Lj. Alemany et al., REACTIVITY AND PHYSICOCHEMICAL CHARACTERIZATION OF V2O5-WO3 TIO2 DE-NOX CATALYSTS/, Journal of catalysis, 155(1), 1995, pp. 117-130
V2O5-WO3/TiO2 samples with compositions similar to those of commercial
de-NOx catalysts (WO3 similar to 9% w/w, V2O5, < 3% w/w) are characte
rised by XRD, surface area and pore size distribution, Fourier transfo
rm infrared, laser Raman, W-vis diffuse reflectance, electron paramagn
etic resonance spectroscopies, and catalytic tests in the reduction of
NOx by NH3. The V2O5-WO3/TiO2 catalysts exhibit higher reactivity tha
n the binary V2O5/TiO2 and WO3/TiO2 samples with the same metal loadin
g, and the temperature window for the SCR reaction is greatly widened.
The catalysts consist of anatase TiO2 and their morphological propert
ies closely resemble that of WO3/TiO2 for (V + W) surface coverages lo
wer than one. Monomeric vanadyls and wolframyls and polymeric WwOy gro
ups are observed in the samples with low vanadia loadings that are app
arently similar to those present on the surface of the binary oxide sy
stems with comparable metal loadings. On increasing the vanadium loadi
ng, polyvanadate species are also formed. EPR, FTTR, FT-Raman, and UV-
vis techniques indicate a strong electronic interaction between V and
W oxide species at the surface of the TiO2 support. This interaction l
eads to a higher reducibility of the ternary sample with respect to th
e corresponding binary ones. A synergism between V and W oxide surface
species is suggested, which accounts for the high reactivity of the t
ernary samples in the SCR reaction. It is suggested that the higher re
ducibility of the samples, due to the electronic interactions between
V and W and the TiO2 support, is responsible for the higher reactivity
of the ternary catalysts, particularly at low temperatures. (C) 1995
Academic Press, Inc.