The effects of CeO2 on the activity and stability of Pt supported catalysts for methane reforming, as addressed by in situ temperature resolved XAFS and TEM analysis

The effects of Ce as a promoter on the activity and stability of Pt/Al2O3 and Pt/CeO2-Al2O3 catalysts for autothermal reforming and partial oxidation of methane (POM) were investigated. The Pt/CeO2-Al2O3 catalyst exhibited higher activity and stability than the Pt/Al2O3 catalyst. Analysis by in situ X-ray absorption spectroscopy under POM conditions reveals that Pt is reduced by heating the catalysts to about 730 K. The overall first-shell coordination numbers suggest changes in Pt cluster morphology with increasing temperature. Transmission electron microscopy showed strong Pt agglomeration with time on stream for the Pt/Al2O3 catalyst. The higher stability of the Pt/CeO2-Al2O3 catalyst was attributed to a combination of different properties: (i) hindrance of carbon deposition on the Pt surface for a reactor fed with low H2O/CH4 ratio; (ii) interaction of Pt[single bond]O[single bond]Ce species in the presence of oxygen, inhibiting vapor and diffusion transport of PtO2 and mainly, (iii) thermal stability of the support, which prevents the loss of surface area, and consequently the sintering of the Pt. [PUBLICATION ABSTRACT]