Kinetics, Isotope Effects, and Mechanism of the Hydrogenation of Carbon Monoxide on Supported Palladium Catalyst

Article abstract of DOI:10.1021/j100242a016

Kinetics and isotope effects for the C-O bond dissciation in the hydrogenation of CO on Pd/Al2O3 catalyst were investigated by using pulse surface reaction rate analysis (PSRA).The rate-determining step was found to be the C-O bond dissociation of the adsorbed CO species.The rate constant for the C-O bond dissociation process per adsorbed CO molecule was determined at various temperatures and Arrhenius parameters of the rate constant were obtained.The rate constant in flowing D2 (k_D) was considerably larger than that in flowing H2 (k_H), indicating an inverseisotope effect.The average value of k_H/k_D was 0.61.The extent of the inverse isotope effect for Pd was more significant than that for Ni (k_H/k_D=0.75).The preexponential factor for k_H on Pd (1.6E4 s^-1) was much smaller than that on Ni (5.4E6 s^-1).It was concluded, that, adsorbed CO is not directly dissociated to surface carbon and oxygen atoms but hydrogen atoms play an important role in the C-O bond dissociation.Further details of the mechamism for the C-O bond dissociation were discussed from the observed kinetics and isotope effects.