The effect of supports on the activity and selectivity of CoNi alloy catalysts for CO hydrogenation

Abstract

The CO hydrogenation activity of 50Co50Ni alloy catalysts strongly depended on the oxide support. Electron-donating oxides such as MgO, PbO, and ZnO lowered the overall activity of the 50Co50Ni metal. The CO conversion as well as the chain growth probability was high over 50Co50Ni/TiO 2 and 50Co50Ni/MnO 2. The infrared spectra of adsorbed NO indicated that the electron density of the 50Co50Ni metal was low when it was supported on electron-accepting oxide. The results of desorption measurements suggest that metal-support interaction has a great influence on the surface concentration of hydrogen and carbon monoxide, and adsorption of carbon monoxide and hydrogen is weakened by increasing the electronegativity of the oxide support. Since the rate of H 2D 2 exchange correlated well with the CO hydrogenation rate, activation of hydrogen is of primary importance in this catalyst system. The low electron density of the alloy supported on the electron-accepting oxides such as TiO 2 and SiO 2 weakens CO adsorption, resulting in an increase in surface coverage of hydrogen. Thus sufficient coverage of hydrogen leads to a high CO hydrogenation rate.