Redispersion Technologies of V on TiO₂ for an Enhanced Catalytic Activity

Sintering and agglomeration of active species in the catalyst is a determining factor adversely affecting the catalytic activity. However, redispersion investigation is typically reported for noble-metal catalysts. In this work, we have put forward two simple technologies for the redispersion of V active species on the TiO₂ support. One is a redox treatment under NH₃ followed by O₂ at 300 °C, and the other is a steam treatment at 180 °C. As a result, the V particle size is reduced from the obvious 1-2 nm to an unrecognizable size on TiO₂, together with forming isolated and polymerized V-O-Ti. At the same time, although the crystal and textural properties are hardly affected, the surface redox ability and acidic-site amount are both increased. The mechanism investigation reveals that both thermal-derived migration and surface hydroxyl of TiO₂ are responsible for the redispersion. In the application of selective catalytic reduction of nitrogen oxide, the conversion of the redispersed catalyst is increased from 46.2% (the fresh catalyst) to as high as 98.0% under the same conditions. Furthermore, the redispersion methods are repeatable for catalysts synthesized by different methods in this work. The above result not only increases the catalytic performance of the as-prepared catalyst but is also in favor of waste-catalyst regeneration.