I. Nova et al., CHARACTERIZATION AND REACTIVITY OF TIO2-SUPPORTED MOO3 DE-NO-X SCR CATALYSTS, Applied catalysis. B, Environmental, 17(3), 1998, pp. 245-258
TiO2-supported MoO3 catalysts, with MoO3 loading similar to that of co
mmercial DeNO(x)-SCR catalysts (in the range 0-11% w/w) have been prep
ared, characterized and tested in the NO reduction by NH3. The structu
ral and morphological characteristics of the anatase-TiO2 support are
not significantly changed upon MoO3 addition. For MoO3 loading below o
r near 9% (w/w) (corresponding to the formation of the theoretical mon
olayer), evidence for the presence of isolated molybdenyl surface spec
ies have been collected by FT-IR, Laser Raman and EPR spectroscopies.
Above this loading, the presence of crystalline MoO3 is observed. The
MoO3/TiO2 catalysts are active in the reduction of NO by NH3: the reac
tivity of the catalysts increases on increasing the MoO3 loading, wher
eas the N-2 selectivity decreases due to the formation of undesired N2
O. The formation of N2O is primarily ascribed to a reaction between NH
3 and NO, and not to the ammonia oxidation reaction. A comparison with
a WO3/TiO2 catalyst having similar molar composition indicates that t
he WO3- and MoO3-containing samples exhibit similar structural and mor
phological characteristics, but different reactivity: the WO3/TiO2 sam
ple is less active but more selective in the SCR reaction. On the basi
s of EPR data, the different catalytic behavior has been tentatively a
scribed to the different redox characteristics of the samples. (C) 199
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