Search / Korean Journal of Chemical Engineering
HWAHAK KONGHAK,
Vol.32, No.3, 402-413, 1994
Mordenite형 제올라이트상에서 탄화수소를 이용한 질소산화물의 선택적 제거
Selective Catalytic Reduction of Nitrogen Oxide by Hydrocarbons over Mordenite-Type Zeolite Catalysts
합성 모더나이트(HM, CuHM)와 천연 제올라이트(NZA, CuNZA)촉매를 이온교환방법에 의하여 제조하고, C2H4, C2H6, C3H6, C3H8과 같은 네 종류의 탄화수소를 환원제로 사용하여 고정층 반응기에서 촉매활성을 고찰한 결과, HM상에서는 C2H4이, 천연 제올라이트에 동이온을 교환한 CuNZA상에서는 C3H6이 우수한 NO전환율을 나타내었다. CuNZA사에서 C3H6을 이용한 여러 반응변수에 대한 연구결과, NO농도의 증가에 따라 NO전환율은 점차적으로 감소하고 C3H6농도의 증가와 함께 NO전환율은 증가하여 실제 배기가스 조건과 유사한 산소농도 4.2%에서 C3H6의 농도가 2,000ppm일 때 NO는 94%까지 제거되었다. 또한 산소농도가 2.0%에서 최적의 NO전환율을 관찰할 수 있었으며, 동이온 교환량이 1.6wt%일 때 급격한 NO전환율의 증가를 관찰할 수 있었다. 400℃이상에서는 함탄소물질에 의한 촉매활성 저하현상이 관찰되지 않았으며, 반응물중에 유입하는 C3H6 과 O2을 각각 중단하여도 NO전환율이 NO공급을 중단한 경우보다 다소 길계 유지되는 것으로 보아 반응중간체로 생각되어 지는 함산소활성물질[Cn’Hm’(O)]이 NOX제거 반응에 중요한 역할을 하는 것으로 생각되어 진다. 또한 HM상에서는 반응중에 생산된 N2O가 NO전환율에 직접적으로 기여하는 것으로 관찰되었다.
The reduction of NO by hydrocarbons such as C2H4, C2H6, C3H6 and C3H8, has been investigated over mordenite type zeolite catalysts. HM, CuHM, NZA, and CuNZA were prepared by ion-exchange method and their deNOx efficiency was examined in a continuous flow fixed-bed reactor. As a result of the activity test, C2H4 appeared to be the best reductant over HM and C3H6 over CuNZA. The reaction variables for C3H6-CuNZA system have been examined for its optimal operating condition. NO conversion reaches about 94% by the feed of 2,000ppm of C3H6 at 500℃. The highest conversion of NO was observed at 2.0% of O2. NO conversion of CuNZA depends on the exchange level of copper ions on the catalyst structure. No deterioration of the catalytic activity for CuNZA was observed at above 400℃ even after 30 hours of on-stream time. Based upon the transient test of CuNZA catalyst with the shut-off of reactants, Cn’Hm’(O) might be a reaction intermediate. N2O formed in the reaction may play an important role for HM catalyst at the reaction temperature above 400℃. It can be concluded that CuNZA is a highly active and promising catalyst for the reduction of NO with C3H6. The reaction path of this catalytic system is the most important key for the high accomplishment of NO conversion.
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