Dresden 2011 – scientific programme
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O: Fachverband Oberflächenphysik
O 97: Heterogeneous catalysis II
O 97.6: Talk
Friday, March 18, 2011, 12:30–12:45, PHY C213
Selective Catalytic Reduction of NO with NH3 at V2O5(010) and Silica supported Vanadium Oxide: DFT Studies. — •Mathis Gruber and Klaus Hermann — Fritz-Haber-Institut der MPG, Faradayweg 4-6, D-14195 Berlin and Sfb 546, (Germany)
The Selective Catalytic Reduction (SCR) of NOx with NH3 over vanadium based metal-oxide (VOx) catalysts has been proven to be one of the most effective NOx reduction processes. Details of the reaction mechanism are still under debate. Adsorption, (de)hydrogenation, reactions with NO, and surface water formation at the VOx catalyst contribute elementary steps. These processes are examined in theoretical studies employing density-functional theory together with gradient corrected functionals. The VOx substrate is modeled by clusters cut out from the clean V2O5(010) surface where peripheral oxygen bonds are saturated by hydrogen. Reduced surfaces are represented by introducing oxygen vacancies. In addition, silica supported vanadium oxide clusters are considered. NH3 is found to interact with the clean V2O5(010) surface only in the presence of OH groups (Brønsted acid sites) where it can form a rather stable surface NH4+ species. Further, NH3 can adsorb at vanadium centers of lower coordination at the reduced surface (Lewis acid sites). This leads to two different SCR reaction scenarios transferring NH3 and NO to N2 and H2O which are discussed by corresponding reaction paths and intermediates.