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Pt/MCM-41을 이용한 NO의 선택적 촉매환원에 관한 연구

Studies on the Selective Catalytic Reduction of NO by Propylene over MCM-41 Supported Pt Catalyst

한상현 양재승 정석진^†

Sang-Hyun Han Jae-Seung Yang Suk-Jin Choung^†

경희대학교 환경응용화학부

School of Environment and Applied Chemistry, Kyung Hee Univ., Korea

HWAHAK KONGHAK, October 2000, 38(5), 578-584(7), NONE

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Abstract

본 연구에서는 Mesopore계열의 분자체 중 활용범위가 증대되고 있는 MCM-41에 platinum을 담지시켜 propylene을 환원제로 하는 선택적 촉매환원 반응을 수행하였다. 먼저 분자체 제조후 구조형성여부 확인을 위하여 XRD, 질소흡탈착등온선, B.E.T표면측정 등을 수행하였으며 NO-TPD를 통해 NO 탈착특성과 표면반응특성을, 그리고 모사 배기가스장치를 통한 NO환원활성을 측정하였다. 전체적인 활성의 경향은 활성금속으로 작용하는 platinum의 특성으로 인하여 저온영역(250℃ 내외)에서 최대 NO환원활성을 보여주고 있으며 이는 NO-TPD를 통하여 볼 때 저온영역(300℃ 이하)의 NO흡탈착이 우세하기 때문인 것으로 판단된다. 담지체 효과에 있어서는 silica type mesopore 담지촉매에 비하여 Al을 골격에 치환시킨 mesopore담지촉매가 더욱 우수한 NO환원 활성을 나타내었다. 이는 치환된 Al이 추가의 흡착활성점으로 작용되기 때문인 것으로 판단되며 흡탈착등온선의 비교로부터 Al/MCM-41이 보다 넓은 것과 일치하는 현상이다. Pt(5 wt%)/Al-MCM-41상에서 10 vol%의 수증기를 첨가했을 때에도 NO환원활성은 저하되지 않았으며, 종래의 Me-ZSM-5에 비하여 내수성 및 내황성이 향상된 보다 실용성있는 SCR촉매로 제안할 수 있는 가능성을 확인하였다.

At present study, platinum doped MCM-41(Si/Al=40) catalyst, which has been widely used as a new type of meso-porous catalyst, was tested for the reduction of NO_x with propylene as reducing agent. In order to confirm the structure, various characterization techniques such as XRD, N₂ adsorption-desorption isotherms, NO-TPD, and BET surface area measurements were performed. Also, by using a simulated flow gas mixture, NO reduction activity test was carried out on various kind of catalyst such as Pt/MCM-41, Pt/Al-MCM-41 and Pt-ZSM-5. The general trends of activity measurements showed that the maximum NO conversions appeared at relatively lower temperature region(low than 250℃) probably due to the existence of Pt on support. This is supported by the existence of larger peaks at lower temperature region from TPD pattern, when compared with that of MCM-41 only. Specially Al exchanged MCM-41 showed the best NO conversion activity than others. It is speculated that the exchanged Al sites give rise to additional active site for NO adsorption, because Al-MCM-41 shows a larger hystersis loop in adsorption-desorption isotherms. 10 vol wt% water was added to the stimulated folw gases, but the NO conversion activity was not changed significantly on Pt/Al-MCM-41. Therefore, newly proposed Pt/MCM-41 catalyst might be a better candate for the practical use in SCR process using propylene than on conventional Me-ZSM-5 catalysts.

Keywords

Hydrocarbon SCR MCM-41 Nitric Oxide

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