The effects of La2O3 on the structural properties of La2O3–Al2O3 prepared by the sol–gel method and on the catalytic performance of Pt/La2O3–Al2O3 towards steam reforming and partial oxidation of methane

The effect of La2O3 content on the structural properties and catalytic behavior of Pt/xLa2O3–Al2O3 catalysts in steam reforming of methane and partial oxidation of methane was investigated. There was a decrease in the density of Pt sites with the increase of La2O3 loadings according to Fourier transform infrared spectroscopy of adsorbed CO and to dehydrogenation of cyclohexane results. However, transmission electron microscopy data indicates an opposite trend. This apparent disagreement could be due to the partial coverage of Pt sites by LaOx species. CH4 turnover rates and specific rates of steam reforming of methane increased for higher La2O3 loadings. The Pt/Al2O3 catalyst was strongly deactivated during partial oxidation of methane, while La2O3-containing catalysts exhibited higher stability. The increase of activity observed during the reactions was ascribed to the ability of the [LaPtxO]Pt0-like species to promote the gasification of coke. This cleaning mechanism led to higher accessibility of the active sites to CH4.