Reaction kinetics of propane catalytic combustion on Cr/gamma-Al2O3, Co/Cr/gamma-Al2O3, and Au/Cr/gamma-Al2O3

摘要

The kinetics of propane oxidation to carbon dioxide and water over Cr/gamma-Al2O3, Co/Cr/gamma-Al2O3, and Au/Cr/gamma-Al2O3 were investigated within the temperature range 563-593K at atmospheric pressure. The rate equations for all three catalysts were obtained in this research. A best-fit reduction-oxidation mechanism was found for the reaction. On the basis of the kinetic analysis, it is concluded that the existence of cobalt in Co/Cr/gamma-Al2O3 can increase the reducibility of chromium oxides; therefore, the reaction rate over Co/Cr/gamma-Al2O3 was more than that over Cr/gamma-Al2O3. Gold in Au/Cr/gamma-Al2O3 also enhanced the rate of propane oxidation; its initial activity was even higher than that of Co/Cr/gamma-Al2O3. However, due mainly to coking, there was a significant decay problem on the surface of Au/Cr/gamma-Al2O3 during the reaction. Moreover, the activation energies and the Arrhenius constants for the reduction and the oxidation steps on Cr/gamma-Al2O3 and Co/Cr/gamma-Al2O3 during complete propane oxidation were obtained. The promotion effect from cobalt oxides on chromium oxides with respect to the activation energies is discussed.