INTEGRATED PROCESS FOR TOTAL UTILIZATION OF WOOD COMPONENTS BY STEAM-EXPLOSION PRETREATMENT

Citation
K. Shimizu et al., INTEGRATED PROCESS FOR TOTAL UTILIZATION OF WOOD COMPONENTS BY STEAM-EXPLOSION PRETREATMENT, Biomass & bioenergy, 14(3), 1998, pp. 195-203
Citations number
12
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Environmental Sciences",Forestry,"Energy & Fuels",Agriculture,"Biothechnology & Applied Migrobiology
Journal title
ISSN journal
0961-9534
Volume
14
Issue
3
Year of publication
1998
Pages
195 - 203
Database
ISI
SICI code
0961-9534(1998)14:3<195:IPFTUO>2.0.ZU;2-R
Abstract
Various species of hardwood chips were subjected to steam-explosion at 180-230 degrees C for 1-20 min. On steaming, hemicellulose was hydrol yzed partially becoming extractable with water, and lignin was degrade d by extensive cleavage of alpha- and beta-aryl ether linkages becomin g extractable with organic solvents and/or dilute alkali. The three ma in components, hemicellulose, lignin, and cellulose, of steam-exploded woods were fractionated by successive extraction with water and 90% d ioxane. The water extracts were decolored and purified by chromatograp hy on synthetic adsorbents and ion exchange resins, yielding a mixture of xylose and xylooligosaccharides (DP2 similar to 10). The xylooligo saccharides were hydrolyzed to xylose with hemicellulolytic enzymes im mobilized on ceramics having controlled pore size. The yield of xylose was 10-20% based on starting materials. The extracted amounts of lign in were different among wood species. Syringyl lignin became more solu ble than guaiacyl lignin on steaming. The lignin extracted was convert ed to thermoplastic materials, lignin-pitch, by phenolysis followed by heat treatment under vacuum. The lignin-pitch was well spun into fine filaments at a speed of 500-1000 m min(-1) in the temperature range 1 50-190 degrees C using the melt-spinning method. The filaments were ca rbonized on heating from room temperature up to 1000 degrees C in a st ream of nitrogen. The carbon fiber was obtained in a yield of more tha n 40% based on the starting materials. The physical properties of the lignin-based carbon fiber was equivalent to a commercial carbon fiber made from petroleum pitch. The residual fibers, mainly cellulose, were hydrolyzed with cellulase derived from Trichoderma viride. Their enzy matic susceptibility was different among wood species. It was higher i n species having lower contents of Klason lignin and guaiacyl lignin. Birch and Mollissima acasia were hydrolyzed more than 90%. Finally, th e economics of this process are discussed assuming a plant processing 100 t of hardwoods per day. (C) 1998 Elsevier Science Ltd. All rights reserved.