Clean Technology, Vol.17, No.4, 370-378, December, 2011
V2O5-WO3/TiO2 계 SCR 촉매의 가스상 원소수은 산화 활성
Activity of V2O5-WO3/TiO2-based SCR Catalyst for the Oxidation of Gas-phase Elemental Mercury
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초록
가스상 원소수은의 산화수은으로의 산화에 대한 V2O5-WO3/TiO2 계 SCR 촉매의 활성이 조사되었다. 상용 SCR 촉매의 경우 원소수은 산화반응에 산화제로 작용하는 HCl의 존재 및 반응조건에 상관없이 반응 후의 모든 촉매에서 수은성분이 검출되지 않았다. 이는 V2O5-WO3/TiO2 계 SCR 촉매에서 HCl에 의한 원소수은의 산화는 수은이 촉매표면에 거의 흡착되지 않는 Eley-Rideal mechanism에 의해 진행되는 것을 나타내는 결과이다. V2O5 함량에 따라 수은 산화활성이 크게 증가되는 것으로부터 V2O5가 수은산화 반응에 주된 활성점 임을 확인할 수 있었다. 그러나 V2O5 함량에 따라 TOF는 감소하는데 이는 촉매표면에 존재하는 V2O5의 구조에 따라 수은산화 활성에 차이가 있다는 것을 의미한다. 동일한 반응온도와 HCl 농도에서 산화 조건에 비해 SCR 조건에서 원소수은의 산화활성은 크게 낮은 것으로 나타났다.
Catalytic activity of V2O5-WO3/TiO2-based SCR catalyst was examined for the oxidation of gas-phase elemental mercury to oxidized mercury. Mercury species was not detected on the commercial SCR catalyst after the oxidation reaction of elemental mercury, regadless of the presence of HCl acting as oxidant and the reaction conditions. This suggests that elemental
mercury oxidation by HCl could occur via a Eley-Rideal mechanism with gas phase or weakly-bound mercury on the surface of V2O5-WO3/TiO2 SCR catalyst. The activity for mercury oxidation was significantly increased with the increase of V2O5 loading, which indicates that V2O5 is the active site. However, turnover frequency for mercury oxidation was decreased with the increase of V2O5 loading, indicating the activity for mercury oxidation was strongly dependent on the surface structure of vanadia species. The activity for oxidation of elemental mercury under SCR condition was much less than that under oxidation condition at the same HCl concentration and reaction temperature.
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