Abstract: The Zr_0.5Al_0.5O_1.75 mixed oxide was prepared by coprecipitation method, and calcined at different temperatures and then used as a support to prepare a 1.5% Pd/Zr_0.5Al_0.5O_1.75 catalyst. The catalyst activity and H₂O resisting properties were evaluated in a mixed gas that simulated the exhaust of lean-burn natural gas fuelled vehicles (lean-burn NGVs). The catalyst was further characterized by N₂ adsorption-desorption, X-ray diffraction, H₂ temperature-programmed reduction, O₂ temperature-programmed desorption and CO chemisorption. It was found that the catalyst activity was greatly influenced by the calcination temperature of the Zr_0.5Al_0.5O_1.75 support. For the catalyst with the support calcined at 950 °C, the light-off temperature (T₅₀) and complete conversion temperature (T₉₀) of methane in the absence of H₂O were 274 and 315 °C, respectively. In the presence of H₂O, T₅₀ and T₉₀ were 325 and 356 °C, respectively. The results indicated that the catalyst had higher catalytic activity at low temperature and higher capability to resist H₂O poisoning.

Key words: zirconium, aluminium, mixed oxide, palladium, supported catalyst, lean-burn natural gas fuelled vehicle