The reactivity of Cu-on-alumina catalysts in the redn. of NO by NH3+O (SCR reaction) and oxidn. of NH3 to N (NH3ox reaction) as a function of the Cu loading shows that (1) the specific rate of the SCR reaction per mol of Cu decreases with increasing Cu loading, whereas the NH3ox reaction rate is nearly independent of the Cu loading and (2) the rate of the NH3ox reaction is significantly higher in the absence of NO than that of the same reaction occurring during the SCR reaction. The catalysts were characterized by ESR, x-ray diffraction anal., and UV-visible diffuse reflectance. The nature of the NO and NH3 adsorbed species was studied using ESR and IR spectroscopies, and IR studies of the reactive coadsorption of NO and NH3 were carried out. The results indicate that the above catalytic effects are due to the formation of nitrate species which block the reactivity of Cu sites. The transformation of NO to N via the intermediate formation of ammonium nitrate was shown, but the data suggest that this is only a secondary pathway of reaction responsible for the formation of N2O as a byproduct. The nature of active Cu species on the surface and the presence of competitive pathways of transformation of NO to N are discussed. [on SciFinder(R)]

Adsorption and reactivity of NO on copper-on-alumina catalysts. I. Formation of nitrate species and their influence on reactivity in NO and NH3 conversion

CENTI, Gabriele;PERATHONER, Siglinda;
1995-01-01

Abstract

The reactivity of Cu-on-alumina catalysts in the redn. of NO by NH3+O (SCR reaction) and oxidn. of NH3 to N (NH3ox reaction) as a function of the Cu loading shows that (1) the specific rate of the SCR reaction per mol of Cu decreases with increasing Cu loading, whereas the NH3ox reaction rate is nearly independent of the Cu loading and (2) the rate of the NH3ox reaction is significantly higher in the absence of NO than that of the same reaction occurring during the SCR reaction. The catalysts were characterized by ESR, x-ray diffraction anal., and UV-visible diffuse reflectance. The nature of the NO and NH3 adsorbed species was studied using ESR and IR spectroscopies, and IR studies of the reactive coadsorption of NO and NH3 were carried out. The results indicate that the above catalytic effects are due to the formation of nitrate species which block the reactivity of Cu sites. The transformation of NO to N via the intermediate formation of ammonium nitrate was shown, but the data suggest that this is only a secondary pathway of reaction responsible for the formation of N2O as a byproduct. The nature of active Cu species on the surface and the presence of competitive pathways of transformation of NO to N are discussed. [on SciFinder(R)]
1995
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/1907516
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