Characterization and De-NOX activity of binary V2O5/TiO2 and WO3/TiO2, and ternary V2O5-WO3/TiO2 SCR catalysts
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The influence of tungsten and vanadium oxides on the microstructure, phase formation and De-NOx activity of selective catalytic reduction (SCR) catalysts has been investigated. Binary (V2O5/TiO2 and WO3/TiO2) and ternary (V2O5-WO3/TiO2) samples with compositions similar to those of commercial SCR catalysts were examined in terms of structural analyses and the reduction of NOx to N2 in the presence of NH3. The TiO2 supported catalysts with different W- and V-loadings (WO3: 10 wt%, V2O5 <10 wt%), heat-treated in the temperature range of 450 oC to 650 oC, have been characterized. The addition of W to TiO2 led to lowering the transition temperature of anatase-to-rutile. Upon the phase transition, WO3 phase segregation was observed. The W-loading in the TiO2 support did not influence the crystallite dimensions and surface area. In the case of the V-loading, the transition temperature was significantly reduced along with an abruptly decreased surface area due to the crystallite growth with increasing V-content. Ternary V2O5-WO3/TiO2 catalysts exhibited higher De-NOx efficiency than binary V2O5/TiO2 and WO3/TiO2 samples with the same amount of loading. In V2O5(3 wt%)-WO3(10 wt%)/TiO2 catalysts, the highest De-NOx activity was achieved in a wide temperature range. A catalyst heat-treatment at 650 oC showed a relatively high efficiency and wider temperature range, maintaining peak activity in comparison with the catalysts prepared at 450 oC.
Abstract
The influence of tungsten and vanadium oxides on the microstructure, phase formation and De-NOx activity of selective catalytic reduction (SCR) catalysts has been investigated. Binary (V2O5/TiO2 and WO3/TiO2) and ternary (V2O5-WO3/TiO2) samples with compositions similar to those of commercial SCR catalysts were examined in terms of structural analyses and the reduction of NOx to N2 in the presence of NH3. The TiO2 supported catalysts with different W- and V-loadings (WO3: 10 wt%, V2O5 <10 wt%), heat-treated in the temperature range of 450 oC to 650 oC, have been characterized. The addition of W to TiO2 led to lowering the transition temperature of anatase-to-rutile. Upon the phase transition, WO3 phase segregation was observed. The W-loading in the TiO2 support did not influence the crystallite dimensions and surface area. In the case of the V-loading, the transition temperature was significantly reduced along with an abruptly decreased surface area due to the crystallite growth with increasing V-content. Ternary V2O5-WO3/TiO2 catalysts exhibited higher De-NOx efficiency than binary V2O5/TiO2 and WO3/TiO2 samples with the same amount of loading. In V2O5(3 wt%)-WO3(10 wt%)/TiO2 catalysts, the highest De-NOx activity was achieved in a wide temperature range. A catalyst heat-treatment at 650 oC showed a relatively high efficiency and wider temperature range, maintaining peak activity in comparison with the catalysts prepared at 450 oC.