Promoting the Effect of Au on the Selective Hydrogenolysis of Glycerol to 1,3-Propanediol over the Pt/WOx/Al2O3 Catalyst

The selective hydrogenolysis of glycerol to 1,3-propanediol (1,3-PDO) is an important yet challenging reaction because it requires the selective cleavage of the sterically hindered secondary C–O bond of glycerol. In this work, we have developed a new catalyst, 0.1Au-2Pt/7.5W/Al, which affords both high glycerol conversion (77.5%) and 1,3-PDO selectivity (54.8%), which are significantly higher than the Au-free counterpart. HAADF-STEM reveals that the structure of 0.1Au-2Pt/7.5W/Al is characterized with ∼2 nm Pt NPs decorated with Au-WOx at the periphery, where the Au additive exists most likely as single atoms. Chemisorption and XPS show that the electron transfer from W to Au can help to weaken the strong metal support interaction (SMSI) between Pt and WOx, and thus greatly enlarges the exposed Pt surface and increases the H-spillover capacity. The 2-butanol dehydration in H2 reveals that the H-spillover capacity is proportional to the number of Brönsted acid sites, which, in conjunction with the only water desorption in H2-TPD results, strongly suggests that the active sites for breaking the secondary C–O bond of glycerol should be Brönsted acid sites generated by the H-spillover at the interface between Pt and WOx, and the modification by the Au additive increases the number of interfacial sites, and thus enhances the 1,3-PDO yield.