Catalytic transformation of glycerol on several metal systems supported on ZnO

Different metal systems consisting in platinum supported on several reducible supports (5% by weight) were synthesized through the deposition–precipitation technique and tested for glycerol hydrogenolysis. Interestingly, supports exhibiting the highest conversions were those with the greatest strong metal–support interaction (SMSI) effect, ZnO and SnO2, eventually forming alloys (Pt–Zn and Pt–Sn, respectively). ZnO was subsequently selected for further studies as support for Rh, Pt, Pd and Au and the resulting solids were tested again for glycerol catalytic transformation under reductive or inert atmosphere at 453 K. Under similar reaction conditions, glycerol conversion order followed the sequence Pt > Rh ≫ Pd ≫ Au. Moreover, the solids reduced at 473 K were more active than those activated at 673 K, which evidences the detrimental effect of the increase in metal particle size and/or alloy formation on the catalytic performance. Quite high yields to lactic acid were achieved in a basic medium (e.g. 68% for Rh/ZnO-473 under H2) whereas yield to 1,2-PDO was more modest (26% for Rh/ZnO-673 under similar reaction conditions).