Reductive Conversion of 5-Hydroxymethylfurfural in Aqueous Solutions by Furan Ring Opening and Rearrangement

Abstract

Biomass-derived 5-hydroxymethylfurfural (HMF) can be converted into chemicals that are useful for polymers, fine chemicals, and fuels. The upgrading of HMF by reductive conversion using supported metal catalysts has been intensively studied. From a practical viewpoint, conversion in water or in an aqueous organic solution is useful because HMF is expected to be supplied as an aqueous solution via the hydrolysis of cellulose. In the reductive conversion of HMF in water, acid catalysis due to water can cause hydrolytic furan ring opening or rearrangement. For instance, diketones can be generated by the hydrolytic ring opening of HMF, and cyclopentanones can be generated by a hydrogenative ring-rearrangement reaction. On the other hand, when the furan ring is not opened or rearranged, furfuryl alcohols, tetrahydrofurfuryl alcohols, and polyols are produced. The product selectivity of the reductive conversion in water is determined by the hydrogenation activity and acid–base properties of the catalytic system. In this chapter, the effect of catalyst functions on product selectivity in the reductive conversion of furfurals in aqueous solutions using heterogeneous catalysts is shown along with some studies on homogeneous catalysts.