Hydrogen Production From Propane Steam Reforming Over Ir/Ce_0.75Zr_0.25O₂ Catalyst

This work mainly investigated steam reforming of propane over a novel Ir/Ce0.75Zr0.25O2 catalyst. Different characterization methods like X-ray Diffraction(XRD), Temperature Programmed Reduction(TPR), High Resolution Transmission Electron Microscopy(HRTEM), X-ray Photoelectron Spectroscopy(XPS) and Oxygen Storage Capacity(OSC) etc were selected to characterize the as-prepared catalysts in order to elucidate the possible catalyst structure-performance relationship.The effect of catalyst calcination temperature was also deeply studied. The results revealed that the doping of Zr greatly improved the redox property and thermal stability of ceria. The Ir/Ce0.75Zr0.25O2 sample presented the excellent catalytic activity and stability. No obvious deactivation was observed after 65 h test at 600 oC even with the stoichiometric compositions. The various products of H2, CO, CO2 and CH4 in the outlet dry gas of propane steam reforming were 67mol%, 9mol% 14mol% and 8mol%, respectively. The high activity of catalyst was attributed to the following reasons:(i) the strong dissociation capacity of Ir species for C-C bond of propane;(ii) support might efficiently activate water molecules which could facilitate the methane steam reforming to enhance H2 selectivity. Meanwhile, the excellent stability of catalyst was probably because of:(i) the strong interaction between Ir species and solid solution support might inhibit the sintering of Ir particles during the reaction process;(ii) the high OSC value made the in-situ coke cleaning occur.It was observed that the calcination temperature significantly influenced the catalyst performance. After calcined at 850 oC, the redox capacity of support declined. Hence, the decline of Ir-support interface caused by the increase of Ir and support particle sizes remarkably weakened the Ir-support interaction. The above factors led to the poor catalytic activity and stability. Characterization results of the aged catalyst indicated that both the sintering of Ir species and carbon formation resulted into the rapidly catalyst deactivation.