A novel one-step synthesis of 1-propanol from hydrogenolysis of glycerol using a Ni-HSiW/Al2O3 catalyst – The impact of H2 pressure on catalyst performance

Hydrogenolysis of glycerol based on biomass is a possible route to obtain various valuable chemicals. Molecular hydrogen is a reactant in hydrogenolysis reactions. Optimizing hydrogen pressure can bring about a number of different benefits and other value added aspects to the process. In addition, hydrogen could also affect the catalyst surface and chemical characteristics which affect the catalyst activity. This study is focused on the influence of the pressure of hydrogen on the hydrogenolysis of glycerol using a 10Ni-30HSiW/α-Al2O3. The catalysts of 10Ni-30HSiW/α-Al2O3 were prepared using a wetness impregnation technique and the catalytic activity is tested in a batch reactor. The characterization of these catalysts were performed using different techniques such as NH3 temperature programmed desorption (TPD), X-ray powder diffraction (XRD), Thermal gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Fourier transformed infrared spectroscopy (FT-IR). The study found that the hydrogen pressure influenced both the conversion of glycerol and the distribution of products. As the H2 pressure increased, the selectivity to 1-propanol (1-PO) increased while the selectivities to acrolein, acetol and other products decrease. Interestingly the conversion of glycerol went through a maximum of 64.8% at 145 PSI of H2 and decreased as the H2 pressure increased. It was found that it is necessary to have high hydrogen pressure to maintain Ni in the metallic or zero oxidation state which accelerated the hydrogenation of acrolein to 1-PO and suppressed the formation of byproducts. However reduction of W6+ to a lower oxidation state (W4+) occurred under a high pressure of H2 which reduces the acidity of the catalyst during the dehydration and decreased the conversion of glycerol.