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Shape-selective catalysis of zeolites = 제올라이트의 형상 선택적 촉매작용
서명 / 저자 Shape-selective catalysis of zeolites = 제올라이트의 형상 선택적 촉매작용 / Byoung-Joon Ahn.
발행사항 [서울 : 한국과학기술원, 1984].
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4102338

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DAC 8404

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Cation exchange will modify the diffusional characteristics of zeolite catalysts. It will also alter the acidic properties of the catalysts. In addition exchanged cation may serve as a major component. Interaction of hydrocarbons with Cu(II) exchanged zeolite was investigated using EPR and ESCA techniques. Acidic properties of zeolite catalysts were studied by i.r. and temperature programmed desorption techniques. It was shown that the acid site strength in ZSM-5 zeolite decreased with increasing radius of exchanged alkalimetal cations. Adsorption and diffusion of cyclohexane, xylene isomers and $C_5-C_9$ paraffins were studied using HZSM-5,-8 and -11 zeolite samples of uniform size. Uptake of p-xylene was rapid in HZSM zeolites but diffusion of m-and o-xylene was substantially slow. The amount taken up indicated that most of the internal surface was not accessible by m-xylene. Reactions of toluene were studied over HZSM-5, -8, -11 and cation-exchanged as well as Mg-modified pentasil zeotites. o-Xylene isomerization was one order of magnitude faster than toluene disproportionation over HZSM-5 at 400℃. It seems that the bimolecular transition state required for transalkylation are not readily formed within the ZSM-5 structure. Only Cs-ZSM-5 showed increased p-xylene selectivity. The para-selectivity increased with increasing degree of cation exchange and with decreasing reaction temperature. It seems that the internal pore structure of Cs-ZSM-5 cannot provide an enough room to form the restricted transition state that leads to m-and o-xylene. The overall conversion of toluene, however, decreased with increasing degree of cation exchange and this was attributed to the reduced acidity. High p-ethyltoluene selectivity was observed over Cs-exchanged and Mg-modified HZSM zeolites. The increased para-selectivity was interpreted in terms of selective diffusion of the smaller para-isomer combined possibly with the sterically favored formation of para-isomer. Isomerization of para-isomer to ortho-isomer seems to proceed through meta-isomer. Cation exchange affects the diffusion and catalytic properties of pentasil zeolites by modifying intracrystalline structure as well as acidic properties. It was found that the molecular shape selective characteristics of ZSM-8 type zeolite was quite similar to ZSM-5 type but different from ZSM-11 zeolite.

서지기타정보

서지기타정보
청구기호 {DAC 8404
형태사항 xiii, 146 p. : 삽도 ; 26 cm
언어 영어
일반주기 저자명의 한글표기 : 안병준
지도교수의 영문표기 : Hak-Ze Chon
지도교수의 한글표기 : 전학제
학위논문 학위논문(박사) - 한국과학기술원 : 화학과,
서지주기 Reference : p. 137-143
주제 Catalysis.
제올라이트. --과학기술용어시소러스
촉매 활성. --과학기술용어시소러스
표면 분석. --과학기술용어시소러스
Surfaces (Technology) --Analysis.
Zeolites.
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