Conversion of biomass sugars to platform chemicals by homogeneous acid catalyst in organic water mixtures

Abstract

Lignocellulosic biomass could serve as an alternative to petroleum for the production of platform chemicals that can be upgraded to bio-based plastics, chemicals, and fuels. The polysaccharides present in the cellular structure of biomass can be hydrolyzed into common sugars, which can be further reacted into important chemical intermediates such as furfural, 5-hydroxymethylfurfural, and levulinic acid. However, current commercial processes typically result in low yields. This work aimed to study the conversion of model sugars (glucose, xylose, and arabinose) into platform chemicals using a homogeneous acid catalyst in a variety of organic-water mixtures, and compare those findings to reactions carried out using biomass under the same conditions. Reactions were performed in 50-50 solvent-water mixtures using sulfolane, tetrahydrofuran (THF), or gamma-butyrolactone (GBL) as the solvent and using a sulfuric acid catalyst. Intermediate wheatgrass was used in the biomass reactions and its composition was determined using standard NREL methods. Similar trends were observed in both pure sugar and biomass reactions in which the solvent choice had little effect on maximum yield of furfural, HMF, or levulinic acid. However, the THF/water solvent achieved maximum yields at lower severities than the other solvent mixtures indicating that a combination of less time, lower temperature, and/or less acid could be used in the THF reactions compared to the others. Compared to previously published research that found the solvent polarity correlated with product yields of furfural in reactions with no acid present, the effects of solvent properties may be minimized by the presence of the acid catalyst. Higher yields were achieved in biomass reactions than in pure sugar reactions, possibly due to unaccounted for reaction pathways or lowering of degradation reaction rates due to a lower initial reactant weight percent.