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

Abstract

De-NO_x 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-NO_x reaction. Preliminary results on the CO + NO reaction indicate that these catalysts have a much better performance than VTiO₂.