Ternary V–Ti–Si catalysts and their behaviour in the CO + NO reaction

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Abstract
De-NOx catalysts with strong mechanical properties and high surface area have been prepared by coating silica microspheres with titania according to the homogeneous deposition–precipitation method. The proportion of titania incorporated was varied between 0.5 and 3.0 theoretical monolayers. These catalysts possess a titania-like behaviour and strong acid properties. Although the Ti–Si carriers are titania-rich, the TiO2 phase is relatively well dispersed and the change in the coordination sphere of TiO2 induced by the silica substrate may account for its strong acid properties. Upon incorporation of vanadium, both dispersed vanadium species and V2O5 crystallites are developed, the former being similar to vanadia species on TiO2. These systems exhibit both strong acidity and redox properties which are primarily associated with characteristics peculiar to the support and the V2O5 components, respectively, which play a key role in the de-NOx reaction. Preliminary results on the CO + NO reaction indicate that these catalysts have a much better performance than VTiO2.