Combined effect of H2O and SO2 on V2O5/AC catalysts for NO reduction with ammonia at lower temperatures

Combined effect of H2O and SO2 on V2O5/AC the activity of catalyst for selective catalytic reduction (SCR) of NO with NH3 at lower temperatures was studied. In the absence of SO2, H2O inhibits the catalytic activity, which may be attributed to competitive adsorption of H2O and reactants (NO and/or NH3). Although SO2 promotes the SCR activity of the V2O5/AC catalyst in the absence of H2O, it speeds the deactivation of the catalyst in the presence of H2O. The dual effect of SO2 is attributed to the SO42- formed on the catalyst surface, which stays as ammonium-sulfate salts on the catalyst surface. In the absence of H2O, a small amount of ammonium-sulfate salts deposits on the surface of the catalyst, which promote the SCR activity; in the presence of H2O, however, the deposition rate of ammonium-sulfate salts is much greater, which results in blocking of the catalyst pores and deactivates the catalyst. Decreasing V2O5 loading decreases the deactivation rate of the catalyst. The catalyst can be used stably at a space velocity of 9000h(-1) and temperature of 250 degreesC. (C) 2002 Elsevier Science B.V. All rights reserved.