Role of WO3 in mixed V2O5-WO3/TiO2catalysts for selective catalytic reduction of nitric oxide with ammonia

Abstract A series ofTiO2-supported V2O5 and V2O5+WO3 catalysts were prepared to study the role of WO3 in the commercial selective catalytic reduction (SCR) catalysts. The activities of these catalysts were measured under both dynamic and steady-state conditions. The catalysts were characterized by temperature-programmed reaction (TPR), ammonia chemisorption and proton magic angle spinning nuclear magnetic resonance (MAS NMR) measurements. The following effects of WO3 on V2O5/TiO2 in the commercial WO3-V2O5/TiO2 (coimpregnated) SCR catalyst are observed; (1) It increases the activity and widens the temperature window for SCR. (2 ) It significantly increases the poison resistance to both alkali metal oxides and arsenious oxide. (3) It reduces ammonia oxidation (as well as SO2 oxidation which is known from the published literature). These results have been correlated directly with ammonia chemisorption and proton MAS NMR measurements. These results suggest that the Bronsted acid sites are the active sites for SCR. Addition of WO3 in V2O5/TiO2 increases the Bronsted acidity (both Bronsted acid site density and strength of the acid, i.e., proton donicity), whereas the alkali poison decreases the Bronsted acidity.

[1]  J. E. Cichanowicz,et al.  Cold selective catalytic reduction of nitric oxide for flue gas applications , 1990 .

[2]  N. Topsoe.  Characterization of the nature of surface sites on vanadia-titania catalysts by FTIR , 1991 .

[3]  M. Shelef,et al.  Selectivity for nitrogen formation in NH3 oxidation in wet and dry systems over mixed molybdenum oxides , 1975 .

[4]  Akira Miyamoto,et al.  Mechanism of the reaction of NO and NH3 on vanadium oxide catalyst in the presence of oxygen under the dilute gas condition , 1980 .

[5]  B. M. Reddy,et al.  Influence of MoO3 and WO3 on the dispersion and activity of V2O5 in vanadia-silica catalysts , 1989 .

[6]  H. Pfeifer,et al.  Study of brønsted acidity of zeolites using high-resolution proton magnetic resonance with magic-angle spinning , 1982 .

[7]  B. Lengeler,et al.  Interaction of arsenious oxide with DeNox-catalysts: An X-ray absorption and diffuse reflectance infrared spectroscopy study , 1991 .

[8]  Gerard Tuenter,et al.  Kinetics and Mechanism of the NOx Reduction with NH3 on V2O5 - WO3-TiO2 Catalyst , 1986 .

[9]  Satoru Kurita,et al.  The effect of the vanadium component on the life of the WO3-TiO2 catalyst used for the reduction of NOx with NH3. , 1982 .

[10]  H. Knözinger,et al.  Vanadia supported on titania-silica: physical characterization and activity for the selective reduction on nitric oxide , 1989 .

[11]  E. I. Ko,et al.  Acidic properties of oxides containing niobia on silica and niobia in silica , 1991 .

[12]  Jyh-Ping Chen.  Mechanism of poisoning of the V2O5/TiO2 catalyst for the reduction of NO by NH3 , 1990 .

[13]  H. Pfeifer,et al.  NMR studies concerning the dehydroxylation of zeolites HY , 1983 .

[14]  Ken Nobe,et al.  Reduction of NO with NH3 on Al2O3− and TiO2-supported metal oxide catalysts , 1986 .

[15]  J. Dumesic,et al.  The generation of Brønsted and Lewis acid sites on the surface of silica by addition of dopant cations , 1987 .

[16]  J. Dumesic,et al.  Acidity of unsupported and silica-supported vanadia, molybdena, and titania as studied by pyridine adsorption , 1988 .

[17]  K. Tanabe,et al.  Isomerization and disproportionation of olefins over tungsten oxides supported on various oxides , 1980 .

[18]  Lanny D. Schmidt,et al.  Kinetics of NH3 oxidation on Pt, Rh, and Pd☆ , 1975 .

[19]  A. Miyamoto,et al.  Oxidation of Ammonia with Lattice Oxygen of Metal Oxides by Pulse Reaction Technique , 1979 .

[20]  A. Baiker,et al.  Selective catalytic reduction of nitric oxide with ammonia: I. Monolayer and Multilayers of Vanadia Supported on Titania , 1987 .

[21]  H. Knözinger,et al.  Ammonia adsorption on vanadia supported on titania-silica catalyst. An infrared spectroscopic investigation , 1989 .