The Effect of Vanadium(V) Oxide Content of V₂O₅-WO₃/TiO₂ Catalyst on the Nitrogen Oxides Reduction and N₂O Formation

In order to investigate the effect of V₂O₅ loading of V₂O₅-WO₃/TiO₂ catalyst on the NO reduction and the formation of N₂O, the experimental study was carried out in a differential reactor using the powder catalyst. The NO reduction and the ammonia oxidation were, respectively, investigated over the catalysts compose of V₂O₅ content (1-8 wt%) based on the fixed composition of WO₃ (9 wt%) on TiO₂ powder. V₂O₅-WO₃/TiO₂ catalysts had the NO reduction activity even under the temperature of 200 .deg. C. However, the lowest temperature for NO reduction activity more than 99.9% to treat NO concentration of 700 ppm appeared at 340 with very limited temperature window in the case of 1 wt% V₂O₅ catalyst. And the temperature shifted to lower one as well as the temperature window was widen as the V₂O₅ content of the catalyst increased, and finally reached at the activation temperature ranged 220-340 .deg. C in the case of 6 wt% V₂O₅ catalyst. The catalyst of 8 wt% V₂O₅ content presented lower activity than that of 8 wt% V₂O₅ content over the full temperature range. NO reduction activity decreased as the V₂O₅ content of the catalyst increased above 340 .deg. C. The active site for NO reduction over V₂O₅-WO₃/TiO₂ catalysts was mainly related with V₂O₅ particles sustained as the bare surface with relevant size which should be not so large to stimulate N₂O formation at high temperature over 320 .deg. C according to the ammonia oxidation. Currently, V₂O₅-WO₃/TiO₂ catalysts were operated in the temperature ranged 350-450 .deg. C to treat NOx in the effluent gas of industrial plants. However, in order to save the energy and to reduce the secondary pollutant N₂O in the high temperature process, the using of V₂O₅-WO₃/TiO₂ catalyst of content V₂O₅ was recommended as the low temperature catalyst which was suitable for low temperature operation ranged 250-320 .deg. C