Selective liquid-phase oxidation of glycerol over Au–Pd/C bimetallic catalysts prepared by electroless deposition

•Series of bimetallic Au–Pd/C catalysts were prepared by electroless deposition.•Glycerol was oxidized on Pd, Au, and Au–Pd catalyst.•Bimetallic catalysts showed increased activity compared to either monometallic catalyst.•Rate enhancement consistent with formation of bifunctional Au–Pd bimetallic sites.

Liquid phase oxidation of glycerol under basic conditions was examined for a series of Au–Pd/C bimetallic catalysts prepared by electroless deposition. Enhanced activity was observed for bimetallic compositions with θAu > 0.30, with a maximum in activity at θAu = 0.50 having a turnover frequency ∼20 times larger than for Pd and ∼4 times larger than for gold. A volcano shaped curve suggests the formation of bimetallic sites composed of Au–Pd in close contact, with the maximum at θAu = 0.50 indicating the largest concentration of bimetallic sites at that coverage. Further increase in the coverage of Au on Pd lead to a catalytic surface approaching that of monometallic Au with lower TOF values. Selectivity to glyceric acid was 80% (±2%) for Pd and Au–Pd bimetallic catalysts below θAu < 0.90. Selectivity to glycerate remained constant as long as there are sufficient Pd sites to rapidly decompose the non-selective H2O2 oxidant that is presumably produced on the Au sites. At the highest Au coverages, selectivity dropped to <60% due to further oxidation of glycerate to C1 and C2 oxygenated products.

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