Liquid-phase glycerol hydrogenolysis by formic acid over Ni–Cu/Al2O3 catalysts

Two series of Ni–Cu/Al2O3 catalysts with different Cu/Ni ratio and different total metal contents were prepared and tested in the glycerol hydrogenolysis to 1,2-propanediol under N2 pressure and using formic acid as hydrogen donor molecule. The results from the deep characterization of the catalysts by N2-physisorption, transmission electron microscopy (TEM), temperature-programed reduction (TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programed desorption of ammonia (TPD-NH3), together with the results from the activity tests allowed deeper understanding of the role played by Ni, Cu, and acid catalytic sites. The kinetic study performed with the optimized catalyst revealed that the OH groups of glycerol and of the target product, 1,2-propanediol, compete for adsorption on the acid sites of the Al2O3 support. 90% glycerol conversion and 82% 1,2-propanediol selectivity after 24 h reaction time were achieved when operating at 493 K.