Mesoporous SSZ-13 zeolite prepared by a dual-template method with improved performance in the methanol-to-olefins reaction
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Keywords:
Chabazite
Space velocity
Ammonium hydroxide
The secondary pores in the nanosized HZSM-5 zeolite have been observed for the first time via129Xe NMR spectroscopy using xenon as a probe; the location of non-framework Al can also be identified.
Isotopes of xenon
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Chabazite
Thermal Stability
Hydrothermal Synthesis
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Clinoptilolite
Chabazite
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Chabazite
Sodalite
Mordenite
Ferrierite
Nanoporous
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ZSM-5
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Chabazite
Analcime
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저온에서 NOx 저감률이 높은 작은 기공을 갖는 Cu-chabazite SCR 촉매는 150 에서 300℃ 범위의 낮은 배기가스 온도를 갖는 박용 디젤엔진에 적용성이 높다. 불행하게도, 박용디젤엔진용 연료는 체적 베이스로 1.5% 이상의 높은 레벨의 황을 함유 할 수 있다. 이것은 공연비 50:1로 엔진 운전시에 배기가스에 이산화황의 레벨이 500 ppm에 해당된다. 배기가스에 포함되어 있는 높은 레벨의 이산화황은 Cu-chabazite SCR 촉매의 NOx 저감률을 감소시키는 역할을 할 수 있다. 본 연구에서는 Cu-chabazite SCR 촉매의 황 피독에 의한 NOx 저감 성능을 연구하기 위하여 벤치플로 시스템을 구축하였다. Cu-chabazite SCR 촉매를 황 피독 시키기 위하여 5% 이산화탄소, 14% 산소, 5% 물과 나머지 질소로 만들어진 배기가스에 500 ppm의 이산화황을 각각 150, 200, 250, 300℃에서 2시간씩 노출 시켰다. 황 피독후 Cu-chabazite SCR 촉매의 불활성 한계를 측정하기 위하여 저온(150~300℃)에서 NOx 저감 성능을 평가하였다. 또한, 600 과 700℃에서 각각 30분씩 탈황 작업을 수행하여, 황 피독된 Cu-chabazite SCR 촉매의 NOx 저감 성능이 회복될 수 있는 온도를 결정하였다.
Chabazite
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Chabazite
Faujasite
Sodalite
Alkaline earth metal
Ferrierite
Mother liquor
Analcime
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The interzeolite conversion of faujasite (FAU-type) zeolites to chabazite (CHA-type) zeolite in the presence of N,N,N-trimethyladamantammonium and N,N,N-dimethylethylcyclohexylammonium cations was investigated over a large compositional range by carefully controlling the reaction mixture compositions. Highly crystalline CHA zeolites were also obtained by the transformation of several zeolite types including EMT, LTL, LEV, RTH, and MFI frameworks. The formation of CHA zeolite from FAU zeolite precursors was substantially faster than that from zeolite L with a similar composition. High-silica CHA zeolites were also produced successfully using a mixture of TMAda with a number of less expensive organic structure-directing agents. The CHA zeolite materials have been synthesized with high crystallinity and with a Si/Al ratio ranging from 5 to 140. Our data support the importance of structural similarity between the zeolite precursors, nucleation/crystallization processes, and the zeolite product in the interzeolite conversion compared to conventional amorphous aluminosilicate gels. Our synthetic methods could be used to prepare other 8-membered ring zeolites such as AEI and AFX frameworks, potential candidates for selective catalytic reduction of NOx, light olefin production, and CO2 abatement.
Chabazite
Faujasite
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(1) The changes in the zeolite chabazite during sorption have been investigated by means of X-ray examination of single crystals and of powders. (2) The heats of sorption for very small additions ammonia to the zeolite have been measured. (3) A theory has been advanced to explain the results.
Chabazite
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