Experimental and Theoretical Investigation of the Role of Bismuth in Promoting the Selective Oxidation of Glycerol over Supported Pt–Bi Catalyst under Mild Conditions

Catalytic biomass conversion under moderate reaction conditions is of great significance as a means of developing synthesis routes to replace petroleum products. The present study demonstrates that a high glycerol conversion (40.9%) and significant dihydroxyacetone (DHA) selectivity (65.1%) can be obtained at 303 K under 1 atm air in a base-free solution during the oxidation of glycerol over a bimetallic catalyst supported on SBA-15 (Pt–Bi/SBA-15). CO chemisorption data and transmission electron microscopy characterization show that Bi was deposited on both the step and terrace sites of the Pt surface and consequently modified the catalytic activity. Kinetic studies revealed that the addition of Bi significantly altered the reaction route such that DHA was produced rather than glyceraldehyde (GLD) during the initial stage of the process. 13C NMR analysis found that glycerol tended to chelate with Bi atoms via hydroxyl groups (−OH) to modify the stereochemistry of the reactants. Density functional theory calculation confirmed that each of the three hydroxyl groups of glycerol were captured by the bismuth species, and the middle −OH simultaneously interacted with the platinum surface resulting in selective oxidation of glycerol to DHA. Bismuth ions (Bi3+) were also determined to promote the isomerization of GLD to DHA, which improved the DHA selectivity. These experimental and theoretical results together explain the high activity of the Pt–Bi/SBA-15 under moderate conditions.