Valorization of Humin-Based Byproducts from Biomass Processing—A Route to Sustainable Hydrogen



The synthesis of biomass-based top value-added chemical platforms, for example, 5-hydroxymethyl furfural, furfural, or levulinic acid from the acid-catalyzed dehydration of sugars results in high yields of insoluble by-products, referred to as humin. Valorization of humin by steam reforming for H2 is discussed. Both thermal and catalytic steam gasification were investigated systematically. Humin undergoes drastic changes under thermal pre-treatment to the gasification temperature. Alkali-metal-based catalysts were screened for the reactions. Na2CO3 showed the highest activity and was selected for further study. The presence of Na2CO3 enhances the gasification rate drastically, and gas-product analysis shows that the selectivity to CO and CO2 is 75 % and 25 %, respectively, which is a H2/CO ratio of 2 (corresponding to 81.3 % H2 as compared to the thermodynamic equilibrium). A possible process for the complete, efficient conversion of humin is outlined.