KINETICS OF SELECTIVE CATALYTIC REDUCTION OF NITRIC-OXIDE BY AMMONIA OVER VANADIA TITANIA/

A kinetic model based on a previously proposed reaction scheme was use d to describe reaction kinetics measurements for the selective catalyt ic reduction of nitric oxide by ammonia over a 6 wt% vanadia/titania c atalyst in the presence of oxygen (2 mol%) at nitric oxide and ammonia concentrations from 100 to 500 ppm and at temperatures of 523 and 573 K. This reaction scheme involves adsorption of ammonia on Bronsted ac id sites (V5+-OH), followed by activation of ammonia via reaction with redox sites (V=O). This activated form of ammonia reacts with gaseous or weakly adsorbed NO, producing N-2 and H2O, and leading to partial reduction of the catalyst. The V4+-OH species formed by the selective catalytic reduction (SCR) reaction combine to form water, and the cata lytic cycle is completed by reaction of the reduced sites with O-2. Wa ter adsorbs competitively with ammonia on acid sites. This reaction sc heme can be used to describe the kinetics of the SCR reaction under la boratory as well as under industrially relevant reaction conditions. ( C) 1996 Academic Press, Inc.