Selective catalytic reduction of NO by NH₃ over V₂O₅-WO₃/TiO₂ catalyst promoted by Mn and another metal (Ce, Cu or Fe)

Abstract

In this work selective catalytic reduction (SCR) of nitrogen oxide by ammonia over V₂O₅-WO₃/TiO₂ catalysts and V₂O₅-WO₃/TiO₂ catalysts that were promoted with manganese and another metal (cerium, copper, and iron) was investigated. Titanium dioxide was prepared by a sol-gel method and vanadium and tungsten were added to TiO₂ by wet impregnation method. Various techniques including nitrogen adsorption, XRD, NH3-TPD, XPS, and ICP-OES were employed to characterize the catalysts. V₂O₅-WO₃/TiO₂ catalysts ware then used in the SCR of NO by NH₃ at a temperature ranging from 100-450℃. Almost complete conversion of NO was achieved by most catalysts 250-350℃. Among the nine catalysts the V₂O₅-WO₃/TiO₂ catalyst containing 3 wt.% vanadium and 12 wt.% tungsten (3V12W) was the best one, which maintained high activity in the widest temperature range. In order to improve the activity of the V₂O₅-WO₃/TiO₂ catalyst under wet condition, manganese and another metal (cerium, copper, and iron) were deposited on the catalyst by an incipient wetness impregnation method. When water vapor was present in the feed stream, the activity of the catalyst became lower because water vapor competed with ammonia for reaction site on the catalyst. However, when the V₂O₅-WO₃/TiO₂ catalysts promoted with manganese and cerium or manganese and iron were employed, the catalysts maintained their activities even when water vapor was present in the feed stream.