Liquefaction of humins from C6-sugar conversions using heterogeneous catalysts

Biomass is considered an important resource for the production of carbon based chemicals to be used for important daily life products (plastics, paints, etc.). Platform chemicals such as furfural, 5-hydroxymethylfurfural (HMF) and levulinic acid (LA) have been identified as interesting biomass derived chemicals with high application potential. However, conventional processes for these chemicals, for instance the acid-catalysed dehydration of a biomass source in water, are associated with the formation of large amounts of carbonaceous, insoluble humin byproducts formed by polymerisation reactions of substrates, intermediates and products. The formation of these humins reduces the carbon efficiencies of the processes. As such, there is a strong incentive to either reduce the amount of humins formed or to develop efficient valorisation technologies for these solid materials. In this respect, it is of high importance to have insight in the molecular structure of humins and their formation mechanism. In this research project, catalytic routes for the conversion of humins derived from glucose conversions to bulk chemicals were explored with an emphasis on catalytic liquefaction in the presence of hydrogen or a hydrogen donor. The findings reveal that the recalcitrant structure of humins may be (partly) depolymerised to a liquid biofuel with the potential to be a source for interesting bulk chemicals after fractionation. This opens new venues for the development of added value outlets for humins beyond the use as a solid fuel. As such, this will have a positive effect on the techno-economic viability of biorefinery schemes involving the conversion of C6 sugars to biobased chemicals like LA and HMF.