Dynamics of SCR reaction over a TiO2-supported vanadia–tungsta commercial catalyst

The dynamics of NH 3 adsorption-desorption and of selective catalytic reduction (SCR) of NO with NH 3 are investigated in this work over a commercial V 2 O 5 -WO 36/TiO2 catalyst by transient response techniques. Linear variations in the inlet concentration of one or more reactants are imposed while analyzing the system outlet response. The transient experiments could be successfully described by a kinetic model based on: (i) a negligible NO adsorption on the catalyst surface; (ii) a non-activated NH 3 adsorption; (iii) a Temkin-type NH 3 coverage dependence of the desorption energy; and (iv) an Eley-Rideal mechanism for the SCR reaction with a non-linear dependence of the reaction rate on the NH 3 surface coverage. The presence of low concentrations of water in the feed stream does not seem to affect the ammonia adsorption-desorption process on the surface but significantly inhibits the SCR reaction; an inhibiting effect of adsorbed NH3 on the SCR reaction is also pointed out.

[1]  Pio Forzatti,et al.  Steady-State and Transient Reactivity Study of TiO2-Supported V2O5−WO3 De-NOx Catalysts: Relevance of the Vanadium−Tungsten Interaction on the Catalytic Activity , 1996 .

[2]  Pär Gabrielsson,et al.  Reducing NOx in diesel exhausts by SCR technique: Experiments and simulations , 1994 .

[3]  A. S. Noskov,et al.  Application of the nonstationary state of a catalyst surface for gas purification from toxic impurities , 1996 .

[4]  P. Forzatti,et al.  Reactivity and Physicochemical Characterization of V2O5-WO3/TiO2 De-NOx Catalysts , 1995 .

[5]  Jyh-Ping Chen,et al.  Role of WO3 in mixed V2O5-WO3/TiO2catalysts for selective catalytic reduction of nitric oxide with ammonia , 1992 .

[6]  Ken Nobe,et al.  Kinetics of nitric oxide reduction with ammonia on "chemical mixed" and impregnated vanadium(V) oxide-titanium(IV) oxide catalysts , 1984 .

[7]  Pio Forzatti,et al.  Dynamics of the SCR‐DeNOx reaction by the transient‐response method , 1997 .

[8]  T. Srnak,et al.  Temperature-programmed desorption/reaction and in situ spectroscopic studies of vanadia/titania for catalytic reduction of nitric oxide , 1992 .

[9]  P. Forzatti,et al.  Characterization and reactivity of TiO2-supported MoO3 De-Nox SCR catalysts , 1998 .

[10]  G. Ramis.  On the consistency of data obtained from different techniques concerning the surface structure of vanadia-titania catalysts: Reply to the comment of Israel E. Wachs , 1990 .

[11]  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 .

[12]  F. Nakajima,et al.  The state-of-the-art technology of NOx control , 1996 .

[13]  A. S. Noskov,et al.  Reverse-process for NOx - off gases decontamination , 1993 .

[14]  David W. Agar,et al.  Extended reactor concept for dynamic DeNOx design , 1988 .

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

[16]  G. Froment,et al.  Chemical Reactor Analysis and Design , 1979 .

[17]  E. Moroz,et al.  The Influence of Support on the Activity of Monolayer Vanadia-Titania Catalysts for Selective Catalytic Reduction of NO with Ammonia , 1995 .

[18]  James A. Dumesic,et al.  Vanadia-Titania Catalysts for Selective Catalytic Reduction of Nitric-Oxide by Ammonia , 1995 .

[19]  Pio Forzatti,et al.  Transient kinetic study of the SCR-DeNOx reaction , 1998 .