Enabling the Development of Furan-based Biorefineries

Abstract

Dilute aqueous solutions of furfural were produced in high yield from biomass hydrolysates using an acid-catalyzed batch reactive distillation (BRD) process that separated the vapor phase from the aqueous reactant medium. Hot water hydrolysates from hybrid poplar, miscanthus, switchgrass and corn stover were dehydrated using sulfuric acid in the BRD configuration to produce furfural in excess of 85% of the theoretical (molar) yield based on the total pentose content. Using xylose as the model compound, and temperature and acid concentration as the variables, the process conditions were optimized by the construction of a three-level statistical model. Hot water hydrolysis of biomass provided with a cellulose- rich solid fraction which has potential for conversion into pulp or cellulosic ethanol, while the liquid fraction, rich in hemicellulose sugars, was converted into furfural. Furfural was converted into furfuryl alcohol with yield in excess of 50% using S cerevisiae (Baker's yeast), and the organism was also capable of converting the furfural that was produced in the BRD reaction. Fractionating the biomass allows for exploration of the concept of the integrated biorefinery where the hemicellulose sugars are not underutilized or encountered as potential inhibitors during microbial conversions of the solid stream, but are converted into furfural, a valuable chemical precursor. Further conversion into furfuryl alcohol using the microbial method offers an environmentally-friendlier alternative to the conventional copper chromite-catalyzed hydrogenation reaction that is used in industry. In this manner, the basis for a biorefinery based on the production of furan-based compounds has been explored.