High yield synthesis of hexitols and ethylene glycol through one-pot hydrolytic hydrogenation of cellulose

Catalytic valorization of biomass has gained a significant global attention in recent years. Cellulose is an interesting bio-renewable feedstock, which can be utilized to replace the fossil fuel derived chemicals to attain a sustainable bio-based economy. Our research shows a one-pot conversion of cellulose through hydrolytic hydrogenation using heteropolyacid (HPA)/zirconia and Ru/C catalyst. The developed catalytic system was found to be highly active towards selective production of hexitols and ethylene glycol. A significant improvement in the catalytic performance towards cellulose conversion was observed when the cellulose was pre-treated using ball-milling (900 rpm, 8 h), as the ball-milling significantly reduced the crystallinity index of cellulose, which decreased the recalcitrance of the cellulose structure. Almost complete conversion (100%) of cellulose was observed when the reaction was performed at 220 °C for 5 h giving hexitols and ethylene glycol yields of 26.2 and 40%, respectively. Based on a series of experiments, a possible reaction pathway was proposed which suggested heteropolyacid/zirconia catalyzed hydrolysis and retro-aldol condensation reactions, accompanying by hydrogenation with Ru/C. Interestingly, HPA immobilized on the composite catalyst shows enhanced stability and recyclability, demonstrating the utilization of a heterogeneous system for tandem conversions of biomass to renewable fuels and feedstocks.