Metal-acid bifunctional catalysts for selective hydrogenolysis of glycerol under atmospheric pressure: A highly selective route to produce propanols

Metal-acid bifunctional catalysts containing platinum and heteropolyacids (HPA) in supported onzirconia have been employed for the selective vapor phase hydrogenolysis of glycerol to propanols (1-propanol + 2-propanol) under normal atmospheric pressure. The Pt-HPA/ZrO2catalysts (HPAs such assilicotungstic acid (STA), phosphotungstic acid (PTA), phosphomolybdic acid (PMA) and silicomolybdicacid (SMA)) were prepared by impregnation method and the calcined catalysts were characterized bymeans of X-ray powder diffraction, FTIR, Raman spectroscopy, BET surface area, CO chemisorption andNH3-Temperature-programmed desorption methods. The characterization results reveal the presenceof well dispersed Pt metallic phase and Keggin structure of HPAs on support. The catalytic performanceduring glycerol hydrogenolysis is well correlated with Pt dispersion and the acidic properties of catalysts.Among the tested catalysts, it was found that Pt-PTA/ZrO2exhibited excellent selectivity to propanols(98%) with total glycerol conversion at 230◦C. A detailed study was made on the effect of various reactionparameters such as the influence of reaction temperature, reduction temperature, glycerol concentration,hydrogen flow rate, feed flow rate and HPA loading to unveil the optimized reaction conditions. Reactiontemperature was observed to have a significant effect on the glycerol conversion and product selectiv-ity. The spent catalysts were also characterized by the X-ray diffraction, NH3-TPD and SEM analysis toinvestigate the changes in catalytic performance and causes of catalyst deactivation.