Partial oxidation of methane using Pt/CeZrO2/Al2O3 catalysts - effect of preparation methods

The effect of the preparation method of Pt/CeZrO2/Al2O3 catalysts on the dispersions of the metal and of the ceria-zirconia on the surface of the alumina and on the catalytic performance of methane partial oxidation reaction was evaluated. The ceria-zirconia materials were supported on the alumina surface by precipitation and impregnation and all the samples contained 1.5 wt.% of Pt. The dispersion of the ceria-zirconia was evaluated by adsorbed CO2 infrared spectroscopy and the dispersion of the metal was determined by the dehydrogenation of cyclohexane. The reducibility of the catalysts was measured by oxygen storage capacity and temperature programmed reduction. The samples prepared by impregnation present higher activity, stability and selectivity to form CO and H2 than the ones prepared by precipitation. The characterization results show that all the samples had practically the same platinum dispersion but the dispersion of the ceria-zirconia material on the alumina was more effective when the impregnation method was used. The impregnation favors a high coverage degree of the alumina by the ceria-based oxides. This means that a larger fraction of platinum particles is in contact with ceria or ceria-zirconia oxide. The metal-support interface is a key factor to avoid the carbon deposits that are responsible for the deactivation of some samples.