Influence of NH3 and NO oxidation on the SCR reaction mechanism on copper/nickel and vanadium oxide catalysts supported on alumina and titania

The influence of ammonia and nitric oxide oxidation on the selective catalytic reduction (SCR) of NO by ammonia with copper/nickel and vanadium oxide catalysts, supported on titania or alumina have been investigated, paying special attention to N2O formation. In the SCR reaction, the VTi catalyst had a higher activity than VAl at low temperatures, while the CuNiAl catalyst had a higher activity than CuNiTi. A linear relationship between the reaction rate of ammonia oxidation and the initial reduction temperature of the catalysts obtained by H-2-TPR showed that the formation rate of NH species in copper/nickel catalysts would be higher than in vanadia catalysts. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) showed that copper/nickel catalysts presented ammonia coordinated on Lewis acid sites, whereas ammonium ion adsorbed on Bronsted acid sites dominated on vanadia catalysts. The NO oxidation experiments revealed that copper/nickel catalysts had an increase of the NO2 and N2O concentrations with the temperature. NO could be adsorbed on copper/nickel catalysts and the NO2 intermediate species could play an important role in the reaction mechanism. It was suggested that the presence of adsorbed NO2 species could be related to the N2O formation. (C) 2002 Elsevier Science B.V. All rights reserved.

[1]  S. Suárez,et al.  Alumina- and titania-based monolithic catalysts for low temperature selective catalytic reduction of nitrogen oxides , 2000 .

[2]  F. Janssens,et al.  Mechanism of the reaction of nitric oxide, ammonia, and oxygen over vanadia catalysts. I. The role of oxygen studied by way of isotopic transients under dilute conditions , 1987 .

[3]  Guido Busca,et al.  FT-IR study of the surface of copper oxide , 1987 .

[4]  H. Nagata,et al.  On Dehydration of Bound Water of Sepiolite , 1974 .

[5]  J. Blanco,et al.  Low temperature multibed SCR process for tail gas treatment in nitric acid plant , 1993 .

[6]  G. Centi,et al.  Role of the support and of adsorbed species on the behavior of Cu-based catalysts for No conversion , 1993 .

[7]  P. Forzatti,et al.  Fourier transform-infrared study of the adsorption and coadsorption of nitric oxide, nitrogen dioxide and ammonia on vanadia-titania and mechanism of selective catalytic reduction , 1990 .

[8]  Bernard Delmon,et al.  Catalytic removal of NO , 1998 .

[9]  Maria Caterina Turco,et al.  Adsorption, Activation, and Oxidation of Ammonia over SCR Catalysts , 1995 .

[10]  J. Zawadzki.  The mechanism of ammonia oxidation and certain analogous reactions , 1950 .

[11]  R. Bilbao,et al.  Theoretical study of the influence of mixing in the SNCR process. Comparison with pilot scale data , 2000 .

[12]  F. Janssen,et al.  Mechanism of the reaction of nitric oxide, ammonia, and oxygen over vanadia catalysts. 2. Isotopic transient studies with oxygen-18 and nitrogen-15 , 1987 .

[13]  J. Fierro,et al.  Influence of nitrogen dioxide on the selective reduction of NOx with a catalyst of copper and nickel oxides , 1993 .

[14]  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 .

[15]  Suresh T. Gulati,et al.  Catalytic Air Pollution Control: Commercial Technology , 1994 .

[16]  O. L. Maaskant,et al.  The shell DENOX system for low temperature NOx removal , 1996 .

[17]  H. Knözinger,et al.  Surface properties and reduction behavior of calcined CuOAl2O3 and CuO-NiOAl2O3 catalysts , 1981 .

[18]  G. Somorjai,et al.  AES and TDS study of the adsorption of NH3 and NO on V2O5 and TiO2 surfaces: Mechanistic implications , 1989 .

[19]  H. Knözinger,et al.  Characterization of mixed copper-manganese oxides supported on titania catalysts for selective oxidation of ammonia , 1993 .

[20]  J. L. Ahlrichs,et al.  Sepiolite Anhydride and Crystal Folding , 1975 .

[21]  P. Forzatti,et al.  Fourier transform infrared study of the adsorption and coadsorption of nitric oxide, nitrogen dioxide and ammonia on TiO2 anatase , 1990 .