title: Fractionation of Eucalyptus grandis chips by dilute acid-catalysed steam explosion.
abstract: Steam explosion of Eucalyptus grandis has been carried out under various pretreatment conditions (200-210 degrees C, 2-5 min) after impregnation of the wood chips with 0.087 and 0.175% (w/w) H2SO4. This study, arranged as a 2(3) factorial design, indicated that pretreatment temperature is the most critical variable affecting the yield of steam-treated fractions. Pretreatment of 0.175% (w/w) H2SO4-impregnated chips at 210 degrees C for 2 min was the best condition for hemicellulose recovery (mostly as xylose) in the water soluble fraction, reaching almost 70% of the corresponding xylose theoretical yield. By contrast, lower pretreatment temperatures of 200 degrees C were enough to yield steam-treated substrates from which a 90% cellulose conversion was obtained in 48 h, using low enzyme loadings of a Celluclast 1.5 1 plus Novozym 188 mixture (Novo Nordisk). Release of water-soluble chromophores was monitored by UV spectroscopy and their concentration increased with pretreatment severity. The yield of alkali-soluble lignin increased at higher levels of acid impregnation and pretreatment temperatures. Thermoanalysis of these lignin fractions indicated a pattern of lignin fragmentation towards greater pretreatment severities but lignin condensation prevailed at the most drastic pretreatment conditions.
authors.affiliation: Research Center in Applied Chemistry, Department of Chemistry, Federal University of Paraná, PO Box 19.081, Curitiba, Paraná 81.531-990, Brazil.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Emmel
authors.forename: Alvaro L
authors.initials: AL
authors.lastname: Mathias
authors.forename: Fernando
authors.initials: F
authors.lastname: Wypych
authors.forename: Luiz P
authors.initials: LP
authors.lastname: Ramos
mesh_terms: D002384:Catalysis; D002482:Cellulose / Q000302:isolation & purification*; D005052:Eucalyptus; D008031:Lignin / Q000302:isolation & purification*; D013227:Steam; D013696:Temperature; D014835:Volatilization
chemical_list: D013227:Steam; C036909:lignocellulose; D002482:Cellulose; D008031:Lignin