Ethanol-water fractionation of sugar cane bagasse catalyzed with acids

Abstract

The conditions for maximizing bagasse ethanol-water fractionation (in cellulose, hemicelluloses and lignin) were established by the evaluation of different variables (time, temperature, catalyst). To this end, the organic compounds of the fibrous material and liquors were quantified. Acetic (2 g/L) and sulfuric (0.5, 1.0 and 2.0 g/L) acids were used as catalysts. An alkaline extraction was applied as a pre-treatment, using 3.6 g/L NaOH, at 100°C, for 1 h. The effects of different conditions of the organosolv treatment on the kinetics, composition of the fibrous material and residual liquor, upon the fractionation of sugar cane bagasse used in this work, were investigated. The kinetic parameters were determined for delignification under six different conditions. The organic compounds of the fibrous material were quantified and lignin (by UV-visible spectroscopy) and carbohydrates, organic acids, furfural and HMF (by HPLC chromatography) were evaluated in residual liquors. The incorporation of sulfuric acid at 160°C produced delignification degrees similar to those obtained by the addition of acetic acid at 180°C, or in the fractionation without catalyst (85-86%). The delignification values showed that fractionations could be stopped at 90 or 120 min, since, after 90 min, the delignification percentage decreases by only about 1%. The incorporation of sulfuric acid extracted a large amount of xylose and produced further degradation of cellulose. Fractionations with acetic acid did not differ largely from the auto-catalyzed ones.