Kinetics of CO and H2 oxidation over CuO-CeO2 catalyst in H2 mixtures with CO2 and H2O

The kinetics of CO and H2 oxidation over a CuO-CeO2 catalyst were simultaneously investigated under reaction conditions of preferential CO oxidation (PROX) in hydrogen-rich mixtures with CO2 and H2O. An integral packed-bed tubular reactor was used to produce kinetic data for power-law kinetics for both CO and H2 oxidations. The experimental results showed that the CO oxidation rate was essentially independent of H2 and O2 concentrations, while the H2 oxidation rate was practically independent of CO and O2 concentrations. In the CO oxidation, the reaction orders were 0.91, −0.37 and −0.62 with respect to the partial pressure of CO, CO2 and H2O, respectively. In the H2 oxidation, the orders were 1.0, −0.48 and −0.69 with respect to the partial pressure of H2, CO2 and H2O, respectively. The activation energies of the CO oxidation and the H2 oxidation were 94.4 and 142 kJ/mol, respectively. The rate expressions of both oxidations were able to predict the performance of the PROX reactor with accuracy. The independence between the CO and the H2 oxidation suggested different sites for CO and H2 adsorption on the CuO-CeO2 catalyst. Based on the results, we proposed a new reaction model for the preferential CO oxidation. The model assumes that CO adsorbs selectively on the Cu+ sites; H2 dissociates and adsorbs on the Cu0 sites; the adsorbed species migrates to the interface between the copper components and the ceria support, and reacts there with the oxygen supplied by the ceria support; and the oxygen deficiency on the support is replenished by the oxygen in the reaction mixture.