CO OXIDATION OVER PD AND CU CATALYSTS .1. UNREDUCED PDCL2 AND CUCL2 DISPERSED ON ALUMINA OR CARBON

CO can be oxidized at 300-400 K by molecular oxygen over dispersed, unreduced PdCl2 or CuCl2 although rates were much lower than those obtained using both compounds together. PdCl2 was much more active than CuCl2, and the addition of water vapor to the feed greatly enhanced the activity of the PdCl2 catalysts but not the CuCl2 catalysts. This system had not been previously characterized by IR spectroscopy, so this technique was employed to determine the Pd and Cu carbonyl and chloro-carbonyl species formed upon the introduction first of CO then, sequentially, of H2O and O2 to establish reaction conditions. The in situ spectra identified PdCl2CO, (PdClCO)n, and CuClCO species as well as a small amount of terminal and bridged CO adsorbed on metallic Pd particles. Based upon the IR results, a thorough kinetic study, and prior aqueous-phase studies in the literature, a reaction model is proposed that involves water as a reactant with the PdCICO species when water vapor is present. In its absence, molecular oxygen appears to interact with PdClCO to produce CO2. © 1991.