선택적 촉매 환원법 재료로서 나노 사이즈 MnOx-CeO2/TiO2 촉매에 대한 미세구조적 특성과 촉매활성 평가
Microstructural property and catalytic activity of nano-sized MnOx-CeO2/ TiO2 for NH3-SCR
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초록
저온용 SCR 촉매인 MnOx의 촉매 활성을 높이기 위해 TiO2 지지체와 함께 조촉매로서 CeO2을 사용하였고, 제조된 나노 사이즈의 촉매 특성과 함께 질소산화물 제거 효율에 대해 고찰하였다. MnOx-CeO2/TiO2 촉매 내에서 CeO2 거동을 확인하기 위해 단일 조성의 CeO2와의 차이점을 미세구조적으로 비교 분석하였다. MnOx-CeO2/TiO2 촉매가 졸겔법을 통해 제조되었으며 낮은 열적 특성으로 인해 평균 285 μm 정도의 큰 입도를 가진 단일 CeO2와는 달리 Ti 지지체와 함께 합성된 촉매의 경우 130 nm 정도로 줄어들었음을 확인하였다. 투과 전자 현경을 이용한 EDS mapping를 통해 Ce-Ti의 강한interaction이 nano-sized powder 제조의 원인인 것으로 확인하였다. 조촉매 첨가로 인해 MnOx/TiO2 촉매에 비해 저온영역에서 20 % 이상의 효율 향상이 있었으며 이는 3성분계 촉매 내에서 CeO2가 나노 사이즈로 잘 분산됨에 따라 촉매 반응에 필요한 산소이온의 교환이 활발히 일어날 수 있었기 때문이다.
Abstract
CeO2 is used as a co-catalyst with TiO2 to improve the catalytic activity of MnOx and characterization of nanosized powder is identified with de-NOx efficiency. A comparison between MnOx-CeO2/TiO2 and single CeO2 was conducted in terms of microstructural analysis to observe the behavior of CeO2 in the ternary catalyst. The MnOx-CeO2/TiO2 catalyst was synthesized by sol-gel method and the average particle size of the single CeO2 is about 285 μm due to the low thermal stability, whereas the particle size MnOx-CeO2/TiO2 is about 130 nm. The strong interaction between Ce and Ti was identified through the EDS mapping by transmission electron microscopy (TEM). The improvement about 20 % of de-NOx efficiency is observed in the low-temperature (150 o C~250 o C) and vigorous oxygen exchange by well-dispersed CeO2 is the reason of catalytic activity improvement.
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