Effect of supports on the activity of nickel catalysts in acetonitrile hydrogenation

Gas-phase hydrogenation of acetonitrile was investigated using nickel black and nickel deposited on MgO, Al2O3, Cr2O3, SiO2, TiO2, ZrO2, ThO2 and UO2, at ambient pressure and 70 °C. Metal surface areas were measured by hydrogen chemisorption. Both reaction selectivity and catalytic activity are affected by support nature. Nickel black, Ni/MgO, Ni/ThO2 and Ni/UO2 catalysts have the highest selectivity to monoethylamine (>80 mol%), while Ni/TiO2 catalysts the least (<20 mol%). All supports increase the catalytic activity of the metal surface area unit (i.e. the intrinsic activity) compared to that of the nickel black. The most efficient is TiO2, which increases the intrinsic activity by about 20 times and the least efficient are MgO and SiO2, with an increase of only 1.5 times. It is assumed that the role of the support is to create new active sites at the metal-support frontiers. The catalytic behavior of the Ni/Al2O3 and Ni/Cr2O3 catalysts, treated at temperatures between 350 and 1050 °C, confirms the role of the metal-support frontiers in the enhancement of the catalytic activity in acetonitrile hydrogenation.