• 제목/요약/키워드: large pore molecular sieves

검색결과 4건 처리시간 0.016초

최근에 개발된 고체산 촉매 (Recent Developed Solid Acid Catalysts)

  • 고태석;서곤
    • 공업화학
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    • 제3권1호
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    • pp.18-23
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    • 1992
  • 최근에 개발된 세 종류의 고체산 촉매를 간단히 설평하였다. 클로버라이트는 매우 큰 세공이 있는 분자체이고, 티타늄실리케이트는 구조가 기존의 분자체와 다르며, Envirocat은 염화알루미늄 촉매를 대체하기 위해 개발된 촉매이다.

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Shape-Selective Catalysis over Zeolite. An Attempt in the Alkylation of Biphenyl

  • Sugi, Yoshihiro;Komura, Kenichi;Kim, Jong Ho
    • 공업화학
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    • 제17권3호
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    • pp.235-242
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    • 2006
  • Liquid phase alkylation of biphenyl (BP) was studied over large pore zeolites. Selective formation of the least bulky products, 4,4'-diisopropylbiphenyl (4,4'-DIPB) occurred only in the isopropylation of BP over some large pore molecular sieves. H-mordenites (MOR) gave the highest selectivity among them. The dealumination of MOR enhanced catalytic activity and the selectivity of 4,4'-DIPB because of the decrease of coke-deposition. Non-selective catalysis occurs on external acid sites over MOR with the low $SiO_2/Al_2O_3$ ratio because severe coke-deposition deactivates the acid sites inside the pores by blocking pore openings. The selectivity of DIPB isomers was changed with reaction temperature. Selective formation of 4,4'-DIPB was observed at moderate temperatures such as $250^{\circ}C$, whereas the decrease of the selectivity of 4,4'-DIPB occurred at higher temperatures as $300^{\circ}C$. However, 4,4'-DIPB was almost exclusive isomer in the encapsulated DIPB isomers inside the pores even at high temperatures. These decreases of the selectivity of 4,4'-DIPB are due to the isomerization of 4,4'-DIPB on the external acid sites. Some 12-membered molecular sieves, such as SSZ-24, MAPO-5 (M:Mg, Zn, Si), SSZ-31, and ZSM-12, which have straight channels, gave 4,4'-DIPB with moderate to high selectivity; however; SSZ-55, SSZ-42, and MAPO-36 (M: Mg, Zn) gave lower selectivity because of cages in 12-membered one dimensional channels. Three dimensional H-Y and Beta zeolites also yield 4,4'-DIPB in low yield because of their wide circumstances for the isopropylation of BP. The increasing the size of alkylating agent enhanced the shape-selective alkylaiton even for the zeolites, such as UTD-1. The ethylation of BP to ethylbiphenyls (EBPs) and diethylbiphenyls (DEBPs) over MOR was non-selective. The ethylation of BP to EBPs was controlled kinetically. However, there was difference in reactivity of EBPs and DEBPs for their further ethylation. 4-EBP was ethylated preferentially among the isomers, although the formation of 4,4'-DEBP was less selective. The least bulky 4-EBP and 4,4'-DEBP have the highest reactivity among EBPs and DEBPs for the ethylation to polyethylbiphenyls (PEBPs). These results show that the environments of MOR pores are too loose for shape selective formation of the least bulky isomers, 4-EBP and 4,4'-DEBP in the ethylation of BP, and that MOR pores have enough space for the further ethylation of 4,4'-DEBP.

비이온성 계면활성제 수용액에서 Na2SiO3와 H2SiF6의 반응을 통한 메조포러스 실리카의 제조 (Preparation of Mesoporous Molecular Sieve by the Reaction of Na2SiO3 and H2SiF6 in the Presence of an Aqueous Nonionic Surfactant Solution)

  • 김진영;권오윤
    • 공업화학
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    • 제29권1호
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    • pp.122-126
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    • 2018
  • 비이온성 계면활성제 수용액 중에서 $Na_2SiO_3$$H_2SiF_6$의 빠른 반응을 통하여 메조포러스 분자체를 제조하였다. 침전은 수초 이내에 형성되었으며, 시료의 XRD분석은 d-spacing이 3.1-5.8 nm인 잘 발달된 피크를 나타내어 메조포러스분자체임을 확인할 수 있었다. 비표면적은 비이온 계면활성제에 따라 $290-1,018m^2/g$의 큰 값을 나타내었으며, 기공분포는 2.5-3.1 nm의 일정한 값을 보여주었다. SEM을 통해 관찰한 입자의 모양은 크기가 ${\sim}0.5{\mu}m$로 균일하고 잘 분리된 구형이었으며, TEM은 기공의 형태가 일정크기의 벌레구멍 모양임을 보여주었다.

Al-SBA-1 분자체에서 acetalization 반응의 합성, 촉매활성화 및 특성 (Synthesis, characterization and catalytic activity of acetalization over Al-SBA-1 molecular sieve)

  • 칸단 벤카타찰람;푸시파라지 헤마라다;팽메이메이;호종표;장현태
    • 한국산학기술학회:학술대회논문집
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    • 한국산학기술학회 2011년도 춘계학술논문집 1부
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    • pp.141-143
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    • 2011
  • Al-SBA-1(Si/Al = 40, 80 and 120) and Al,Mg-SBA-1 (Si/(Al+Mg) = 40 and 80) molecular sieves were synthesized and characterized. Acetalization of n-heptanal with methanol was studied under autogenous pressure between 80 and $150^{\circ}C$. Since protonation of n-heptanal was fast, addition of methanol to the same to formed hemiacetal slowly whereas conversion of hemiacetal to acetal was fast. The catalysts exhibited nearly similar conversion irrespective of their difference in acidity, and all of them showed more than 80 % conversion either at 80 or $100^{\circ}C$. Hence it is evident that the difference in acidity is not so important in differentiating the activity of the catalysts. The large pore size and hydrophilic and hydrophobic properties are suggested to be the main factors that control acetalization.

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