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

✍ Scribed by Hyun Chan Lee; Dong Hyun Kim

• Publisher: Elsevier Science
• Year: 2008
• Tongue: English
• Weight: 756 KB
• Volume: 132
• Category: Article
• ISSN: 0920-5861
• DOI: 10.1016/j.cattod.2007.12.028

✦ Synopsis

The kinetics of CO and H 2 oxidation over a CuO-CeO 2 catalyst were simultaneously investigated under reaction conditions of preferential CO oxidation (PROX) in hydrogen-rich mixtures with CO 2 and H 2 O. An integral packed-bed tubular reactor was used to produce kinetic data for power-law kinetics for both CO and H 2 oxidations. The experimental results showed that the CO oxidation rate was essentially independent of H 2 and O 2 concentrations, while the H 2 oxidation rate was practically independent of CO and O 2 concentrations. In the CO oxidation, the reaction orders were 0.91, À0.37 and À0.62 with respect to the partial pressure of CO, CO 2 and H 2 O, respectively. In the H 2 oxidation, the orders were 1.0, À0.48 and À0.69 with respect to the partial pressure of H 2 , CO 2 and H 2 O, respectively. The activation energies of the CO oxidation and the H 2 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 H 2 oxidation suggested different sites for CO and H 2 adsorption on the CuO-CeO 2 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; H 2 dissociates and adsorbs on the Cu 0 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.