Effect of SO2 on the catalytic activity of Ga2O3-Al2O3 for the selective reduction of NO with propene in the presence of oxygen

The effect of coexisting SO2 on the catalytic activity of Ga2O3-Al2O3 prepa red by impregnation, coprecipitation and sol-gel method for NO reduction by propene in the presence of oxygen was studied. Although the activity of Al 2O3 and Ga2O3-Al2O3 prepared by impregnation (Ga2O3/Al2O3(I)) and coprecipi tation (Ga2O3-Al2O3(CP)) was depressed considerably by the presence of SO2, NO conversion on Ga2O3-Al2O3 prepared by sol-gel method (Ga2O3-Al2O3(S)) w as not decreased but increased slightly by SOz at temperatures below 723 K. From catalyst characterization, SO2 treatment was found to cause two impor tant effects on the surface properties: one is the creation of Bronsted aci d sites on which propene activation is promoted (positive effect), and the other is the poisoning of NOx adsorption sites on which NO reduction procee ds (negative effect). It was presumed that the influence of SO2 treatment o n the catalytic activity is strongly related to the balance between the neg ative and positive. The activity enhancement of Ga2O3-Al2O3(S) by SO2 was a ccounted for by the following consideration: (1) increase of the propene ac tivation ability by SO2, (2) incomplete inhibition of NOx adsorption sites by SO2. (C) 2001 Elsevier Science B.V. All rights reserved.