Total oxidation of methane at low temperature over Pd/TiO2/Al2O3: effects of the support and residual chlorine ions

A novel catalyst, Pd supported on TiO2/Al2O3 has been investigated for the total oxidation of methane. Static reaction between CH4 and 18O2 in the presence of catalyst was performed to investigate the reaction pathway and a redox mechanism with Pd-PdO as the active species was suggested. The TPR and 18O-isotope exchange experiments were carried out to characterize the catalysts to reveal the key factors influencing the activity. It was shown that addition of titania into alumina enhanced the reduction as well as the oxygen mobility of palladium oxide and thus generated catalyst with much higher activity for the reaction. It was also found that the existence of residual chlorine ions on the catalyst surface would lower the oxygen mobility and reducibility of the supported palladium oxide and consequently inhibit the activity of the catalyst for methane total oxidation.