A DFT study on the behavior of NO2 in the selective catalytic reduction of nitric oxides with ammonia on a V2O5 catalyst surface

DFT calculations were carried Out to Study the behavior of NO2 in the selective catalytic reduction of nitric oxides with ammonia on the surface of the V2O5 catalyst. The results showed that NO2 Could readily reoxidize V4+-OH through two reaction routes: (1) NO2 directly reoxidizing V4+-OH to V5+=O and (2) NO2 reacting with H2O or NH3 to produce HNO3. which subsequently reoxidizes V4+-OH to V5+=O. The rate-determining step of route 1 is the desorption of cis-HNO2 from the reoxidized V5+=O, being endothermic by 9.91 kcal/mol. Route 2 possesses an energy barrier of 7.44 kcal/mol, less than route 1. This energetic comparison shows that route 2 is the predominant reaction mechanism at low temperature. Reactions of the by-product, HNO2, were also investigated. The results showed that both cis-HNO2 (route 1) and trans-HNO2 (route 2) can either react with NH3, producing H2O and N-2, or react with themselves, producing H2O, NO and NO2. A systemic description of the behavior for NO2 in "fast" SCR on V2O5 Surface, including the reaction routes and energy profiles, has been Proposed in our work. (C) 2009 Elsevier B.V. All rights reserved.