Imidazole: Prospect Solvent for Lignocellulosic Biomass Fractionation and Delignification

TitleImidazole: Prospect Solvent for Lignocellulosic Biomass Fractionation and Delignification
Publication TypeJournal Article
Year of Publication2016
Authorsb Morais ARC a, Pinto JV c, Nunes D c, Roseiro LB a, Oliveira MC d, Fortunato E c, Bogel-Łukasik R a
JournalACS Sustainable Chemistry and Engineering
KeywordsBiomass, Biorefineries, Capillary electrophoresis, Cellulose, Cost effectiveness, Crystallinities, Delignification, Enzymatic hydrolysis, Fractionation, Green solvents, Hemicelluloses, Hydrolysis, Imidazole, Lignin, Lignocellulose, Molecular biology, Nuclear magnetic resonance spectroscopy, Pre-Treatment, Pretreatment, Recovery, Refiners, Solvents, Straw

The future widespread production of biomass-derived fuels, chemicals, and materials requires cost-effective processing of sustainable feedstock. The use of imidazole as a solvent for biomass creates a novel approach that helps to accomplish this idea in a green fashion. This work proposes imidazole as a novel solvent for wheat straw pretreatment, which allowed the production of cellulose- and hemicellulose-rich fractions and added-value products from depolymerization of lignin. Various temperatures (110, 140, and 170 °C) and processing times (1, 2, and 4 h) of pretreatment were investigated. Both cellulose and hemicellulose recovery were highly dependent on reaction temperature. The best result for the recovery of cellulose-rich material was obtained at 170 °C for 2 h, achieving 62.4% w·w-1, whereas native wheat straw is composed by only 38.8% w·w-1 cellulose. For the same conditions, optimal results were also obtained regarding the enzymatic hydrolysis yield (99.3% w·w-1 glucan to glucose yield) in cellulose-rich material. This result was possible to be obtained due to morphological and structural changes in cellulose-rich materials accompanied by extensive delignification (up to 92%). The presence of added-value phenolic compounds in recovered imidazole was analyzed by capillary electrophoresis and HPLC-MS. Vanillin and other lignin-based products were identified. Finally, the high purity of recovered imidazole was demonstrated by 1H and 13C NMR. © 2015 American Chemical Society.