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Dynamics of the SCR‐DeNO x reaction by the transient‐response method
Author(s) -
Lietti Luca,
Nova Isabella,
Camurri Stefano,
Tronconi Enrico,
Forzatti Pio
Publication year - 1997
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690431017
Subject(s) - catalysis , chemistry , adsorption , desorption , selective catalytic reduction , ternary operation , activation energy , redox , kinetics , reaction mechanism , reaction dynamics , steady state (chemistry) , reaction rate , kinetic energy , inorganic chemistry , analytical chemistry (journal) , chromatography , organic chemistry , molecule , physics , quantum mechanics , computer science , programming language
The unsteady‐state kinetics of NH 3 adsorption–desorption and of selective catalytic reduction (SCR) of NO with NH 3 were studied over model V 2 O 5 /TiO 2 and V 2 O 5 –WO 3 /TiO 2 catalysts by transient response techniques. Over both catalysts the dynamic experiments could be successfully described by a kinetic model assuming (1) negligible NO adsorption on the catalyst surface; (2) nonactivated NH 3 adsorption; (3) a Temkin‐type NH 3 coverage dependence of the desorption energy; (4) a nonlinear dependence of the SCR reaction rate on the NH 3 surface coverage. Thus, the results are supportive of an Eley‐Rideal mechanism for the SCR reaction and of a significant heterogeneity for adsorption–desorption process and surface reaction of the catalyst surface. The binary and ternary catalysts exhibit similar acid properties, but different activity in the SCR reaction, possibly related to the superior redox properties of the WO 3 ‐containing sample. Over both samples the estimates of the activity energies for NH 3 desorption at zero coverage and for the surface reaction of NO with NH 3 are similar and in the 23–26 and 14–16 kcal/mol ranges, respectively.