Diols Production From Glycerol Over Pt-Based Catalysts : On the Role Played by the Acid Sites of the Support

A series of 1 wt% AuPt (6:4) catalysts were prepared by sol immobilization using acidic [TiO2, H-Mordenite, SiO2, MCM-41, sulphated ZrO2 (S-ZrO2)] and one basic (MgO) oxide supports. A careful characterization of the catalyst was performed by HRTEM and FTIR spectroscopy. EDX analysis showed that on all catalysts only alloyed AuPt nanoparticles are present, but the final size of AuPt particles is significantly affected by the support. Indeed, on TiO2 the mean AuPt nanoparticles diameter is 3.7 nm, whereas for all the remaining supports, larger AuPt nanoparticles with diameter of 6-7.5 nm were obtained. AuPt catalysts result very active in catalyzing the liquid phase hydrogenolysis of glycerol to 1,2-propandiol (68% conversion after 16 h) and 90% selectivity with ethylene glycol, 1-propanol and 2-propanol as main by-products. The role of the support has been highlighted in terms of acidic properties. The medium strength of Lewis acid sites of TiO2 leads to the best performance in terms of activity, selectivity and stability of the catalytic system.