AES AND XPS STUDIES OF THE INFLUENCE OF NI ADDITION ON PD AL2O3 CATALYTIC ACTIVITY AND SULFUR RESISTANCE/

The influence of nickel addition on Pd/Al2O3 activity, selectivity and sulfur resistance during the selective hydrogenation of styrene was s tudied. The electronic state of palladium was followed by X-ray photoe lectron spectroscopy (XPS) and the palladium and nickel depth profile in the pellets by Auger electron spectroscopy (AES). The presence of N i (in concentrations lower than 2%) caused a decrease in catalytic sel ectivity, and an increase in the sulfur resistance. XPS measurements s howed a depletion in the Pd electronic state depending on the Ni conce ntration at the surface, and AES showed a differential spatial distrib ution of Pd and Ni depending on the Ni concentration.