과잉 산소 존재 하에서 Ru-HZSM-5촉매를 사용한 NO 분해 반응 및 선택적 촉매 환원 반응에 관한 연구

배재용; 정상철; 이화영

Journal of the Korean Industrial and Engineering Chemistry, Vol.9, No.3, 355-360, June, 1998

A Study on Direct Decomposition and Selective Catalytic Reduction of NO over Ru-HZSM-5 Catalyst in the Presence of Excess Oxygen

배재용, 정상철, 이화영

초록

본 연구에서는 여러 귀금속 이온 교환 HZSM-5 촉매상에서 NO의 선택적 환원 반응 및 과잉 산소 존재 하에서 탄화수소 환원제를 첨가하지 않은 조건에서의 직접 분해 반응을 수행하여 NO 제거 활성을 비교 검토하였으며, Cu-HZSM-5 촉매의 활성과도 비교하였다. 사용한 촉매 중 Ru-HZSM-5 상에서 탄화수소 환원제 없이 NO+O₂ 반응을 수행한 결과 최대 45%의 NO에서 N2로의 전환율을 얻을 수 있었으며 수증기의 첨가에 대해서도 상당한 저항성을 나타내었다. 이러한 Ru-HZSM-5의 높은 활성은 NO를 과잉 산소 존재 하에서 NO₂로 전환시키는 능력이 우수하기 때문이라고 생각된다. Ru-HZSM-5 촉매상에서 NO는 기상 탄화수소 환원제가 없는 과잉 산소 존재 하에서는 먼저 NO₂로 산화된 후 이어 N₂로 분해되는 반응 경로를 거치는 것으로 생각되며 촉매 표면에 흡착되는 NO₃는 이 반응의 일종의 중간 생성물이라 판단된다.

Reduction activity of precious metal-loaded HZSM-5 for NO has been studied and was compared to that of Cu-HZSM-5 in the presence of excess oxygen. It was found that among the catalysts used in this study, Ru-HZSM-5 was the most active catalyst for the reduction of NO to N₂ in the absence of hydrocarbon reductant. The highest conversion obtained was 45%. No severe inhibition of water vapor to the reduction was observed. It is suggested that the higher catalytic activity of Ru-HZSM-5 may result from the better ability to oxidize NO to NO₂ in the presence of excess oxygen. A proposed reaction mechanism for the reduction of NO to N₂ in the presence of excess oxygen is that NO is oxidized to NO₂ on the surface of Ru-HZSM-5 catalyst and the adsorbed NO₂ on the surface is then decomposed to N₂. NO₂ is supposed to the reaction.

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