Effect of Cs+ on the hydrogenolysis of glycerol to higher value sustainable and green chemicals using a supported Ni-HSiW catalyst

Abstract

Alkaline earth metal of Cs ion (Cs+) was exchanged into a 10Ni-30H4SiW/Al2O3 catalyst, which was used as a bifunctional catalyst for the hydrogenolysis of glycerol. The catalysts were characterized by XRD, BET, NH3-TPD, FTIR techniques, and the catalyst activity was evaluated in a batch reactor. The catalysts with exchanged Cs+ have little effect on the glycerol conversion; however a significant effect on the product distribution was observed which could be attributed to the changes in acidity of the catalyst. The Keggin structure of catalyst remains unaltered after substitution of protons by Cs+ on Ni-H4SiW/Al2O3 based on the characterization data. Among the catalysts studied, 10Ni-30Cs1H3SiW12O40/Al2O3 with 1 proton substituted by 1Cs+ showed the best selectivity to 1,3-propanediol (1,3-PD) and 1-propanol (1-PO); however, 10Ni-30Cs4SiW12O40 with all the protons substituted by Cs+ has low selectivity to 1-PO and high selectivity to 1,2-propanediol (1,2-PD) and ethylene glycol. For 30HSiW/Al2O3 without Ni, exchanging H+ with Cs+ resulted in catalysts with low activity for glycerol conversion and different product selectivity than the catalysts with Ni, namely, high selectivity to acrolein and 1-PO while no ethylene glycol, 1,2-PD or 1,3-PD were detected. The product selectivity could be rationalized by the changes in mechanism from dehydration v.s. dehydrogenation as the rate determining step.