• Title/Summary/Keyword: 고체 촉매

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Application of Chiral Ligands Heterogenized over Solid Supports on Enantioselective Catalysis (고체 담체에 고정화된 키랄리간드의 비대칭 촉매반응에의 응용)

  • Lee, Kwang-Yeon;Kawthekar, Rahul B.;Kim, Geon-Joong
    • Applied Chemistry for Engineering
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    • v.17 no.6
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    • pp.565-574
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    • 2006
  • The trend towards the application of single enantiomers of chiral compounds is undoubtedly increasing. Among the various methods to obtain one single enantio-riched compound selectively, enantioselective catalysis is the most attractive method. Especially, it is important to increase the activity, selectivity and lifetime of usually expensive chiral catalysts with a minute quantity in the enantioselective synthesis. Immobilization of active homogeneous catalysts is a fashionable topic in asymmetric catalysis, providing the inherent advantage of easy separation and better handling properties. Many different ways have been investigated to improve the enantioselectivity of products and to recycle the catalysts. This review mainly focused on the present scope and limitations of different types of enantioselective heterogeneous catalysts.

Production of Levulinic Acid from Glucosamine Using Solid Acid Catalyst (고체 산촉매를 이용한 글루코사민으로부터 레불린산 생산)

  • Park, Mi-Ra;Kim, Hyo Seon;Kim, Sung-Koo;Jeong, Gwi-Taek
    • Korean Chemical Engineering Research
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    • v.56 no.1
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    • pp.61-65
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    • 2018
  • In this study, the conversion of glucosamine, which is a major monomer in chitin/chitosan of crustacean shell, using solid acid catalyst was performed to obtain chemical intermediates such as levulinic acid and 5-hydroxymethyl furfural (5-HMF). The conversion reaction was optimized with four reaction factors of selection of ionic resin catalyst, reaction temperature, catalyst amount, and reaction time. As an optimized result, the highest levulinic acid yield was achieved approximately 36.86% under the determined conditions (Amberlyst 15 as a solid-acid catalyst, $180^{\circ}C$, 5% catalyst amount and 60 min). On the other hand, 5-HMF yield was found to be 0.91% at the condition.

Mesoporous Silica Catalysts Modified with Sulfonic Acid and Their Catalytic Activity on Ring Opening Polymerization of Octamethylcyclotetrasiloxane (술폰산으로 표면개질된 메조기공 실리카 촉매의 제조 및 Octamethylcyclotetrasiloxane 개환중합에서의 촉매 활성)

  • Lee, Yeonsong;Hwang, Ha Soo;Lee, Jiyoung;Lo, Nu Hoang Tien;Nguyen, Tien Giang;Lee, Donghyun;Park, In
    • Applied Chemistry for Engineering
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    • v.31 no.4
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    • pp.383-389
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    • 2020
  • Mesoporous silica solid catalysts modified with sulfonic acid were prepared for cationic ring-opening polymerization of octamethylcyclotetrasiloxane (D4). Two sets of MCM-41 (1.7 and 2.8 nm) and SBA-15 (8.1 and 15.9 nm) with different pore sizes were used as catalyst supports. The surface of silica materials was modified with (3-mercaptopropyl)trimethoxysilane by silylation reaction and oxidized to sulfonic acid. The structures of the prepared catalysts were examined by X-ray diffraction and nitrogen adsorption-desorption. The pore size, specific surface area, and pore volume of the modified solid catalysts decreased slightly. In addition, the modification of the sulfonic acid on the silica surface was confirmed by using infrared spectroscopy and nuclear magnetic resonance spectroscopy. To observe the effect of the particle size on the catalytic activity, it was observed with a scanning electron microscope. The catalysts were used to synthesize PDMS through a ring-opening polymerization of D4, and the conversion and polymerization rate of the polymerization reaction depended on the pore size, specific surface area, particle size, and particle agglomeration of the catalysts. In order for the polymerization rate, the catalyst prepared with SBA-15 of 8.1 nm pore size had the fastest reaction rate and showed the best catalytic activity.

Production of Dry Oxidant through Catalytic H2O2 Decomposition over Mn-based Catalysts for NO Oxidation (NO 산화를 위한 Mn계 촉매상 과산화수소 분해를 이용한 건식산화제 생성)

  • Jang, Jung Hee;Choi, Hee Young;Han, Gi Bo
    • Clean Technology
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    • v.21 no.2
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    • pp.130-139
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    • 2015
  • The NO oxidation process has been applied to improve a removal efficiency of NO included in exhaust gas. In this study, to produce a dry oxidant for the NO oxidation process, the catalytic H2O2 decomposition method was proposed. A variety of the heterogeneous solid-acidic Mn-based catalysts were prepared for the catalytic H2O2 decomposition and the effect of their physico-chemical properties on the catalytic H2O2 decomposition were investigated. The results of this study showed that the acidic sites of the Mn-based catalysts has an influence on the catalytic H2O2 decomposition. The Mn-based catalyst having the abundant acidic sites within the wide temperature range in NH3-TPD shows the best performance for the catalytic H2O2 decomposition. Therefore, the NO oxidation efficiency, using the dry oxidant produced by the H2O2 decomposition over the Mn-based catalyst having the abundant acidic properties under the wide temperature range, was higher than the others. As a remarkable result, the best performances in the catalytic H2O2 decomposition and NO oxidation was shown when the Mn-based Fe2O3 support catalyst containing K component was used for the catalytic H2O2 decomposition.

A Study of Membrane Reactor Process for DME synthesis (반응 및 분리공정이 결합된 DME제조 공정개발에 관한 연구)

  • 박상진;윤민영;서봉국;이규호
    • Proceedings of the Membrane Society of Korea Conference
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    • 2004.05b
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    • pp.163-167
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    • 2004
  • Dimethyl ether(DME)는 대기 오염 문제와 에너지 문제가 대두됨에 따라 저공해 경유 대체 연료로 각광받고 있는 물질이다. 최근 들어 메탄올로부터 고체산 촉매를 이용하여 DME를 합성하고자 하는 연구가 활발히 진행 중이다[1-4]. 메탄올로부터 DME의 합성시 촉매로는 제올라이트나 SiO$_2$/${\gamma}$-Al$_2$O$_3$를 사용하기도 하지만 ${\gamma}$-Al$_2$O$_3$나 변형된 ${\gamma}$-Al$_2$O$_3$가 일반적으로 사용된다.(중략)

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Improved Performance of Direct Carbon Fuel Cell by Catalytic Gasification of Ash-free Coal (무회분탄 연료의 촉매 가스화에 의한 직접탄소연료전지의 성능 향상)

  • Jin, Sunmi;Yoo, Jiho;Rhee, Young Woo;Choi, Hokyung;Lim, Jeonghwan;Lee, Sihyun
    • Clean Technology
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    • v.18 no.4
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    • pp.426-431
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    • 2012
  • Carbon-rich coal can be utilized as a fuel for direct carbon fuel cell (DCFC). However, left-behind ash after the electrochemical oxidation may hinder the electrochemical reactions. In this study, we produced ash-free coal (AFC) by thermal extraction and then tested it as a fuel for DCFC. DCFC was built based on solid oxide electrolyte and the electrochemical performance of AFC mixed with $K_2CO_3$ was compared with AFC only. Significantly enhanced power density was found by catalytic steam gasification of AFC. However, an increase of the power density by catalytic pyrolysis was negligible. This result indicated that a catalyst activated the steam gasification reactions, producing much more $H_2$ and thus increasing the power density, compared to AFC only. Results of a quantitative analysis showed much improved kinetics in AFC with $K_2CO_3$ in agreement with DCFC results. A secondary phase of potassium on yttria-stabilized zirconia (YSZ) surface was observed after the cell operation. This probably caused poor long-term behavior of AFC with $K_2CO_3$. A thin YSZ (30 ${\mu}m$ thick) was found to be higher in the power density than 0.9 mm of YSZ.

Catalytic Decomposition of $SF_6$ by Hydrolysis and Oxidation over ${\gamma}-Al_2O_3$ (${\gamma}-Al_2O_3$ 촉매상에서 가수분해와 산화반응에 의한 $SF_6$ 촉매분해 특성)

  • Lee, Sun-Hwa;Park, No-Kuk;Yoon, Suk-Hoon;Chang, Won-Chul;Lee, Tae-Jin
    • Clean Technology
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    • v.15 no.4
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    • pp.273-279
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    • 2009
  • $SF_6$, which has a high global warming potential, can be decomposed to sulfur and fluorine compounds through hydrolysis by $H_2O$ or oxidation by $O_2$ over solid acid catalysts. In this study ${\gamma}-Al_2O_3$ was employed as the solid acid catalyst for the abatement of $SF_6$ and its catalytic activity was investigated with respect to the reaction temperature and the space velocity. The catalytic activity for $SF_6$ decomposition by the hydrolysis reached the maximum at and above 973 K with the space velocity of $20,000\;ml/g_{-cat}{\cdot}h$, exhibiting a conversion very close to 100%. When the space velocity was lower than $45,000\;ml/g_{-cat}{\cdot}h$, the conversion was maintained at the maximum value. On the other hand, the conversion of $SF_6$ by the oxidation was about 20% under the same conditions. The SEM and XRD analyses revealed that the ${\gamma}-Al_2O_3$ was transformed to ${\alpha}-Al_2O_3$ during the hydrolysis and to $AlF_3$ during the oxidation, respectively. The size of $AlF_3$ after the oxidation was over $20\;{\mu}m$, and its catalytic activity was low due to the low surface area. Therefore, it was concluded that the hydrolysis over ${\gamma}-Al_2O_3$ was much more favorable than the oxidation for the catalytic decomposition of $SF_6$.

Solid Bases as Racemization Catalyst for Lipase-catalyzed Dynamic Kinetic Resolution of Naproxen 2,2,2-Trifluoroethyl Thioester (리파아제에 의한 나프록센 2,2,2-트리플로로에틸 씨오에스터의 Dynamic Kinetic Resolution을 위한 라세미화 촉매로서의 고체 염기)

  • 김상범;원기훈;문상진;김광제;박홍우
    • KSBB Journal
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    • v.19 no.3
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    • pp.215-220
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    • 2004
  • A variety of solid bases such as inorganic bases, basic anion exchange resins, and resin-bound bases were tested as a catalyst for racemization of (S)-naproxen 2,2,2-trifluoroethyl thioester in isooctane at 45$^{\circ}C$. Among the various bases, DIAIOM WA30, which is a weakly basic anion exchange resin with a tertiary amine based on a highly porous type styrene-divinylbenzene copolymer, showed the highest catalytic activity. The second-order interconversion constant of DIAION WA30 was 8.6${\times}$10$\^$-4/ mM$\^$-1/h$\^$-1/ and about 3 times higher than that of trioctylamine under the same conditions. The rate of DIAION WA30-catalyzed racemization decreased with increasing an amount of water added to the reaction medium. Lipase-catalyzed kinetic resolution of racemic naproxen 2,2,2-trifluoroethyl thioester was successfully carried out under in situ racemization of substrate with DIAION WA30 in isooctane at 45$^{\circ}C$. More than 60% conversion and 99% enantiomeric excess for the desired (S)-naproxen product were obtained. Furthermore, such a solid base catalyst could be easily separated and reused in contrast to trioctylamine.

Selective Dehydration of Sorbitol to Isosorbide over Sulfonated Activated Carbon Catalyst (설폰화 활성탄 촉매를 이용한 솔비톨의 아이소소바이드로의 탈수반응)

  • Kang, Hyo Yoon;Hwang, Dong Won;Hwang, Young Kyu;Hwang, Jin-Soo;Chang, Jong-San
    • Korean Chemical Engineering Research
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    • v.51 no.2
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    • pp.189-194
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    • 2013
  • A sulfonated activated carbon (AC-$SO_3H$) was used as a solid acid catalyst for dehydration of sorbitol to isosorbide and its catalytic performance was compared with the commercial solid acid such as acidic ion exchange resin, Amberlyst-36, and sulfated copper oxide. The catalytic performance with 100% sorbitol conversion and 52% isosorbide selectivity was obtained over AC-$SO_3H$ at 423.15 K. Although AC-$SO_3H$ possessed only 0.5 mmol/g of sulfur content, it showed the similar dehydration activity of sorbitol to isosorbide with Amberlyst-36 (5.4 mmol/g) at 423.15 K. Based on the high thermal and chemical stability of AC-$SO_3H$, one-step reactive distillation, where isosorbide separation can be carried out simultaneously with sorbitol dehydration, was tried to increase the recovery yield of isosobide from sorbitol. The reactive distillation process using AC-$SO_3H$, the turnover number of AC-$SO_3H$ was 4 times higher than the conventional two-step process using sulfuric acid.