Performance, structure and mechanism of Pd–Ag alloy catalyst for selective oxidation of glycerol to dihydroxyacetone

The mechanism of the oxidation of glycerol to dihydroxyacetone over Pd–Ag catalysts was discussed. Characterization results suggest that the metal composition of the surface of the crystalline Pd–Ag alloy particles is almost the same as the bulk composition. The synergetic effects of Pd and Ag appear on the oxidation of the secondary OH group of vic-diols. The reaction order with respect to glycerol concentration over Pd–Ag/C was zero, suggesting the strong interaction between glycerol and the catalyst surface. The reaction order with respect to O2 pressure was 0.4, suggesting that the rate-determining step is the reaction involving oxygen species. These reaction trends and characterization results support the mechanism where the terminal OH group of glycerol is adsorbed on the Ag site and the neighboring secondary OH group (CH–OH) is attacked by the oxygen species dissociatively adsorbed on the Pd site.

Over Pd–Ag alloy catalyst glycerol adsorbed on Ag reacts with adsorbed oxygen on Pd to produce dihydroxyacetone.Figure optionsDownload high-quality image (126 K)Download as PowerPoint slideHighlights
► Pd–Ag alloy catalyst selectively oxidized the secondary OH group of vicinal diols.
► The composition of the surface of the Pd–Ag particles was almost same as the bulk.
► The terminal OH group of glycerol is adsorbed on Ag.
► The 2-position of the adsorbed glycerol reacts with adsorbed oxygen over Pd.