(758d) Mixed Catalysts for the Conversion of Hemicellulose and Cellulose

Direct catalytic conversion of lignocellulosic biomass to biofuels could improve the carbon efficiency of biofuel production.  We report the use of maleic acid, a dicarboxylic acid, mixed with Lewis acids such as lithium chloride and aluminum chloride to catalyze the fractionation of biomass into an aqueous solution of pentose (primarily xylose) and insoluble cellulose and lignin, followed by the conversion of the xylose to furfural under higher temperature and pressure.  This method achieved 80-90% yield of xylose through hydrolysis of the hemicellulose from various biomass sources (switchgrass, poplar, pine) and achieved 54-61% yield of furfural (based on original biomass).  The residual solids contain cellulose that has increased reactivity for hydrolysis by cellulolytic enzymes.  SEM imaging suggests that maleic acid pretreatment is effective in fibrillating biomass, thus significantly increasing the accessible surface area of cellulose for enzymatic or catalytic conversion. This hybrid approach combines pretreatment for biochemical conversion with thermochemcial processing. We present a kinetic analysis of biomass hydrolysis and formation of aldehydes and discuss application of results from pure sugars to results from biomass conversion.