Catalytic oxidation of propene over Pd catalysts supported on CeO2, TiO2, Al2O3and M/Al2O3oxides (M = Ce, Ti, Fe, Mn)

Abstract

In the following work, the catalytic behavior of Pd catalysts prepared using different oxides as support (Al2O3, CeO2and TiO2) in the catalytic combustion of propene, in low concentration in excess of oxygen, to mimic the conditions of catalytic decomposition of a volatile organic compound of hydrocarbon-type is reported. In addition, the influence of different promoters (Ce, Ti, Fe and Mn) when added to a Pd/Al2O3catalyst was analyzed. Catalysts were prepared by the impregnation method and were characterized by ICP-OES, N2adsorption, temperature-programmed reduction, temperature-programmed oxidation, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Catalyst prepared using CeO2as the support was less easily reducible, due to the stabilization effect of CeO2over the palladium oxides. Small PdO particles and, therefore, high Pd dispersion were observed for all of the catalysts, as confirmed by XRD and TEM. The addition of Ce to the Pd/Al2O3catalysts increased the metal-support interaction and the formation of highly-dispersed Pd species. The addition of Ce and Fe improved the catalytic behavior of the Pd/Al2O3catalyst; however, the addition of Mn and Ti decreased the catalytic activity in the propene oxidation. Pd/TiO2showed the highest catalytic activity, probably due to the high capacity of this catalyst to reoxidize Pd into PdO, as has been found in the temperature-programmed oxidation (TPO) experiments.