-Mordenite
HY
1000 ppm NO, 329 ppm C,H..
0.4
0.5
0.8
-
4.2
14.0
19.0
4.5
13.0
9.0
12.0
13.0
49.0
58.0
9.0
at 4OOOC
<
0.6
13.0
4.8
23.0
49.0
23.0
35.0
31 .O
13.0
28.0
5.6
8.9
59.0
65.0
19.0
at 5OOOC
<
1.1
32.0
8.9
20.0
29.0
11.0
17.0
40.0
7.4
12.0
5.4
8.5
38.0
48.0
26.0
10% 0, at 3.7 LlHG MHSV Whg mass hourly space velocity1
conversion to nitrogen was observed to go
through a maximum with increasing reaction
temperature. In the region where significant
nitrogen was formed carbon monoxide, in addition to carbon dioxide, was found in the product gas stream. At higher temperatures where
nitrogen formation decreases, the hydrocarbon
was completely oxidised to carbon dioxide. It
was also found that the temperature of maximum nitric oxide reduction to nitrogen was
dependent upon the hydrocarbon species, with
maximum conversion occurring at a
temperature about 100°C lower when C,H,
was used as reductant, instead of C,H,.
A number of ion-exchanged zeolites have
been examined for their selective nitric oxide
reduction activity by hydrocarbons (10, 13, 14).
Using a gas mixture containing 1000 ppm nitric
oxide, 250 ppm C,H,, and 2 per cent oxygen
at a mass hourly space velocity of 18
litresihour/gram, the order of activity
(temperature for maximum nitric oxide reduction to nitrogen) was copper (250°C)<cobalt
(350°C)<H (400°C)<silver (450-600°C)<zinc
(6OOOC). Maximum conversions to nitrogen
were 30-40 per cent and were relatively independent of the cation. Activities of various
copper ion-exchanged zeolites were (conversion
to nitrogen at 25OOC): Cu-ZSM-5 (31%)>cuMordenite (26%) Cu-L-type (25%)>cuFerrierite (23%). The effect of space velocity on
conversion was studied for Cu-ZSM-5, HZSM-5, and alumina catalysts. Conversion over
alumina dropped rapidly at gas hourly space
velocities greater than about 5000 per hour, HZSM-5 conversions showed a modest decline in
the range of 5-20,000 per hour with a rapid fall
at higher space velocities, and conversion over
Cu-ZSM-5 was stable up to 48,000 per hour
with a fall at higher values. These results show
that transition metal ion-exchanged zeolites can
have substantially higher activity than the Hform systems, with the copper-exchanged
catalysts showing most promise.
Using laboratory gas mixtures more typical of
engine exhaust, together with actual engine
-
8
I
Table I V
Selective Nitric Oxide Reduction over Copper-Mordenite and Copper-ZSM-5
I
Nitric oxide conversion to nitrogen, per cent
HC
Catalyst
(ppm as C , )
Cu-Mordenite
CU-ZSM-5
200OC
3OOOC
4OOOC
5OOOC
C,H, (1001
C,H, (700)
C,H, (2500)
C,H, (5000)
0
3
15
38
58
2
13
2
12
33
45
2
2
6
8
C,H, (700)
C,H, (2500)
C,H, (5000)
C,H, (2500)
CH, (250)
-
23
12
20
3
4
3
-
0
0
12
16
12
0
0
40
55
30
50
68
15
0
47
58
43
0
6OOOC
40
37
7
250 ppm NO. HC ias indicatedl. 5% 0,. 1 3 %CO,, and 10% H,O in N, at 20,000ih gas hourly space velocity
evaluation, Held and co-workers (18) have
reported results on a number of transition metal
ion-exchanged zeolites. Cu-Mordenite; Cr-, Fe-,
Mn-, V-, Cu-, Co-, Ni-, and Ag-Y zeolite; CuX zeolite; and Ir-, Pt-, Rh-, Ni-, Co-,and CuZSM-5 were all reported to have some activity
for selective reduction of nitric oxide by
hydrocarbons in the presence of excess oxygen.
The Cu ion-exchanged systems showed the
highest activities of those tested. They also
showed that there was an inhibition of activity
when water was added to the reaction gas mixture. Studies of the two most active catalyst
systems, Cu-ZSM-5 and Cu-Mordenite, with a
gas mixture containing 1000 ppm nitric oxide,
400 ppm C,H,, and 1.5 per cent oxygen at
35OOC and a gas hourly space velocity of
13,000 per hour showed that nitric oxide conversions over Cu-Mordenite dropped from 37
to 17 per cent with the inclusion of 10 per cent
water vapour. Under the same conditions, the
more hydrophobic Cu-ZSM-5 catalyst showed a
drop in nitric oxide conversion from 50 to 37
per cent. A conventional autocatalyst
monolithic substrate was coated with CuZSM-5 for engine evaluation. Under steadystate conditions at about 4OOOC inlet
temperature and a gas hourly space velocity of
approximately 15,000per hour, nitrogen oxides
conversions of 35 to 45 per cent were observed
at air:fuel ratios of 17.5-19: 1. A correlation
exists between nitrogen oxides conversion and
the hydrocarbonxitrogen oxides ratio in the
exhaust gas mixtllre, with the highest nitrogen
oxides conversions occurring at the highest
hydrocarb0n:nitrogen oxides ratios.
In our laboratories, monolithic substrates
have been coated with Cu-Mordenite and CuZSM-5 catalysts for laboratory flow reactor and
engine evaluation. Laboratory flow reactor
results are summarised in Table IV.It should
be noted that under these conditions no s i d i cant nitric oxide conversion was observed in the
absence of hydrocarbons, indicating that direct
decomposition was not contributing to nitric
oxide conversion. As was found by other
workers, nitric oxide conversion went through
a maximum as a function of temperature. Carbon monoxide formation was observed during
the onset of nitric oxide conversion. Complete
conversion of hydrocarbon to carbon dioxide
was observed at higher temperatures associated
with declining nitric oxide conversion. These
results show that zeolite type, the hydrocarbon:nitric oxide ratio, and the hydrocarbon
species all have a significant effect on nitric
9
oxide reduction activity. Consistent with other
reports, the Cu-ZSM-5 catalyst gave higher
conversions than the Cu-Mordenite catalyst.
Maximum conversions increased with increasing hydrocarbon concentrations (increasing
HC:NO ratio). The use of C,H, instead of
C,H, as reductant resulted in an increase in
temperature for maximum nitric oxide conversion from 4OOOC to - 5OOOC. The use of CH,
resulted in minimal nitric oxide reduction at
temperatures up to 600OC. The dependence on
hydrocarbon species and concentration,
together with the observation that carbon
monoxide formation occurs simultaneously
with nitric oxide reduction, implies that
hydrocarbon partial oxidation or decomposition
products are involved in the reaction
mechanism. In separate experiments we have
exposed a Cu-ZSM-5 catalyst first to a
C,H,/O, mixture and subsequently to a
NO/O, mixture. Immediately upon switching
to the NO/O, mixture, significant nitric oxide
conversion is observed which decays with time,
implying that hydrocarbon-containing species
deposited on the catalyst surface are involved in
the reaction, and are being depleted with time.
We have also shown that carbon monoxide and
hydrogen are much less effective than
hydrocarbon for selective nitric oxide reduction
over these catalyst systems. Iwamoto has
classified reductants into two groups, selective
(C,H,, C3H,, C,H,, C,H,) and non-selective
(H2,COYCH, and C2H,) based upon similar
observations (10). His group has also investigated the role of oxygen, showing that up
to about 2 per cent oxygen in the reactant
stream strongly activates nitric oxide reduction
with a slight inhibition observed at higher concentrations. Our studies have shown similar effects with the added observation that exposure
of a Cu-Mordenite catalyst to nitric oxide and
C H in the absence of oxygen resulted in a
reddish colour change to the catalyst, implying
the presence of reduced metallic copper. This
occurs even when the reactant gas mixture is
net oxidising and may indicate that the importance of oxygen is in maintaining copper in an
active oxidation state.
-
,
At present there is very little information
available on catalyst durability but, as expected¶ there are indications that the zeolite
systems would be limited to temperatures less
than 600°C to avoid thermal degradation. Initial resistance to sulphur dioxide poisoning has
been indicated (14) although longer term
poisoning effects remain to be assessed.
Future Work and Requirements
for a Practical Emission Catalyst
A much better understanding of the
mechanism(s) involved in the selective nitric
oxide reduction reaction with hydrocarbons
must be obtained as a basis for development of
improved catalyst systems. These studies,
together with engine evaluations, must address
a number of possible limitations of present
technology for vehicle applications. Some of
these limitations include:
Thermal stability of the present Cu-zeolite
systems
t Effects of potential poisons, particularly
sulphur compounds
The relatively narrow range of temperatures
and low space velocities associated with optimum performance
The effects of cyclic engine operation, particularly the effects of varying emission rates of
hydrocarbons versus nitrogen oxides on catalyst
function.
The importance of these last two effects is
demonstrated by the work of Held and coworkers (18). They tested Cu-ZSM-5 catalysts
on a vehicle under the transient FTP cycle.
Nitrogen oxides conversions of about 15 per
cent were obtained during cold-start (bag 1)
and about 30 per cent during hot-start (bag 3)
tests. The lower conversions were ascribed to
low catalyst temperatures during cold-start and
the generally higher space velocities incurred in
the FTP during the hot-start test. It was also
noted that under acceleration conditions where
significant nitrogen oxides are formed, the
nitrogen oxides:hydrocarbon ratio was unfavourable for nitrogen oxides reduction. The
requirement for high hydrocarb0n:nitrogen oxides ratios was found to be a major problem in
*
*
*
10
studies using a diesel engine. Diesel engines
have inherently low hydrocarbon emissions and
injection of hydrocarbons into the exhaust
stream was necessary to obtain significant
nitrogen oxides conversion.
Finally, a complete automotive emission control catalyst system must have adequate
hydrocarbon and carbon monoxide activity in
addition to nitrogen oxides removal. The
catalyst systems described above show deficiencies in hydrocarbons and, particularly, carbon
monoxide activity which would require the use
of a dual function catalyst system. The first
component would be the selective nitrogen oxides reduction catalyst, followed by a conventional platinum group metal catalyst for
hydrocarbons and carbon monoxide removal.
Such concepts are already described in the patent literature. It is obvious that a practical
selective nitrogen oxides reduction catalyst for
automotive applications is some time away, but
the exciting results obtained in the past several
years and the high level of activity in this area
are reasons for encouragement.
References
9 M. Iwamoto, H. Yahiro and K. Tanda, “Suc1 R. A. Searles, Platinum Metals Rev., 1988, 32,
( 3 123
~
2 B. J. Cooper and S. A. Roth, Platinum Metals
Rev., 1991, 35, (4), 178
3 B. Harrison, B. J. Cooper and A. J. J. Wilkins,
Platinum Metals Rev., 1981, 25, (l), 14
4 Off. 3., 30th August 1991, 34, L242
5 B. Harrison, M. Wyatt and K. G . &ugh,
“Catalysis”, Vol. 5, R. Sot. Chem., London,
1982, pp. 127-171
6 J. W. Hightower and D. A. VanLeirsburg, in
‘‘The Catalytic Chemistry of Ninogen a i d e s ” ,
ed. R. L. Klimisch and J. G. Larson, 1975,
Plenum Press, New York, p. 63
7 B. Harrison, A. F. Diwell and M. Wyatt,
Platinum Metals Rev., 1985, 29, (2), 5
8 M. Iwamoto, S. Yokoo, K. Sakai and S. Kagawa,
3. Chem. SOC.,Faraday Trans., 1981, 77, 1629
cessful Design of Catalysts”, ed. T. h i ,
Amsterdam, 1988, pp. 219-226
10 M. Iwamotoand H. Hamada, Catal. Today, 1991,
10, 57
11 Y. Li and W. K. Hall, 3. Phys. Chem., 1990,94,
6145
12 Y. Li and W. K. Hall,3. Catal., 1991, 129, 202
13 S. %to, Y. Yu-u, H. Yahiro, N. W o a n d M.
.
1991, 70, ~1
Iwamoto, ~ p p l Catal.,
14 M. Iwamoto, H. Yahiro, S. Shundo, Y. Yu-u and
Appl. Catal., 1991, 69, L15
N. &no,
15 Y. Kintaichi, H. Hamada, M. Tabata, M. Sasaki
and T. Ito, Catal. Lett., 1990, 6 , 239
16 H. Hamada, Y. Kintaichi, M. Sasaki, T. Ito and
M. Tabata, Appl. Catal., 1990, 64, L1
17 Op. cir. (Ref.16), 1991, 75, L1
18 W. Held, A. Konig, T. Richter and L. Ruppe,
SAE Paper No. 900496, 1990
Rhodium-Iron Resistance Thermometer
For some twenty years the rhodium-iron
resistance thermometer has been regarded as
one of the most reliable for low temperature
measurement, and in various forms has been
used from millikelvin regions up to room
temperature. Although it is known that the annealing treatment is one of the most important
factors controlling the thermometric properties
of such thermometers, only limited information
is available about their stability when the
rhodium-iron (mole fraction 0.5 per cent) is in
the form of wire.
A resent communication from the National
Research Laboratory of Metrology, Japan,
reports on the effects of annealing on a new
type of rhodium-iron thermometer, in which
the 50 pm diameter wire is wound bifilarly
around a cross-shaped frame machined from
fused silica. (0. Tamura and H. Sakurai,
“Rhodium-Iron Resistance Thermometer with
Fused-Silica Coil Frame”, Cryogenics, 1991,
31, (lo), 869-873). The use of fused silica
enables the sensing element to be annealed at
temperatures above 600OC. The four lead wires
and the protective sheath are made of platinum.
The influence of annealing temperatures between 700 and 900OC upon the resistance of the
thermometer has been investigated, and a
calibration method proposed for cryogenic use
of the thermometers.
It is concluded that an annealing temperature
of 8OOOC is required to remove the strain produced in the wire by coiling; thermometers annealed at or above this temperature have similar
temperature-resistance characteristics and,
after calibrating the deviation from a reference
function at only three calibration points, can be
used with an accuracy better than 0.5 mK over
the range 4.2 to 25 K. Self-heating effects were
found to be of a reasonable magnitude.
11
1
111-V Semiconductor Vapour Growth
APPLICATION OF PALLADIUM-SILVER DIFFUSION MEMBRANES
AND THE RESTORATION OF HYDROGEN OUTPUT
By J. S. Roberts
Department of Electronic and Electrical Engineering, University of Sheffield
The class of semiconductors based on Group
I11 and V elements can be fabricated into efficient light emitters and lasers for the red and
near infrared spectral regions. Commercially
these devices are used as optical read-write
systems, such as those found in compact disc
players and data storage systems. An important
111-V alloy commonly used in semiconductor
lasers is AliX,Ga~,-,,As,where x = 0 to 0.35.
The aluminium component of the alloy is particularly sensitive to oxygen, which is readily
incorporated during vapour phase epitaxial
growth. Substitutional oxygen within the
crystal lattice lowers the optical efficiency of the
material by creating centres which trap minority carriers, the precursors to light emission.
In order to realise large scale uniform single
crystal layers of AlGaAs the epitaxial growth
technique most favoured is Metal Organic
Vapour Phase Epitaxy (MOVPE). The precursors
for
this
process
are
usually
trimethylaluminium, trimethylgallium and arsine, which are transported to a heated (7OOOC)
GaAs substrate by a carrier gas of ultra pure
hydrogen. Oxygen, inadvertently incorporated
during crystal growth, can arise from a number
of sources including the hydrogen carrier, the
arsine, alkoxide impurities in the metal-alkyl
and leaks, either real or virtual, within the
stainless steel pipework of the reactor.
High purity hydrogen can be generated by a
number of techniques including boil off from
the liquid, gettering using a metalorganic
polymer or diffusion through a series of
palladium-silver membranes (1). The latter is
potentially the most efficient as the unit can be
made leak tight to all gases except hydrogen.
The diffusion of hydrogen through 23 per
cent palladium-silver membranes is a well
established technique for purifying commercial
grade cylinder hydrogen (2). The hydrogen diffusion process results in the dissociation of each
molecule into two protons and two electrons,
followed by diffusion through the palladiumsilver lattice. On reaching the high purity
region the protons and electrons combine to
reform hydrogen. With appropriate equipment
hydrogen of 99.9999 per cent purity or better
may be obtained, suitable for use as a transport
medium for metal alkyl vapour and as a carrier
gas during the manufacture of semiconductor
materials (3). Generally the membrane takes
the form of a 1.5 mm internal diameter tube
sealed at one end and internally supported.
Hydrogen is diffused from the outer to the inner surface of the tube using an input pressure
of 280 psi. A number of these membranes are
brazed into a stainless steel output manifold.
Within this department, hydrogen is obtained from an “EP-20” diffusion unit, which has
an output of 20 standard litres per minute at an
operating temperature of about 300°C and an
input pressure of 280 psi. The purity of the
hydrogen output is better than can be determined by simple analytical measurements,
necessitating mass spectrography for accurate
analysis. Indeed the luminescence efficiency of
unintentionally doped AlGaAs from a number
of reactors indicates that the purity of the
hydrogen exiting from the palladium-silver
membranes is not a controlling factor of the
overall material quality.
Should the hydrogen supply to the diffusion
unit become depressurised, it can be arranged
for the input to be automatically switched to
nitrogen. The exchange of nitrogen for
hydrogen promotes reverse diffusion through
the membrane and the removal of hydrogen
12
from the diffuser and associated equipment. In
addition, cooling the membrane in the absence
of hydrogen prevents embrittlement of the
fragile diffusion tubes.
On a number of occasions, when cylinder
hydrogen has been re-introduced to the diffuser
after a nitrogen purging process, there has been
a serious reduction in the rate of hydrogen output, apparently due to some form of contamination of the membrane. The nitrogen purge was
undertaken while the unit was at 31OOC using
high purity gas, but without an oxygen removal
catalyst in the input line. The low hydrogen
output could therefore result from the formation of an oxide on the surface of the membrane. One such faulty membrane was removed
from its housing and etched for 2 minutes in a
hydrofluoric acid solution made from 40 per
cent hydrofluoric acid stock diluted by 50. A
simple PVC tube, closed at one end, served as
a container for the etchant. The palladiumsilver membrane
membrane tube
tube was
was then
then washed for
for
several minutes in a flow of de-ionised water
and dried at 100°C for about 15 minutes. The
hydrofluoric acid treatment was choosen to profluoride, which as
mote the formation of silver fluoride,
has a high water
Water solubility. The
the hydrate has
reassembled diffuser initially gave only a
modest improvement in hydrogen flow but on
increasing the temperature from 310 to 36OOC
the full output of the unit was realised. The
operating temperature was then returned to
31OOC without any reduction in the pure
hydrogen gas output.
Conclusion
The MOVPE process requires a source of
oxygen-free carrier gas, this can be readily
achieved using a palladium-silver membrane
diffusion system. In the event of the external
(input) surface of diffuser elements becoming
oxidised a simple etch in hydrofluoric acid is
able to recover the hydrogen flow. The method
relies on the conversion of the oxide to a
fluoride, which in the case of the silver fluoride
hydrate is known to have a highwater solubility.
Acknowledgements
“EP-20” hydrogen diffusion units are supplied by
Hydrogen Engineering Applications Ltd. > Stevenage,
Hertfordshire, and incorporate diffusion membranes
manufactured byT.M.K.K.,Tokyo,usingpalladiumsilver tubes manufactured by Johnson Matthey.
References
1 G. J. Grasshoff, C. E. Pilkington and C. w .
Corti, Platinum Metals R e v . , 1983, 27, (4),157
2 D. A. Stiles and p. H. Wells, platinum Metals
R e v , , 1972, 16, (41, 124
3 C.W.C., Platinum Metals Rev., 1981, 25, ( l ) , 12
Tungsten-Iridium Alloys at High Temperatures
The benefit of alloying additions of palladium
in improving the oxidation resistance of
tungsten alloys at elevated temperatures has
been reported in this journal recently (1). Now,
the enhancement of the high temperature
strength of tungsten by alloying with iridium is
the subject of a new study at the Arizona State
University (2).
The investigators report that dilute alloys
containing up to 1 weight per cent iridium in
solid solution display considerably enhanced
yield and tensile strengths at high
temperatures. For a tungsten-0.8 weight per
cent iridium alloy, a yield strength improvement of 75 per cent is observed at 1727OC. This
gain becomes progressively less marked as the
temperature increases towards 2327OC. The incremental strength benefit was found to be
linearly dependent on the iridium concentra-
tion, consistent with the mechanism of solid
solution strengthening by atoms in substitutional positions causing symmetrical lattice
distortion. Examination of the fracture
behaviour showed that iridium promotes the intergranular failure mode at lower temperatures.
These results demonstrate that iridium is a
viable alternative to rhenium as a strengthening
alloying element in tungsten. Earlier work by
the authors has shown that iridium also improves the fabricability of tungsten at ambient
temperatures, and is better than rhenium. Such
findings should encourage the use of tungsteniridium alloys in industrial applications.
C.W.C.
References
1 C.W.C., Platinum Metals Rev., 1991, 35, (3), 133
2 A. Luo, K. S. Shin and D. L. Jacobson, Scr.
Metall. Muter., 1991, 25, (lo), 2411
13
Reduction of Platinum Corrosion
in Molten Glass
THE INFLUENCE OF PHOSPHATE GLASS MELTS ON THE
MICROSTRUCTURE AND RUPTURE TIME OF PLATINUM METALS
By Bernd Fischer
Faculty of Technology, Friedrich-Schiller-University,Jena. Germany
In order to ensure the high quality necessary f o r use i n scientific instruments, most high-technology optical glasses are melted in platinum
containers. In general, this noble metal has excellent corrosion and erosion resistance, as well as low solubility, when in contact with molten
glass. Therefore the dangers of discoloration and reduction in optical
transmission are low. Glass melts may be contaminated by the uptake of
corrosion and erosion products if the glass is melted in ceramic materials.
The use of platinum, instead of ceramics,f o r both containers and stirrers
enables glass melts to be stirred more thoroughly and hence become more
homogeneous. In this way a better quality and higher yields of glass are
obtained. Even totally new glass systems which have superior optical properties, but which would attack ceramics very quickly, can be melted i n
platinum vessels and produced to extremely high quality. Generally,
platinum or its alloys enables optical glass to be produced with high
purity, homogeneity and the absence of streaks and bubbles.
The platinum used in the glass industry for
melting pots, for coating melting vats, for stirrers and for other auxiliary equipment has to
withstand high thermal and mechanical
stresses. For many types of glass the process
conditions are under close control and as a
result the platinum apparatus has a very long
service life. On the other hand during the
manufacture of certain glasses elements such as
phosphorus, lead, silicon and boron, arising
from the decomposition of their compounds,
form low melting point eutectin which may
cause considerable corrosion of the metal.
Nowadays there is an increasing tendency to
melt even such glasses in platinum containers,
since the required high quality glass often cannot be produced by melting in ceramic containers. Thus, it is necessary to study the basics
of such reactions in order that they can be
reduced, or avoided.
In the first part of this paper the corrosion of
Platinum Metals Rev., 1992, 36, ( l ) , 14-25
platinum during the melting of phosphate glass
of a selected composition is discussed. Appreciable corrosion of platinum can be expected
during the preparation of phosphate glass;
therefore a study has been made of the corrosive action of the phosphate glass in order to
develop procedures which would enable such
glasses to be melted successfully in platinum
crucibles. Reports of related work on the production of lead glass, barium crown glass and
glass ceramics will follow.
Experimental Procedure
The composition of the phosphate-based
batch was as follows: 60 per cent Al(PO,),, 15
per cent Zn(PO,),, 15 per cent Mg(P0,)2 and
10 per cent BPO,. Cold drawn 99.9 platinum
wire samples 1.5 mm diameter and 70 mm long
were exposed for various times either to a
melting phosphate batch or, in a long time exposure test, to a melt at 137OOC for up to 500
14
Fig. 1 The hot tensile
strength and elongation to
rupture of platinum is shown
as a function of the time of
exposure to a melting
phosphate mixture, at a
temperature of 137OoC,and
to remelting phosphate glass
lumps
,
T
12
, " I
24
I
Lump melting
(Rernel ting)
8
0
.-
. 20:
u
I
4
0
2-
- 4
w
Batch melting
B
2
hours. Prior to testing the platinum was annealed for 2 hours at 140OOC to recrystallise and
stabilise its microstructure. In the long term
tests the samples were only put into the melt
when it was in the form of a homogeneous
phosphate glass. In this way it was possible to
differentiate between the effects of the starting
mixture and the actual melt upon the platinum.
After exposure - at the same temperature - the
hot tensile strength, elongation to rupture, and
time to rupture of the samples were determined. The data given below are the average values
from five measurements. The platinum samples
were investigated further by light- and scanning
electron-microscopy, electron microprobe,
secondary ion mass spectrometry (SIMS) and
X-ray diffraction analysis. For the creep tests
specially developed apparatus was used which
enabled data to be obtained at temperatures up
to 90 per cent of the melting point of the sample, in the case of platinum at up to 160OOC (1,
2). In order to obtain the high testing
temperatures, the samples were heated directly
by an electric current. Regulating the power
supply ensured a constant temperature despite
changes in the electrical resistivity of the
samples, resulting from a reduction of their
cross-sectional area. Due to the temperature
gradient along the sample, the holding clamps
stayed significantly below the testing
temperature. This apparatus has proved its efficiency over many years for testing high melting
point metals at temperatures up to 2000°C;
6 8 1 0
20
EXPOSURE TIME, minutes
4
40
60
even higher test temperatures and various test
atmospheres can be realised.
Results
The results obtained showed that the hot
strength of platinum is reduced drastically as
the phosphate batch starts to melt, but it does
not change during long term exposure tests in
the molten glass, even after long times. From
Figure 1 it can be seen that the melting mixture
reduces the hot tensile strength considerably in
the first 15 minutes, and that the elongation to
rupture is reduced to zero. This reduction in
strength, and the embrittlement of the
platinum are demonstrated even better by creep
testing. As shown in Figure 2, the time to rupture of platinum at constant load, and its rupture elongation are reduced to zero by the
melting phosphate batch after only 2 minutes;
this means that the samples fail under load
without any deformation taking place if they
are cooled and then reheated to the test
temperature.
In contrast, during the long term exposure
test in a phosphate glass melt, reductions in the
hot tensile strength and the standing time are
not observed during exposure times of up to
500 hours, Figure 3, provided that the amount
of melt lost by vaporisation is replaced by the
addition of glass pieces. If the replenishment is
achieved by adding the phosphate mixture,
however, the reactions on melting cause an appreciable reduction in the standing time but not
15
E
w'
0
a
3
W'
9 800-
S t a r 11ng cond I t tons
-a
I-
P
LJmp melting (Remelting)
2
0
0
g400-
0
5
- 4
0
c
2
c:
s
6
8 10
20
EXPOSURE TIME, minute5
2
l2
40
I
60
0
210-
0
0
I
I 6oo
500
3
400
0
$a-\
Lump adding
(Remelting)
Starting conditions
2
c
"
0
!k
5
(r
3
Fig. 2 The time to rupture
and the elongation to rupture
of platinum at a constant load
of 1.7 N and a temperature
of 137OoC, as functions of
the reaction times with a
melting phosphate mixture
and with melting phosphate
glass lumps
E
W
3
300
3
.200g
100
5
50
10
EXPOSURE
TIME,
100
hours
in the hot tensile strength. The values of
fracture elongation behave accordingly.
Since the results of the long term exposure
tests reveal the changes in the properties of the
platinum better than the hot strengthhpture
test, in later work only the former were studied.
Scanning electron microscopy investigations
of platinum which had been annealed prior to
testing showed that after the exposure test the
fracture area displayed transcrystalline deformation, this is evident in Figures 4(a) and q b ) .
During translation on the slip planes a shear lip
(Scherlippe) formed in places where the metal
finally fractured. The ductile metal showed
appreciable reduction in cross-section in the
fractured area.
After reaction with the melting phosphate
mixture intercrystalline brittle fracture occurs,
exposing crystal grain boundaries, Figures 4(c)
5oo
Fig. 3 Hot tensile strength
and time to rupture, at a load
of 3.9 N, of platinum as a
function of the time of reaction in a phosphate glass
melting at 137OOC
and 4(d). At the edge of the samples the early
stages of melting can be seen, Figure 4(e). The
fracturing suggests the uptake of alien elements
leading to a reduction in the melting point of
the sample. Platinum forms low melting point
phases and eutectics with many of the elements
that are present in glass and this must be considered as the main reason for possible failure
(3-5). In the platinum-phosphorus system a
eutectic of platinum and R,P2 exists at 3.8
weight per cent phosphorus and a temperature
of only 588OC,see Figure 5. At 6 weight per
cent phosphorus the R , P , phase forms; this
starts to melt at 59OOC.
As a result of metallographic and
microanalytical investigations the following
observations can be made about the reduction
in the high temperature mechanical properties
of platinum samples caused by the melting
16
Fig. 4 Fracture surfaces produced by tensile
creep testing of platinum samples in both the
starting condition and after reaction with a
melting phosphate mixture at 137OoC/4 min
and showing:
(a) starting condition, general view showing
transcrystalline deformation fracturing
(b) starting condition, shear lip (Scherlippe) on
edge of sample
(c) intercrystalline brittle fracture following reaction with a phosphate batch
(a) intercrystalline brittle fracture on the edge of
a sample after reaction with the melting
phosphate mixture
( e )following reaction with the phosphate mixture
the start of melting can be seen on the edge of
the sample
17
_
_
_
_
_
_
_
_
~
_
_
_
~
_
_
~
_
~
~
CONCENTRATION OF PHOSPHORUS, weight per cent
0
4
6 a l 0
1 5 2 0
30,
2
1
1600
800
K"
\
4001
-
I
.
.
.
.
0
10
20
30
40
50
60
CONCENTRATION OF PHOSPHORUS, atomic pl
'0
cent
Fig. 5 The platinum-phosphorus phase
diagram shows a eutectic at 3.8 weight per
cent phosphorus, at 588OC
phosphate mixture: if cold deformed platinum
is recrystallised at a moderately high
temperature a fine grained microstructure
results, see Figure 6(a). In a high melting point
glass melt a coarse microstructure forms in the
platinum by collective recrystallisation, Figure
6(b). In this way detrimental alien elements can
diffuse rapidly along the grain boundaries into
the platinum. Coarse grains occurred in
platinum which was in the as-annealed starting
condition, as well as in samples which were exposed to the melting phosphate mixture or to
the glass melt. The formation of widened grain
boundaries, however, is only observed after exposure to the phosphate mixture, see Figures
6(b) and 6(c).
In samples that had been exposed to the
melting mixture, the diffusion of phosphorus
into the grain boundaries of the platinum was
always detected. The line scan for phosphorus,
Figure 6(d), the "/PO/+ secondary distribution image, Figure 6(e), and the mass spectrogram, Figure 7, all show the uptake of
phosphorus at the platinum grain boundaries.
The "/PO/+ ions occurred with I l l ' + in the
mass spectrometric investigations, since
primary oxygen ions were used. In Figure 7 the
grain boundary area analysed is shown,
together with the 47/PO/+ secondary ion
distribution. The mass spectrogram also reveals
a series of alien elements and impurities, but it
is necessary to bear in mind the high sensitivity
of the SIMS method.
Following reaction with the mixture,
phosphorus was the only additional element
detected in the products that occurred on certain areas of the surface of the platinum.
Figures 8(a) and 8(b) show, respectively, optical and X-ray images of such an area. By comparison with a standard, the phosphorus
content was determined to be 5.3 weight per
cent. This is in good agreement with the phase
Pt,P, shown in the phase diagram at 6.0 weight
per cent phosphorus.
Additionally, on the surface there are areas
that have been molten. These consist of a eutectic of platinum and a Pt-P phase. The
photomicrographs Figures 9(a) and 9(b) show a
solidified platinum eutectic particle at the edge
of the sample. This particle would be liquid at
the service temperature, due to the melting
point reduction resulting from the uptake of
phosphorus, and likely to drop into the liquid
glass. In this way glass can be contaminated by
minute platinum particles. Even in small
amounts these may be harmful to the optical
properties of glass. The uptake of phosphorus
in eutectically solidified areas of the platinum
has been confirmed by microprobe analysis,
Figure 9(c), and by SIMS, Figure 9(d). No
other contaminations were detected at a level
exceeding that of the initial platinum. In the
hot-stage microscope the start of melting of the
Pt-P phase was found to be about 58OoC,
Figure 10, which is in good agreement with the
figure of 590OC given for Pt,P, in the phase
diagram. At 63OOC droplets of the melt were
clearly observed. Above this temperature some
evaporation from the sample was seen, an indication of the relatively low thermal stability of
the Pt-P phase. With further increases in
temperature the molten areas within the
material also increased.
During glass melting, the decomposition of
the Pt-P phase results from its low thermal
stability and explains the presence of
microscopically small particles of fairly pure
platinum within the glass.
18
Fig. 6 After recrystallisation and reaction with
melting phosphate mixtures (137OoC14 min)
sectioned platinum wires show:
(a) f i e grained microstructure following
recrystallisation at 6OOOC
(b) coarse grained structure following
recrystallisation and reaction with the phosphate
batch
(c) following exposure to the phosphate mixture,
scanning electron microscopy reveals an enlarged grained boundary
(d) the electron microprobe analysis line trace
for phosphorus shows a build up of phosphorus
at the grain boundary
(e) ‘/PO/+ uecondary ion-distribution photo
)
showing enrichment
(primary ions: 0 1 +again
of phosphorus at the grain boundaries following
reaction with the phosphate mixture
19
AnalySed grain
boundary area
47~
SQU
Fig. 7 The mass spectrogram of a grain boundary
area near the edge of a
platinum sample following
reaction with a melting
phosphate batch (1 37OoC/4
min)
31
P‘
I
16
272831 3940 47
566364
MASS NUMBER
Finally, the formation of Pt,P, by the reaction of platinum with the melting phosphate
batch was confirmed by X-ray crystallography.
Discussion
Changes in the morphology of platinum were
detected after the reactions involving the
melting phosphate mixture (even though these
were relatively short term), but not after testing
in a phosphate glass melt. The results showed
that during the heating and melting of a
phosphate batch phosphorus is set free, as the
element. This diffuses preferentially along the
grain boundaries, especially into coarse grained
platinum, causing hot shortness. Platinum
lo3
forms a liquid phase with phosphorus which
changes the mechanical properties of the
platinum. Some areas of the platinum surface
consist of a eutectic melt, part of which gets into the glass melt causing platinum inclusions.
Phosphorus can be produced easily by the
reduction of compounds in the phosphate
batch; additionally it is known that such reactions are catalysed by platinum. As can be seen
from the thermogravimetric curves in Figure 11
the mass loss during heating in the presence of
platinum is greater than it is in the absence of
platinum. Furthermore, during the melting of
metaphosphates phosphoric acid forms and this
attacks platinum, also Pt,P, may be produced
Fig. 8 Following reaction
with a melting phosphate
batch (137OoC/4 min) a
platinum-phosphorus phase
occurs near the edge of the
platinum sample
(a) optical photomicrograph,
(b) the X-ray image using
phosphorus K, radiation
20
Fig. 9 Areas on the surface of a platinum sample after reaction with a melting phosphate mixture
(1370OC14 min)
(a),(b)the eutectic melt consists of platinum (light coloured) and a platinum-phosphorus phase (grey)
(r) scanning electron microprobe Line scan image of the euteetie for phoaphorua
(d) "/PO/+ secondary ion-distribution photo of the eutectie (primary ions: O,'), platinumphosphorus phase (bright) and platinum (dark)
by a secondary reaction. Once the phosphate
mixture is molten and phosphate glass formed
the remaining phosphorus is tied up and no
reaction with platinum will occur, providing
that no other reducing agents are present. This
explains the observation that in the long term
21
tests at up to 500 hours carried out with
phosphate glass melts, no uptake of alien
elements was detected even by the highly sensitive SIMS technique, neither was any change
in microstructure observed.
Investigations with other batches and glass
melts, which will be discussed in a later article,
showed results comparable to those with the
phosphate glass. Generally one may state that
there are a number of chemical elements, including phosphorus, lead, arsenic, antimony,
boron, silicon and bismuth, which when present at even low concentrations cause embrittlement and a reduction in time to rupture
strength of platinum because of grain boundary
cracking (5).
As long as these elements exist in the glass as
stable compounds-generally as oxides-they
do no harm. However, as soon as they occur as
elements their diffusion into platinum takes
place. In this way low melting point phases,
eutectics or even peritectics form and influence
Fig. 10 High temperature photomicrographs 01 a platinuui sample after reartion with a melting
phosphate batch (1370OC14 inin). The melting of thr platinum-phosphoruu phase begins at about
58OOC. A scanning electron microscope imagr after cooling to room temperature is also shown
22
Fig. 11 Thermal analysis of the reaction of
~
a phosphate batch with and without contact
with platinum: (a) batch in contact with
platinum wire, (b) batch without contact with
platinum wire (heating rate about 6 O C per
min; atmosphere: stationary air; alumina
crucible; sample weight 500 mg; sample
loosely poured; substance for comparison,
alumina)
‘
i
- L
1
O
4; 4
3:
7
Za3
zi
.
Mx)
.
700 800
.
.
,
]
,
900 loo0 1100 1200 1300 1400
TEMPERATURE, ‘C
the properties of the platinum. Therefore the
conditions under which glasses are melted are
of decisive importance. If the conditions can be
controlled in such a way that no elements harmful to platinum occur then it will be possible to
keep the corrosion of platinum low, and to process glass melts in contact with platinum. In
reality many corrosion failures of platinum are
not caused by its low resistance to attack by the
relevant glass but result from neglect of process
factors.
If reducing conditions exist, because of the
composition of the mixture, or the presence of
impurities such as carbon, or by improper
handling, then “dangerous” elements may be
formed which will then corrode the platinum.
Figure 11, in the temperature range 850 to
940OC showed an endothermic reaction, with a
maximum at 92OoC, during which the mixture
did not change. When operating below these
temperatures no sintering reaction was observed. Above 92OOC a very porous low strength
body was formed, while at still higher sintering
temperatures the porosity decreased.
Based on thermal analysis and other experimental observations a sintering time of 2
hours, at temperatures of 920, 960, 1000 and
1050°C, was selected for the pretreatment of
the batch. The sintered material produced in
this way was broken into pieces and used for
corrosion tests, as was material which had not
been pretreated.
In a melting mixture that had not been
Reducing Corrosion and
Increasing Service Life
By making technological changes to the glass
melting process the aggressive nature of the
melt can be reduced and the working behaviour
of the platinum improved.
The investigations on phosphate glass have
shown strong corrosion of platinum by the
melting batch, but no effect by the melt itself.
Therefore platinum corrosion can be appreciably reduced if the reactions that take
place during the heating and melting of the
mixture are completed before the platinum is
brought into contact with the batch. This may
be achieved by presintering the batch before
melting or by using premolten glass lumps.
Thermal analysis of the phosphate mixture,
c
0
‘
ii
960
950
&l
SINTERING TEMPERATURE,*C
,
!
o
l
4
W
Fig. 12 Time to rupture and elongation
to rupture data for platinum in the unsintered condition, and after sintering at
the given times, both in the starting conditions and after reaction with the melting
phosphate batch at 137OOC and constant
load of 1 . 7 N
batch 0 sintered batch
23
premelted in a ceramic pot then, after it has
been cooled and broken into pieces it is finally
melted in a platinum container. Figures 1 and
2 show that premelted phosphate glass lumps
have no detrimental effects on the high
temperature
mechanical properties
of
platinum. Platinum samples subjected to tensile testing after contact with molten sintered
phosphate glass or with lump melted glass failed in a transcrystalline manner, as did platinum
in the as-received condition. The uptake of
alien elements and related metallographic structural changes were not seen in platinum which
had been in contact with melts prepared from
sintered mixtures or glass lumps.
Thus by presintering the batches or by using
lump remelted material the corrosion of
platinum is greatly reduced. Since the glass
melt or the raw glass does not affect the
platinum a continuous melting process can be
set up. In this case the untreated mixture is first
melted in ceramic containers, then in the second stage the melt is treated in platinum containers only.
In this way glass can be made from mixtures
containing elements normally too aggressive to
be brought into contact with platinum ware,
while glass which is usually processed in
platinum ware can now be produced to a higher
quality. Thus it is now possible to produce
phosphate glass of improved quality using
platinum containers.
Fig. 13 The microstructure of DVS-platinuni in
the as-received condition (a), (b) consist of fine
grains in which are embedded small particles of
zirconium dioxide; (e) after reacting with a
phosphate glass melt, for 250 hours at 137OOC
the DVS-platinum has retained its fine grained
structure
pretreated the time to rupture and the elongation to rupture of platinum during tensile creep
testing was quickly reduced to nearly zero. In
contrast, a melt from a batch which had been
presintered at 920 to 105OOC had no effect on
the mechanical properties of the platinum, this
is shown by the data in Figure 12.
During lump remelting the batch is first
Platinum Merals Rev., 1992, 36, (1)
Platinum with Improved
Properties
The
former
Forschungsinstitut
fur
Nichteisenmetalle in Freiberg, Sachsen
(Freiberger NE-Institute GmbH) developed a
dispersion hardened platinum known as DVSplatinum (8). This was made from foils produced by rolling an alloy of platinum containing
0.3 to 0.5 per cent zirconium, the foils then being annealed in an oxygen-containing atmosphere. A number of foils were then welded
together by compression at high temperatures,
and the final “sandwiched” sheet was made by
cold and hot rolling this layered structure.
DVS-platinum has a fine grained structure
24
Fig. 1 4 Time to rupture
and elongation to rupture
data for DVS-platifium, at a
constant load of 20 N, and
pure platinum, at a constant
load of 4 N. Both have
diameter 1.5 mm and are
held at 1370OC.
Az: starting conditions are:
140OoC/2 hours in air
Ge: reaction with a
phosphate
mixture
at
1 3 7 0 ° / 3 0 minutes
Sch: reaction with I-.
phosphate glass melt at
137OoC/250 hours
5
u-
2a
3
a
2
+
DVS
PLATINUM
PURE
PLATINUM
with small embedded particles of zirconium however, the effect on the properties of DVSdioxide, Figure 13. This kind of structure pro- platinum is rather small.
In contrast to pure platinum, for DVSduces excellent resistance to grain growth at
high temperatures and an appreciable increase platinum no appreciable grain coarsening is
in the time to rupture strength. It may be weld- observed. After exposure to the phosphate mixed, but as welding is done by adding pure ture and to a phosphate glass melt a small
amount of corrosive attack is seen at a few
platinum the welds constitute weak points.
places
on the rim of the samples, Figure 13(c).
The corrosion resistance of DVS-platinum
has been tested in phosphate glass. For these The uptake of alien elements is never observed.
tests a specially prepared and treated phosphate DVS-platinum not only exhibits a better long
batch of similar composition to those discussed time to rupture strength but because of its
earlier was used. In one series of long term tests stable fine grained microstructure and the
approximating to a practical application iron coverage of grains by zirconia it also possesses
and powered sugar (for reduction) were added a higher resistance to corrosion.
in order to test the DVS-platinum under extreme conditions. Iron is known to be an ele- Acknowledgement
T h e author wishes to thank Professor Dr. Ch. J.
ment which causes intercrystalline oxidation in
platinum, thus reducing its hot strength; the Raub, Forschungsinstitut fur Edelmetalle und
Metallchemie, Schwabisch Gmiind, for encouraging
liberation by reducing agents of elements harm- discussions and for translating this article into
English.
ful to platinum has been considered above.
The results of these long term tests are shown
References
in Figure 14. It is apparent that DVS-platinum
1 B. Fischer, H. Topfer and R. Helmich, Silikatexhibits a much greater time to rupture, and
technik, 1984, 35, (]I), 329
reasonable elongation to rupture, even if one 2 B. Fischer, H. Topfer and R. Helmich, East
German Patent 245,576; 1987
considers that the load on DVS-platinum is 20
N (2 kg/mm2), five times greater than the 4 N 3 G. Reinacher, Glastech. Ber., 1975, 48, ( I ] ) , 221
4 D. Menzel, Prakt. Metallogr., 1976, 13, ( 3 ,211
of pure platinum, even without contact with 5 B. Fischer, Diss. B, T H Chemnitz, 1983
glass (Figure 14). For pure platinum the time to 6 Metal Industry, Handbook and Directory; Iliffe &
Sons Ltd., London, 1960
rupture and the elongation to rupture are both
lowered significantly by the action of the 7 E. Dahl, Acta Chem. Scand., 1967, 21, ( 9 , 1131
Cirtner, D. Adam and W. Molle, Neue Hiitte,
melting batches and by the aggressive 8 S.
1979, 24, (3), 103
phosphate glass which contains iron and a 9 D. Adam and S. Gartner, East German Patent
120,385; 1976
reducing agent. Under identical conditions,
25
Platinum Group Organometallics
COATINGS FOR ELECTRONICS AND RELATED USES
By Professor A. Z. Rubezhov
Institute of Organo-Element Compounds.
U.S.S.K. Academy of Sciences,
Moscow
Platinum group organometallics have recently been the subject of intensive investigation designed to establish the basic characteristics of their
derontposition, which results in the formation of metallic or nietalcontaining coatings. This review has been compiled from a literature
search and indicates some of the applications that are, or could be, of
commercial significance.
This survey is devoted to some aspects of the
use of organometallic platinum group compounds for the preparation of materials suitable
for industrial applications, mainly in electronics
( 1 , 2 ) . The detailed chemistry of organometallic
platinum group compounds is not included, as
a number of monographs on this subject are
available (3, 4, 5 ) . In some instances, however,
information about co-ordination complexes of
platinum group metals will be included. The
possible practical use of organometallic
platinum group compounds for the deposition
of coatings and films by various decomposition
techniques was suggested in early works on
synthesis, see for example (6). To date,
however, organic derivatives of platinoids have
found little commercial use despite fairly extensive data, especially in the patent literature.
The reasons for this include the high cost of the
compounds, the lack of suitable coating equipment, and, in some cases, the lack of routine
production processes for the synthesis of the
required complexes.
A brief outline of general coating and film
deposition techniques based on organometallic
platinum group compounds is first given.
To date, there are two main decomposition
methods for the production of coatings, namely
vapour phase decomposition and decomposition in solutions. The decompositions of
organometallic compounds in the solid state
and as components of various viscous compositions, such as pastes and polymers, can be
Platinum Metals Rev., 1992, 36, (11, 26-33
regarded as separate techniques. These types of
organometallic compounds can decompose to a
metal, or to an oxide under the influence of
heat, electric discharge, electron beam, and
laser radiation, and these techniques are
employed for vapour phase decomposition.
Decomposition of organometallic compounds
in solution is frequently performed thermally,
photochemically, electrochemically or via
chemical reduction and hydrolysis. Each
method will now be considered separately, and
a list of the compounds and metals used in each
will be given.
The requirements for vapour phase thermal
decomposition are as follows ( 1 , 2):
(a) the compound should be transformed into
the vapour phase without decomposition
(b) the compound should be highly volatile
(c) organic products resulting from the decomposition of the organometallic compounds
should be gaseous, and should not contaminate
the coating
(d) the organometallic compounds should be
non-toxic and ideally should be stable to air and
moisture.
The first two of these are the determining factors. In order to characterise the volatility of
organometallic compounds, the vapour
pressure-temperature equation should be applied. However, for organometallic platinum
group compounds, this is known only for
ruthenocene (7), CpPtMe, (8) and MeC,H,PtMe, (8). For a number of compounds
26
sublimation point (sub1m.p.) and boiling point
(b.p.) data are available, but in most cases there
are no known quantitative values for the
volatility of the organometallic platinum group
compounds.
Most of the data on the decomposition of
organometallic platinum group compounds is
concerned with their thermal decomposition.
(The formation of iridium oxide films via
vapour deposition in an oxygen discharge (9) is
not considered in this review.) Information on
each metal is considered separately.
Ruthenium
Complexes potentially suitable for the deposition of ruthenium films are ruthenium carbonyls, ruthenium carbonyl halides, ruthenium
cyclopentadienyls,
ruthenium
acetylacetonates, and some of their organic and
co-ordination
derivatives.
Pentacarbonyl
ruthenium, Ru(CO),, with a vapour pressure
of 50 mm Hg at 18OC (lo), starts to decompose
at -18OC to form Ru,(CO),, and at a
temperature of 22OOC decomposition to the
metal occurs. The thermal decomposition of
trinuclear Ru,(CO),, to the metal has been
studied by infrared spectroscopy and thermogravimetric analysis (1 1). A bright metallic
film is formed on decomposition of
Ru(CO),Cl, or of RuCOBr at 2OO0C, in the
absence of air (10, 12). Annealing Ru(CO),Br
(b.p. 118OC, sub1m.p. 140OC) or Ru(CO),I
(b.p. 114OC, sub1m.p. 120OC) in a stream of
oxygen and phosgene leads to the formation
of ruthenium films (10).
However, the thermal decomposition of
ruthenium carbonyls and ruthenium carbonyl
chlorides, like analogous platinum metals
derivatives, is accompanied by severe corrosion
of the equipment and the support materials,
also, the majority of these ruthenium compounds are moisture- and oxygen-sensitive.
Thermodynamic functions have been determined for ruthenium and osmium carbonyls,
M(C0) 5 , in the gaseous state (13).
Some volatile ruthenium compounds, namely
mixed dienecarbonyls (14) and diene-Pdiketonate ruthenium complexes (15) and
individual ruthenium tris-p-diketonates are
mentioned in the literature. The latter compounds are patented for use in the formation of
ruthenium films on various substrates via the
deposition of (acac) ,Ru or (F,acac),Ru
vapour onto a suitable support, heated to the
decomposition point of the compound (16-18).
Ruthenocene, (C,H,),Ru, is the most promising compound for the formation of
ruthenium films. First, it is a commercially
available product, and it is suitably volatile
(sub1m.p. 100°C/lO-l mm), air-stable, nontoxic and may be prepared in a highly pure
state. Attention was first drawn to the possibility of preparing high purity ruthenium via
ruthenocene decomposition in 1964 (19). A
pure ruthenium film was generated at 595OC in
a hydrogen atmosphere; iron ( - 0.01 per cent)
and palladium ( 0.005 per cent) were present
as admixtures, and silicon and boron as trace
elements.
Patented
applications
for
ruthenocene include: the preparation of layer
resistors (20), additives to liquid crystals (21)
and for plating multilayer electrodes with oxides and metals (22). The plasma-induced
vapour phase decomposition of ruthenocene
enables thin metallic films to be produced at a
sufficiently high rate (23, 24).
-
Osmium
According to data in the literature (lo), on
decomposition, osmium carbonyl halides are
capable of forming bright osmium fdms. Thin
films of osmium metal were prepared via the
decomposition of OsO, complexes with
terpenes in a hydrogen stream at 3OOOC (25,
26). It should be noted that osmium tetroxide
exhibits high volatility, but its high toxicity,
equal to that of hydrogen cyanide, precludes its
use for fdm preparation. The application of a
solid complex of OsO, with dioxane has been
patented. It is less volatile than osmium tetroxide and also less toxic (27). Among other
osmium derivatives, it should be noted that
cyclooctatetraene(tricarbony1)osmium has been
patented for the deposition of coatings from the
gas phase (14), while osmocene, bis(cyc1opentadienyl)osmium, has been recommended as an
27
additive to liquid crystals (21) and also for the
preparation of high purity osmium (28). The
thermal decomposition of Os, (CO)
to
metallic osmium has been reported in the
literature (1 1).
Rhodium
The ability of rhodium carbonyls and
rhodium carbonyl halides to form bright
rhodium films on decomposition has been
known for some time (10). For example,
[Rh(CO),l, on heating without solvent, and
Rh, (CO) , ? on heating in air, deposit a rhodium
film (1 1). A dimeric carbonylrhodium chloride
[Rh(CO)? C11 ? melts at 123OC, readily sublimes
above 100°C, and decomposes at around 300°C
in a stream of carbon dioxide to deposit a bright
metallic film. In the presence of oxygen or
COCl,, [Rh(CO) C11 “flares up” and “burns
out”, thus depositing bright rhodium films
(10).
Among other volatile rhodium compounds,
tris(ally1)rhodium and liquid r-allyl-aallyl(cyclopentadienyl)rhodium (29) as well as
rhodium complexes with 0-diketones should be
mentioned. For example, the reduction of
tris(trifluoroacety1acetonato)rhodium
with
hydrogen in the vapour phase has been proposed for the preparation of thin rhodium films
(30). At a vaporisation temperature of 13OoC, a
reduction temperature of 25OOC and a
hydrogen flow-rate of 16 ml/min, thick uniform
films with good adhesion and good electroconductivity were deposited. X-ray phase analysis
revealed no admixtures in the films. The use of
acetylacetonates of rhodium and other metals
for the production of fuel elements has been
patented (31), and data on the vapour pressures
and heats of sublimation of rhodium and
iridium tris(trifluoroacetonate) complexes have
been published (32).
Iridium
Iridium occupies a special place among the
refractory metals because of its hardness, high
resistance to oxidation and ability to form carbides. The temperature dependence of the coefficient of thermal expansion for iridium is close
to that of carbon (6). The known volatile
iridium compounds include carbonyl hydrides
and chlorides, which are readily decomposed
and sublimed to form bright metallic films (lo),
tris(r-ally1)-iridium (29), r-cyclopentadiene-rcyclopentadienyliridium (29) and iridium 0diketonates (31-33). The decomposition of
tris(acety1acetonato)iridium in a stream of
hydrogen at 115 to 132OC, with deposition onto
a support heated to between 400 and 75OoC,
yields an iridium film. The use of
tris(acety1acetonato)iridium for the preparation
of fuel elements, has been claimed (31). Other
volatile organometallic iridium compounds,
namely r-cyclooctadiene-r-cyclopentadienyliridium (34) and *-cyclooctadieneiridium
acetylacetonate (34) should be mentioned. A
four nuclear carbonyl, Ir, (CO)
is readily
sublimed in a stream of carbon monoxide under
atmospheric pressure (29).
Palladium
Palladium is one of the less expensive
platinum group metals, and the chemistry of its
organometallic compounds is well developed
(4, 5 ) . In decreasing order of volatility, the
volatile compounds are: r-allyl-r-cyclopentadienylpalladium r-C, H ,Pd-r-C H, (sub1m.p.
3O-4O0C/1-2 mm) (35), bis(r-ally1)palladium
(a-C, H,),Pd (sub1m.p. 35-4OoC/10- mm)
(36), and bis(trifluoroethy1dithiocarbonato)
palladium compound (CF CH OCS 2 ) Pd
(sub1m.p. 130-150°C/10-1-10-2 mm) (5).
The volatile co-ordination compounds of the
metal with sulphur- and nitrogen-containing
ligands have been the subject of a review (37)
and
reported
elsewhere
(38-42).
r-Allyl-r-cyclopentadienylpalladium(43-49,
bis-x-allylpalladium chloride (44, 46), and
bis(acety1acetonato)palladium (47, 48) have
been used for the preparation of films. The
characteristics of the thermal decomposition of
bis-a-allylpalladium chloride in the solid state
(49-52) and the thermal stability of a series of
r-allylpalladium complexes (53) have been
studied by differential thermal analysis and
thermogravimetric analysis. The thermal
decomposition of bis(hexafluoroacetonato)
,
28
palladium follows a radical mechanism (54),
bis-?r-allylpalladium chloride decomposes to
precipitate metallic palladium which catalyses a
further decay of the complex. The initial
decomposition temperature is 137OC, and
palladium is precipitated at 160-225OC. On
precipitation of the palladium, secondary reactions of the allylchloride moieties occur,
resulting in the contamination of the metallic
palladium by carbon. The catalytic activity of
the metal, which precipitates on decomposition
of (C,H,PdX)2, is considered elsewhere (55).
At 130-135°C/10-2 mm and at a pumping rate
of not less than 1-1.5 pmls, a palladium film
was deposited onto a support heated at 200 to
35OOC. The maximum film thickness was 8 pm,
and no chlorine was present. The resulting
films exhibited good adhesion to ceramics,
fluoroplast-4, sodium chloride and potassium
chloride crystals.
Bis(acety1acetonato)palladiumis vaporised at
150°C/10-4 mm and is decomposed to the
metal at 35O-40O0C. The addition of an oxidiser, such as carbon dioxide, suppresses the
codeposition of carbon. Good results were obtained for a palladium film deposited from
C, H, PdC, H, . The compound vapours
entered the reactor either at 40-5OoC/1 mm or
at 70-8OoC/760 mm; and rapid film formation
occurred on a suitable support heated to 300OC.
The thickness of the palladium film depended
on the time that the support was located in the
C,H,PdC,H, vapour stream. The films
obtained exhibited good adhesion.
Platinum
Historically, chlorocarbonyl complexes were
the first platinum compounds to be employed
for film formation. Precipitation of platinum
occurs during thermal decomposition of
platinum carbonylchloride compounds at
100-120°C/0.01-0.02 mm, the temperature of
the metallised support being 600OC. Thus thin
uniform films were produced on platinum,
molybdenum and nickel wires (56). The use of
carbon dioxide as a carrier gas prevents the
decomposition of the compound in the
evaporator and reduces the possibility of
preliminary decomposition taking place on the
way to the support. Reduction of the carbonylchloride vapours with hydrogen prevents
the formation of coarse grained films, and promotes the formation of smooth, uniform
platinum films.
The preparation of thin platinum films via
the
thermal
decomposition
of
bis
(acety1acetonato)platinum has been described
(57, 58). The (acac),Pt compound vaporises
at 180°C/10-4 mm, and the deposition of
lO-lOOA thick films onto a silicon support
heated to 500-6OO0C is carried out at a vapour
pressure of 20-200 mm. Hydrogen is not
suitable as a carrier gas, because it results in the
formation of a black non-volatile compound.
The films are contaminated by carbon.
The thermal decomposition of trimethyl(acetylacetonato)platinum at 165OC was
investigated in a flow type system, with pumping of the decomposition products at
250-30O0C (59-61). Platinum was deposited as
a bright metallic film, and acetylacetone and
methane were identified in the decomposition
products.
The other most suitable platinum derivatives
for film formation via deposition from the
vapour
phase,
are
tetrakis(trifluoroph0sphine)platinum Pt(PF,), (b.p. 7OOC) (62),
bis-?r-allylplatinum (C, H 5 ) 2pt
(sublm.p.
40°C/10-2 mm (63), ?r-allyl-?r-cyclopentadienylplatinum C, H, PtC, H,
(sub1m.p.
40°C/10-2 mm) (63), trimethyl-?r-cyclopentadienylplatinum Me,Pt-r-C,H,
(sublm.p.
100°C/10-2 mm) (8, 65) and its monomethyl
derivative (8). The production of platinumgallium films has been reported (66).
Decomposition in Solution
Having reviewed the literature on the application of organometallic platinum group
compounds for the preparation of coatings and
films via vapour phase deposition, the decomposition of organometallic compounds in solutions is now considered. In this case the
majority of the data is concerned with thermal
decompositions which is due to the fact that
electrochemical and chemical deposition of
29
I
Organometallic Platinum Group Compounds for Film Deposition
~
Organometallic compound
compound
Support
Support
Reference
Reference
Temperature
Temperature
67
67
67
67
67
67
Synthetic
Synthetic fibres
fibres
(DieneIPdCI,
Polymer
Polymer
Os0,terpene
Glass
Glass
I
50-150°C
50-1 5OoC
I
69
69
3OOOC
3OOOC
H,
H, stream
stream
70
70
(DieneIPdCI,
LML'
(M =Pd, Pt,
Pt, Rh,
Rh, Ir,
Ir,
Ru, 0s; L,L'=cyclic
L,L'=cyclic
hydrocarbon ligands)
ligands)
Electrodes
Pd, DBA,
Pd,DBA,
(DBA = dibenzylideneacetone)
Plastics
Plastics
71
71
I
1
I
Glass"
Glass"
IC,H,PtCI,lH
Zeolites,
Zeolites, metal
metal
oxides
oxides
CpRh(CO),H
I
I
I
72
72
73
73
Rh,(COl,CI,
Rh,(CO),CI,
CODPtCI,
68
68
1
I
"
Divinylbenzene,
Divinylbenzene,
polystyrene
polystyrene
I
74
74
74
74
75
75
For data on application of the compounds: C,H.M(XlC,H.IM=Rh
l r . X = S R SeR TeR AsR PR 1. (LMXI lL=cyclic r-enyl; M=Pd,
Pt; X=halogenl; [QM(COI € ] + A - IM=Ru. 0s;Q=C.H.. C.H.; € L i e f i n ; ALAIX;. PF., BPh:: haiogenide);'M(Csl.(PR,IX (M=Ru, Rh,
yd, F't; R=Ph; X=CI, Brl~L,Rh(COICL see Refs. 76-80
Preliminary treatment with CI,SICH,I,CN
metals from solutions are being seldom used.
Films of metals and metal oxides may be produced on a variety of supports from
organometallic compounds and their mixtures
via thermal decomposition. The method is
technologically facile, and as a rule the following procedures are carried out (1):
(i) The solution is applied to a sample, the solvent is evaporated, the organometallic compound is decomposed at ambient temperature
and the film formed is then annealed into the
sample at elevated temperatures.
(ii) The heated sample is placed in the solution,
Platinum Merals Rev., 1992, 36, (1)
held there until it becomes coated, and the film
is then annealed into the sample.
(iii) A stream of the solution is directed under
pressure onto the sample being plated, which is
heated to the specified temperature.
Organometallic platinum group compounds
for use with this technology require the following (1):
(a) high solubility of the organometallic compound in organic solvents
(b) the organometallic compounds should not
undergo sublimation, even at elevated
temperatures
30
(c) the organic solvent and organic decomposition products should be completely vaporised at
the decomposition temperature of the
organometallic compounds.
In view of these requirements, the literature
is now considered. It should be noted that the
majority of organometallic platinum group
compounds exhibit hlgher solubility than inorganic compounds. The first requirement,
therefore, is easy to meet. Any organometallic
platinum group compound is potentially
suitable for the formation of films from solution, via thermal decomposition. The determining factor is the availability of the compound
and its possible commercial production. Information on the use of organometallic platinum
group compounds for film deposition via thermal decomposition is given in the Table. This
shows that a wide range of compounds, covering practically all types of platinum group
organometallic compounds, have been
patented. These compounds can be readily
prepared under both laboratory and industrial
conditions.
The literature contains no data on the
photochemical and electrochemical decomposition of organometallic platinum group compound solutions.
There is however information on the
chemical deposition of platinum metals from
solutions of the corresponding organometallic
compounds. The deposition is carried out in
the presence of a suitable reducing agent, frequently hydrogen. Thus platinum films can be
deposited on aluminium oxide and other nonconducting supports by the reaction of
hydrogen with solutions of the diene platinum
complexes (8 1-84).
Therefore, by this method, platinum metals
alloyed with silver and gold (85) or nickel (86)
may be deposited from mixed a-complex solutions. One-electron reagents of the sodium
naphthalenide type have been patented as
reducing agents (87).
Coatings may be prepared by thermal decomposition of organometallic compounds which
are generally applied to the support as a paste,
or in a pure form. (The preparation of metallic
ruthenium and platinum by thermolysis of
Ru,(OOCPh),(PhCOOH), and (DMSO),PtCl,,
respectively, has been reported (88, 89)).
Osmium films were also produced on glass by
heating osmium tetroxide complexes with
terpenes (90, 91). Ruthenium films were
prepared by the pyrolysis of Ru,(CO),, (92),
and platinum films by the decomposition of
Me,PtC,H, (66, 92). Ruthenium plated electrodes were made by annealing pastes containing
tris(acety1acetonato)ruthenium
and
trichlorosilane (93), and thick palladium and
platinum films were produced by thermolysis
of the corresponding resinates (94, 95).
Another application of organometallic
platinum group compounds in electronics
relates to the production of multilayer circuits
for computers. Usually circuit boards or
substrates prepared from a polymeric material,
such as polyamides or polyphenolformaldehyde, are subjected to chemical and electrochemical metallisation, frequently with
copper or nickel. The metallic films thus formed become metallic patterns and the prepared
circuits are layered and perforated. It is
desirable that the holes are metallised. In order
to produce well metallised circuits, chemical
metallisation catalysts are employed, these being incorporated into the polymer. The composition is then heated to the decomposition
temperature of the organometallic compound to
form the metal. Copper and nickel are
deposited on the materials thus formed.
Palladium compounds are mainly used for these
applications and there are a number of patents
relating to complexes with phosphines (96),
with phosphites (97, 98), tris(dibenzy1ideneacetone)dipaUadium and olefinic and
acetylacetonate derivatives of palladium
(98-103). For the metallising of polymers, see
also (104-108).
Summary
It is apparent, therefore, that organic
platinum metals compounds have some specific
applications in electronics, but to date these
have been limited due to difficulties in producing the compounds on an industrial scale.
31
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Osmium-Ruthenium Coatings
To accommodate new uses, the cathodes in
travelling wave tubes need to operate at higher
frequencies and output powers; thus they have
to function at higher temperatures and current
densities. The life of coated tungsten cathodes
is limited by tungsten diffusion; to prevent this
the cathodes operate at 950OC~(brightness
temperature).
Therefore the degradation of a porous
tungsten cathode impregnated with barium
calcium aluminate and coated with an osmiumruthenium film has been studied (N. f i t a ,
ZEEE Trans. Electron Devices, 1991, 38, (ll),
2554). During tests tungsten diffused into the
surface, converting it to osmium-rutheniumtungsten. The activation energy for the
tungsten diffusion coefficient was 8.4 eV, giving a stable period for the coating of over
100,000 hours at a cathode temperature of
105OoCe,and the coating could be operated at
a current density of 30 A/cm2.
33
An Important Work of Reference
Chemistry of t h e Platinum Group Metals: Recent Developments
EDITED BY F. R. HARTLEY, Elsevier Science Publishers, Amsterdam, 1991, 642 pages,
ISBN 0-444-88 189- 1, U.S.$274.50, Dfl.480
The declared aim of this very readable and
welcome volume is to cover recent
developments in the chemistry of the platinum
group metals. The variety of treatments and
styles used depends partly on the subject matter
of each chapter, partly on when the area of
technology was last reviewed and partly on the
particular interests and expertise of each individual author. The result is a collection of
chapters in a variety of styles, but each is useful
and interesting, in its own way.
The opening chapter is by Professor F. R.
Hartley of the Cranfield Institute of
Technology, Bedford, U. K., and considers the
occurrence, extraction, properties and uses of
the platinum group metals. The dominant producers of the platinum group metals are South
Africa, the U.S.S.R. and, to a lesser extent,
Canada. The route for conversion of the South
African ore into final concentrate is indicated,
as are the classical separation and more recently
developed solvent extraction methods for
dividing the concentrate into the six individual
metals. The physical and chemical properties of
the six metals are described. Therefore the
principal applications of the platinum group
metals depend on either their nobility or their
catalytic properties.
At first sight nobility and catalytic activity
might seem unlikely properties to be exhibited
by the same element, but their nobility depends
on the large number of valence d-electrons
which are available for tight cohesive bonding.
These same valence shell d-electrons provide
orbitals having characteristics which match
those of a range of simple substrates such as
hydrogen, carbon monoxide and unsaturated
hydrocarbons, and thus promote their reactivity. The predominant uses of platinum are in
autocatalysts and jewellery, while palladium
finds application principally in the electrical
and dental areas, uses of ruthenium are mainly
in the electronics and electrochemical areas,
and the market for rhodium is strongly led by
its requirement in autocatalysts.
Catalytic Activity
The general introduction to catalysis by the
platinum group metals, written by G. C. Bond
of Brunel University, U. K., puts the subject into good historical perspective and draws most
of its exemplification from the heterogeneous
field, although the common factors present in
homogeneous, heterogeneous and enzymic
catalysis are indicated. The analytical techniques available for structure determinations of
chemisorbed layers are described, and there are
sections on catalyst poisons, metallic catalysts
and supported metal catalysts. The various
types of useful reactor configurations are considered, as are the kinetics and reactor modelling aspects. Important industrial applications
of the platinum group metals catalysts include
ammonia oxidation, power station and
automobile emission control, petroleum reforming, and catalytic hydrogenation in fine
chemicals manufacture.
Benefits of Catalytic Combustion
The chapter on catalytic combustion by D.
L. Trimm of the University of New South
Wales, Australia, describes an extension of
pollution control technology, using the heat
produced, preferably with the minimum production of unwanted pollutants. The design requirements for catalytic heaters are discussed,
with indications that the combustion efficiency
depends on the material used to support the
platinum or platinum/palladium catalyst, on
fuel flow rate, the type of fuel used and oxygen
diffusion from the ambient atmosphere.
Therefore the use of catalytic combustion in gas
turbines can reduce the temperature of gas
phase free radical reactions to below 165OoC,
34
thus reducing nitrogen oxide emissions by an
order of magnitude.
Synthesis Gas Chemistry
The chapter on the use of platinum group
metals catalysis in the synthesis of chemicals
from syngas by G. R. Steinmetz and Z. R.
Zoeller of Eastman Chemical Company, Tennessee, U. S.A. ,indicates that the dramatic rise
in crude oil prices in the early 1970s gave a corresponding surge in the quest for alternative
carbon sources. This need followed the significant developments in organometallic chemistry
and the result was an explosive growth in the
use of organometallic catalysts (particularly
homogeneous systems) for the generation of
chemicals from synthesis gas. The platinum
group metals have played an integral part in
these developments and several processes have
either been commercialised or are under consideration; these include the Monsanto process
for the rhodium-catalysed carbonylation of
methanol to acetic acid, and the Tennessee
Eastman and Halcon SD rhodium-catalysed
carbonylation of methyl acetate in the presence
of hydrogen and dimethyl ether to yield acetic
anhydride. Rhodium based catalyst systems are
also used in the Johnson Mattheymnion Carbide/Davy McKee hydroformylation process
for the conversion of olefins (for example propylene) to aldehydes. One common feature of
these three rhodium-based processes is that
most or all of the oxygen component is retained. Current economics dictate that a new process must possess both high selectivities and a
high overall yield.
There is some overlap of the content of the
syngas chapter with that written by A. W.
Parkins of King’s College, London, on recent
developments in platinum group metal catalysts
in the chemical industry, but both
heterogeneous and homogeneous processes are
considered here, and the growing interdependence of these two areas of catalysis is
recognised. This chapter deals with both major
and minor processes of interest to industry,
including the rhodium-catalysed reactions
indicated
above,
the
vapour
phase
palladium-catalysed route to vinyl acetate, the
Wacker process for the palladium-catalysed
production of acetaldehyde from ethene,
supported palladium catalysts for the
hydrogenation of unsaturated hydrocarbons,
and platinum catalysed hydrosilylation reactions. Fischer-Tropsch reactions for the synthesis of higher hydrocarbons and other
chemicals from methane and syngas, based on
ruthenium catalyst systems, are described by
Steinmetz and Zoeller and by Parkins. The
Texaco molten salt process for the conversion
of
syngas
to
alcohols/esters
in
tetrabutylphosphonium iodide (m.p. 96OC) in
the presence of ruthenium carbonyl is also
described, together with a number of other
reactions with industrial potential.
Catalysis in Molten Salts
The chapter by J. F. Knifton of Texaco
Chemical Company, Austin, Texas, U.S.A., on
platinum group catalysis in molten salts is a
valuable review of the wide range of chemical
reactions now studied in this type of medium,
which should be considered in parallel with
homogeneous and heterogeneous catalysis in
the methodology of both laboratory and commercial scale operations. In addition to the
alcohol synthesis mentioned above, this technique has been used for the direct synthesis of
ethylene glycol (ruthenium-rhodium catalyst or
ruthenium alone), or ethene and propene
(ruthenium-cobalt) from syngas.
C-H Bond Activation
The review of C-H bond activation by J. R.
Chipperfield of the University of Hull, U.K.,
covers this important area of work as far as the
recent developments in homogeneous catalysis
are concerned. The homogeneous systems are
dealt with in the context of the heterogeneous
industrial processes concerned with dehydrogenation, cracking and partial oxidation.
Oxidation Chemistry
The comprehensive chapter on oxidation by
E. S. Gore of Johnson Matthey, New Jersey,
U.S.A., gives an historical introduction,
35
indicating that the first example of catalysis by tions by E. N. Balk0 of the Engelhard Corporaa metal was reported by Sir Humphry Davy in tion, New Jersey, U.S.A., the area considered
1817 who described the oxidation of inflam- is platinum group metals coated anodes in
mable gases over platinum. The declared pur- which the requirements for industrial anodes
pose of this chapter is to review the present are listed and then the anodic characteristics of
state of platinum group metals catalysed platinum, iridium and ruthenium and their oxhomogeneous oxidations with the emphasis on ides are considered in some detail. At least 80
reactions of synthetic and industrial potential per cent of the chlorine production in the
and on recent developments since 1980. Even western world is now manufactured on
so, the chapter has four hundred references and ruthenised titanium. This review is primarily
covers a wide spectrum of organic chemical concerned with several of the most widely used
transformations, including the reactions of platinum group metals coatings in their comaliphatic and aromatic hydrocarbons, alcohols, mon industrial applications, that is oxygen and
ethers, sulphides and amines. Although chlorine discharge.
An authoritative chapter on the role of
platinum is well established for use in commerplatinum
group metals in the photodecomposicial heterogeneous catalytic processes, it was
not until 1962 that the use of a platinum group tion of water, written by A. Mills of the Univermetal (palladium) in an industrial homogeneous sity College of Swansea, U. K., includes both
catalytic process was first reported, this being homogeneous and heterogeneous systems and
in the Wacker process for the conversion of indicates the relevance of this approach to the
ethene into acetaldehyde.
conversion of solar energy into chemical
energy.
Electro- and Photochemistry
At the present state of knowledge, the
A chapter indicating the importance of heterogeneous systems are considered to be
platinum group carbonyls in developing the more durable. Homogeneous catalysts for
potential of catalytic processing is written by J. either hydrogen or oxygen evolution will reA. Davies and C. T. Eagle of the University of quire substantial further development before
Toledo, Ohio and Williams College, they are likely to offer a serious alternative to
Massachusetts, U. S.A., respectively. The prin- their heterogeneous counterparts, such as colcipal sections in this chapter are on photo- and loidal platinum or powdered hydrated
electrochemistry and reduction reactions. The ruthenium(IV)oxide, respectively.
use of light to generate thermally active
catalysts has led to the catalytic synthesis of Homogeneous Catalysis
functionalised compounds from arenes and by Palladium and Platinum Systems
alkanes under exceptionally mild conditions.
The contribution by G. K. Anderson of the
Through an understanding of fundamental University of Missouri, U.S.A., is on the
electrode processes, it may prove possible to organometallic and homogeneous catalytic
design solution phase systems or modified elec- chemistry of palladium and platinum and is
trodes capable of exerting a significant elec- very substantial with over four hundred
trocatalytic effect on the reduction of carbon references, in spite of its focus being on work
dioxide, an alternative to hydrocarbons as a ma- carried out only in the past ten years. Both the
jor initial source of carbon. Platinum group car- organometallic aspects of the topic and the use
bonyls have begun to show promise as catalysts of these species in catalytic reactions are
for a number of novel reduction reactions described.
Soluble palladium catalyst systems have been
which have potential for future developments,
including the reduction of nitrogen oxides by widely applied in organic chemical synthesis
using, for example, carbonylation reactions;
carbon monoxide.
In the chapter on electrochemical applica- both platinum and palladium systems have
36
featured in catalytic hydrogenation, hydroformylation and hydrosilylation reactions.
Iridium and Rhodium Systems
Another very substantial review, with over
five hundred references, has been contributed
by F. H. Jardine of the North East London
Polytechnic, U.K. The organometallic and
homogeneous catalytic chemistries of rhodium
and iridium are described, including
hydrogenation and dehydrogenation reactions,
hydroformylation, hydrosilylation and carbonylation and decarbonylation. In general, only recent work is covered but a special feature
is made of rhodium(I1)carboxylate catalysed
cyclisations involving alpha-diazo esters or
ketones, a topic which has been overlooked in
previous reviews.
The chapter by W. Levason of the University
of Southampton, U.K., on the chemistry of the
platinum metals in high oxidation states brings
up to date a topic frequently reviewed in the
past. The text is in a highly summarised form
and is a very useful reference work for inorganic chemists working in this area. For
halides, oxides and the related anions, there is
sufficient resemblance between the chemistries
of the six elements to allow the topics to be
treated together. For the co-ordination
chemistries with neutral ligands, however, the
differences currently seem large enough for
them to be treated separately. There are 443
references in this chapter and it also includes an
addendum covering the 1989 literature,
whereas the main text covers principally the
years 1981 to 1988.
Activity with Biologically
Important Molecules
Amino acid and peptide complexes are
reviewed by H. Kozlowski and L. D. Pettit of
the University of Wroclaw, Poland and the
University of Leeds, U. K. , respectively. Interest in the interaction of platinum metals with
biologically
important
molecules
was
stimulated some twenty years ago with the
discovery by Barnett Rosenberg and colleagues
at Michigan State University, that certain
platinum complexes exhibit anti-cancer activity. Intensive research to explain the chemistry
and biochemistry of platinum complexes which
behave as cytotoxic agents and to produce effective and less toxic anti-cancer drugs has led to
huge projects based on the chemistry of
platinum complexes with many biologically active ligands, including amino acids and peptides. Amino acid complexes of the platinum
group metals are also of interest as catalysts
and, as such, have been the subject of several
recent studies; this may become a rewarding
field for research, although it is made difficult
by the kinetic inertness of many of the complexes formed and the complicated aquochemistry of the metal ions themselves.
A review of cancer chemotherapy involving
platinum and other platinum group complexes
has been written by C. A. McAuliffe, H. L.
Sharma and N. D. Tinker of the University of
Manchester Institute of Science and
Technology, U.K. The parent of this class of
platinum drugs is “cisplatin” and this is widely
used for the successful treatment of ovarian and
testicular cancers and, to a lesser extent, head
and neck tumours. A very significant research
effort on the synthesis and evaluation of candidate platinum compounds for new drug formulations has now led to the introduction of the
second generation drug “carboplatin” which
produces less severe side effects in patients.
Electronic Applications
The final chapter in this wide ranging book is
written by P. D. Gurney and R. J. Seymour of
Johnson Matthey Technology Centre, Reading,
U.K., and indicates the many uses for the
platinum group metals in electronics. Platinum
finds most of its applications in the thin film
area but palladium and ruthenium are predominant in the formulation of thick film conductor
and resistor systems. In fact, 51 per cent of the
demands for palladium and ruthenium in the
western world are in the electrical/electronics
area. A wide variety of platinum group metal
compounds have been used to deposit thin
metal films via chemical vapour decomposition
techniques, while physical vapour deposition
37
involves the production of a metal film via
sputtering or evaporation at low pressure.
Platinum silicide, made by the sputtering of a
thin platinum film onto a silicon surface,
finds application in bipolar integrated circuits
and in Complementary Metal Oxide Semiconductor (CMOS) structures. Amongst other
topics discussed in this chapter are platinum
group metal alloys for liquid metal ion sources
(LMIS) and the use of platinum group metals
in magnetic data storage media, thin-film
magneto resistive sensors, magneto-optic
media, and gas sensors. Ruthenium oxide finds
wide application in thick film resistors, and
palladium-silver systems are the basis of the
most widely used thick film conductors as well
as being valuable components in multilayer
ceramic capacitors.
The use of platinum group metals is helping
in the development of the new high
temperature superconducting systems; they are
being used in the formation of barrier layers for
thin films of these materials. Platinum group
metals complexes have also been incorporated
into semiconductors, and into one-dimensional
conductors where the columnar structures
result in the compound having highly
anisotropic properties.
Overall, this book reviews progress in the
development of knowledge on the chemistry of
the platinum group metals in the areas where
there have been significant technological advances during the last ten years. There are good
links throughout between scientific investigation and its commercial application, although
one very important application area, that is
automotive emission control catalysts, only
receives brief comments, and there is no discussion of the platinum fuel cell catalyst systems
which are currently receiving significant attention in both research and commercial development. The book provides a useful and
stimulating reference work, particularly as it
covers many different fields of scientific
research in the same volume and it should
therefore appeal to a wide range of research
workers, particularly those interested in
developing new areas of platinum metals
research or commercial applications in a
synergistic manner.
D.T.T.
Efficient Ruthenium Dye-Sensitised Solar Cell
To-date, a large scale use of photovoltaic
devices for electricity generation has not
developed because the available technology is
prohibitively expensive. However, a recent
letter from the Swiss Federal Institute of
Technology describes a photovoltaiccell system
for which a commercially realistic energy conversion efficiency is claimed (B. O'Regan and
M. Griitzel, Nature, 1991, 353, (6346), 737).
Colourless, optically transparent films of
titanium dioxide, displaying the fundamental
absorption edge of anatase (band gap 3.2 eV)
are deposited on conducting glass sheet. These
10 pm films, which consist of particles with an
average size of 15 nm and a particle surface
roughness factor of 780, gave linear photocurrent response up to full sunlight.
The subsequent deposition of a monolayer of
the trimeric ruthenium complex dye
RuL2(p(CN)Ru(CN)Lr2), (where L is
2,2'bipyridine-4,4'dicarboxylic acid and L' is
2,2'-bipyridine) onto the titania results in a
deep brownish red coloration of the film. The
high surface area of the semiconductor film and
the ideal spectral characteristics of the dye lead
to a high proportion of the incident solar energy
flux being harvested in a cell employing this
system in the photoanode; the counter electrode consisting of conducting glass coated with
a few monolayers of platinum. The very fast
electron injection observed with dyes such as
this tri-ruthenium complex, combined with
their high chemical stability, makes these
compounds look attractive for practical
development.
Exceptionally high efficiencies for the conversion of incident photons to electrical current
are claimed, with the device harvesting 46 per
cent of the incident solar energy flux. The
overall light to electric energy conversion yield
is 7.1 to 7.9 per cent in a simulated solar light
and 12 per cent in diffuse daylight. With current densities greater than 12 mA/cm2 and with
at least five million turnovers being achieved
without decomposition, practical applications
may be feasible. The technology described thus
seems to represent a significant advance in
D.T.T.
photovoltaic cell technology.
38
Versatility of Palladium Compounds
Carbonylation: Direct Synthesis of Carbonyl Compounds
BY H. M. COLQUHOUN, D. J. THOMPSON AND M. V. TWIGG, Plenum Press, New York, 1991,
296 pages, ISBN 0-306-43747-3, U.S.$65
The authors have used their experience of industrial catalysis to provide an authoritative
and practical account of carbonylation.
The volume deals with the carbonylation of
organic compounds, principally mediated by
transition metal catalysts but also including
relevant reactions which use stoichiometric
reagents. The major parts of the book are
organised according to the chemical nature of
the product. In addition, there are useful sections which deal with mechanistic and practical
aspects of carbonylation.
The use of carbon monoxide is proving increasingly useful in organic synthesis and the
chapter on practical aspects of carbonylation is
a valuable guide to chemists not experienced in
handling these materials. It includes valuable
details on the properties of carbon monoxide
and metal carbonyls, it describes the handling
of these materials and also deals with the equipment and procedures required to carry out reactions and isolate the products. The major
sections of the book on organic syntheses are
organised in a clear and concise way. They contain practical details of selected compounds and
point out limitationsof particular methodology.
The chapter on aldehydes describes their synthesis from halocarbons using either soluble
palladium catalysts or stoichiometric iron
reagents. Hydroformylation of alkenes is also
discussed with an emphasis on the commercial
rhodium catalysts and to a lesser extent cobalt.
The section on ketones describes their synthesis from halocarbons (using iron reagents or
palladium catalysts) and from dienes (using
palladium, rhodium or cobalt catalysts).
The synthesis of carboxylic acids from alkyl
and benzyl halides with palladiumtriphenylphosphine or anionic nickel carbonyl
catalysts and from vinyllic halides using
palladium or cobalt catalysts is described.
There is discussion of the Monsanto based
Platinum Metals Rev., 1992, 36, (l), 39
rhodium catalyst systems which have become
the dominant technology for the carbonylation
of methanol to acetic acid. This catalyst is less
useful for the carbonylation of higher alcohols
where strong acids find some application.
Other sources of carboxylic acids are alkynes,
diazonium ions (using palladium catalysts) and
aldehydes.
The preparation of esters via similar
substrates is described, and in addition the
hydroesterification of alkenes with carbon
monoxide and ethanol using bimetallic catalysts
containing platinum or palladium with tin
halide as co-catalyst is discussed, as is the carbonylation of organometallic reagents such as
Grignard, organothallium, organoboron and
organosilicon reagents with palladium or cobalt
catalysts.
The Tennessee Eastman rhodium process for
the production of acetic anhydride is described
along with other routes to acid anhydrides.
There are further sections on the synthesis of
amides, acyl halides, lactones, lactames and
related heterocycles.
A chapter is devoted to decarbonylation
where aromatic aldehydes can be useful starting
materials. Palladium-on-carbon catalysts have
been employed at high temperatures and also
homogeneous rhodium systems under less extreme conditions.
The final chapter deals with the preparation
and recovery of precious metals catalysts. This
includes sufficient detail to enable a qualified
chemist to prepare relevant catalysts of interest.
This volume demonstrates that palladium
compounds serve as versatile catalysts in organic
synthesis involving carbon bond-forming reactions. The authors have provided a good balance
between established reactions and emerging
chemistry. It should serve as a useful text for synthetic chemists working in a research and
M.J.H.R.
development environment.
39
Platinum in the Eighteenth Century
A FURTHER SPANISH CONTRIBUTION To AN UNDERSTANDING
OF ITS DISCOVERY AND EARLY METALLURGY
By A. Galhn and R. Moreno
Department of Chemistry, Informatic Faculty and E.T.S.I. de Montes,
Polytechnic University of Madrid, Spain
It is generally accepted that the first description of “platina” to appear
in Europe was by a young Spanish naval officer, Antonio de Ulloa, whose
famous work “Relacibn del Viaje a la America Meridional” was published in 1748. Important though this was, of even greater significance was
the fact that the primary metallurgy of platinum must have been
established much earlier, enabling it to be extracted, purified and
manufactured. These processes appear to have been kept secret from
other European countries, and until recently their details had not been
deduced. Now manuscripts discovered in the Colombian Archives enable
known methods of purification to be linked to the description of the
primitive manufacturing process.
The date ofthe discoveryof platinum has often
been debated, but current opinion favours the
claim of Antonio de Ulloa (1) over that of
Charles Wood (see (2) where W. Watson refers
to a letter in which C. Wood communicated to
him in 1741 the existence of platina). Earlier
this century, however, in a little known
publication, a Peruvian historian named Luis
Ulloa ascribed the discovery to Jose Sanchez, a
Spanish assayer who had worked at the Casa de
la Moneda de Santa F6 de Bogota (3). Unfortunately Luis Ulloa did not support this attribution with any bibliographical evidence.
From his biographical details, however, there is
no doubt that he was extremely knowledgeable
about the archives of Colombia, Ecuador and
Peru, and therefore it would not be surprising
if he knew of the existence of documents concerning platinum that pre-dated the arrival in
South America of Antonio de Ulloa.
In a work published in 1985 (4) Espinosa Baquero, a Spanish-American author, reproduced
a manuscript by Jose Sanchez de la Torre y Armas (5). This included a balance sheet, dated
1726, for a separation of gold and platinum,
and is very likely the manuscript referred to
Platinum Metals Rev., 1992, 36, (I), 40-47
earlier by Luis Ulloa, when attributing the
discovery of platinum to Sgnchez.
The Sanchez manuscript has been studied by
Espinosa Baquero and also by Luis Fermin
Capitan (6) but their interpretations of the
separation procedure differ from that of the
present authors.
Background to the Early
Metallurgy of Platinum
Historically the significance of the various
claims concerning the discovery of platinum,
arising from the writings of Ulloa, Wood and
even Sanchez, have been complicated by the
fact that they considered only the native metal,
“platina”, which may have been adulterated
with other metals, and which received no kind
of scientific purification.
Of even greater importance is the fact that
fabricated platinum articles existed in the first
third of the Eighteenth Century, necessitating a
refining or purification process and, in the
absence of the means to melt it, a hot-pressing
or sintering process that enabled the platinum
to be worked subsequently (7).
The possibilities of platinum fabrication were
40
acknowledged by experts in other European
swords, boxes and buckles, not any piece is to be
found today, either for the no appreciation that
countries, dating it before the voyage of
this invention got from its residents, or for the reAntonio de Ulloa to South America. In a letter
quests from foreigners who wanted to verify the
from William Watson to Georg Mattias Bose,
fact of the fusion they doubted about, they have
entirely vanished”.
dated 15th January 1751, (included in the
review by M. Morin (8)), the following This is not a technical report, but it gives the
reference is made to “platina’ ’:
opinions of Mutis upon the advantages of
platinum
for industrial applications. It includes
“It is not possible to forge, but it has already been
found in America the way of moulding hilts of a report of melting tests carried out in the Casa
swords”.
de la Moneda de Santa Fe to make two medals
On the other hand, in 1750 Watson had already embellished with the head and shoulders of the
King.* Although no details of the refining or
noted in the Philosophical Transactions:
melting
procedures are given, Mutis says:
“But the Spaniards have a way of melting it down,
“The fusions that on this occasion have been
either alone, or by means of some Flux; and cast
it into Sword-hilts, Buckles, Snuff-boxes, and
other Utensils.” (2)
Charles Wood adds (see (8) pp.31-32) that they
may achieve the fusion by adding another
metal, or non-metal. He supports this assertion
by referring to cupellation experiments carried
out in Jamaica by M. Brownrigg, where a
weight loss occurred during the process due to
impurities. However, cupellation was not a
guarantee of pure platinum, as it would not be
possible to eliminate all the lead from the
cupellation residue because of the solidification
of the lead-platinum alloy prill before the
cupellation was properly finished. None the
less, objects made from pure platinum may
have existed, and if they did then they could
have been taken from Cartagena de Indias to
Jamaica where Wood could have obtained
them.
In his survey of the literature on platinum,
Morin writes-although possibly without first
hand knowledge:
“The Spaniards have found the secret of its fusion, since they have fused hilts of swords, boxes,
tobacco-boxes, etc.. ..” (8)
practiced in order to form those samples, have
been very easy and yet without all that difficulty . . . with the result that, being the fusion of
this metal very easy . . .
The portrait of the royal person in medal number
1 is the sample of the pure platina . . .”
Thus, it seems unquestionable that pure
platinum could be “melted”, although this
may actually mean “hot-forged”, but the result
for medal number 1 was not excellent. The
craftsman who carried out the “melting” was
Francisco de Benito, the engraver at the Casa
de la Moneda de Santa Fe. According to Manjarres (lo), the Junta de Comercio asked for information about the method used by Benito,
the engraver from la Ceca, who had been
awarded a prize for discovering the procedure
which he had been recommended to keep
secret. This he apparently did, because there is
no record of it in the Archivo General de Indias.
The medals resulted from a revival of interest
in platinum by the Junta de Comercio, who
knew of the Santa Fe directive concerning
platinum. According to Manjarres, this directive required that the platinum which was
separated from gold in the Casas de la Moneda
was to be thrown into the rivers, as it was impossible to melt, but more especially to avoid its
fraudulent use as an adulterant. The Viceroy
These comments were all corroborated in a
much later, 1774, report on platinum by Jose
Celestino Mutis, Director of the Real Expedicidn Botinica al Nuevo Rein0 de Granada, the
*In Reference 10, Manjarres indicates that
manuscript being in the Real Jardin Botinico
de Madrid (9). Referring to earlier times, Mutis the American publisher Jose Toribio Medina
possessed a platinum medal from Santa Fe
notes that:
which carried a bust of King Carlos 111, and
“Although in this city, small pieces of platina wonders if this medal was one sent by the
were fused years ago, forming hilts for ceremonial Viceroy.
Platinum Metals Rev., 1992, 36, ( 1 )
41
encouraged experimentation with the platinum, they consisted of primary unrefined gold
and in 1774 he reported that although it had not which naturally contained platinum or were
been known how to melt platinum, this had gold adulterated with platinum.
By virtue of the first refining procedure
now been achieved as a result of the experiments carried out; as proof of this he sent adopted, we are of the opinion that the bars
the medals carrying the portrait of the King, as were new unrefined material. Initially the gold
was melted several times to give what Sanchez
related by Mutis.
With hindsight it seems curious that a regarded as “clean” 18 carat gold, free of
melting process was not known in Santa FC, platinum, together with a gold residue which
although one had been available earlier. It is, contained the platinum. There was, additionalperhaps, also surprising how quickly it was re- ly, a melting loss of 58 castellanos. Clearly the
discovered when experimentation started. gold and platinum cannot have been perfectly
Again, it is interesting to consider that before alloyed, since if they had been they would have
the arrival of Ulloa platinum had been been inseparable by simple melting. It must be
fabricated in a primitive way, but over a period concluded that the platinum was present as parof only thirty years this ability had been lost, ticles in the body of the gold, resulting from incomplete initial fusion before the bars were
perhaps due to lack of interest.
Thus, as a working hypothesis we will cast. When the gold was re-melted, the insoluassume that Francisco de Benito re-discovered ble platinum could be separated with a strainer.
This procedure saved Sanchez from having to
the process that had been used in la Ceca in the
first part of the century, making use of informa- refine the whole of the 5958 castellanos by the
tion contained in a manuscript stored in the next procedure, known as inquartation.
A flow-sheet of the whole process is shown in
Casa de la Moneda de Santa FC which he was
the
Scheme. In the manuscript Sanchez claims
probably able to access when commencing his
that he obtained 3000 castellanos of clean gold,
study of the fusion of platinum.
free from platinum, although admittedly only
The Bogoti Manuscript
18 carat. This is unlikely to be strictly true
The manuscript of Jose Sgnchez de la Torre since some platinum would probably have
y Armas contains a mass balance and a cost dissolved during the melting processes,
analysis for refining a batch of gold which con- although possibly only trace amounts. This
tained platinum (5). The report is unclear does not seem to have been noticed by him, and
because it mixes the language of the time, it would not have changed in a perceptible way
which was probably associated with commercial the colour or the melting point of the gold, or
aspects of the process, with mention of the its mechanical properties. Also, at low concenbalances. The author makes no attempt to trations it would have been difficult to detect by
describe the technical aspects of the process us- fire assay.
It is considered that both the separation by
ed; this has to be deduced from the comments
that he makes about the difficulties of the pro- melting and the formation of an 18 carat alloy
cess as he tries to justify the high costs involv- are evidence that the bars had originated from
ed. Important technical conclusions about costs the incorrect melting of natural gold, containand weights of materials can be deduced from ing some platinum. If the gold had been intenthe report, as will now be demonstrated.
tionally adulterated, the separation would be
impossible if alloying had occurred, and the
The Separation Procedure
gold alloy would probably have been of a higher
The manuscript refers to six bars of gold mix- quality, for example, a 22 carat coinage alloy.
ed with platinum and having a total weight of Also in an adulterated alloy the platinum would
5958 castellanos. The origin of the bars is not presumably have been well alloyed in order to
given and, therefore, it is not known whether make it more difficult to detect.
Platinum Metals Rev., 1992, 36, ( 1 )
42
GOLD CONTAINING PLATINUM
(platinum forming nodules)
J
’
Fusions and refusions
18 CARAT
LOSS
GOLD
GOLD CONTAINING
PLATINUM
Inquartation, silver is added
in the ratio of
4:1IAg:Au + Pt
Taken aside or separation
with nitric acid
(with mercury remainders)
Calcination
Calcination
i
v
43
The second part of the procedure for refining
the gold is based on inquartation, which is a
well known process for refining gold although
little used in practice. It is based on the solubility in nitric acid of silver and the base metals
commonly present in the alloy. The gold to be
refined is melted with three to four times its
weight of silver; when this alloy is treated with
nitric acid everything dissolves except the gold
which remains as a powder at the bottom of the
container, and can be easily separated by decanting the solution. This method is unlikely to
have been used for normal gold refining
because of the high cost of nitric acid, as will be
shown later in the analysis of costs. Other
methods such as “real foundation” and “fusing precipitation” (12) might have been preferred, the use of inquartation being limited to
assaying. But it will be shown next that inquartation was the only process available to Sanchez
which could have been used to separate
platinum and gold.
Sanchez carried out the inquartation correctly, using a 4:l ratio of silver to the 2900
castellanos of platinum-containing gold, in
order to transform the gold-base metal alloy into a silver-base metal alloy soluble in nitric acid.
The problem he faced, as he acknowledged,
was in achieving an homogeneous alloy since
the platinum did not alloy readily with silver at
the temperature of his furnaces. He notes:
“. . . happening to make a new alloy in some
granules, when the platina flocculates and does
not have itself enough silver, for the water to
cause its effect”.
It was necessary for the alloy to be
homogeneous, so that when the silver dissolves
it leaves behind a finely divided residue of gold
and platinum and not platinum nodules. Actually, under these conditions platinum has
some solubility in nitric acid, particularly in
strong acid (but this would not necessarily have
been available in this case), something which
does not happen with gold. However, we do not
think that this solubility is likely to have been
noticed by Sanchez.
Thus, after the inquartation a mixture of gold
and platinum powders is left; the silver and
base metals having been dissolved in the nitric
acid. Sanchez does not specifically indicate how
he achieves the further separation of the two
noble metals, but the key information is contained in the detail of the costs:
“Por el cost0 que hay y que se tuvo . . . plata
consumida, peones, azogado del or0 que sale para
separar la platina calcinada . . .”
[“By the cost that there is and was . . . consumed
silver, labourers, treatment with mercury of the
leaving gold in order to separate the calcined
platina . . .”I
There seems to be little doubt that he separated
the platinum and gold by amalgamation with
mercury, which would rapidly dissolve the fine
gold powder leaving behind the platinum which
does not alloy with mercury. This residue
would then be calcined to yield practically pure
platinum.
Espinosa Baquero, in his interpretation of the
process, suggested that aqua regia was used
rather than nitric acid (4), basing it on a remark
by Sanchez “that it dissolves the gold and the
platinum”. Sanchez does not mention aqua
regia, however, and the large mass of silver based alloy would be unlikely to dissolve in the
reagent owing to the formation of insoluble
silver chloride; this would prevent or make difficult the dissolution of the rest of the alloy.
Capitan proposes that the platinum is all
dissolved by the nitric acid (6), this assumption
possibly being based upon the work of Mathieu
Tillet (1714-1791). This work was not published until 1779, however, so the information
would not have been available to Sanchez in
1726; even if they had been contemporaries
they were unlikely to have meet in Santa Fe.
Furthermore, the solubility of platinum in
nitric acid is quite limited and repeated cupellations and partings in nitric acid would be required to effect a separation.
Having obtained a solution of platinum in
nitric acid, Capitan next proposes that Sanchez
separated the silver from the platinum by
cementation with brass, but this process was
not widely known at that time.
The procedure that we deduce from the
manuscript is in keeping with the information
known at that time; in addition to the fact that
44
it was mentioned in the Sanchez manuscript,
the amalgamation process was well known at
that time, being used on alluvial gold grains
to separate them from admixed platinum
particles.
We have deduced from the manuscript that
Sanchez was neither a scientist nor an investigator. He is far more likely to have been an
assayer applying the established procedures of
his craft. It is probable that these assay procedures had been known in the Ceca de Santa
FC for some years and were passed from one
assayer to another, as was the case with other
craftsmen's knowledge at that time. For the
moment, however, this is the oldest written
document on the subject from which any
technical conclusions can be drawn.
In the light of present knowledge, we consider that the platinum obtained by Sanchez
would have been practically pure, although it is
certain that his objective would have been the
separation of platinum from the gold, rather
than the refining of the platinum. Sanchez
states that he produced calcined platinum and
platinum grains, in which state the platinum
could be readily hot-forged. This suggests an
improvement in the mechanical properties
compared to those of native platinum, which
was not malleable and could not be worked.
Since the process described was the only one
then available for the production of pure
platinum, we propose that it may well have
been the one used for the platinum that was
fabricated into the buckles, boxes and other
articles which circulated in the neighbourhood
of Santa FC de Bogota.
It also seems likely to have been the process
used many years later by the engraver Francisco de Benito to mint the medals that carried
the King's bust.
Finally, it is surprising that the gold
separated by the nitric acid and amalgamation
stages should have the unusual fineness of 21
carat. Gold refined by this procedure would
normally be expected to be almost pure.
The Analysis of Costs
The study of the refining costs presented by
Sanchez is very interesting because of the picture it presents of the problems, both technical
and economic, that were caused by the
adulteration of gold with platinum.
Table I
Yields and Costs of the First Refining
~
Gold obtained = 2250 castellanos of fine gold (3000 Cs 18 carat gold)
Value of this gold = 6 4 7 4 . 4 patacones
Cost of the loss in gold = 1 0 5 . 1 4 patacones (58 Cs of original alloy")
Fusion cost = 3 2 3 . 6 6 patacones"
Total cost = 428.8 patacones
We suppose the original alloy to be of an average fineness of 630 O/OO in gold.
* * He does not compute the fusion expenditures, but indicates i t is the middle per cent,
we understand that it is the melted metal, that is, of 3000 Cs of 1 8 carat gold.
Units of Weight for the Gold
1 marco = 50 castellanos = 8 onzas
1 castellano = 8 tomines = 9 6 granos
1 onza = 6 castellanos + 2 tomines
1 onza = 8ochavas
1 ochava = 6 tomines
3 granos
1 marco = 228.86 gramos (sistema
metric0 decimal)
+
Monetary Units
1 doblon = 2 Cs gold (8385Gr fine gold)
1 doblon = 4patacones
1 patacon = 1 onza silver (28,608 Gr silver)
1 patacon = 8 reales
1 real = 3 4 meravedies
45
I
Table II
Yields and Costs of the Second Refining
Gold obtained = 1 5 0 4 castellanos of fine gold ( 1 7 1 9 Cs 1 8 carat gold)
Value of this gold = 4 3 2 9 patacones
Platina obtained = 3 2 5 Cs (We d o not know its value but it might be worthless)
Cost of the nitric acid = ( 2 6 1 pounds) = 2 3 4 9 patacones
Cost of manual labour and consumable = 1 4 5 patacones
Physical loss in weight = 5 6 9 Cs = 1 0 3 1 . 3 patacones”
Total cost = 3525 patacones
As w e shall see in the balance o f weights, he does not recognise this sum as a loss but
he imputes it t o platinum (in order not t o recognise such physical waste); w e evaluate
this loss as referred t o original alloy (it is an estimation) and therefore it is equivalent
t o 3 5 8 Cs of fine gold
The costs of the first refining operation, the
repeated fusions stage, are shown in Table I. It
can be seen that the cost of this part of the procedure is equivalent to 6.6 per cent of the value
of the gold recovered.
The costs for the second part of the operation, that is the recovery of the gold from the
2900 castellanos of platinum-containing residue
by the inquartation process, are given in Table
11. These costs amount to 81.4 per cent of the
value of the gold recovered!
The difference between the costs of the two
refining stages is considerable; those for the
first stage appear reasonable, while those for
the second are clearly prohibitive. The most
significant charge is for nitric acid, which
amounts to 54 per cent of the value of the gold.
When averaged over the whole yield, the total
refining cost amounts to 36 per cent of the value
of the gold recovered.
As we have noted previously, it was very fortunate for Sanchez that the platinum was not
already alloyed perfectly with the gold. If this
had been the case the extrapolated costs for
treating the whole mass of alloy by inquartation
would have risen to 7240 patacones, based on
costs of 4826 patacones for nitric acid, 298
patacones for manual labour and 2116
patacones for process losses (735 castellanos of
fine gold), so increasing the refining costs to 67
per cent of value of the refined gold.
These data provide ample justification for the
attitude of the Spanish Administration in attempting to prevent, at all costs, the adulteration of gold with platinum. It did not signify,
as has often been inferred, any lack of interest
in the proper scientific investigation and exploitation of this new metal.
The act of throwing the platinum into the
rivers can easily be justified. The cost to the
Spanish Crown of the introduction of just 5.4
per cent of platinum into the gold alloy would
be the value of 2515 castellanos of gold compared to 3750 castellanos of separation costs,
and all for a fraudulent gain to the miner of just
325 castellanos. Under these circumstances,
when the fraud was successfully achieved it
would have been better to “turn a blind eye”,
in the knowledge that the normal cupellation
assay methods would be unlikely to detect low
levels of adulteration.
Where the platinum addition was high, the
same result could be achieved by diluting its
concentration by adding more pure gold.
Nevertheless, the policy of dumping the
platinum was reasonable in the sense of
‘‘avoiding temptation”, particularly since
platinum had no recognised value or uses in
those days.
The balance of weights shown is somewhat
confusing in that it is not a balance of physical
weights. It is an accounting balance in terms of
46
the weights of 18 carat gold, this being the
fineness of the first gold product obtained. This
may have led Sanchez to make certain mistakes,
or possibly even to make intentional falsifications so that the true gold losses were difficult
to detect.
The first stage is clear, from the 5958
castellanos to be refined he obtained 3000
castellanos of 18 carat gold (which he called the
“first benefit”) and another 2900 castellanos of
gold containing platinum, giving a loss of 58
castellanos. He inquarts the 2900 castellanos
with silver in the proportion 1:4, so obtaining
290 Marcos (14,500 castellanos) of granulated
silver-rich alloy, which he subjects to the
separation process, and this is where the accounting problems begin.
Sanchez claims to have obtained 144,434
granos of gold; by implication pure gold, since
he said that it made 2006 castellanos of 18 carat
gold alloy. These are not physical weights,
however, since what he actually obtained was
1719 castellanos of 21 carat gold alloy. These
weights are all definitely self-consistent. From
now on, in balancing the accounts he began to
make mistakes. He used the calculated weight
of 2006 castellanos to derive a figure of 894
castellanos for the loss, whereas he should have
used the weight he actually had, namely the
1719 castellanos of 21 carat alloy. He then
reduced the presumed value content of the loss
by 25 per cent to refer the presumed content of
the loss to 18 carat, which is a nonsense. He
calculated a content of 64,366 granos (670
castellanos) as the waste and described it as
“what is identifyed as platina”. From the 894
castellanos he calculated the loss as 15 per cent
of the original mass of 5958 castellanos, and
refers to it all as platinum. This is unlikely,
since it assumes no loss of gold, which is improbable considering the complexity of the
operations.
On the other hand, he physically delivered
only 325 castellanos of platinum and not 894,
the difference being a real loss. The platinum in
the original material would thus have been
much less than 15 per cent.
It is apparent that Sgnchez de la Torre had
been able to achieve a balance of accountable
material, which would not have been possible
for the true physical items. Attributing all the
loss to the “valueless” platinum enabled him to
avoid admitting the gold losses, which would
have been a serious matter and one for which he
would have been held responsible. Saying that
there were “894 castellanos recognised as
platina” did not, however, stop him saying in
the last paragraph of the report “I deliver 325
castellanos of calcined platina”. The difference
is unimportant, since it would have been much
more serious to acknowledge equivalent losses
of gold.
References
7 J. C. Chaston, “The Powder Metallurgy of
1 Antonio de Ulloa and Jorge Juan, “Relacion
Hist6rica del Viaje a la America Meridional”, 4
vols., Madrid, A. Marin, 1748
2 W. Watson, “Several Papers concerning a new
3
4
5
6
Semi-Metal, called Platina; communicated to the
Royal Society”, Philos. Trans., 1750, 584-596
Luis Ulloa Cisneros, “Historia Universal”,
Publications of the Instituto M a c h de Libreria y
Ediciones, Barcelona, S.L., 1932, 6 vols.
Armando Espinosa Baquero, “Nuevos datos
sobre el descubrimiento del platino y su
metalurgia en la Nueva Granada en el siglo
XVIII”, Quipu, 1985, 2, (l), 7-21
Jose Sinchez de la Torre y Armas, Manuscript:
Archivo Nacional de Colombia, W a s de Tolima,
V01.5, folios 330-331
L. F. Capitin, “Separating Platinum from Gold
During the Early Eighteenth Century: The
Methods Used in Spanish South America”,
Platinum Metals Rev., 1989, 33, (2), 73-80
Platinurn Metals Rev., 1992, 36, (1)
8
9
10
11
12
Platinum”, Platinum Metals Rev., 1980, 24, (2),
70-79
M. Morin, “La Platine, L’or blanc ou le huitieme
Metal”, Paris, 1758 (Avec approbation & Permission du Roy)
Jose Celestino Mutis, Informe sobre la Platina,
June 15th 1774, Real Jardin Bothico de Madrid
Ramon de Manjarres, “D. Jorge Juan y D.
Antonio de Ulloa, La Medicion del Arc0
Terrestre, La Historia del Platino (conclusion)”,
Revista de Archivos Bibliorecas y Museos, Tercera
E v a , January 1913, Madrid, 58-91
Expediente del Platino, Audiencia de Santa Fe,
Legajo 835, Doc.3, Archivo General de Indias
Seville
A. Galin and R. Moreno, “La Separaci6n del Or0
de la Plata. Un problema de la Metalurgia en la
America Colonial”, ZnvestigacGn y Ciencia, 1992
(in press)
47
ABSTRACTS
of current literature on the platinum metals and their alloys
PROPERTIES
Hydrogen Adsorption
Pt(1 10)(1x 2) Surfaces
STM Investigation of the Adsorption and
Temperature Dependent Reactions of
Ethylene on Pt( 11 1)
and J. FIJSY, Appl. Surf. Sci., 1991, 52,
(1/2), 77-84
A thin Co overlayer on a Pt(llO)(lx2) surface
substantially modifies the adsorption energy of H, . A
new state appears with an adsorption energy near 9
kcal/mol, which is lower than that usually observed
on bulk Pt and bulk Co. At above one monolayer
desorption conditions appear similar to those observed on bulk Co.
T. A. LAND. T. MICHELY. R. J. BEHM, J . C. HEMMINGER
and G. COMSA, Appl. Phys. A , 1991, A53, ( S ) ,
4 14-417
The adsorption and reactions of C,H, adsorbed in
UHV on Pt(ll1) were studied as a function of
temperature by STM. The STM images at 160K
show an ordered structure of adsorbed C, H,, which
on annealing to 300K produces ethylidyne (C-CH,)
irreversibly. The ethylidyne on Pt(ll1) is not visible
to STM at room temperature, but cooling allows the
ethylidyne ordered structure to be observed. Annealing at >430K causes further dehydrogenation, leaving only C on the surface. Further annealing at
XOOK produces graphite islands, having seveTal
superstructures with lattice parameters of up to 22A.
The Role of Defects in the Specific
Adsorption of Anions on P t ( l l 1 )
P. N. ROSS, 3. Chim. Phys. Phys. Chem. Biol., 1991,
88, (7-8), 1353-1380
The specific adsorption of anions from HC1 and
H,SO, acids was studied on Pt(ll1) surfaces with
two types of induced defects: a step-terrace structure
and a random up-anddown stepped surface. All step
defects lowered the work function of the surface in
direct proportion to the step density, indicating a
local dipole at the step with its positive end outward
from the surface. The local work function at the step
and thus the local potential of zero charge (pzc) is
lower at the step than at atomically flat terraces. The
difference in pzc controls the coupling of H adsorption and anion desorption. On atomically flat (111)
terraces having the most positive pzc of all Pt surfaces, the processes are completely decoupled in
dilute acids, with desorption of anions from terraces at
potentialsmoreanodicthanfor Hadsorption. (44Refs.)
Scanning Tunneling Microscopy of Pt/Co
Multilayers on Pt Buffer Layers
s. L. TANG, P. F. CARCIA, D. COULMAN and A. I. MCGHIE,
Appl. Phys. Lett., 1991, 59, (22), 2898-2900
Systematic STM studies of the surface structure of
multilayers sputter-deposited on various Pt
buffer layer thicknesses showed that it evolved
toward nanometer-scale crystallites with distinct,
mostly six-sided polygonal grain boundaries with increasing Pt buffer layer thickness. It is concluded that
improved (111) texture and the appearance of distinct
grain boundaries contributed to the higher magnetic
coercivity of the multilayer on a Pt buffer layer.
Pt/&
on
Cobalt/
M. ALNOT
Observation of Inverse U-Shaped Profiles
after Platinum Diffusion in Silicon
and H. RYSSEL, Appl. Phys. Lett.,
1991, 59, (lo), 1209-1211
Studies of inverse U-shaped profiles of Pt in Si obtained after diffusion at 7OOOC were performed by
deep level transient spectroscopy to determine the initial concentration of vacancies. The Pt profiles were
called ‘inverse U-shaped profiles’ because in the
bulk, a higher concentration of Pt was found than at
the surface. Pt diffusion was found to offer, for the
first time the possibility to check and improve process
simulation models which are based on point defects.
H. ZIMMERMANN
Microstructural and Magnetic Characterization of Rapidly Solidified and Annealed
Pt-Co-B Alloys
and J . E. WITTIG.
1991, 70, (lo), 6137-6139
The intrinsic coercivity (Hit) of Pt-Co alloys
significantly increased on the addition of B and by
rapid solidification processing. After rapid solidification by double anvil splat quenching with subsequent
annealing at 65OOC for 30 min, Pt42C045Bllshowed
an HI, as high as 14 kOe. The magnetic hardening
mechanism is a combination of inhibited magnetic
domain nucleation and difficult reverse domain
growth caused by the interaction of the magnetically
anisotropic Co borides with the L l U Pt-CO matrix.
N. QIU, J. A. TEUBERT, R. A. OVERFELT
3. Appl. Phys.,
Thermodynamics of the
Platinum Metals Systems
Uranium-
pure Appl. Chem., 1991, 63, (lo),
1401- 1408
The thermodynamics of the systems: U-Pt, U-I’d, URh, U-Ir, U-0s and U-Ru are critically assessed. The
isothermal sections of the ternary U-Rh-F, U-Ru-F,
U-0s-F and U-Ir-F systems were found, and the
Gibbs energies of formation of URu,, U,Ru,,
URu,C,.,, U,RuC,, URh,, UOs,, UIr, and UIr,
were determined between 900 and 1200 K. Thermodynamic results of the intermetallic phases and the
platinum rich solid solution regions are discussed.
H. KLEYKAMP,
48
The Effect of Hydriding on the Physical
Structure of Palladium and on the
Release of Contained Tritium
E. STORMS and C. TALCOTT-STORMS,
Fusion Technol.,
1991, 20, (2), 246-257
The behaviour of T released from a contaminated Pd
cathode was compared with the pattern found in cells
which were claimed to produce T by cold fusion.
Void space is produced in Pd when subjected to H absorption and desorption cycles. This void space can
produce channels through which H can be lost from
the cathode, thus reducing the H concentration. This
effect is influenced by impurities, the electrode
shape, charging rate, the H concentration achieved
and the length of time of maximum concentration.
Formation of Decagonal Quasicrystal in
the Al-Pd-Mn System and Its Structure
D. HIRACA, W. SUN, F. J. LINCOLN, M. KANEKO
MATSUO, 3pn.
Appl. Phys., 1991, 30,
3.
and Y.
(9A),
2028-2034
Studies of formation of a decagonal quasicrystal in
Al,,Pd,,_,Mn, alloys (x=8-20) showed that the
decagonal quasicrystal was formed as a coexisting
phase with an icosahedral phase in the composition
range of x = 10-15, and as a single phase at a composition of x about 20. It is proposed that the structure
of Al-Pd-Mn decagonal quasicrystal may be interpreted as a tiling formed by atom cluster linkages.
Effect of Ordering Processes on Electrical and Magnetic Properties of
Pd2Cu,-xAlloy (0.40 \< x \< 0.48)
A. A. SENCHENKO, I. I. PIRATINSKAYA, L. P. Z E L E N N and
Yu. A. VERESHCHAGIN, Fiz. Met. Metdoved., 1991,
(8), 106-111
Studies of transformation of crystal structure, electrical resistance and magnetic susceptibility of
Pd,Cu, --x alloys with x =0.40-0.48 were performed
under homogeneous conditions near to the
stoichiometric region at 300-1200K. The results
showed that ordering was accompanied by compression of the crystal lattice, and by sharp changes in
electrical resistivity and diamagnetic susceptibility.
The results were evaluated on the basis of density
state in ordered and disordered alloys.
Constitutional Studies of MolybdenumPalladium Alloys Using Ultra-Rapidly
Solidified Samples
and 1. N. PRATT, 3. Less-Common Met.,
1991, 175, (l), 71-78
Studies of phase relationships in the Mo-Pd system at
880-1 100°C were performed using ultra-rapidly
solidified samples. The finely divided microstructures produced by this technique were found to
achieve equilibrium on annealing more rapidly than
conventionally prepared materials. The solubility
limits of the Pd-rich and Mo-rich terminal solid solutions were established.
R. CURLER
Hydrogen-Induced
Ordering
Palladium-Rich Pd-Mn Alloys
in
K. BABA. Y. NIKI, Y. SAKAMOTO and T. B. FLANAGAN, 3.
Less-Common Met., 1991, 172-174, 246-253
Hydrogen-induced formation of an L1, ordered
structure from an a-L1 ,,(Ag,Mg-type) structure
was observed in the presence of H , at a pressure of
5.0 MPa at 726K in the a-phase of rapidly quenched
alloys of Pd-Mn alloys containing 12.5-31.0 at.%
Mn. In Pd-29.0 at.% Mn and Pd-31.0 at.% Mn
alloys the /3, -L1 ,-s (M=2) structure transforms
under the effect of H, into the /3,-L1,, (M=4)
structure, where the domain size increases from M =2
to M=4.
Thermodynamic Stability of Palladium
Alloys: Part I: The Palladium-Niobium
System
M. 1. STICKNEY, M. S. CHANDRASEKHARAIAH, K. A.
GINGER~CHand J. A. SPEED, Metall. Trans. A, 1991,
ZZA, (9), 1937-1943
The Pd activities of 12Pd-Nb alloys, with compositions from 60Pd40Nb to 97Pd3Nb, were determined
experimentally with a twin-chamber Knudsen cell
mass spectrometer at 1450-1750 K. The results
showed a strong interaction in the solid state between
the Pd and the Nb atoms.
Effect of Soluted Hydrogen on the
Mechanical Properties of PalladiumRhodium Alloys
N. I. TIMOFEEV and F. N. BERSENEVA, Fiz. Met.
Metallov., 1991, (7), 147-152
Studies of structural changes and physico-mechanical
properties of Pd-Rh alloys containing up to 25 at.%
Rh were performed during H implantation in the
alloy. The results showed that the mechanism of property changes in the Pd-Rh-H system can be
characterised both for Pd alloys containing
monovalent noble metals, and for these alloys containing transition elements. Depending on the concentration of the soluted H and on the phase
compositions in the Pd-Rh alloys, the observed effects were either a simultaneous rise in their stability
and ductility, or their sudden embrittlement.
Mechanical Alloying of the Pd-Si System
in Controlled Conditions of Energy
Transfer
F. PADELLA, E. PARADISO, N. BURGIO, M. MAGINI, S.
MARTELLI, w. GUO and A. IASONNA,
Less-Common
3.
Met., 1991, 175, (l), 79-90
The composition Pd,Si,, was milled, starting from
pure elemental powders, in different milling conditions, and the mechanical alloying process was followed by X-ray and differential scanning calorimetry
measurements. For high levels of energy transfer the
system evolves towards the formation of the intermetallic Pd, Si. At lower levels of energy transfer,
formation of a stable intermetallic phase was hindered
and the product was a fully amorphous phase.
49
Thermal Stability and Phase Studies of
Crystalline Zr Pd Hydrides
CHEMICAL COMPOUNDS
and R. C. BOWMAN, 3.Less-Common
Met., 1991, 172-174, 29-35
Studies of the crystalline metal hydrides Zr,PdH,
for x<2.0 showed that they underwent an endothermic reaction above 8WK, and decomposed to ZrH,
and ZrPd on further heating. When the crystalline
hydride has x>3.0, it undergoes abrupt endothermic
transitions around 550K @OK) which leads to the
formation of lower H content ternary hydrides.
Upon further heating above 800K, the ternary
hydrides go through more endothermic reactions
forming a mixture of phases that includes ZrPd,
ZrH, and ZrO,.
Ligand-Stabilized Bimetallic Colloids
Identified by HRTEM and EDX
,
J. S. CANTRELL
Investigations of Rh-Based Multilayers
for Soft X-Ray Applications by HighResolution Electron Microscopy
z. G. LI, D. J. SMITH, s.-c.Y. TSEN, P. BOHER and PH.
G. SCHMID, A. LEHNERT, J:O. MALM and J.-0.BOVIN,
Angew. Chem., Int. Ed. Engl., 1991,30, (7), 874-876
The synthesis of ligand-stabilised bimetallic colloids
and the identification of their shell structures is
described. Au colloids of diameter 18 nm were
covered by Pt or Pd shells, when aqueous solutions of
the colloids is added to a solution of H,PtCI, or
H ,PdCI, and H ,NOHCI, stabilising the particles
formed
with
p-H,NC,H, S0,Na.
Uniform
heterogeneous AuPt agglomerates of a Au core surrounded by Pt crystals of 5 nm, with two kinds of
intergranular structures are found. For AuPd a
homogeneous system of Pd and Au solid solutions is
formed. The sequence of metals can also be reversed,
so that 15 nm Pd colloids can be prepared and coated
with Au.
-
HOUDY, 3.Appl. Phys., 1991, 70, (6), 2905-2910
A series of Rh-based multilayer structures was
developed for soft X-ray applications by using
‘trilayer’ structures and low density B,C spacing
material. The microstructure of the multilayers was
studied and compared with those of W- and Ni-based
multilayers. Rh crystals with f.c.c. structure but with
different preferred orientations were identified in Rhbased layers. High reflectivity and selectivity for Xray mirrors was obtained in the case of WiRh/C
multilayers due to significant improvement in their
microstructure, especially the interface roughness.
Magnetic Properties of U(Ru,,Rh,) Si,
Single Crystals (0 x < 1)
<
Y. MIYAKO, S. KAWARAZAKI, H. AMITSUKA, C. C.
PAULSEN and K. HASSELBACH, 3.Appl. Phys., 1991,
70, (lo), 5791-5793
The temperature dependence of the non-linear
susceptibility of URu,Si, was studied in order to
determine the properties of the phase transition at
17.5 K. Various magnetic phases of U(Rul,Rh,)Si,
were studied as a function of x by means of specific
heat, susceptibility, and neutron scattering methods.
Two successive phase transition occurred when
x=0.3.
Electrical
Ceramics
Conductivity
of
BaRuO
and A. EDGAR, Solid State Commun.,
1991, 79, (4), 355-357
BaRuO, and Bal,&RuO, ceramics contain a mixture of 4H and 9R polytypes whose volume fraction
depends on quenching temperature and the concentration of K dopant. Both polytypes have a room
temperature resistivity of 10 mQcm, but with opposite signs for the temperature coefficient. The
negative temperature coefficient for the 9R polytype
is ascribed to localisation effects arising from the
existence of two distinct crystallographic Ru sites.
B. SZYMANIK
-
Metallic Properties in the Series
K 2 Pd(II)H, 9
Na Pd(0)H2
and
Li, Pd(0)H2 Correlated with the Stabilization of a Formally Zero-ValentPalladiumHydrogen Complex
,
K. KADIR, M. KRITIKOS, D.N O ~ U and
S A. F. ANDRESEN,
3. Less-Common Met.,
1991, 172-174, 36-41
New hydrides, Li,PdH, and K,I’dH,, were compared with Na,PdH,. The Li,PdH, and Na,PdH,
were found to be metals and their structures were
characterised by linear, formally zero-valent PdH,
complexes in an alkali atom framework. The Pd-H
bond lengths was 1.68 A. In K,PdH,, with the
Na,PtH,-type structure, the larger and more electropositive K atom allows a four-co-ordinated d s
square planar I’d com lex to be formed. The Pd-H
bond length was 1.63f. The electrons were localised
and K, PdH, was a yellow-green non-conducting
powder.
N-Bonded TCNQ in Stacked Dimeric
Systems. Synthesis and Crystal Structure
of [Ru(PPh,),(TCNQ)I, (TCNQ= 7,7,8,
8-tetracyanoquinodimethane)
L. BALLESTER, M. C. BARRAL, A. GUTIl?RREZ, R. JIMkNEZAPAF’JCIO, J. M. MARTfNEZ-MUYO, M. F. PERPINAN, M. A.
MONGE and C. RUfZ-VALERO, y. Chem. soc., Chem.
Commun., 1991, (19), 1396-1397
The reaction of RuCI,(CO),(PPh,), with AgBF, in
tetrahydrofuran (thf) resulted in the formation of
IRu(C0) (PPh, ) ,(tho l(BF, ), which when further
reacted with PPh, in CH,Cl, and LiTCNQ in
of
MeOH
yielded
purple
crystals
tRu(PPh,),(TCNQ)I (1). The crystal structure of
this compound showed ‘a tetrahedral environment of
the Ru atom with the TCNQ molecule co-ordinated
via N. All the TCNQ units act as bridges bonding
two Ru atoms via opposite nitrile groups which gives
rise to dimers [Ru(PPh,),(TCNQ)I,.
,
50
ELECTROCHEMISTRY
Platinum Electrocatalysts Applied to Carbon Fibres
Electrochemistry at Platinum Single
Crystal Surfaces in Acidic Media:
Hydrogen and Oxygen Adsorption
A. A. VEDENYAPIN. A. W. KRYLOVA. A. C. GAZARYAN, T.
1. KUZNETSOVA. 0.A. MALYKH, G. 1. EMEL'YANOVA, A. L.
LAPIDUS and s. v. WSHIN, Elektrokhimiya, 1991, 27,
J. CLAVILIER, A. RODES. K. EL ACHI and M. A.
ZAMAKHCHARI, J. Chim. Phys. Phys.-Chim. Biol.,
1991, 88, (7-8), 1291-1337
A review of the adsorption properties of H , and 0,
at the Ptlacid solution interface, and their
dependence on the crystalline surface structure of the
Pt electrode is presented. Unusual adsorption states
are seen on (111) and (100) oriented electrodes, which
appear to be controlled by two-dimensional long
range order. Studies on the Pt(hkl)/solution system
are- examined; these include the electrochemical
behaviour of stepped surfaces, surface reconstruction
in solution, size of the ordered domains and the
characterisation of point defects and ordered defects.
(75 Refs.)
In situ Infrared Studies of Glucose Oxidation on Platinum in an Alkaline Medium
and C. C. LIU, J . Electroanal. Chem. Interfacial Electrochem., 1991, 309, (1
and 2), 131-145
The oxidation of a-(+)-glucose on a Pt electrode in
0.1 M NaOH was investigated by in situ FTIRabsorption spectroscopy in the range -0.76 to +0.46
V vs. Hg/HgO, O H . The surface adsorbates involved linear CO and bridged CO. The linear CO persisted on Pt in the entire potential range, with gradual
shifts to higher frequencies, of 70 /cmN, while the
bridged CO disappeared as the electrode potential
reached -0.05 V. The oxidation products were carboxylic acid and CO,. A potential excursion up to
+0.46 V caused a pH swing of >8 in the spectroelectrochemical thin layer, due to glucose oxidation.
1. T. BAE, E. YEAGER, X. XING
-
Structural Effects in Electroca~lysis.
Ethylene Glycol Oxidation on Platinum
Single-Crystal Surfaces
'.
N. M. MARKOVIC, M. L.
L. AVRAMOV-IVIC,
AVRAMoVJVIC, N. S. MARINKOVIC
MA"KoV1C
R. R.
R. ADZIC, J. Electroanal. Chem. Interfacial
and R.
3.
Electrochem., 1991, 312,
312, (1
(1 and 2), 115-130
Elecrrochem.,
oxidation of ethylene
ethylene glycol (EG) was studied on
The oxidation
Pt single crystal surfaces in 0.1 M NaOH. Strong
structural dependence of the reaction kinetics occurstructural
orientations investigated.
investigated. The onset of
red for all 12 orientations
sequence
the
reaction
occurs
in
the
sequence
Pt(llO)>Pt(lOO)-Pt(lll). The peaks of the voltamPt(llO)>Pt(lOO)-Pt(ll1).
metry curves
curves for the low-index
low-indexplanes decrease in the
order (lll)>(llO)>(lOO).
(lll)>(llO)>(lOO). Either the (111) or the
(100)
(100)oriented
oriented steps cause a decrease
decrease in the activity
activity of
the (111) plane. Surfaces near the (100) plane have
higher
higher activity
activity than Pt(111).
1). The (111) oriented steps
in the Pt(ll0) plane increased the activity,
activity, while the
(100) oriented
oriented steps decreased it. PtOH layer formaformation and onset of EG oxidation
oxidation occurred
occurred together,
together,
showing the reaction
reaction involves interaction
interaction of the adsorbed
sorbed and dehydrogenated
dehydrogenated EG with R(OH),,.J,.
P~(OH),,.J,.
(7), 848-853
Studies were performed of Pt/C fibre catalysts
prepared by impregnation of C fibres by H,PtCI,
solution or by electrochemical deposition of Pt on C
fibres from the analogue solution at 0.2 V. The
results showed that Pt/C fibre catalysts prepared by
electrochemical deposition have greater dispersion
than those obtained by impregnation. It is suggested
that two types of polarisation processes with different
rates occur on the catalyst surfaces.
Oxidation of Sulfur Dioxide in SulfurModified Platinum-Graphite Packed Bed
Electrodes
S. E. LYKE and S. H. IANGER,. _
7. Electrochem. ~ O C . ,
1991, 138, (6), 1682-1687
The oxidation of dissolved SO, at Pt supported in
porous graphite sheet electrodes was studied at
450-750 mV (RHE) using various Pt loadings and
SO, concentrations. Controlled reductive pretreatment of the electrodes in the presence of SO, was
found to produce catalytic effects which resulted in
enhanced steady-state oxidation currents due to formation of a S-modified Pt surface. In hybrid cells
with fuel cell type 0 , gas diffusion cathodes
operating in the electrogenerative mode, the
pretreated Pt-graphite anodes were used to oxidise
3-500 mM SO, in 3M H,SO,.
Irreversible Adsorption of Chlorophyll on
an Amalgamated Platinum Electrode in
Aprotic Solvents
L.
L. F.
F. LAFI,
LAFI. L.
L. A.
A. KHANOVA and M. R. TARASEVICH,
TARASEVICH.
Elektrokhimiya,
Elekfrokhimiya, 1991,
19919 27,
27, (8),
(8),961-%8
Studies of
of adsorption
adsoWion of
of chlorophyll on
on an
amalgamated P
t electrode in various aprotic solvents
Pt
were performed under controlled potentials. The adsorption of chlorophyll was stable and it could only
desorb
&sorb with the surface
surface held
heid under a significant
negative potential. The adsorption was affected by
by
the amount of adsorption substance and on its concentration in solution, and also by the adsorption conditions.
Investigations of the O 2 Reduction Reaction at the PlatinumlNafion Interface
Using a Solid-state Electrochemical Cell
A. PARTHASARATHY, c. R. MARTTN and s. SRIMVASAN,
3. Electrochem. SOC.,1991, 138, (4), 916-921
The processes occurring at the PtiNafion interface in
the absence of a contacting electrolyte phase was investigated in an electrochemical cell to determine
such conditions in a SPE fuel cell. From cyclic
voltammetric measurements the purity of the Nafion
and the roughness factor of the electrode were found.
51
Characteristics of a Rechargeable Cell
Constructed by Coupling Na,,,WO and
Na,,Pd,O,
Photocatalytic Hydrogen Production with
Semiconductor Particulate Systems: An
Effort to Enhance the Efficiency
and T. KISHI, Solid State
Ionics, 1991, 46, (1,2), 63-66
The electrochemical behaviour of NaPd,O, and
Na,WO, was investigated in 0.5 M H,SO, at 25OC.
A Na depleted surface layer can be formed on the
electrode surface of NaPd,O, by anodic prepolarisation, and this surface layer absorbs or desorbs
H' reversibly at 1.0 V vs. SHE. A new type of
rechargeable cell with a long cyclability can thus be
constructed by coupling Na,_,WO, and Na,,Pd ,0,
in an acidic solution.
M. ASHOKKUMAR
Y. MURANUSHI, T. MIURA
-
Adsorption of Nitroethane on Rh-Ru
Catalytic Systems
and P. MARUTHAMUTHU, Inl. 3.
Hydrogen Energy, 1991, 16, (9), 591-595
H, production in visible light (437 nm) with the
following semiconductor particulate systems,
Ag(I)/WO,, Fe(III)/WO, and Cr(III)/WO, and mixed semiconductors, W0,-PtICdS and W0,-CdS was
studied in the presence of an electron relay,
methylviologen, MV? + . Pt loaded C d S powders
mixed with WO, powders (W0,-Pt/CdS) showed a
notable enhancement in the photocatalytic activity as
compared to that of W0,-CdS. The sample sintered
at 8OOOC had higher efficiency than that sintered at
300OC.
Vesm. Mosk. Univ., Ser. Khim.,
1991, 32, (4), 392-395
The adsorption of nitroethane was studied on skeletal
Rh-Ru catalysts containing 5, 10, 20, 50, 60, 90 and
95 at.% Ru which had preliminary pretreatment
under various conditions. At 40-60°C, a decrease of
stationary potential was observed with nitroethane
adsorption. It was explained by an increase in
temperature in H SO,, resulting in the formation of
active electrochemical phases, which affect the potential. A maximum rise of potential of 10 mV was found
on Rh in ethylamine.
Photodissociation of Phosgene on
P d ( l l 1 ) at 1 9 3 n m
c. n. FLOES, x.-Y.zm and J. M. WHITE, 3. Phys.
PHOTOCONVERSION
Photocatalysis of the Homogeneous
Water-Gas Shift Reaction under Ambient
Conditions by Cationic Iridium(II1) Complexes
T. M. GRISHINA,
Photoinduced Dissociation and Desorption of N 2 0 on a P t ( l l 1 ) Surface
3.Phys.
Chem., 1991, 95, (21), 8054-8059
N ,0 adsorbed on a Pt( 111) surface was irradiated by
UV light, and the photochemistry was studied by
XPS, UPS and TPD. Upon radiation at 50K, adsorbed N ?0 undergoes dissociation and desorption.
Photon energies >4.35 eV are required. The cross
section is in the range 10- i9-10-'u c m ? . This is the
first UV photon-driven chemistry in this system.
J. KISS, D. LENNON, S. K. JOand J. M. WHITE,
Photon-Driven Chemistry in Coadsorbed
N,O and CO on P t ( l l 1 )
and J. M. WHITE, 3.Phys. Chem., 1991, 95,
(20), 7852-7857
The UV photon-driven chemistry of coadsorbed N ?0
and CO on Pt(111) at 47 K was investigated by XPS,
UPS and TPD. Results depend on the order of adsorption. When one monolayer of N 2 0is dosed first
and CO is coadsorbed the UV irradiation causes CO,
production, much being desorbed during the irradiation, but when one monolayer of CO is dosed first the
photon-driven production of CO, is not detectable.
Whatever the order of adsorption there is photondriven desorption of N,O, but the cross-section is
higher for N , O bound to R than it is for N 2 0
separated from Pt by CO layer.
J . KISS
Chem., 1991, 95, (23), 9431-9436
The UV photodissociation of phosgene (C1,CO) on
Pd( 111) was studied by isothermal mass spectroscopy
during irradiation and by TPD and XPS following irradiation. Phosgene absorbs reversibly on Pd(ll1) at
110K and photodissociates when irradiated with 6.4
eV photons, thus resulting in the evolution of CO and
retention of C1 adatoms. The initial photodissociation
cross-section is (5.320.8) x lo-'* cm'.
n. ZIESSEL, Angm. Chem., Inr. Ed. Engl., 1991, 30,
(7), 844-847
The first highly efficient light-assisted water gas shift
reaction to take place under the extremely mild conditions of room temperature, ambient pressure,
neutral pH and visible light is reported. It is catalysed
by Ir"' pentamethylcyclopentadienyl complexes containing novel 4,4'-bipyridine ligands, substituted by
electron-withdrawing groups which enhance the
catalytic activity.
Formation of Paramagnetic Complex
from Bischelate of Palladium (11) with
Dehydrogenated N-(3-Hydroximinol-2Methylbutyl-2) Hydroxylaminooxime and
o-Phenanthroline
A. KOSAREVA, E. G. BOGUSLAVSKII and S. V.
LANOKOV, Izv. Akad. Nauk SSSR, Ser. Khim.,
L.
1991, (9), 1959-1961
Paramagnetic Pd complexes were formed during interaction in pure ethanol of o-phenanthroline and
diamagnetic bischelate of Pd(I1) containing ligand
anions
of
N-(3-hydroximinol-2-methylbutyl-2)
hydroxylaminooxime. The paramagnetic Pd complexes
contained
co-ordinated
anion-radical
dehydrogenated 1,2-hydroxylaminooxime.
52
Chemiluminescence of Tryptophan with Temperature Effect on Photolytic
Electrogenerated Tris(2,2'-Bipyridine) Deposition of Platinum Ohmic Contacts
Ruthenium(lI1)
and Schottky Diodes
and M. KIRISAWA, Chem. Lett. Jpn.,
1991, (8), 1373-1376
A system
for
producing
electrogenerated
chemiluminescence based on the reaction of electrogenerated Ru(bpy) ' (1) with tryptophan (2) is
described. The orange luminescence is generated by
the reaction of (1) with (2) in acidic solution. The
lowest detection limit was 0.1 pmol for (2), and this
system should therefore be useful for selective and
sensitive detection of tryptophan and related compounds.
K. UCHIKURA
+
Electron-Transfer Quenching of a
Photoexcited Ruthenium Complex by
Stearyl Viologen in Barium Stearate
Langmuir-Blodgett Films
and M.MATSUDA, 3. Phys.
Chem., 1991, 95, (23), 9403-9405
Photoinduced electron transfer of the Ru complex
tris(4,7-diphenyl-l,lO-phenanthroline)Ru, that is
(Ru(dpphen),'+) to stearyl viologen (SV?') in Ba
stearate LB assembly systems was studied by a
steady-state quenching method. Even when the
monolayer of the Ru complex was in direct contact
with the layer of SV? quencher at the hydrophilic
interface, the quenching of the Ru complex had low
efficiency, indicating that Ru(dpphen), l' is located
at a more hydrophobic region. In an assembly where
both Ru(dpphen),?+ and SV?' exist within the
same monolayer, the quenching efficiency depended
strongly on the two-dimensional density of SV' +.
The results showed that electron-transfer rate
decreases exponentially with distance and agrees with
the conclusion that electron-transfer quenching proceeds via an electron-tunnelling mechanism.
and H. VAN DEN BERGH, Appl. Phys. A,
1991, A53, (3), 265-272
The deposition of Pt from Pt bihexafluoroacetylacetonate by an Ar laser inducing laser chemical
vapour deposition was investigated. The process can
be photolytic or pyrolytic, depending on the laser
power. Photolytic deposition takes place in the adsorbed phase or in the gaseous phase, depending on
the temperature induced by radiation absorption.
The effect of the substrate base temperature and the
precursor product vapour pressure confirms
photolytic deposition from the adsorbed phase for
low powers and from the vapour phase onwards for
high powers. The deposits obtained have a typical
96% Pt composition and good device characteristics
are obtained by this method in Schottky diodes.
C. GARRIDO
T. MIYASHITA, Y. HASEGAWA
+
A Novel Photosynthetic Mimic Reaction
Catalysed by K[Ru(H-EDTA)ClI.2H,O;
Reduction of Carbon Dioxide to Formate
and Formaldehyde in the Presence of an
Aqueous Suspension of Pt-CdS-RuO,
M. M. TAQUI KHAN, N. NAGESWARA RAO and D. CHATTERJEE,
Photochem. Photobiol. A : Chem., 1991,
3.
60, (3), 311-318
An efficient photocatalytic reduction of CO, to
HCOOH and HCHO is reported, using the title Ru
compound, and Pt-CdS-RuO, as photon absorber at
505 nm. The system produces 0.22 M of HCOOH
and 0.10 M of HCHO in 6 h of photolysis at rates of
3.05 x lo-' 1Wh and 2 . 0 10-I
~ M/h, respectively.
The rates of formation exhibit a first-order
dependence on the catalyst and dissolved CO, concentrations. The reaction shows D isotope effects
(kH/kD) of 1.5 and 2.0 for the formation of HCOOH
and HCHO, respectively. The rate of formate decomposition was slower by 2 orders of magnitude than the
formate formation rate, even at high formate
concentrations.
APPARATUS AND TECHNIQUE
Microstructure and Superconducting
Properties of Bi-Sr-Ca-Cu-0 System
Prepared by a Melt Process
K. EGAWA, T. UMEMURA, S.-I.KINOUCH1, M. WAKATA and
s. UTSUNOMIYA, 3pn. 3. Appl. Phys., 1991, 30, (7A),
L1160-L1162
O Y , x=O, 0.2, 1.0, was
Bi,Sr,Ca, + ~ X C ~ 2 + Iwhere
prepared from powders and calcined several times at
84OOC for 30 h. It was melted in a Pt crucible at
>lOOO°C and splat-quenched onto Cu. The
microstructure and superconducting properties were
examined. The magnetic field dependence of the intragrain critical current density was improved by
enriching the Ca and Cu contents. Two precipitates
were found: (Ca,Sr),CuO., and the much smaller
(lpm) Sr-Pt-0 compounds. The latter may be more
effective in enhancing the pinning force.
All-Solid-state Glucose Sensor Using
Proton-Conductive Thick Film
N. MATAYOSHI, N. MIURA
and N. YAMAZOE, 3Pn.
7.
Appl. Phys., 1991, 30, (9A), L1594-L1597
A solid state glucose sensor using a proton-conductor
thick film was tested as a miniaturised enzyme sensor. A planar electrochemical cell, of sputtered
Au(reference electrode)/antimonic acid thick
fdm(proton conductor)/sputtered Pt-glucose oxidase
(sensing electrode) was fabricated on a porous Al ? 0
substrate. In phosphate buffer solution the e.m.f. of
the sensor vaned logarithmically, with change in
glucose concentration in the range 5 x lo-' to
4 x lo-' M, following a Nernst equation. The 90%
response time was 1 minute. The glucose sensitivity was fairly stable for 10 days, and the Nernst slope
-54 mV/decade was very close to that of the response
to H, O,, indicating that the glucose sensing signal
was generated by responding to the H,O, produced
by the enzymatic reaction of glucose. Extensions of
this type of sensor to other enzymes is possible.
-
53
Bulk Single Crystal Growth of Bi,,TiO,,
by the Czochralski Method
Y. OKANO, H. WADA. T. F U K U D A ~s. ~MIYAZAWA,
~
Jpn.
J. Appl. Phys., 1991, 30, (7B), L1307-LI309
A Pt wire was used as an initial seed crystal and
crystals were grown from melts of differing
TiO, :Bi,O ratios to produce the title photorefractive crystal. Crystals were grown in a 15 kW r.f.
heating Czochralski furnace with a Pt crucible of 50
mm diameter. Crystals of diameter up to 2 cm and 3
cm long were grown from a Bi,O, rich melt, with an
upper limit of 11 mol% TiO,.
Detection of Nitrite Using Electrodes
Modified with an Electrodeposited
Ruthenium-Containing Polymer
J. N. B A R I S C I ~ ~ ~G.GWALLACE,
.
Selective Conversion of Decane into
Branched Isomers. A Comparison of
PlatinumlZSM-22, Platinum/ZSM-5 and
PlatinumlUSY Zeolite Catalysts
J. A. MARTENS, R. PARTON, L. UYlTERHOEVEN. P. A.
JACOBS and G. F. FROMENT, Appl. Catal., 1991, 76,
( I ) , 95-1 16
Detailed product distribution from the bifunctional
conversion of decane over Pt/ZSM-22, Pt/ZSM-5 and
Pt/USY catalysts were compared. Pt/ZSM-22 produced high yields of feed isomers under mild reaction
conditions. It is suggested that isomerisation of
decane on ZSM-22 is a zeolite pore-mouth catalysis.
Type C hydrocracking of methylnonanes does not occur on PtlZSM-22, due to the limited access of these
molecules in the zeolite pores.
Anal. Lett., 1991, 24,
( 1 l), 2059-2073
The electrochemical detection of nitrite in flowing
solutions using a polymer modified electrode with
electocatalytic properties is described. The modifier
used was an electrodeposited film of the
[R~(bpy)~(vpy),l complex where bpy is 2,2'bypyridyl and vpy is 4-vinylpyridine. The modified
electrode enhances the response to nitrite and avoids
surface fouling. The electrodeposited fdms thus produced exhibit high mechanical stability.
+
HETEROGENEOUS CATALYSIS
Combinations of Platinum and Palladium
on Alumina Supports as Oxidation
Catalysts
and J:E. OT9-20
The effects of the total Pd+Pt content, the mol%
ratio of Pd+Pt, the hydrothermal treatment of the
catalyst wash-coat, and the 0, concentration on the
light-off temperature were studied for the complete
oxidation of xylene isomers, propene, and CO. The
light-off temperatures had a minimum at a Pd:Pt mol
% ratio of 80:20, and decreased with increasing total
metals concentration, increasing 0, concentration
and hydrothermal treatment of the Al ,O , wash-coat .
M. SKOGLUNDH, L. 0. LOWENDAHL
TERSTED, Appl. catal., 1991, 77, (I),
Effect of Gamma Irradiation on Textural
and Dehydrogenation Properties of
Pt/AI 0 System
and N. A. YOUSSEF, Radial. Phys.
Chem., 1991, 38, (3), 307-311
Pt/Al,O, catalysts with 0.2-2 mol% Pt were
prepared and irradiated with y-radiation to a dose of
50 Mrad. Textural properties were found from the
low temperature N, adsorption. The catalytic
dehydrogenation of cyclohexane was determined for
irradiated and non irradiated catalysts. y-Irradiation
caused textural changes of the metal/metal oxide
system depending on the metal content, and
increased the dispersion of the metal on the
surface.
A. M. YOUSSEF
Influence of Iridium, Rhenium and Lanthanum on Propane Aromatization over
Platinum/ZSM-5 Catalysts
R. MAGGIORE. S. SCIRE, S. GALVAGNO, C. CRISAF'ULLI
G. TOSCANO, Appl. Catal. A: General, 1991, 79,
and
(I),
29-40
A study of the effect of operating conditions on the
conversion of propane to aromatics over PtMe/ZSM-5 catalysts (Me=Ir, Re, La) showed that
the catalytic behaviour of Pt-Me/ZSM-5 depended on
the nature of the added elements. Pt-Ir/ZSM-5 was
the most selective catalyst, with a yield of 61.2%.
Effects of Hydroxylation of a Silica Surface on the Metal Dispersion in Supported Platinum Catalysts
M. AM, s.-L.GUO and Y. NISHIYAMA, Appl. Catal.,
1991, 77, ( I ) , 141-148
The effect of the surface hydroxyl groups of porous
SiO , on the degree of Pt dispersion was studied using
SiO, supports with the same surface area but with an
increasing number of these functional groups. The
suppons were prepared by immersing a calcined
50, in H,O at 70°C and Pt was deposited on it by
wet impregnation with aqueous solutions of Pt
tetraamine dichloride (PTD) and chloroplatinic acid.
Catalysts with PTD reduced at 4OOOC showed that
maximum Pt dispersion occurred on supports with
moderately hydroxylated surfaces.
Catalytic Palladium-Based Membrane
Reactors: A Review
and S.
Can. J. Chem. Eng., 1991, 69, (5),
J. SHU, B. P. A. GRANDJEAN, A. VAN NESTE
KALIAGUINE,
1036-1060
A review of literature on catalytic membrane reactors
using H permeable Pd and I'd-Ag alloys is presented.
Factors involved in H purification, design parameters
of the membranes and reactors, hydrogenation and
dehydrogenation reactions and H diffusion are
discussed. Thin Pd coatings on porous inorganic and
polymeric supports are expected to increase the implementation of this technology.
54
Maximum Conversion of Dehydrogenation in Palladium Membrane Reactors
Conversion of Primary Amines to N,N’Disubstituted Ureas
Using
Mont-
J . Chem. Eng. Jpn., 1991, 25, (3,664-666
A comparison of the maximum conversions for
cyclohexane dehydrogenation in Pd membrane reactors using cocurrent and countercurrent flow models
with the maximum conversion, determined thermodynamically, in a conventional catalytic reactor, is
presented. In the countercurrent reactor there was no
limit to the rise in the conversion, and 100% conversion is attainable. The maximum conversion of the
cocurrent reactor was the same as that determined
thermodynamically.
morillonitebipyridinepalladium(I1)Ace ta-
Adsorption Properties of Ni-Pd Catalysts
Supported on the N 2 0 3
Polymer-Bound Palladium Acetate as a
Catalyst for the Reduction of Nitro and
Azo Groups
N. ITOH,
A. A. VEDENYAPIN, S. V. W S H I N . L. T. KONDRAT’EV and
A. L. LAPIDUS, Izv. Akad. Nauk S S S R , Ser. Khim.,
1991, (8), 1746-1750
Studies of the surface compositions of Ni-Pd/Al,O,
catalysts were performed by adsorption methods and
by X-ray spectroscopy. The results showed that
bimetallic catalysts differ from monometallic Pd- and
Ni-catalysts by dispersion of metallic phases, depending on a method of preparation and on the presence
of K’ promoter. Catalysts prepared by the immersion method had more strongly Pd enriched surfaces,
as compared to those prepared by precipitation.
Design of the Catalyst for Partial Oxidation of Ethylene by Applying an Electrochemical Device
K OTSUKAand A. KOBAYASHI,
Chem. Lett. Jpn., 1991,
(7)/(8), 1197-1200
An electrochemical device composed of a H,PO,
membrane on which were attached Pt and Pd blacks,
Ru, Rh, 0 s and Ir, MiH,PO,/M’, where M=anode
metal and M’ =cathode metal, was demonstrated as a
probe of the catalysts for the partial oxidation of
C,H, . From the results a catalyst, Pd-Ru-graphiteH,PO,, has been designed for the selective synthesis
of CH,CHO from C,H, - a Wacker oxidation. The
formation rate of CH,CHO was 3.18 pmollmin.
Oxidative Leaching of Cu Atoms from
PdCu Particles in Zeolite Y
z . ZHANG, L. xu and w. M. H. SACHTLER, J . Catal.,
1991, 131, (2), 502-512
Nay-supported PdCu samples of various Cu:Pd
ratios were prepared by ion exchange with
precursors. ReducPd(NH,),
and Cu(NH),),
tion of Cu was enhanced by Pd. Reduction with H,
resulted in bimetallic PdCu particles and protons of
high Bronsted acidity. Complete oxidation of the Cu
component occurred at 5OOOC and the Cu ions leached from PdCu particles migrated to small zeolite
cages. After complete leaching of Cu, the
monometallic Pd particles were discerned from the
original particles in PdCu/NaY and PdCu,/NaY by
their propensity to form TPD-detectable hydrides.
+
te and Di-Tert Butyl Peroxide
B. M. CHOUDARY, K. KOTESWARA RAO, S. D. PIROZHKOV
and A. L. LAPIDUS, Synth. Commun., 1991, 21,
(18&19), 1923-1927
A simple convenient method for the synthesis of
N,N’-disubstituted ureas from primary amines is
reported, using a Pd(I1) complex anchored on an inexpensive clay support, and with a cocatalyst of
cupric chloride as reoxidant. The conditions are room
temperature and atmospheric pressure.
and M. SRINIVASAN, React.
Polym., 1991, 14, (3), 263-268
Pd(0Ac) , anchored to a copolymer containing
pyridyl and carboxyl groups was used as a catalyst for
the hydrogenation of azo and nitro groups under 1
atm H , pressure and 3OOC. The selective hydrogenation of azobenzene to hydrazobenzene was highly
selective on using the polymer-bound Pd catalyst,
and is reported for the first time. The catalyst is quite
stable and has been well used for more than a year.
R. MANI, v . MAHADEVAN
Reactions of Formic Acid and Formaldehyde on Rh(l11) and R h ( l l 1 ) (2 x 2)0 Surfaces
surf. SCl., 1991,248,
(1/2), 57-76
The adsorption and decomposition of HCOOH and
HCHO on the Rh(ll1) surface was studied by
H E E L S . HCOOH adsorbed on the surface via the
lone pair electrons on the hydroxyl 0, and H bonding
among the molecules in the adlayer is indicated. At
140K a formate intermediate was formed, which
decomposed to CO,, CO, H , and H,O via two channels. Adding 1/4 monolayer of 0 atoms to the
Rh( 111) surface shifted the formate decomposition
temperature to 330K. Below 130K on a clean Rh( 111)
surface HCHO dehydrogenated completely to adsorbed CO and H atoms. Exposing an 0 predoped
surface to HCHO resulted in formation of adsorbed
paraformaldehyde, CO, formate and q ’ -HCHO.
C. H O U T M A N a n d M . A. BARTEAU,
-
Infrared Spectroscopy of High Pressure:
Interaction of H, and D2 with Rh/AI,03
and S. D. WORLEY, 3. Phys.
Chem., 1991, 95, (22), 8881-8886
A novel high pressure-IR-cell reactor was used to
study the interaction of ultrapure, high-pressure H,
and D, with Rh/Al,O, films. The H, may dissociate
on the Rh sites to produce a weakly bound Rh-H surface species, with the remaining H spilling over to the
support where it reacts with surface hydroxyl groups
to produce H,O. The new Rh-H species was easily
removed by reduction under H, pressure.
J. P. WEY, W. C. NEELY
55
Effects of Polymer Support on the
Substrate Selectivity of Covalently Immobilized Ultrafine Rhodium Particles as
a Catalyst for Olefin Hydrogenation
M. OHTAKI. M. KOMIYAMA, H. HIRAI and N. TOSHIMA,
Macromolecules, 1991, 24, (20), 5567-5572
Immobilised ultrafine Rh particles were prepared
from a protective polymer, and deposited onto a
cross-linked polymer support, by forming the amide
bond between the primary amino group contained in
the support and the methyl acrylate residue in the
protective polymer of the Rh. The catalytic activity of
the Rh was investigated by olefin hydrogenations.
Activity strongly depended on the substrates used.
The Rh preferentially hydrogenated hydrophilic
substrates. Substrates containing a carboxyl group
were hydrogenated by the immobilised catalyst more
easily than by the dispersed catalyst. The difference
in hydrogenation rates can .be correlated with the
solubility parameter of the substrate. Electrostatic interaction between substrates and the polymer support
leads to increased reaction rates.
New Rhodium Complexes Anchored on
Modified USY Zeolites. A Remarkable
Effect of the Support on the Enantioselectivity of Catalytic Hydrogenation of
Prochiral Alkenes
A. CORMA, M. IGLESIAS. c . DEL PINO and F. SANCHEZ,
A. KURUSU. M. INOUE and T. INUI, Shokubai, 1991, 33,
(2), 129-136
Alcohol synthesis from syngas over supported Irbased composite catalysts was examined. Ir catalysts
promoted with Mo, V and Cr had the highest activity
for alcohol formation. The predominant formation of
MeOH and 2-methylalcohols on the Ir-Cr catalyst
strongly suggests that CO insertion occurs. Alcohols
produced on Ir/Cr303seem to be formed in the same
way as for the Ir-Cr composite catalyst. Ir/MoO, had
the highest CO conversion, but CH, was the main
product.
A Mild, Osmium Tetraoxide-Catalyzed
Method for the Oxidation of Sulfides to
Sulfones
s. w.KALDOR and M. HAMMOND. Tetrahedron Lett.,
1991, 32, (38), 5043-5046
OsO, was examined for the chemoselective oxidation
of sulphides to sulphones, in the presence of the cooxidant N-methylmorpholine-N-oxide.
One mole per
cent of the catalyst was sufficient at room
temperature to oxidise a variety of sulphides to the
corresponding sulphones in nearly quantitative
yields. The oxidation is tolerant of the presence of a
number of other functional groups.
3.
Chem. SOC.,
Chem. Cornmun., 1991, (18), 1253-1255
Studies of Rh-complexes with N-based chiral ligands
which were anchored on a modified USY-zeolite containing profuse supermicropores showed a
remarkable increase of enantioselectivity (>%YO) in
the hydrogenation of N-acyldehydmphenylalanine
derivatives. The zeolite supported-Rh catalysts were
re-used several times with no loss of activity or Rh
content. The increase obtained in the enantioselectivity indicated that this type of catalyst is a truly
heterogeneous counterpart of the homogeneous
catalysts for the hydrogenation of prochiral alkenes.
Catalytic and Physical-Chemical Properties of Indium Modified Iridium-Alumina
Catalysts for Dehydrogenation of Highest
Normal Paraffins
A. V. ZAITSEV, A. P. T W P A E V . V. YU. ROROVKOV, 0 D.
STERLIGOV. G. V. ISAGULYANTS and V. B. KAZANSKII,
Izv. Akad. Nauk SSSR, Ser. Khim., 1991, (lo),
2222-2227
Spectroscopic studies of monometallic and In
modified Ir/Al, 0, catalysts during dehydrogenation
of high n-paraffins showed that Ir-In/Al,O catalysts
had higher activity and increased selectivity towards
the highest olefins. In modified the Ir surface, forming mixed clusters. At the same time, a decrease was
observed in the number of surface Ir atoms capable
of adsorbing H, at 300K, but the number of centres
of high temperature H?dissociation which adsorbed
H , on the support noticeably increased.
Alcohol Synthesis from Syngas on
Supported Ir-Based Composite Catalyst
HOMOGENEOUS CATALYSIS
a-Stacking and the Platinum-Catalyzed
Asymmetric Hydroformylation Reaction:
A Molecular Modeling Study
L. A. CASTONGUAY, A. K. RAP& and C. J. CASEWIT, 3.
Am. Chem. SOC.,1991, 113, (19), 7177-7183
The importance of steric factors in determining the
regioselectivity of a class of Pt(I1) hydroformylation
catalysts (L,
Pt(C0)X) was theoretically studied by
using an augmented Dreiding force field. The
differential stabilisation of the initially formed Pt
alkyl complexes resulting from styrene insertion into
a Pt-Hbond formed either the primary phenethyl
product or the secondary a-methyl styryl
intermediate.
A Homogeneous Platinum Catalyst in the
Stationary B F , . H 2 0 Phase for the
Hydrogenation of Arenes
1. T. HORVATH, Angew. Chem., Int. Ed. Engl., 1991,
30, (8), 1009-1011
A stationary liquid-phase catalyst comprising
PtCl (CH ,CN) in BF ,. H I0 on clay or silica supports was prepared and used for the hydrogenation of
various aromatic hydrocarbons under mild conditions. The catalyst was tested for continuous performance in a tubular trickle-bed reactor. Products are
separable by simple filtration, and the hydrogenation
proceeds selectively, in a 1: 1:1: 1 mixture of benzene,
toluene, o-xylene and 1,2,4-trimethylbenzene.
56
Platinum(I1) Catalysed Selective Remote
Oxidation of Unactivated C-H Bonds in
Aliphatic Carboxylic Acids
3. Chem. Soc., Chem. Commun.,
1991, (18), 1242-1243
The use of the 'chelate effect' in achieving the selective oxidation (hydroxylation) of C-H bonds of
aliphatic chains by Pt" in aqueous medium under
mild conditions is reported. By adding a co-oxidant
that is capable of reoxidising Pt" to F'"' it is possible
to make the system catalytic in Pt". In the presence
of Pt(IV),Pt(I1) ion was found to catalyse the hydroxylation of unactivated C-H bonds of aliphatic carboxylic acids in water.
L.-c. KAO and A. SEN,
Isomerisation and Carbonylation of
Esters Catalysed by Platinum Phosphide
Complexes in the Presence of Lewis
Acids
N. w. KOZITSYNA and I. I. MOISEEV, Akad. Nauk
SSSR, Kinet. Katal., 1991, 32, (4), 985-989
Polynuclear Pt phosphide complexes IPPh, Ptl,
(n =8-10) in RCOOR solution, containing acid types
BF,, SbFI, CF,COOH or C,H,OCF(CF,)CF,OC,F,SO,H, catalysed the isomerisation of
methylformate in acetic acid, and carbonylation of
methylacetate in acetic anhydride at 20-25OC and in
Ar or CO, respectively.
Palladium-Catalyzed Insertion of Isocyanides into the Silicon-Silicon Linkages
of Oligosilanes
and M. MURAKAMI,
Chem. SOC.,1991, 113, (6), 8899-8908
Oligosilanes were reacted with isocyanides when promoted by a Pd catalyst. Heating oligosilanes with excess 2,6-disubstituted aryl isocyanide in the presence
of Pd(I1) acetate led to the complete insertion of isocyanide into all Si-Si linkages, giving oligo(sily1imine)
derivatives. The oligo(sily1imine)s were isolated and
characterised in the complete insertion reaction with
oligosilanes up to a hexasilane. New skeletal rearrangement of oligosilanestook place in a Pd-catalysed
reaction of substituted aryl isocyanide with tetra- and
hexasilanes, yielding 3,3-bis(silyl)-1-aza-2,4-disilacyclobutane derivatives.
Y. ITO, M. SUGINOME, T. MATSUURA
3. Am.
Synthesis and Catalytic Activity of Pd(I1)
Complexes with Bi- and Tridentate
Salicylaldimines Containing Sterically
Hindered Phenols
and A. A. MEDZHIDOV,
Akad. Nauk SSSR, Kinet. Katal., 1991, 32, (3),
594-599
The synthesis of binuclear Pd chelates with tridentate
salicylaldimines is reported. The catalytic activity of
the Pd complexes was studied during the hydrogenation of nitrobenzene in a homogeneous medium. The
dependence of the activity on solvents and circumferential ligand substitutes is discussed.
A. A. FUAEV. V. T. KASUMOV
Efficient Palladium Catalysts for the
Copolymerization of Carbon Monoxide
with Olefins to Produce Perfectly Alternating Polyketones
E. DRENT, 1. A. M. VAN BROEKHOVEN and M. J. DOYLE,
3. Organomet. Chem., 1991, 417, (1-2), 235-251
Highly efficient homogeneous Pd catalyst systems
were developed to produce perfectly alternating
copolymers of CO with C,H,. CO, C,H, and propene mixtures are converted into the corresponding
alternating CO/olefin terpolymers where C, units
randomly replace C,H, units in the chain. The
catalyst systems are formed by combining an
equimolar quantity of a suitable bidentate phosphine
ligand with a Pd(I1) species in which the counter
anions are very weakly co-ordinating. For
diphenylphosphinoalkanes: Ph,P(CH,),PPh,, the
most efficient system to produce high molecular
weight polyketones has m = 3. High rates with conversions of > l o b molecules of CO and C,H, per Pd centre are obtained.
Palladium-Catalyzed Intramolecular Addition of Amines to Acetylenes. Synthesis
of Cyclic Imines
Y. FUKUDA, s. MATSUBARA and K. UTIMOTO, 3. Org.
Chem., 1991, 56, (20), 5812-5816
Intramolecular aminopalladation of alkynylamines
gave intermediary alkenyl I'd compounds that
hydrolysed and isomerised to thermodynamically
stable cyclic imines. Treating 3-alkynylamines with
PdCl ,(MeCN) , gave exclusively 1-pyrrolines in good
yields; 5-alkynylamines afforded 2,3,4,5-tetrahydropyridines selectively. Treating 4-alkynylamines with
Pd(I1) gave mixtures of both 5- and 6-membered
cyclic imines.
Palladium Catalyzed Carboxylation of
Cyclohexane with Carbon Monoxide
and Y. FUIIWARA,
Chem. Lett. Jpn., 1991, (8), 1437-1438
Very high turnover numbers have been obtained for
the carboxylation of cyclohexane with CO to form
cyclohexanecarboxylic acid using Pd(0Ac) ,. The
product yield was 8.8% based on the starting alkane
and the turnover number was 205.
K. NAKARA,J. WATANABE, K. TAKAKI
Synthesis of a,fi-Disubstituted Aldehydes
from Metallated 1-Aza-l,3-Butadienes
and Palladium Phosphine Complexes
U. M. DZHEMILEV, A. G. IBRAGIMOV, D. L. MINSKER, R. R.
MUSLUKHOV and G. A. TOLSTIKOV, Izv. Akad. Nauk
SSSR, Ser. Khim., 1991, (lo), 2339-2348
a,/l-Disubstituted aldehydes were prepared from
metallated I-aza-1,3-butadienes in the presence of
Pd(acac), +2Ph,P catalysts by reactions of N-, 0and S-containing ally1 electrophiles with Mg
azaenolate and organic halogenides. The reaction performed with the Pd phoshine catalyst was highly
regio- and stereoselective.
57
Kinetics of the Water Gas Shift Reaction ELECTRICAL AND ELECTRONIC
Catalyzed by Rhodium(II1) Chloride in ENGINEERING
Aqueous Picoline Studied by Use of a
Continuous-Flow Stirred Reactor
Magnetoresistance of Co/Pd and Co/Pt
B. s. L. NETO, K.H. FORD, A. J. PARDEY, R. c. R I N K E R ~ ~Multilayer
~
Films for Magneto-Optical
P. c. FORD, Inorg. Chzm., 1991, 30, (20), 3837-3842
Data Storage Applications
Homogeneous water gas shift catalysis by R. A. HAJJAR, T.-H. wu and M. MANSURIPUR, J. Appl.
Rh(III)CI, . 3 H 2 0 in aqueous picoline solution in a
continuous-flow stirred reactor is described. The
catalysis rates were non-linear in total IRhl over the
range 3-20 mM, which was interpreted by the system
having dinuclear and mononuclear Rh species present, with the mononuclear cycles being more reactive. The rates have a non-linear dependence on PCo
over range 0.3-1.8 atm, although this was independent of [Rhl. There may be reversible addition of CO
to the catalytically active species prior to rate-limiting
in the mono- and dinuclear catalytic cycles.
CORROSION PROTECTION
Cathodic Protection System
and J , S. MURTY, AntiCorros. Methods Mater., 1991, 38, (6), 4-7
Steel corrosion in sea water and methods of overcoming it are discussed, with particular reference to the
design and implementation of a cathodic protection
system for steel piles. An impressed current cathodic
protection system was chosen, and typical current requirements for various steel structures are given. The
design characteristics and application for different
types of anodes are given. Pt clad Nb anodes were
selected as having the highest current carrying capacity, lowest anode consumption and longest life. The Pt
metal available on the anodes is expected to last
longer than the designed life of the cathodic protection system, assuming that only 90%of the Pt can be
used. The anodes have current output of 25-35 A.
R. S. ROHELLA, B. C. SWAIN
Effect of Paint Damage and Under-Way
Conditions upon Ship ICCP Current
Demands
and P. KHAMBHAITA, Corros. Prev.
Control, 1991, 38, (4), 85-89
The dimension and conductivity scaling modelling
technique was used to assess three impressed current
cathodic protection systems on ships’ hulls. Up to six
Pt foil anodes, each mounted on a polymethyl
methacrylate shield placed directly on the plate were
tested. The current output of these systems in static
and simulated under-way conditions with an intact
paint coating and with damage along the hull were examined. Potential profiles with anodes in different
places are presented. The best protection overall
came from the two-zone system: with one potentiostat, midship reference electrodes (RE), two forward and two after anodes, plus second potentiostat,
stern RE, and two stern anodes. Modelling predicts
the performance and current output of impressed
current cathodic protection systems.
D. J. TIGHE-FORD
Phys., 1991, 70, (lo), 6041-6043
Galvanomagnetic, magnetic and magneto-optical properties of multilayered Comd and Co/Pt films with
varied Co content were studied. In Corn films, an increase of Co content resulted in a decrease of the s-d
slope approaching the value for a pure Co films. The
magnetic and electronic properties of these films were
correlated with the magnetoresistance measurements
performed with fields applied parallel and perpendicular to the plane of the samples.
Through-Wafer Optical Communication
Using Monolithic JnGaAs-on-Si LED’S
and Monolithic PtSi-Si Schottky-Barrier
Detectors
G. W. TURNER, C. K. CHEN, B.-Y. TSAUR and A. M. WAXMAN, IEEE Photonics Technol. Lett., 1991, 3, (@,
761-763
Through wafer optical communication has been
shown for the first time using two vertically stacked
Si wafers, the upper one with InGaAs-InAlAs doubleheterostructure LEDs grown by MBE on its top surface and the lower one with PtSi-Si Schottky barrier
detectors fabricated on its bottom surface. IR radiation emitted by the LEDs in a band peaking at l . 12
pm just beyond the Si absorption edge is transmitted
through the upper Si wafer, focused with a lens of
focal length 25 mm, transmitted through the lower Si
wafer and detected by the Pt-Si detectors. In a single
LED-detector pair the detector S:N ratio was lO:l,
for a LED drive current of 1 mA at room
temperature.
Annealing Studies on Pdln-GaAs Schottky Diodes
H. SHARDA, K. PRASAD, L. FARAONE and A. c. NASSISemicond. sci. Technol., 1991, 6 , (8),
765-770
Pdh-GaAs Schottky diodes were fabricated using
either spin-on or evaporated Pd sources. Barrier
heights and electrical characteristics were measured.
The ideality factor for both diodes was close to 1.
Ageing at temperatures up to 2OOOC for 1000 h produced little or no change in diode parameters; but annealing at 2SOOC for up to 1000 h produced a gradual
degradation of diode parameters. This degradation
was significantly faster during a 4OOOC anneal, and is
attributed to the atomic intermixing and/or diffusion
at the Pd-GaAs interface. Pd spin-on devices had a
much longer operating life compared to the
evaporated ones. The spin-on technique is
economical, simple and easy to implement in any existing GaAs device technology.
BIAN,
58
Palladium as a Lead Finish for Surface
Mount Integrated Circuit Packages
D. c. ABBOTT, R M. BROOK, N. MCLELLAND and J. s.
IEEE Trans. Componenu, Hybrids Manuf.
Technol., 1991, 14, (3), 567-572
The use of a thin preplated Pd Pb finish as an alternative to SnPb solder is discussed for surface mount
IC packages. Tests performed on the Pd included
wetting, solder joint metallurgy, wire bonding, interaction with molding compounds and electrochemical characteristics.
Reliability
and
performance tests were also run, including operating
life, temperaturehumidity, thermal cyclekhock, Pb
finish performance and mechanical tests. Pd plated
leadframes were successful on small outline packages
(8-28 pin) and fine pitch packages.
WILEY,
AC Complex Impedance Investigation for
RuO -Glass Composites
B. K. KOO, K. s. NO and H. G. KIM, IEEE Trans. Components, Hybrids, Manuf. Technol., 1991, 14, (3),
580-584
The AC complex impedance spectra of Ru0,-glass
composites were investigated from 1 kHz-13 M E ,
as functions of RuO, content and heat treatment conditions. Since the amount of Ru ion in the PbOB,O1-Si0,-AI,O3-Zn0 system increases with increasing reaction temperature and time, the electronic properties of the matrix are changed. Samples
reacted at low temperature and for short times showed vertical lines in complex impedance spectra plots,
which indicated that the samples consisted of lone
capacitor circuits. As temperature and time increased, the spectra consisted of semicircle arcs representing R C combination circuits. Samples with more
RuO ,showed a change from a vertical line to semicircle arcs at a lower reaction temperature. A sample
with 5 vol.% RuO, and reacted at 1000°C had an
equivalent circuit model which was only resistive.
TEMPERATURE
MEASUREMENT
A GoldlPlatinum Thermocouple
Reference Table
M.GOTOH, K. D. HILL and E. G. MuRDOCK, Rev. sci. In-
strum., 1991, 62, ( l l ) , 2778-2791
The thermoelectric voltage of the Au/Pt thermocouple was measured over the range 0-%2OC, by comparison with calibrated Pt resistance thermometers.
From 0 to 50OOC the measurements were taken in a
stirred liquid bath, while from 660 to 964OC they
were performed in a pressure controlled Na-fded
heat pipe furnace that provided an isothermal intercomparison environment. Measurements were made
at the freezing points of In, Sn, Zn, Sb and Ag, at the
melting point of Ga and at the liquidus point of the
Ag-Cu eutectic. A reference function was obtained
that gives e.m.f. as a function of temperature to
within k10 mK from 0 to 962OC.
MEDICAL USES
Design and in Vitro Studies of a NeedleType Glucose Sensor for Subcutaneous
Monitoring
D. S. BINDRA, Y. ZHANG, G. S. WILSON, R. STERNBERG, D.
R. THBVENOT, D. M O A and
~ G. REACH, Anal. Chem.,
1991, 63, (17), 1692-1696
A new miniaturised glucose oxidase based needletype glucose microsensorhas been developed for subcutaneous glucose monitoring. The sensor has a 10
cm long Teflon coated Pt-Ir wire of 0.25 mm 0.d.
with a 1 mm long bare part acting as a sensing cavity.
The reference electrode was Ag/AgCl, and the whole
sensor was coated with 5% polyurethane solution in
98% THF-2% DMF.
The Effect of Some Platinum Compounds
on the Activity of the CTP Synthetase of
Ehrlich Ascites Tumor Cells: In Vitro and
In Vivo Studies
R. L. GANEVA, N. C. SPASSOVSKA and D. D. GENCHEV, 3.
Inorg. Bwchem., 1991, 43, (4), 717-722
The effect of cis-diamminedichloroPt(I1): (cis-DDP),
trans-DDP, spermine Pt(I1) and K,RCI, on the activity of CTP synthetase in the cytosol of Ehrlich
ascites tumour cells was studied. For in vitro study
the pt compounds were added to the incubation mixture for the enzyme assay. A concentration dependent
inhibition of CTP synthetase was found, which was
strongest for the trans-DDP. Ascites cells from mice
pretreated in vivo with Pt compounds showed that inhibition is strongest for cis-DDP and K, PtQ, .
Synthesis and Characterizationof Highly
Lipophilic Antitumor Platinum(I1) Complexes
A. R. KHOKHAR, Q. xu and s. AL-BAKER, 3. Coord.
Chem., 1991, 24, (l), 77-82
The preparation and characterisation of a series of
highly lipophilic Pt(I1) complexes of .type
[Pt(OCOR),(A)I or [Pt(OCOR),(A'),I are described,
where R=a highly branched or long chain alkyl
group of 4-13 C atoms, A=lR,ZR-diaminocyclohexane, cis-l,2-diamir1ocyclohexane, 1,l-bis
(aminomethy1)cyclohexane or ethylenediamine and
A' = neopentylamine or cyclopentylamine.
Myoglobin Oxygen Binding Curves
Determined by Phosphorescence Quenching of Palladium Porphyrin
and C. H.
Appl. Specmsc., 1991, 45, (7), 1177-1182
A completely optical method has been developed for
evaluating myoglobin-0, saturation. Using this solution 0, concentrations were computed for functioning heart muscle by measuring the phosphorescence
decay of a soluble Pd porphyrin, 5,10,15,20-teuakis
(4-sulphanatophenyl)-porphyrinPd(II), according to
the Stern-Volmer quenching relationship.
J. J. KELLY, K. A. KELLY, S. A. HARTLEY
BARLOW,
59
NEW PATENTS
METALS AND ALLOYS
CHEMICAL COMPOUNDS
Platinum-Aluminium-Copper Alloys for
Jewellery
Preparation of Stable Platinum
Compounds for Use in Platinum Pastes
MINTEK
European Appl. 42 1,73 1A
The colour of intermetallic Pt-Al compounds is
modified from yellow through orange to Cu red by
the addition of Cu. The alloys consist of 50-81 wt.%
Pt, 5-30 wt.% Al and 1-47.5 wt.% Cu, and may be
formed by addition of Cu to the compound PtAl, or
by melting individual components together in an inert atmosphere. The addition of Cu gives a range of
aesthetically pleasing colours, and the alloys are used
in the jewellery trade.
TANAKA KIKINZOKU KOGYO
Palladium Based Alloys for Metal
Powders
LEACH & GARNER
U.S. Patent 5,000,779
Metal powder alloys consist of at least one of Pd, Au
and Ag; Cu; and 0.20-0.80 wt.% of at least one
metalloid from B, P, Si and Li; with preparation including atomisation and rapid solidification. A
preferred metal powder contains 40 wt.% Pd, 30
wt.% Ag, 30 wt.% CU,0.5 wt.% B and 0.5 wt.% P,
and has particle size 4 0 0 pm and grain size <10 pm.
The alloys have increased hardness, the supersolidus
temperature is reduced, and the metal powders have
optimum particle and grain size for supersolidus
sintering.
High Brightness White Gold Alloy
Japanese Appl. 3/87,323
An alloy having high brightness contains 75 wt.%
Au, 8-12 wt.% Pd, 7-5 wt.% Ag, 5 4 wt.% Ni and
5-4 wt.O/o Cu and/or Co in total. The alloy is an 18
carat Au (white Au), has high brightness similar to
Pt, and has good physical, mechanical and chemical
properties.
NIPPON KIKINZOKU KO.
Platinum Alloy Material for Colouring
Ornaments Black
AGENCY OF IND. SCI. TECH. Japanese A@!. 3/100,159
A Pt alloy material consists of 3-20 wt.% Pt and 3-20
wt.% of at least one of Cu, Fe, Co and Ti. The process includes heat treatment in a low oxidation atmosphere and cooling the material to room
temperature with air, water or oil, and the material is
used for black colouring of ornaments to give a lustre.
Silver-Palladium Alloy Powder
Preparation
A Ag-Pd alloy for use in thick film pastes is prepared
by dissolving a Ag-Pd alloy in HNO, , and then adding a reducing agent to obtain a precipitate of the
Ag-Pd alloy. The process is suitable for mass production, giving an alloy powder of uniform quality which
is capable of providing good electric and soldering
properties when used as pastes.
KOJUNDO KAGAKU KENK.
Platinum Merals Rev., 1992, 36, (l), 60-68
Japanese Appls. 3/99,087-89
Pt camphene mercaptate, Pt limonene mercaptate or
Pt terpineol sulphide are useful materials for Pt pastes
used to prepare Pt catalysts, electronic parts,
corrosion-proofing layers or liquefied Pt film
materials; and have good storage stability and are
easily prepared. Preparation comprises reacting
platinic acid salts with camphene mercaptan,
limonene mercaptan or terpineol sulphide respectively, extracting with chloroform, washing, evaporating,
and in the final step crystallising the products to give
light yellow crystals.
ELECTROCHEMISTRY
New Electrode for Oxygen Generation
Process
T D K CORP.
British Appl. 2,239,260A
A new electrode for 0, generation has a metal
substrate such as Ti coated with alternate layers of
composite oxides containing (a) 40-79.9 mol% Ir oxide and 60-20.1 mol% Ta oxide, and (b) 80-99.9
mol% Ir oxide and 20-0.1 mol% Ta oxide. The electrode has good adhesion, long life at low cell voltage
and current densities up to 100 A/dm?, and low 0 ,
overvoltage and enhanced durability when used for
O ? generation by electrolysis of aqueous solutions.
Electrolytic Cell with Hollow Anodes
Containing Platinum
PEROXID-CHEMIE c.m.b.H. European Appl. 428,171A
An electrolytic cell has alternating cathodes and
anodes which are shaped hollow bodies, with the effective anode surface consisting of R valve Pt
overlayer made by hot isostatic press! L_ IPt foil onto
a metal substrate. The cell blocks are useful electrochemical reactors for production of peroxo and
perhalogenate compounds, have a long working life
and high current density, and can be used together,
with low energy consumption.
Production of High Purity Ammonium
Paratungstate
GTE PRODUCTS CORP.
U.S. Patent 5,021,133
A cemented tungsten carbide-Pt anode is used in the
electrolysis of an electrolyte consisting of ammonium
hydroxide and an ammonium salt, where electrodissolution decomposes the cemented tungsten carbide to form a solution of ammonium tungstate from
which ammonium paratungstate is crystallised. A
product of high purity is obtained without firing the
starting material to tungstic oxide and without digestion in sodium hydroxide.
60
Electrochemical Oxygen Separator with
Iridium Anode
Japanese Appl. 3194,086
An electrochemical separator has an integrated electrochemical cell consisting of a cathode for electrolytic reduction of 0,, an ion-exchange membrane
used as a solid electrolyte, and an Ir anode used for
generating 0,. The cell is used to separate 0, from
a gas mixture by supplying the mixed gas to the
cathode, and collectingthe 0, from the anode. By using an Ir anode the cell operates under low voltage
and at increased efficiency.
JAPAN STORAGE BATTERY
Electrolysis Electrodes with
Platinum Protective Coating
Porous
PERMELEC ELECTRODE LTD. Japanese
Appl. 3/126,884
Electrodes are manufactured by electrodeposition of
a PbO, coating layer on a metal or alloy base, followed by forming a porous Pt protective layer by electrodeposition or electroless plating. The electrode
consists of multiple layers of PbO, and multiple
porous Pt layers. An insoluble electrode is obtained.
ELECTRODEPOSITION AND
SURFACE COATINGS
Metal Surface Substitution Using
Palladium Plating Solution
A process to effect metal surface substitution has as
the first stage an etching process in a mixed solution
of NaOH, KOH, KCN and NaCN at 5-35OC, and as
second stage electroless plating using a 0.1-1.0 gfl
solution of PdCI,, Pd(NO,),, PdSO,, Pd(COOH),
or its salt, at pH 10-12, and at 5-35OC. The process
is useful for plating onto thin metal foil or film of
electronic devices, and for forming Al foil patterns.
ORIENT TOKE1 KK.
Membrane Coating for Spinning Nozzle
TANAKA KlKlNZOKU KOGYO
A mixture consisting of chloroplatinic acid and Pt
metal chlorides such as PdCl ,,IrCl and RuCI, in an
organic solvent is used to coat the spinning face of a
spinning nozzle which consists of an alloy of Pt and
Au, Ta and stainless steel. The coating is then dried
and sintered to form a thin membrane having a micro
structure of Pt and Pt group metal oxides which is
very stable and has good anti-corrosion properties.
Palladium Deposition Bath Containing
Ethylenediamine
French Appl. 2,652,823
A basic aqueous bath for chemical deposition of Pd
contains Pd chloride, hydrazine as reducing agent,
ethylenediamine as the Pd ion complexing agent and
a stabiliser. The complexing agent is present in sufficient amount to complex all of the Pd ions and the C1
ions near the plating surface, and the bath has an
autocatalytic action.
OFF. NAT. AEROSPATIALE
Radionuclide Source Preparation
Russian Patent 1,266,366
An increased power radionuclide source has a radionuclide oxide layer on a Pt wire, and is prepared
by electromechanicallycoating a 0.3 mm Pt wire with
the hydroxide of Cm-244 at 1200 pglcm’ of surface.
The composition is then calcined at 80OOC in air to
obtain a Cm oxide layer of 0.5 mm thickness. Formation of the radionuclide source is thus simplified.
V.M. RADCHENKO
APPARATUS AND TECHNIQUE
Determination of Nitrous Oxide and
Oxygen in Gas Mixtures
European Appl. 432,649A
A sensor used in medical anaesthesia for determination of N,O and 0, concentrations in a N,O, 0, and
N, mixture has Pt electrodes separated by a solid
electrolyte wall, preferably of yttria stabilised ZrO,.
A negative voltage is applied to the electrodes which
are first exposed to a gas containing a known amount
of O , , and then to the gas mixture for determination.
Comparison of the current plateaux obtained gives
the N , O and 0, concentrations.
GTE LABS INC.
Platinum Resistance Thermometer for
Use in a Gas Detector
World Appl. 9115,998A
A gas detector to monitor the concentration of a component of a gas mixture, for example 0, or CI dioxide, has a catalyst coated Pt resistance thermometer
which effects an exothermic decomposition of the
component and generates a signal indicating its concentration. A cheap, accurate and reliable sensor with
no moving parts is obtained which is specific to the
gas to be detected, and can detect a wide range of concentrations.
MICROSYSTEM DESIGN
Platinum Cup for Pyrolysis of Pulp
Samples
U.S. Patent 5,002,894
A Pt cup is used for pyrolysis of samples of paper
making materials for measurement of the lignin content by mass spectrometry. The Pt cup is welded to
a ribbon of poor heat conducting metal such as
stainless steel, and is electrically puked for a short
time for pyrolysis of the samples at 530-570OC. The
method is used for quality control of pulp manufactured in a paper making mill.
P. SHAKKOTTAI
Ruthenium Concentration Sensor for
Atomic Fuel Reprocessing Plant
A Ru concentration sensor for detecting RuO, concentration uses oscillators where an organic membrane is provided on the surface of an electrode. Ru
concentration is measured by the difference in frequency change between oscillators in sample and
reference environments. The sensor enables RuO,
concentration to be detected on the spot with high
sensitivity, and is useful in atomic fuel reprocessing.
HITACHI K.K.
61
Durable Gas Sensor Element
A gas sensor element consists of an insulating base
plate such as AI,O, or SiO,, a pair of comb shaped
Pt or Au electrodes, a SnO, or ZnO, gas sensor, a Pt
andlor Pd catalyst layer up to 5 nm thick, and a
heater. The gas sensor is kept at 15OOC and is used
for reducing gases such as CO and H,. The sensor
has a simple structure, high sensitivity, good
durability and is stable over a long period of time.
KURABE K. K.
Enzyme Electrode with Conductive
Platinum Base Body
An enzyme electrode consists of a conductive base
body of Pt, Au or C, having its surrounding part
covered with a hydrophobic insulator such as
polyethylene, and the section covered with an immobilised enzyme film such as glucose oxidase
through a permselective membrane. The electrode
can be assembled simply, and has good durability.
KANZAKl PAPER MFG. K.K.
Heat Resistant Humidity Sensing
Element
SHINETSU CHEM. IND. K.K.
A humidity sensing element consists of an insulating
base plate, a pair of Ag-Pd, Ru oxide or Au electrodes
on the base plate, and a polysiloxane film. The sensor
can be used at <lOO°C, and has high heat resistance,
high response speed, and low hysteresis.
Small Heat Generating Device
A vaporised industrial alcohol such as CHIOH is
passed through a porous body, and then through a Pt
honeycomb catalyst where the alcohol decomposes to
CO, and H,O, generating heat which is collected in
the Pt honeycomb. The heat can be used in the form
of hot air or by contacting a conductor with the hot
Pt honeycomb. Heat can be generated safely and easily with this small apparatus.
T. MOTOE
High Sensitivity Gas Sensor Element
A gas sensor element consists of polyaniline between
more than two conductive electrodes of Pt, Au, Ag,
graphite, Sn or In oxide and Si. The electrodes can be
clad, deposited or sputtered on the polyanilinefilm to
form the element. Various gases such as NH,,CH, ,
H,O, H,S, NO and others can be detected.
SUMITOMO C H E U IND. K.K.
Material for Detecting Combustible Gas
3189,162
A combustible gas detecting material consists of at
’t, Pd, Rh, Ir, Au or Ag supported in fine
least one of FPt,
Ru,
granular form on metal oxide(s) of at least one of Ru,
Cr, Mn, Fe, CO or Ni, present as a thin film on a
transparent base plate. The material is used for detection of combustible gas by light signals, and can be
assembled in a light control system. The gas detection
device has excellent explosion-proof properties, and
is hardly affected by electromagnetic interference.
AGENCY OF IND. SCI. TECH.
AGENCY
Gas Sensor with Long Term Stability at
Low Temperatures
A gas sensor consists of a base plate made of an insulator material, a gas sensitive layer containing
0.1-1 wt.% (total) of Pt and Pd in the proportion
1-3, and an n-type oxide semiconductorcoating layer
carrying 2-10 wt.% ofa noble metal, for example Sn
oxide carrying 3 wt.% Pt. The catalytic activity of the
gas sensitive layer is stable over a long period, even
at low temperatures.
FUJI ELECTRIC MFG. K.K.
Gas Sensor for Detecting Oxygen and
Ozone
A gas sensor consists of a semiconductor base plate
such as a p-type silicon wafer, an insulating layer, a
La fluoride laye: having La:F atomic ratio 1:2-1:3,
and a 100-500 A laminated Pt electrode having properties intermediate between those of Pt and Pt
black. The gas sensor is useful for detecting 0, and
0, at normal temperatures, and functions by absorbing the gas on the electrode and detecting the change
in properties.
OAK SEISAKUSHO K.K.
Platinum-Rhodium Melt Crucible with
Longer Operational Life
German Appl. 4,001,430
Alkali metal monofluorophosphatesare produced using a cylindrical PtlRh melt crucible 80 cm high and
8.0 cm in diameter which is heated to 800-1200OC.
A direct potential is applied between the cooling aggregate (cathode) and the crucible (anode). The crucible has a longer operating life than other known
crucibles, making the process more economical.
BENCKISER-KNAPSACK
JOINING
Platinum Bonding Layer for X-Ray
Target
U.S. Parent
Patent 5,008,918
5,008,918
A composite stmcture
structure for use as an X-ray tube target
consists of a refractory metal portion bonded to a
graphite substrate via a Pt bonding layer containing
a bonding agent of W, Ni, Mo, V
V or Ti. The bonding
t containing at least 0.8 wt.% W to give
alloy can be P
Pt
a pull strength of at least 2600 psi. The product has
thermal stability
stabilitv at 135OoC,
135OOC. and a brazed bond having superior strength and heat transfer is provided.
GENERAL
GENERAL ELECTRlC
ELECTRlC CO.
CO.
High Strength Palladium Solder Alloy
A Pd based solder alloy contains 20-40 wt.% Pd,
50-70 wt.% Cu and 5-15 wt.% of at least one of Fe,
Ni and Co. The alloy is used for soldering Ti or Ti
alloy members with sufficientlyhigh tensile strength,
and is suitable for producing thin walled Ti parts and
joint type Ti members, used for example in
aeroplanes and so on.
TANAKA KIKINZOKU KOGYO
62
HETEROGENEOUS CATALYSIS
Production of Amines for Polyurethane
Foam
BAYER A.G.
Bis- and tris(3-dimethylaminopropy1)amine compounds are produced by hydrogenation of
3-dimethylaminopropionitrile using a catalyst consisting of 0.1-10 wt.% Pd on an Al,O, or spinel support. Selectivity to the bis product is increased by
using an Al,O, support, and to the tris product by
using a spinel, preferably LiAl spinel. The products
are obtained with high yield and are useful for
polyurethane foam production.
Platinum or Palladium Catalyst for
Preparation of N-Alkylaminophenols
SUMITOMO CHEM IND. K.K. European Appl. 427,572A
N-alkylaminophenols are prepared by reductive
alkylation of an aminophenol with an aldehyde or
ketone, in an organic solvent, and in the presence of
H, and a catalyst consisting of Pt or Pd with at least
one metal from Groups IB, IIB, IVB, VB and VIB on
an activated C support. Side reactions are suppressed,
and the catalyst can be used repeatedly with a high
yield of desired products, which are used as
intermediates for various dyes.
Rhodium Catalyst System for
Preparation of Perfumery Intermediate
4-Tertiary-butyl-cyclohexanolcan be prepared mainly in its isomeric cis form by hydrogenation of
4-tertiary-butyl-phenol or 4-tertiary-butyl-cyclohexanone in the presence of Rh supported on Al ,0 ,,
charcoal or others, in combination with HBF, or a
substituted BF , compound. The catalyst system can
be recycled, has long service life, and gives high
selectivity.
FIRMENICH S.A.
Platinum-Zeolite Exhaust Purification
Catalyst
A catalyst for purification of exhaust gases from internal combustion engines consists of a zeolite layer or
a support (metal or zeolite) loaded with at least 1.3
parts wt. Pt, or at least 0.8 parts wt. Pd, or at least
0.7 parts wt. Rh. The catalysts have better high
temperature durability and conversion of NOx.
TOYOTA JIDOSHA K.K.
Three-Way Catalyst with Enhanced High
Temperature Activity
FORD MOTOR CO. LTD.
European Appls. 430,435A and 430,437A
A three-way catalyst for vehicleemission control consists of a carrier such as cordierite coated with an
Al,O, support, optionally having 2-30 wt.% La,O,
discontinuously deposited on it, then 0.05-5 wt.% of
deposited Pd and up to 8 wt.% of a discontinuous
TiO, phase adjacent to or deposited on the Pd component. The catalyst reduces light-off temperatures
by 20-100OC. It may also include F’t.
Iridium Catalyst for Preparation of
Chlorofluoroethanes
ATOCHEM.
Chlorofluoroethanes are prepared by hydrogenation
of a perhalogenoethaneat 50-300°C and 1-20 bar using a catalyst consisting of 0.1-10 wt.% Ir on a support of Al,O,, AIF, or active charcoal. Use of the Ir
catalyst improves selectivity so that only one Cl atom
is eliminated from the starting material.
Platinum Catalyst for Isomerisation of
Alkanes
U.S. Patents 5,004,859 and 5,017,541
Isomerisable hydrocarbons are isomerised by contact
with a bed of catalyst particles consistingof an M,O,
support, 1-15 wt.% of a Friedel-Crafts metal halide,
preferably Al chloride, and 0.01-2 wt.% of a surfacelayer Pt group metal component, preferably Pt.
Isomerisation is at 40-250°C and 1-100 atm
pressure, and an organic promoter such as CCI ,is optionally present in the feed or catalyst. The method
is used for isomerisation of 4-7C alkanes, giving increased octane numbers for a 5-6C naphtha stream.
UOP
New Noble Metal Catalytic Composites
with Long Life
U.S. Patent 5,013,703
New catalytic composites of silicalite impregnated
with at least 8 wt.% of Pt, Pd, Rh, Ir, Os, Ru, Au
and/or Re have > 60% dispersion of the noble metal
resulting from base pretreatment and double impregnation stages in the preparation. The composites
have hydrophobic molecular sieve properties, long
life, and are not combustible or pyrophoric. The Pt
composite can be dispersed in a PTFE matrix and used to catalyse isotopic exchange between H , and
H 0 vapour.
UOP
,
Molybdenum Promoted Catalyst for
Production of Lower Alcohols
TEXACO INC.
U.S. Patent 5 ,O 13,764
Lower aliphatic alcohols are prepared from the reaction of CO and H , in the presence of a catalyst composition consisting of 0.5-6.0 wt.% Pd, 2.0-15.0
wt.% of one or more of Cs, K, Na and/or Rb, and
1.0-10 wt.% Mo as a promoter, on a support which
is especially Al,O,, The catalyst is devoid of Cu and
Th, and is useful for production of alcohol mixtures
containing a substantial amount of 2-7C alcohols,
used for example as fuel extenders or gasoline
substitutes.
Platinum Wire Catalyst for Use in a
Carbon Dioxide Laser
U.S. Patent 5,020,069
A catalyst for use in a laser consists of a Pt wire coated
with a layer of Pt black and is preferably carried on
an insulating support. The wire is heated by passing
a current through it, and is used in a CO, laser for reconverting CO and 0, lasing by-products to form
CO, at 150-300OC. The low temperature catalyst has
prolonged activity.
HUGHES AIRCRAFT CO.
63
New Poison Resistant Three-Way Catalyst
with Silica and Alumina Layers
Palladium Catalyst for Preparation of
Bisnaphthalic Acid
A new catalyst for removal of hydrocarbons, CO and
NOx from car exhaust consists of a support, a SiO,
layer loaded with Pd, and an Al,O, layer loaded with
Pt andlor Rh. The new catalyst is resistant to poisoning, and operates over a long time without degradation. In an example the catalyst consisted of a
monolithic support, a SiO, layer impregnated with
0.5 gfl Pd, and an AI,O, layer containing La and Ce,
impregnated with 0.5 gfl Pt and 0.1 gA Rh.
Bisnaphthalic acid, its alkyl derivatives or salts are
prepared by dimerisation of 4-halonaphthalic acids or
their alkyl derivatives at 9O-12O0C in the presence of
a PdlC catalyst, in an aqueous alkaline medium containing bases, formic acid and lower alcohols. The
products are prepared in 60-84% yield, and are used
for polyimide resins or pigments.
TOYOTA JIDOSHA K.K.
Differentially Charged Impregnation of
Exhaust Purification Catalysts
TOY0 KOGYO K.K
An exhaust gas purification catalyst consists of a sup-
port with an A,O, coating layer supporting metals
such as Pt and Rh. Preparation is characterised by
differentiating the charged states of the noble metal
ions and the Al,O, layer during impregnation,
equalising those of the second noble metal ions and
the Al, 0, layer. Thermal deterioration of the catalyst
can be prevented.
Exhaust Purification Catalysts
Alcohol Fuelled Engines
for
NIPPON SHOKUBAI KAGAKU
Japanese Appls. 3172,949-50
Catalysts for purifying exhaust gas from internal combustion engines using alcohol as a fuel consist of a
3-dimensional structure coated with a catalyst composition containing: (a) 0.5-4.0 g of R,Pd or Rh and
1.0-20 g of Ag on stable Ce oxide (50-200 g) containing at least Mg, Ba, Ca, Sr or Y; or (b) 0.5-1.5 gfl
Pd and 5-10 gA Ag on AI,O (80-150 gfl) containing
at least one oxide of Ti, Si and Zr. The catalysts
decompose CO, CH, OH and HCHO in the exhaust
gas at low temperature, and catalyst (a) shows improved heat stability of the Ce oxide.
,
NIPIWN STEEL CHEM. K.K.
Preparation of Malonic Acid Esters in
High Yield
NIPPON KOKAN K K .
Malonic acid esters are prepared from reaction of
dibromomethane, an alcohol and CO in the liquid
phase, in the presence of a catalyst consisting of Pd,
Rh and/or Co or a compound supported on a C carrier
of activated charcoal, C black or graphite. Malonic
acid esters can be prepared in high yield, and are
useful for pharmaceutical intermediates.
Exhaust Gas Purification Catalysts with
Ultrafine Platinum and Rhodium
Catalysts for exhaust gas purification are prepared by
coating the surface of a ceramic catalyst support,
preferably a honeycomb support, with a mixture of Pt
and Rh organosols in an organic solvent, and then
vaporising the solvent. The method provides
ultrafine Pt and Rh particles uniformly dispersed on
the support, without heating in H, and then air. The
catalysts are used for removal of CO, hydrocarbons
and N 0 x contained in exhaust gases.
TODA KOGYO K. K.
Selective Low Temperature Removal of
Carbon Monoxide from Hydrogen
CO is selectively removed from H , gas by contacting
with a supported Ru catalyst at 100-200OC. In an exPalladium Catalyst for Preparation of
ample the catalyst consisted of 1 wt.% Ru on yIntermediates for Amino Acids
AI,O,, and after treatment in N,/H,was used to
Im. K.K.
K.K.
3174,346 purify H , gas containing 60 ppm CO. As CO can be
DAICEL CHEM. IND.
Japanese
2-0x0-4-phenylbutanoic acid derivatives are removed at low temperature, inexpensive heating
2-0x0-4-phenylbutanoic
prepared by reduction
reduction of 2-0~0-4-phenyl-3-butenoic media can be used.
prepared
acid derivatives in
in solution,
6-10.5, in the
solution, at pH
p H 6-10.5,
presence of a Pd catalyst. Reaction can take place in Waste Gas Purification Catalysts with
a solution or a slurry, with water as the most ap- Improved Heat Resistance
propriate solvent. The products can be formed selec- TOYOTA JIDOSHA K.K.
tively in excellent yield, and are useful intermediates.
intermediates.
Japanese Appls. 3194,830 and 3198,644
Waste
gas
purification
catalysts are produced by imCatalytic Converter with Different Inflow
mersing an inorganic support in (a) a solution conand Outflow Catalysts
taining Pt andlor Rh, Ir andlor Ru, and citric acid,
NIPPON sn0KuB.u KAGAKU Japanese Appl. 3177,625
or (b) an aqueous Pd solution, drying, then immersA catalytic converter contains exhaust gas purifica- ing in a solution containing Rh, Ir andlor Ru salts and
tion catalysts in a converter unit, with the catalyst on citric acid; then drying, calcining and reducing.
the exhaust gas inflow side containing Pd and Rh, Citric acid promotes inter-diffusion of the Pt group
and that on the outflow side containing Pt, Rh and metals, and prevents grain growth and evaporation of
optionally Pd. The volumetric ratio of inflow to Ir or Ru. The catalysts are used to remove hydrocaroutflow catalysts is 1:8 to 3: 1. The catalyst converter bons, CO and NOx from car exhaust, and have imhas improved hydrocarbon purification.
proved activity, heat resistance and durability.
ASAHI CHEMICAL IND. K K .
64
Platinum-Zinc Oxide Whisker Catalyst
for High Temperature Oxidation
Lanthanum-Aluminium-Platinum Waste
Gas Purification Catalyst
MATSUSHITA ELEC. IND. K.K.
A catalyst for purifying waste combustion gas contains a double oxide of formula LaAl,,&O, where x
is 0.01-1, and B is Pt or Pd. In an example a
honeycomb body was coated with a mixture of the
double oxide and Al,O,. The precious metals are
highly dispersed over the catalyst which is resistant to
high temperatures (>8OO0C) even in an oxidising atmosphere, and is used to purify waste gas.
An oxidation catalyst for gas or liquid phase reactions
consists of a tetrapod shaped whisker of ZnO optionally coated with porous SiO, or Al,O, and supporting 0.5-1.0% Pt on its surface. The whisker of
ZnO has a core with needle crystals projecting in 4
directions from the core centre. The catalyst has
superior properties, giving high speed reaction, and is
used for high temperature oxidation, for example
cleaning waste gas from combustion devices.
Ruthenium Catalysts for Ammonia
Production
SHIN NENSHO SYST. KE.
JUpa?teSe Appl. 3/106,445
Catalysts for NH, production are obtained by supporting a c1-free Ru compound - such as a carbonyl
complex or nitrate - on a reduction resistant oxide,
evacuating and/or reducing in a H,stream to obtain
a metallic Ru catalyst, and supporting a Sm, La or Ce
compound on the catalyst. The catalystshave high activities for the synthesis of NH, from N, and H,,
particularly when the support is AI,O,; and have
water and heat resistance.
Exhaust Purification Catalyst with High
Activity
A catalyst with high activity for purification of exhaust gases consistsof a tungstate; F’t, Pd or Rh as the
metal and/or oxide; and Ba or La molybdates supported on a moulded inorganicpellet or a gas filtering
refractory three-dimensional material, and is
preferably treated at 700-10OO0C in air. In an example, a catalyst containing Pt, Rh, BaWO,, BaMoO, ,
Al,O, and a cogealite support was prepared.
NIPPON SHOKUBAl KAGAKU
High Temperature Combustion Catalyst
A new high temperature combustion catalyst for complete burning of a fuel gas and 0, containing gas to
give only CO,, H,O and heat energy consists of Pt
group elements and high purity magnesia single
crystal fine powder 0.01-0.2 Fm in diameter. The
catalyst has higher heat resistance and is not sintered
even at 125OoC, and is used for body warmers,
kerosene stoves or boilers, or for car exhaust purification or deodorising apparatus.
UBE INDUSTRIES K.K.
BABCOCK-HITACHI K.K.
Palladium Catalyst for Vinyl Acetate
Preparation
Germon Appl. 3,940,125
A catalyst for gas phase preparation of vinyl acetate
from ethylene, acetic acid and 0, consists of Pd
and/or its compounds, optionally Au and/or its compounds, alkali compounds, and optionally Cd compounds as activators, on a SiO, or SiO,/Al,O,
carrier having specifiid surface characteristics, and
using a binder such as a Mg carboxylate for the carrier particles. The selectivity and space/time yield of
the catalyst are raised, and side reactions are reduced.
HOECHST A.G.
New Platinum-Tin Reforming Catalysts
New catalysts are prepared by a two-stage impregnation process in which an inorganic oxide support is
first impregnated with a solution of a Sn salt, a
halogen compound and an organic acid, and then
with a solution of a Pt compound and a halogen compound; finally activating in a reducing atmosphere.
INST. MEXICANO DEL. P.
Three-Stage Removal of Oxygen and
Hydrogen from Inert Gas
0 , and H , are removed from inert gases by first passing over a catalyst of 48-51% Ni and 26-28% Cr at
180-250OC to remove 0,, then over a catalyst of
0.45-0.55% Pd/AI,O, where H, reacts with residual
0, to produce H ,0, and fmally over the Ni catalyst
where residual H, reacts with NiO to produce H,O
and regenerate Ni. Lower 0 , and H, contents in the
inert gases are obtained using this method.
ELECTROTHERM. EQUIP. R.
HOMOGENEOUS CATALYSIS
Platinum-Carbon Catalyst with Ultrafme
Particles
Rhodium Catalyst for Preparation of
Difunctional Monomers
DU PONT DE NEMOURS co. European Appl. 428,979A
A Pt catalyst is prepared by depositing Pt on C by immersing a C powder support in a mixed solution containing H, PtCl,, a colloid coagulation protector and
a reducing agent with an aldehyde group. The C
powder support has had hydmphilic treatment and
can be, for example, acetylene black. Ultra pure
water is used as the solvent and for washing, giving
a catalyst with ultra fine Pt particles dispersed on C.
3-Pentenoic acid and carboxylic acid anhydride
derivatives are prepared by carbonylation of allylic
butenols and allylic butenol esters. The allylic compound is reacted with CO at 10-250°C in the
presence of 0.005-0.50 wt.% of a Rh catalyst and a
HBr or HI promoter, with a pmmoter:Rh molar ratio
of 1:l. The products are useful as difunctional
monomers and intermediates in the synthesis of
adipic acid, and can be prepared selectively.
FUJI ELECTRIC MFG. K.K
65
Palladium Catalyst for Preparation of
Adipic Acid Precursors
Rhodium Hydrocarbonylation Catalyst
for Ethylidene Diacetate Production
RHONE-POULENC CHIM.
WACKER CHEMIE G.m.b.H. German Appl. 3,934,860
Ethylidene diacetate is prepared by reaction of
methyl acetate with CO and H, at 180-220°C and
50-250 bar absolute, using a catalyst consisting of
0.05-0.50 rnol % of a Rh compound, 0.04-0.50 mol
YO of a Pd or Ru compound, an ether-phosphane
ligand to give a 1: 1-2 Rh:ligand rnol ratio, and 3-15
rnol % of an alkali(ne earth) iodide. High conversions
with high selectivity to the product can be obtained.
European Appls. 433,189A and 433,191A
A Pd catalyst, especially Pd chloride, and metal
halides are used in the preparation of (a)
1,6-hexenedioic acid &om the reaction of CO with a
butenediol, or (b) hex-3-ene dioic diesters from the
reaction of diacryloxy-substituted butene, an alcohol
and CO. The reactions take place in a basic, aprotic,
polar solvent, at 50-150°C, at 10-250 bar pressure,
and with 0.001-1 molA Pd. Both products are
precursors for adipic acid, and can be produced with
high selectivity using a metal halide.
Rhodium Catalyst System for Production
of Moist-Grain Preservatives
U.S. Patent 5,008,451
Carboxylic acid anhydrides are produced by reacting
a carboxylic ester and CO at 50-300°C and an initial
pressure of 1-100 atm, under anhydrous conditions,
in the liquid phase, and in the presence of a catalyst
system consisting of a Rh compound, an iodide promoter, and a proton donor. The process can be used
to produce methylene and oxymethylene bis-esters.
CHEVRON RESEARCH CO.
Preparation of Symmetrical
Diarylacetylene Compounds
Symmetrical diarylacetylenes are prepared by reaction of an aryl halide with acetylene in the presence
of a Pd catalyst and a base. The acetylene is fed into
the liquid reaction mixture using an intensive
gasifier, and the aryl halide is a stable, cheap, easily
prepared bromide. The products are obtained from
one reaction stage, with high yield and selectivity, at
high spaceltime yields, and are used as intermediates
for diary1 olefins.
BAYER A.G.
Rhodium Catalyst System for Production
Platinum Catalyst for Deblocking N- of Aldehydes
Formyl Protected Compounds
HOECHST A.G.
W.R. GRACE & COCONN.
U.S. Patent 5,017,690
The formyl groups are removed from the N atom of
an N-formyl aspartame compound by heating at
70-75OC using a catalyst consisting of 5% Pt on C or
Pt chloride, with P present at 0.1-5 wt.% of the
aspartame compound, and in the presence of a promoting amount of aniline or methylene dianiline. The
method is used to deblock N-formyl protected amino
acids, peptides and polypeptides, and minimises formation of the diketopiperazine by-product.
Aldehydes are produced by reacting olefinically unsaturated compounds with CO and H, in a
homogeneous phase at 20-150OC and 0.1-20 Mpa in
the presence of a catalyst system containing Rh and
an ammonium salt of a sulphonated phosphite
triester. The catalyst system is especially useful in
hydroformylation of 4-20C olefins with non-terminal
unsaturation. Use of the organic P compound
prevents side reactions and the catalyst retains its
activity for very long periods.
Ruthenium Catalyst for Lactone
Preparation
FUEL CELLS
MITSUBISHI KASEI CORP.
Platinum-Iridium-Iron
Catalyst
Phosphoric Acid Fuel Cell Cathode
Japanese Appls. 3174,377 and 3183,974
Lactones are prepared by liquid phase hydrogenation
of dicarboxylic acids, dicarboxylic anhydrides andlor
dicarboxylic acid esters at Ru 5O-25O0C, under
0.1-100 kglcmz H , , and in the presence of a catalyst.
The yield and selectivity to lactones can be improved
markedly if the concentration of diols in the reaction
zone is controlled below 5 wt.%, or catalyst deterioration can be prevented if the concentration of dicarboxylic anhydrides is kept below 3 wt.%.
Ruthenium Catalyst for Selective
Production of Cycloolefms
Cycloolefinsare produced by partial hydrogenation of
monocyclic aromatic hydrocarbons in the presence of
a Ru catalyst, and by dispersing at least one dissolved
Zn oxide or hydroxide into the reaction system, with
water or alcohol as solvent. Cycloolefms are produced
with a high invert ratio and high selectivity.
ASAHl CHEMICAL IND. K.K.
for
INT. FUEL CELLS CORP.
U.S. Patent 5,013,618
A catalyst for 0, reduction in a phosphoric acid fuel
cell consists of a ternary noble metal alloy of Pt, Ir
and one of Ti, Mn,Ni, CQ, V, Cr or Fe, preferably
Cr or Fe. The catalyst is used on the cathode of a
phosphoric acid fuel cell, and has high activity and
stability, showing 50% less surface area loss in use
than a conventional PtCrCo catalyst.
Platinum-Iron
Alloy
Catalyst
for
Phosphoric Acid Fuel Cell Electrode
A Pt alloy catalyst is produced by depositing a Pt
alloy on a C support, then depositing Fe, and heating
in a controlled manner to 900-1000°C for 5-30
seconds to form a Pt-Fe alloy. The Pt alloy catalyst
has smaller crystallite size, and is used for a
phosphoric acid fuel cell electrode, giving a higher
cell performance at a current >200 mAlcm’ .
FUJI ELECTRIC MFG. K.K.
66
ELECTRICAL AND ELECTRONIC Palladium-Silver Conductor Paste
NIPPON CHEMICON K.K.
ENGINEERING
Magneto-Optical Recording
Containing Palladium
Element
A magneto-optic recording element has a substrate
and a recording layer containing a Tb, Fe and Co
alloy with added Zr and Pd. The recording layer has
improved corrosion and oxidation resistance without
affecting the magneto-optic recording properties.
EASTMAN KODAK CO.
Multilayer Platinum-Cobalt Films for
Magneto-Optical Recording
world Appl. 91/8,578A
Multilayer fdms no more than 75 nm thick consist of
alternating layers of Pt and Co deposited by a sputtering process using Kr or Xe or a mixture as the sputter
gas. All of the Co layers are a maximum of 1.2 nm
thick, and all of the Pt layers are a maximum of 2.4
nm thick, with a Pt:Co layer thickness ratio of 1-5.
The deposited films are used in magneto-optical
recording, and have a higher coercivity than fdms
sputtered in Ar.
DU FQNT DE NEMOURS CO.
High Coercivity Thin Film Magnetic
Recording Medium
U.S. Patent 5,004,652
A thin fdm magnetic recording medium has ,a
substrate, a sputtered Cr underlayer 300-3000 A
thick, and a sputtered magnetic layer 200-1000 A
thick consisting of an alloy of 8-20 at.% Pt, 70-80
at.% Co, 10-20 at.% Cr and 2-10 at.% Ta. The
magnetic recording medium has high coercivity,
resolution, amplitude and loop squareness values,
low bit shift, and is used for high recording density
read/write memory devices in computers.
HMT TECHN. COW.
Silver-Palladium Alloy Sheath for High
Temperature Superconductor
U.S. Patent 5,017,553
A metallic sheath for a superconductingcore is a layer
of Ag-Pd alloy having 10-50 wt.% Pd and containing
5-45 wt.% of interdispersed particles of W, Mo or Ni
or mixtures of these of 0.05-75 pm diameter; and
may have an inner or outer wall of Ag. A superconductor having a high strength, thermally matched,
high-temperature sheath is provided, which is useful
for fine wires or magnet windings.
WESTINGHOUSE ELEC. COW.
Ruthenium-Containing Screen Printing
Ink for Forming Resistors
MATSUSHITA ELEC. IND. K.K.
A screen printing ink consists of a Ru compound optionally mixed with another metal compound, carboxylic acids of terpenoids or their esters as viscosity
increasing agent, and an additive consisting of an
aliphatic carboxylic acid. The ink is used to form a
resistor for a thermosensitive printer head, electrode
and resistors. A good quality thin resistor film can be
prepared by screen printing and calcination.
A conductor paste consists of 5-30 parts wt. Pd
powder, 70-95 parts wt. Ag powder, and 0.5-10
parts wt. glass frit to which 0.1-10 parts wt. metal
iodide was added. The paste is used for forming conductor patterns and electrodeson Al nitride compacts.
Longer Life Soft Magnetic Thin Film
MATSUSHITA ELEC. IND. K.K. Japanese
Appl. 3154,705
A soft magnetic thin fdm has a laminated structure
consisting of 2-100 nm Fe thin fdms and 1-50 nm
fdms of at least one kind of metal or at least 2 kinds
of alloy of Pt, Rh, Ir, Ru,Au, Ag, Re or Ta. The soft
magnetic thin film can be used at least as part of the
core of a magnetic head, which has longer life and is
suitable for high density writehead information.
Vertically Magnetic Recording Medium
Japanese Appl. 3/58,3 16
A magnetic recording medium consists of a nonmagnetic substrate with a Co-Pt-B-0 magnetic layer
composed of SO-lOOhi diameter acicular crystals
having a face centred cubic lattice. The magnetic
crystal form, size and orientation are controlled to
give greatly enhanced coercivity in the vertical direction. In an example a magnetic recording medium
had a polyamide fdm substrate with a Pt underlayer
and a Co-Pt-B-0 magnetic layer.
SONY C O W .
Plasma Deposited Magnetic Recording
Medium
MATSUSHITA ELEC. IND. K.K. Japanese
Appl. 3178,114
A magnetic recording medium has a substrate with a
7-type Fe oxide magnetic layer including one of Pd,
Rh, Os, Ru, Co, CU, Ti, V or Nb, where the
magnetic layer is deposited in a plasma state
generated by electron cyclotron resonance (ECR).
The magnetic properties and recording fidelity of the
medium are improved by utilising the activity of the
ECR plasma.
Manufacture of a Superconductor Wire
with a Platinum Core
A superconductor wire consisting of a superficial oxide superconductor film formed on a continuous fine
wire of Pt or ceramic is manufactured by shifting the
fine wire continuously, while sputtering the thin
superconductor fdm onto it, and then heating in an
0, atmosphere to effect crystal growth of the fdrn.
NICHIDEN ANERUBA K.K.
Magnetic Alloy Memory with Thermal
Hysteresis of Magnetisation
Gennan Appl. 4,030,476
TOSHIBA K.K.
A magnetic alloy has as the main phase an isomolar
compound phase of formula Pt(Fel,Mn.JSn,
in
which x=O-1 exclusive. The magnetic alloy exhibits
significant thermal hysteresis of magnetisation, and
allows production of magnetic memories of simple
structure and operation for recording systems.
67
Thermoseneitive Circuit Breakers for
Automatic Fire Alarms
Low Toxicity Platinum Anti-Tumour
Agents
A thermosensitive circuit breaker has an insulating
substrate with sprung contact plates, and a Pt, Pd or
Mo dispersing plate on these plates. The dispersion
material acts as a catalyst for oxidising processes on
its surface. The circuit breaker has reduced inertia,
and is used in electrical engineering, for example in
automatic fire signalling.
New oxalate-diaminocyclooctane Pt(I1) complexes
and stereoisomers are prepared from dinitrato
(diaminocyclooctane) Pt(I1) and oxalic acid. The
complexes are anti-tumour agents with low toxicity,
used at a dosage of 5-600 mglday.
TEMPERATURE
MEASUREMENT
U.S. Patent 5,019,337
An alloy composition for dental or medical use consists of 35-60 wt.% Zr, 1-60 wt.% Pd and 1-60
wt.% Ru, while another composition has Pt, Rh, Ir,
Os, Ru, Al, Si or Co as the second element. The alloy
has a cubic CsCl or B, type structure which can
undergo stress-induced transformations at body
temperature. The alloy is used for casting crowns,
bridges, dental or medical implants or prosthetic
devices, and has enhanced ductility, adequate
strength, and biocompatibility.
M. A. AKIMOV
Zirconium-Palladium-Ruthenium Alloy
for Dental or Medical Use
AMER. DENTAL ASSOC. H.
Thermocouple-Type Temperature
Sensor
ASAHI GLASS K.K.
The Pt-Rh thermocouple of a thermoelectric
temperature sensor has an insulating tube inserted in
a metal-boride ceramic protective tube to prevent
deterioration of the thermocouple by reducing gas at
high temperatures. The tip of the insulating tube is
covered with a cap made of a Pt group metal. The
thermocouple has extended life, and is used to
measure the temperature of hot metal and molten
steel continuously, for extended periods of time.
Melt-Adhered Platinum-Rhodium
Thermocouples for High Temperature
Measurements
KOBE STEEL K.K
TSUMURA & CO.
Pt-Rhthermocouples are melt-adhered on the surface
of a Ti(alloy) material test piece by incorporating a
thin Ta plate between the thermocouple and test
specimen. Temperature measurements of Ti(a1loy)
materials can then be made at 130OOC or above which
is requisite for recognising thermal properties of these
materials for use in the space and aero industries.
MEDICAL USES
New Platinum Anti-Tumour Compounds
European Appl. 423,7076
New Pt(1V) complexes containing axial hydroxy or
mono- or dicarboxylate groups are used as antitumour compounds, and have lower kidney and bone
marrow toxicity than known Pt-containing antitumour compounds. Certain of the complexes are
water soluble, while others are lipo-soluble and can
therefore be used in liposomes, in oil-water emulsions, injected as oil solutions, or used topically.
BRISTOL-MYERS SQUIB.
Low Toxicity Platinum Anti-Tumour
Complexes
New y-butyrolactone Pt complexes have a cis, trans-],
or trans-d 1,2diaminocyclohexane ring, and have
high anti-tumour activity and low toxicity. In an example, one of the complexes was used to treat L1210
leukaemia in mice.
TORAY IND. INC.
Platinum Complex for Tumour Inhibition
or Radio-Sensitisation
BRIT. COLUMBIA CANCE.
U.S. Patent 5,026,694
A composition for tumour inhibition or radiosensitisation consists of a square planar Pt(I1) complex of formula PtX,(NR,H)L and an excipient;
where n is 1 or 2, X is an anion, R is H or alkyl or
NRR is piperidino or morpholino, and L is a radiosensitising ligand. The complex is used at 0.1-5
mgkg and can bind DNA, sensitise hypoxic cells to
radiation and is directly toxic to tumours.
Laser Beam Reflectors Containing
Ruthenium
A laser beam reflector is prepared by laser beam irTOSHIBA K.K.
radiating a sintering of 5-60 wt.% Ru, 0.5-3 wt.%
Zr andlor Ti, 0.001-0.1 wt.% C and balance Mo in
vacuum or under an inert gas atmosphere, to densify
the mixture. The method provides reflectors free
from surface degradation due to oxidation or corrosion, for use in laser knives or other surgery devices,
and used in place of conventional Cu reflectors.
New Platinum Complexes with AntiTumour or Anti-Microbial Activity
S. HANESSIAN
Canadian Patent 1,282,058
New Pt complexes are derived from vicinal diamines
substituted by carboxy, hydroxy or alkoxy groups,
for example diamino sugars, and are useful as antimicrobial or anti-tumour agents. Compared with
known Pt complexes they have better water solubility, more rapid excretion, improved transport in the
body, improved biocompatibility, and a more selective interaction with DNA receptors.
The New Patents abstracts have been prepared from
material published by Derwent Publications Limited.
68

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