Aqueous-Phase Glycerol Catalysis and Kinetics with in Situ Hydrogen Formation

Hydrodeoxygenation (HDO) is a widely used technology to convert biomass-based feedstock into value-added fuels and chemical products that usually require highpressure hydrogen (H-2) to remove excess oxygen in the biomass feedstock. To make this process safer and more sustainable, we investigated glycerol conversion under an inert atmosphere in aqueous media using multimetallic catalysts (comprised of Ru, Re, and Pt) supported on activated carbon. Here we report a trimetallic Ru-Re-Pt catalyst that converts glycerol to value-added products such as 1,2-propanediol (1,2-PDO) and linear alcohols with higher selectivity with in situ formed H-2 (without using external H-2). Thus, the proposed system eliminates use of expensive hydrogen while giving high selectivity unlike the hydrogenation with external hydrogen. The results of catalyst screening showed high glycerol conversion (83%) with liquid-phase product selectivity of 72% and 1,2-PDO selectivity of 43% at 493 K and autogenous pressure with optimized Ru-Re-Pt/C trimetallic catalyst in the presence of a solid base promoter (MgO). To infer the mechanism of hydrogenation with in situ-formed H-2, temporal concentration-time profiles at various operating conditions were elucidated using a kinetic model. Such a model provides valuable mechanistic insights and guidance for developing optimal catalyst formulations for maximizing hydrodeoxygenation products with in situ-formed hydrogen.