Influence of sulfur dioxide on the selective catalytic reduction of NO by decane on Cu catalysts.

The selective catalytic removal of NO in oxygen rich atmospheres has been investigated in the presence of sulfur dioxide on a series of Cu catalysts. The reactivities correlated with the reducibility of Cu species determined by temperature programmed reduction with hydrogen. Without sulfur dioxide in the feed, the activity is related to the reducibility of Cu species. The addition of SO2 to the solid shifts the TPR peaks to higher temperatures. The magnitude of this effect is lower for acid zeolites such as MFI and BEA. Sulfation results in a small inhibition of the reactivity for deNOx in the case of Cu/Al2O3, no or little change in the case of Cu/zeolites, and a promotion of activity in the case of Cu/TiO2 and Cu/ZrO2. The oxidation of decane on Cu/TiO2 and Cu/ZrO2 is inhibited by SO2 at low temperatures, but remains close to 100% in presence or absence of SO2 on Cu/TiO2 above 600K. In the case of Cu/ZrO2 the addition of SO2 increases the rate of oxidation above 640 K. The positive effect of SO2 on deNOx is attributed to the promotion of a bifunctional mechanism in presence of strong acid sites.