Fractionation of Eucalyptus grandis chips by dilute acid-catalysed steam explosion

• Published in: Bioresource technology 2003, Vol.86 (2), p.105-115
• Main Authors: Emmel, Alexandre, Mathias, Alvaro L, Wypych, Fernando, Ramos, Luiz P
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Alkali-soluble lignin; Applied sciences; Biological and medical sciences; Catalysis; cellulose; Cellulose - isolation & purification; Dilute sulfuric acid; Enzymatic hydrolysis; Eucalyptus; Eucalyptus grandis; Exact sciences and technology; Factorial design; fractionation; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; hemicellulose; Hydrolysis, pyrolysis and by-products; lignin; Lignin - isolation & purification; Polymer industry, paints, wood; Steam; Steam explosion; sulfuric acid; Temperature; Thermoanalysis; ultraviolet-visible spectroscopy; Use of agricultural and forest wastes. Biomass use, bioconversion; Volatilization; Wood; wood chips; Wood. Paper. Non wovens; xylose
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/S0960-8524(02)00165-7

Steam explosion of Eucalyptus grandis has been carried out under various pretreatment conditions (200–210 °C, 2–5 min) after impregnation of the wood chips with 0.087 and 0.175% (w/w) H 2SO 4. 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) H 2SO 4-impregnated chips at 210 °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 °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 l 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.