Mechanisms of CO oxidation reaction and effect of chlorine ions on the CO oxidation reaction over Pt/CeO2 and Pt/CeO2/γ-Al2O3 catalysts

Abstract

The reaction orders and activation energies of CO oxidation reaction over Pt/γ-Al2O3, Pt/CeO2 and Pt/CeO2/γ-Al2O3 were investigated for stoichiometric gas mixtures. The effect of residual chlorine originating from catalyst precursors on the CO oxidation activity of Pt/γ-Al2O3, Pt/CeO2 and Pt/CeO2/γ-Al2O3 was also studied. Indirect evidence was collected indicating that platinum was selectively deposited on alumina surface when Pt/CeO2/γ-Al2O3 catalyst was prepared from the physical mixture of pure oxides. The reaction orders of CO and O2 was found approximately as −2.0 and +1.0, respectively, over the Pt/γ-Al2O3 catalyst, but as −1.0 and 0.0 over the Pt/CeO2 and Pt/CeO2/γ-Al2O3 catalysts. The activation energy of CO oxidation reaction over Pt/γ-Al2O3 catalyst under stoichiometric conditions was around 120.0kJ/mol. On the other hand, over Pt/CeO2 catalysts activation energies were measured to be around 70kJ/mol. Surface reaction mechanisms were postulated to explain the differences in the reaction orders and activation energies.