Activity and N2 selectivity of sol-gel prepared Pt/alumina catalysts for selective NOx reduction

We prepared 1 and 2 wt% Pt/Al2O3 catalysts by a single-step sol-gel process and tested their activity and N-2 selectivity for NOx reduction with propene. Our results show that when compared to the impregnation catalysts, the single-step sol-gel catalysts have superior N-2 selectivity both in terms of percentage of NO converted to N-2 (similar to 70% or greater) and comparable activity. All of the catalysts tested show a minimum in N-2 selectivity at the point of maximum NOx conversion. Both the value of the minimum selectivity and the NO2 conversion are functions of oxygen concentration in the feed. The N-2 selectivity at peak conversion exhibits a minimum at similar to 6.8% O-2 Increasing the feed oxygen concentration beyond 6.8% has many beneficial effects including broadening of the temperature window, suppression of NO2 formation and increasing the N-2 selectivity without significantly changing the maximum NOx conversion. The sol-gel catalysts show remarkable robustness after exposure to high temperatures, SO2, and long time exposure to reactants. (C) 2000 Academic Press.