Synthesis of a highly stable Pt/CeO2/Al2O3 catalyst for gasoline engine emission control by adjusting Pt distribution

For a CeO2/Al2O3-supported Pt catalyst system, the distribution of Pt is of significant importance to its hydrothermal stability and catalytic performance. Generally speaking, impregnation of a Pt precursor on CeO2/Al2O3 composite is a commonly applied approach to synthesize the catalyst. In this work, partially calcined CeO2 on Al2O3 was used as the support to modify Pt distribution. The characterization results reveal that for conventional Pt/CeO2/Al2O3, Pt is distributed on the outer surface of CeO2/Al2O3; although high dispersion of Pt is obtained for the fresh sample, severe aggregation of Pt species inevitably takes place upon hydrothermal aging treatment, leading to drastic catalyst deactivation. On the other hand, when Pt is principally embedded into the CeO2 region, the Pt/CeO2/Al2O3 catalyst has better hydrothermal stability; however, it still shows undesirable catalytic performance owing to the comparatively low dispersion of Pt on the surface. Fortunately, when Pt species are partially embedded into the CeO2 region, and the other portion is located on the outer surface of CeO2, a favourable balance between the dispersion and hydrothermal stability is realized, which consequently brings about superior three-way catalytic performance after hydrothermal aging treatment.