Carbon-supported WOx–Ru-based catalysts for the selective hydrogenolysis of glycerol to 1,2-propanediol

New C-supported bimetallic Ru-WOx catalysts, prepared by co-impregnation of RuCl3 and Na2WO4, proved highly efficient for the liquid-phase hydrogenolysis of aqueous glycerol into 1,2-propanediol (1,2-PDO). The tuning of the catalyst composition and major reaction parameters, specifically operating at 150 degrees C, 5 bar H-2, and Ru : W = 4 : 1 mol/mol, allowed conversion of glycerol and 1,2-PDO selectivity of 73 >= 99% and 88-98%, respectively, with a carbon loss of x/C offered a steady performance for up to 7 subsequent recycles during which leaching of Ru was negligible, while loss of W decreased from an initial 5 wt% (1st run) to 0.1 wt% after 5 runs. The catalyst characterization, in particular EDX analysis and high-resolution TEM images, confirmed a uniform dispersion of Ru and W on the C surface with the presence of small Ru nanoparticles (below 2 nm) and randomly aggregated dots which could be ascribed to WOx clusters of size below 100 nm. Based on both the Bronsted and the Lewis acidity of WOx species, a reaction mechanism was proposed through an initial dehydration of glycerol followed by a Ru-catalysed hydrogenation process.