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This content will become publicly available on April 14, 2017

Title: Influence of catalyst synthesis method on selective catalytic reduction (SCR) of NO by NH3 with V2O5-WO3/TiO2 catalysts

We compared the molecular structures, surface acidity and catalytic activity for NO/NH3/O2 SCR of V2O5-WO3/TiO2 catalysts for two different synthesis methods: co-precipitation of aqueous vanadium and tungsten oxide precursors with TiO(OH)2 and by incipient wetness impregnation of the aqueous precursors on a reference crystalline TiO2 support (P25; primarily anatase phase). Bulk analysis by XRD showed that co-precipitation results in small and/or poorly ordered TiO2(anatase) particles and that VOx and WOx do not form solid solutions with the bulk titania lattice. Surface analysis of the co-precipitated catalyst by High Sensitivity-Low Energy Ion Scattering (HS-LEIS) confirms that the VOx and WOx are surface segregated for the co-precipitated catalysts. In situ Raman and IR spectroscopy revealed that the vanadium and tungsten oxide components are present as surface mono-oxo O = VO3 and O = WO4 sites on the TiO2 supports. Co-precipitation was shown for the first time to also form new mono-oxo surface VO4 and WO4 sites that appear to be anchored at surface defects of the TiO2 support. IR analysis of chemisorbed ammonia showed the presence of both surface NH3* on Lewis acid sites and surface NH4+* on Brønsted acid sites. TPSR spectroscopy demonstrated that the specific SCR kinetics was controlled bymore » the redox surface VO4 species and that the surface kinetics was independent of TiO2 synthesis method or presence of surface WO5 sites. SCR reaction studies revealed that the surface WO5 sites possess minimal activity below ~325 °C and their primary function is to increase the adsorption capacity of ammonia. A relationship between the SCR activity and surface acidity was not found. The SCR reaction is controlled by the surface VO4 sites that initiate the reaction at ~200 °C. The co-precipitated catalysts were always more active than the corresponding impregnated catalysts. Finally, we ascribe the higher activity of the co-precipitated catalysts to the presence of the new surface WOx sites associated surface defects on the TiO2 support that increase the ammonia adsorption capacity.« less
 [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [4] ;  [2]
  1. Chongqing Univ., Chongqing (China). College of Materials Science and Engineering; Lehigh Univ., Bethlehem, PA (United States). Operando Molecular Spectroscopy & Catalysis Lab.
  2. Lehigh Univ., Bethlehem, PA (United States). Operando Molecular Spectroscopy & Catalysis Lab.
  3. Chongqing Univ., Chongqing (China). College of Materials Science and Engineering
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Science Division and Center for Nanophase Materials Sciences
Publication Date:
OSTI Identifier:
Grant/Contract Number:
AC05-00OR22725; SC0012577; 51274263; 51204220; UNCAGE-ME
Accepted Manuscript
Journal Name:
Applied Catalysis. B, Environmental
Additional Journal Information:
Journal Volume: 193; Journal Issue: C; Journal ID: ISSN 0926-3373
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE Catalysts; Supported; TiO2; V2O5; WO3; Synthesis; Co-precipitation; Incipient-wetness impregnation; Selective catalytic reduction (SCR); NO; NH3; O2; Spectroscopy; Raman; Infrared; TPSR; HS-LEIS; XRD