Structural sensitivity of NO decomposition over a V-O-W/Ti(Sn)O2 catalyst

NO decomposition at 673 K as a function of contact times over a V-O-W/Ti(Sn)O2 catalyst obtained by sol–gel method and pretreated at 673 K in helium stream was investigated and compared with that over a Cu-ZSM-5 catalyst. Feed containing 4% NO in a helium stream was used in both the cases. The V-O-W/Ti(Sn)O2 catalyst showed higher activity as well as higher selectivity to dinitrogen than the Cu-ZSM-5 catalyst over the whole range of used contact times (0.375–15 g s cm−3). The highest activity of the V-O-W/Ti(Sn)O2 catalyst, especially at higher normalised contact times (τ/τmax > 0.25), was shown to result from vanadia-like surface layer formation with high tungsten content. It was also shown that the decrease in activity as contact time decreased is connected with tungsta monolayer formation on the V-O-W hybrid crystallites composed of tungsta, V-W oxide bronze and vanadia.