388355 High Yield Production of Furfural from Hemicellulose Hydrolyzates Using a Facile Hybrid Enzyme-Chemo-Catalytic Technology
We propose an integrated process with low energy input for high-yield production of furfural from hemicellulose hydrolyzates. Due to the prevalent recognition that furfural is a versatile platform chemical for fuels and chemicals, there is a critical need for economically viable technologies for its production from the hemicellulose portion of biomass. Attempts to produce furfural in aqueous media (either from untreated biomass or from hydrolyzates) proved energy-intensive. Although hemicellulose hydrolyzates provide xylose, it is now broadly recognized that the best yields can be obtained by dehydration of the corresponding keto-sugar, xylulose, and by executing this reaction in non-aqueous reaction media (e.g. DMSO, gamma-valerolactone and ionic liquids (ILs)). The challenge then, for cost-effective and high-yield furfural production, is to devise a cohesive pathway to efficiently transfer xylose from biomass hydrolyzate into the non-aqueous reaction medium; produce furfural in high yield; and isolate it for downstream processing, all with low energy input and recycling of process streams.
Our technology addresses this challenge, and we propose a hybrid enzyme- and chemo-catalytic process that first converts xylose to more reactive xylulose and subsequently integrates with a downstream catalytic dehydration step that achieves high yields of furfural. The conversion of xylose to xylulose and its near-complete recovery is accomplished through a novel enzyme-based simultaneous-isomerization-and-reactive-extraction (SIRE) process. The recovered xylulose is then dehydrated to furfural in an acidic ionic liquid (IL) reaction medium and simultaneously extracted into a low-boiling tetrahydrofuran (THF) solvent to prevent side reactions, increase process yields and facilitate easy product recovery. Reactions of ketoses to furans can be conducted at milder operating conditions in IL-media compared to aqueous media (IL rxn T ~ 50 °C; aqueous rxn T > 150 °C) while achieving high product yields. Finally, a key feature of this technology is that it permits recycling and reuse of the catalysts, solvents and reaction media.