Mechanism of SO2 promotion for NO reduction with NH3 over activated carbon-supported vanadium oxide catalyst

SO2 shows a significant promoting effect on the activity of V2O5/AC catalys t for NO reduction with ammonia at low temperatures (180-250 degreesC). In the present study, the mechanism of the SO2 promotion was studied, It was f ound that the promoting effect of SO2 on the catalytic activity is due to t he formation of a sulfate species on the catalyst surface. The sulfate spec ies is linked to carbon surfaces other than vanadium or mineral surfaces. T here is a synergetic role between carbon and V2O5 for the formation of surf ace sulfate species. A possible mechanism is proposed. SO2 is adsorbed and oxidized by oxygen to SO3 on the vanadium surface, and the formed SO3 shift s to the carbon surface and converts into sulfate species. The formed sulfa te species acts as a new acid site, improves significantly the NH3 adsorpti on, and hence promotes the activity of the catalyst. During the reaction in the presence of SO2 at low temperatures, the sulfate species stays on the catalyst surface, while the ammonium ions react with NO continuously to avo id the formation and deposition of excess ammonium sulfate salts on the cat alyst surface. (C) 2001 Academic Press.