KAKSI SANAA TIEDEKUNNAN VÄRILLÄ JA LOPUT
Transcription
KAKSI SANAA TIEDEKUNNAN VÄRILLÄ JA LOPUT
HELSINGIN YLIOPISTO HELSINGFORS UNIVERSITET UNIVERSITY OF HELSINKI MATEMAATTIS MATEMAATTIS-LUONNONTIETEELLINEN TIEDEKUNTA MATEMATISK MATEMATISK-NATURVETESKAPLIGA FAKULTETEN FACULTY OF SCIENCE Maija Hakola, Marianna Kemell, Petro Lahtinen, Markku Leskelä, Timo Repo, Tiina Riekkola, Pauli Wrigstedt LIBERATION OF CELLULOSE FROM THE LIGNIN CAGE INTRODUCTION Catalytic and alkaline oxidations are novel and highly efficient methods for the isolation of cellulose and lignin from lignocellulosic biomasses. These methods loosen the wood matrix and liberate cellulose with a high yield. Cellulose from these pretreatment processes is more susceptible to enzymatic hydrolysis than that obtained with the current state of art pretreatment technique, steam explosion. University of Helsinki P.O.Box 55 FI-00014 University of Helsinki, Finland Anne Kallionen, Matti Siika-aho, Niklas von Weymarn VTT – Technical Research Centre of Finland P.O.Box 1000 FI-02044 VTT, Finland During the oxidative pretreatment the wood chips loose their macroscopic structure. The SEM images from the isolated cellulose fraction show that chemical pulping and the catalytic treatment reveal cellulose fibers in a rather similar way (Figure 1). On the other hand, after steam explosion the wood matrix is still rather similar to non-treated spruce sample, although the macro structure of wood is affected. a b c d CATALYTIC AND ALKALINE OXIDATION Catalytic and alkaline oxidations are carried out in alkaline water solution (0.25 M Na2CO3) at elevated temperature and under oxygen pressure. In catalytic oxidation also copper(II)phenanthroline catalyst is applied which makes the use of lower reaction temperatures and shorter reaction times possible. These pretreatments are significantly effective methods to separate cellulose from lignocellulosic biomass. After separating the cellulose fraction from the reaction mixture, also lignin can be isolated for further processing e.g. by treating the filtrate with a strong acid. These methods can be considered as an environmentally benign concepts based on in situ catalysts and pressurized air or oxygen as the oxidant. Also various raw materials can be applied, e.g. bagasse, spruce, pine, eucalyptus and birch wood, leaves/needles and bark, and wheat straw. Figure 1. The SEM images of (a) non-treated spruce, (b) steam exploded spruce, (c) chemical spruce pulp and (d) the filtrated solid fraction from a catalytic pretreatment reaction. The authors thank Tekes – the Finnish Funding Agency for Technology and Innovation and the Academy of Finland for financial support. Part of the research leading to these results has also received funding from the European Community’s Seventh Framework Programme FP7/2007-2013 under grant agreement no CP-IP 228589-2 AFORE. Maija Hakola, Marianna Kemell, Petro Lahtinen, Markku Leskelä, Timo Repo, Tiina Riekkola, Pauli Wrigstedt LIBERATION OF CELLULOSE FROM THE LIGNIN CAGE University of Helsinki P.O.Box 55 FI-00014 University of Helsinki, Finland Anne Kallionen, Matti Siika-aho, Niklas von Weymarn VTT – Technical Research Centre of Finland P.O.Box 1000 FI-02044 VTT, Finland HYDROLYSIS EXPERIMENTS After 20 h catalytic oxidation at 120 °C approximately 50 % of the total mass is solubilized and the filtrated homogeneous solid material contains more than 76 % of the original total carbohydrates and 95 % of the original glucose. Accordingly, most of the mass loss originates from the dissolution of lignin and wood extractives and the dissolution of cellulose is minor (Figure 2). By contrast to catalytic oxidation, in steam explosion hemicelluloses are totally solubilized whereas lignin mostly remains in the solid fraction. The catalytic and alkaline oxidation methods produce easily hydrolyzable cellulose and the hydrolysis rate is notably high; a 95 % yield is achieved already after 24 hours with a rather low enzyme loading (Figure 3). After four hours catalytic pretreatment the matrix of spruce is loosened enough for the effective enzymatic hydrolysis and extended pretreatment time does not substantially improve the hydrolysability. No toxic compounds are formed and the enzymatic hydrolysis can be done in the pretreatment solution without filtering. Also due to the high hydrolysability of the catalytically pretreated material, the enzyme dosages can be decreased remarkably. Figure 3. Enzymatic hydrolysis of catalytically pretreated spruce and steam exploded spruce (SE spruce). CONCLUSIONS Catalytic and alkaline oxidations are highly selective methods to isolate cellulose from lignocellulosic materials. The obtained solid carbohydrate material contains 95 % of the original glucose and is well susceptible to enzymatic hydrolysis. The solubilized lignin can be also isolated and used as raw material for the production of various chemicals. REFERENCES Figure 2. Carbohydrate and lignin contents of untreated spruce, after catalytic pretreatment (Cat.Ox.) as a function of reaction time and after steam explosion (SE Spruce). 1. Hakola, M., Kallioinen, A., Kemell, M., Lahtinen, P., Lankinen, E., Leskelä, M., Repo, T., Riekkola, T., Siika-aho, M., Uusitalo, J., Vuorela, S., von Weymarn, N., (2010): Liberation of Cellulose from the Lignin Cage: A Catalytic Pretreatment Method for the Production of Cellulosic Ethanol. ChemSusChem, 3:10, p. 1142-1145. HELSINGIN YLIOPISTO HELSINGFORS UNIVERSITET UNIVERSITY OF HELSINKI MATEMAATTIS-LUONNONTIETEELLINEN TIEDEKUNTA MATEMATISK-NATURVETENSKAPLIGA FAKULTETEN FACULTY OF SCIENCE