Selective catalytic reduction of NO with propene over Au/CeO2/Al2O3 catalysts

Selective catalytic reduction of NO by propene under an oxygen-rich atmosphere has been investigated over Au/ CeO2, Au/CeO2/Al2O3 and Au/Al2O3 catalysts prepared by deposition-precipitation. The results demonstrated that Au/16%CeO2/Al2O3 had good low-temperature activity, selectivity towards N2 and stability, which is superior to that of Pt/Al2O3. It was also found that adding 2% water vapour to the feed stream enhanced the NO conversions at low temperatures while the presence of 20 ppm SO2 increased NO conversions at higher temperatures. It is particularly interesting that under the simultaneous presence of 2% water vapour and 20 ppm SO2, the NO conversions to N2 were significantly increased and the temperature window was widened significantly. The catalysts were characterized by Xray diffraction (XRD), high resolution transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (HRTEM-EDX) and temperatureprogrammed reduction (H2-TPR) techniques. Both XRD and HRTEM revealed that CeO2 was highly dispersed on the alumina support, and HRTEM combined with EDX showed that gold particles were preferentially deposited on those highly dispersed CeO2 particles. The gold deposition made CeO2 more reducible and interaction between gold and those highly dispersed CeO2 particles became stronger than that with the bulk CeO2, and this interaction is probably responsible for the superior catalytic performance of the Au/CeO2/Al2O3.

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