The present work aims at clarifying the effects of CeO2 addition to Al2O3 support on the surface chemical characteristics and catalytic activity of supported Rh catalysts for low-temperature steam reforming of propane. Steam reforming of propane was carried out at 500 °C over Rh catalysts supported on alumina modified with different CeO2 loading (0, 5, 10, 20, 50, 75, and 100 wt%). The Rh catalyst supported on 20 wt% CeO2-modified alumina (2Rh/20CeAl) showed the highest propane and steam conversions, followed in decreasing order by those with 10, 5, 50, 75, 0, and 100 wt% CeO2. TPR results show that the interaction between ceria and rhodium improves the reducibility of both rhodium oxide and ceria. XPS analysis indicates strong ceria-alumina interaction and strong Rh-support interaction for Rh catalysts with CeO2 loading less than 20 wt%. Field-Emission SEM and AES results revealed that at 20 wt% CeO2 loading, ceria was dispersed as separate nano-particles with sizes of 100-200 nm on the alumina surface. At high CeO2 loading (≥50 wt%) ceria particles formed conglomerates covering alumina surface. The 2Rh/20CeAl catalyst showed the highest activity for propane steam reforming possibly because the high CeO2 dispersion created a large area of ceria-alumina interface which helped increase Rh dispersion, and the strong interaction between Rh and support helped enhance the reducibility of ceria and rhodium oxide. Rh loaded onto the interfacial region of ceria and alumina is considered to be most active for the 2Rh/20CeAl catalyst.
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