Acid in ionic liquid: An efficient system for hydrolysis of lignocellulose
2008
Li, Changzhi | Wang, Qian | Zhao, Zongbao K.
Acid in ionic liquid was demonstrated as an efficient system for hydrolysis of lignocellulosic materials with improved total reducing sugars (TRS) yield under mild conditions. TRS yields were up to 66%, 74%, 81% and 68% for hydrolysis of corn stalk, rice straw, pine wood and bagasse, respectively, in C₄mimCl in the presence of 7 wt% hydrogen chloride at 100 °C under atmospheric pressure within 60 min. Different combinations between ionic liquids, such as C₆mimCl, C₄mimBr, AmimCl, C₄mimHSO₄, and SbmimHSO₄, and acids, including sulfuric acid, nitric acid, phosphoric acid, as well as maleic acid, afforded similar results albeit longer reaction time was generally required comparing with the combination of C₄mimCl and hydrochloric acid. FT-IR spectra and elemental analysis of the recovered residues indicated that modification of lignin occurred during sulfuric acid catalyzed hydrolysis. In addition, kinetic modeling based on experimental data suggested that the hydrolysis likely followed a consecutive first-order reaction sequence, where k₁ and k₂, the rate constants for TRS formation and TRS degradation, were determined as 0.068 min⁻¹ and 0.007 min⁻¹, respectively. This novel system may be valuable to facilitate cost-efficient conversion of biomass into biofuels and biobased products.
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