XPS analysis of chlorine residues in supported Pt and Pd catalysts with low metal loading

Platinum and palladium on alumina, silica and fibrous silica from different precursors were studied and correlated with catalytic activity in gas-phase ortho-xylene hydrogenation. Chlorine is retained on alumina carrier material in noble metal catalysts with low metal loading after reduction under flowing hydrogen at 400 °C. Silica supported catalysts have very little chlorine after the reduction. Metal/support atomic concentration ratios obtained by X-ray photoelectron spectroscopy (XPS) analysis show increase in the particle size during the reduction of the catalyst, but the sintering is not necessarily involved in chlorine migration. Catalyst precursors were compared by means of chlorine residues and correlations on surface composition of catalyst with ortho-xylene hydrogenation activity were observed.