Role of group V elements on the hydrogenation activity of Ni/TiO2 catalyst for the vapour phase conversion of levulinic acid to γ-valerolactone

Influence of group V elements such as Ta, Nb and V on the product distribution in the vapour phase hydrogenation of levulinic acid (LA) over Ni/TiO2 catalyst was examined at ambient pressure. The Nb promoted Ni/TiO2 demonstrated a high selectivity towards gamma-valerolactone (GVL) compared to other catalysts at 275 degrees C. The TPR results showed a lower H-2 uptake over Ta and V modified Ni/TiO2 which was explained due to a strong interaction between these oxide species with nickel. Presence of a high ratio of ionic nickel (Ni2+) on Ta and V modified catalyst could be a possible reason for the formation of valeric acid (VA) through the ring opening of GVL. The high GVL selectivity over the Ni-Nb/TiO2 catalyst attributed to the presence of a high proportion of Lewis acid sites in conjunction with finely dispersed Ni species on the catalyst surface. This however, is accomplished by the pyridine adsorbed diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and CO-chemisorption results.