Synergetic effect of platinum or palladium on gold catalyst in the selective oxidation of D-sorbitol

Monometallic Au, Pt and Pd on carbon catalysts show poor activity in the liquid phase oxidation of D-sorbitol to gluconic/gulonic acids. However, by using bimetallic based catalysts (Au-Pt or Au-Pd) a great enhancement in the activity has been observed with respect to all the monometallic catalysts tested probably due to a synergetic effect between Au and Pt or Pd. In fact physical mixture of monometallic catalysts presented poor activity. Bimetallic showed a resistance to poisoning by dioxygen and by reaction products as high as gold monometallic catalyst, but also an improved selectivity toward monooxidation with respect to monometallic.