• Title, Summary, Keyword: metal catalyst

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Polymerization of Tetrahydrofuran with New Transition Metal Catalyst and Its Mechanism: (p- Methylbenzyl)- o -cyanopyridinium Hexafluoroantimonate

  • 강준원;한양규
    • Bulletin of the Korean Chemical Society
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    • v.18 no.4
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    • pp.433-438
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    • 1997
  • (p-Methylbenzyl)-o-cyanopyridinium hexafluoroantimonate, a new catalyst, was synthesized by the reaction of o-cyanopyridine with α-bromo-p-xylene followed by exchange of counteranion with SbF6θ. We examined the effect of the catalyst on the bulk polymerization of tetrahydrofuran under various conditions. The catalytic activity was best in the presence of 1 : 1 of epichlorohydrin used as cocatalyst versus catalyst concentration. The resulting polymers had relatively low conversions in 1.0-40%. Their number average molecular weights were in the range of 800 to 5300. Propagation rate increased with increase in temperature according to an Arrhenius expression giving an activation energy of 62 KJ/mol. We also found catalyst proceeds via a cationic mechanism.

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Field Emission Characteristics and Growth Analysis of Carbon Nanotubes by Plasma-enhanced Chemical Vapor Deposition (플라즈마 화학 기상 증착법을 이용한 탄소나노튜브의 성장 분석 및 전계방출 특성)

  • 오정근;주병권;김남수
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.12S
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    • pp.1248-1254
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    • 2003
  • Carbon nanotubes(CNTs) are grown by using Co catalyst metal. CNTs fabricated by PECVD(plasma enhanced chemical vapor deposition) method are studied in terms of surface reaction and surface structure by TEM and Raman analysing method and ate analysed in its electrical field emission characteristics with variation of space between anode and cathode. Acetylene(C$_2$H$_2$) gas is used as the carbon source, while ammonia and hydrogen gas are used as catalyst and dilution gas. The CNTs grown by hydrogen(H$_2$) gas plasma indicates better vortical alignment, lower temperature process, and longer tip, compared to that grown by ammonia(NH$_3$) gas plasma. The CNTs fabricated with Co(cobalt) catalyst metal and PECVD method show the multiwall structure in mid-circle type in tip-end and the inner vacancy of 10nm. Emission properties of CNTs indicate the turn-on field to be 2.6 V/${\mu}{\textrm}{m}$ We suggest that CNTs can be possibly applied to the emitter tip of FEDs and high brightness flat lamp because of low temperature CNTs growth, low turn-on field.

Field Emission Characteristics and Growth Analysis of Carbon Nanotubes by plasma-enhanced chemical vapor deposition (플라즈마 화학 기상 증착법을 이용한 탄소나노튜브의 성장 분석 및 전계방출 특성)

  • Oh, Jung-Keun;Ju, Byeong-Kwon;Kim, Nam-Soo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.71-75
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    • 2003
  • Carbon nanotubes(CNTs) are grown by using Co catalyst metal. CNTs fabricated by PECVD(plasma enhanced chemical vapor deposition) method are studied in terms of surface reaction and surface structure by TEM and Raman analysing method and are analysed in its electrical field emission characteristics with variation of space between anode and cathode. Acetylene($C_2H_2$) gas is used as the carbon source, while ammonia and hydrogen gas are used as catalyst and dilution gas. The CNTs grown by hydrogen($H_2$) gas plasma indicates better vertical alignment, lower temperature process and longer tip, compared to that grown by ammonia($NH_3$) gas plasma. The CNTs fabricated with Co(cobalt) catalyst metal and PECVD method show the multiwall structure in mid-circle type in tip-end and the inner vacancy of 10nm. Emission properties of CNTs indicate the turn-on field to be $2.6\;V/{\mu}m$. We suggest that CNTs can be possibly applied to the emitter tip of FEDs and high brightness flat lamp because of low temperature CNTs growth, low turn-on field.

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Catalytic Oxidation of Ammonia over Metal Supported on Alumina at Low Temperature (금속담지 활성알루미나 촉매의 암모니아 저온연소반응)

  • Lim, Yun-Hui;Lee, Ji-Yeol;Park, Byung-Hyun
    • Journal of the Korean Applied Science and Technology
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    • v.30 no.3
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    • pp.371-379
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    • 2013
  • In order to improve the selective oxidation reaction of gaseous ammonia at a low temperature, various types of metal-impregnated activated alumina were prepared, and also physical and chemical properties of the conversion of ammonia were determined. Both types of metal (Cu, Ag) impregnated activated alumina show high conversion rate of ammonia at high temperature (over $300^{\circ}C$). However, at lower temperature ($200^{\circ}C$), Ag-impregnated catalyst shows the highest conversion rate (93%). In addition, the effects of lattice oxygen of the developed catalyst was studied. Ce-impregnated catalyst showed higher conversion rate than commercial alumina, but also showed lower conversion rate than Ag-impregnated sample. Moreover, 5 vol.% of Ag activation under hydrogen shows the highest conversion rate result. Finally, through high conversion at low temperature, it was considered that the production of NO and $NO_2$, toxic by-products, were effectively inhibited.

Study of toluene decomposition using nonthermal plasma and catalyst (저온플라즈마와 촉매를 이용한 톨루엔 분해 연구)

  • Lim, Yun Hui;Lee, Ju-Yeol;Shin, Jae-Ran;Choi, Jin-Sik;Park, Byung Hyun
    • Journal of the Korean Applied Science and Technology
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    • v.31 no.4
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    • pp.541-548
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    • 2014
  • This study was performed to obtain high conversion efficiency of $C_7H_8$ using non-thermal plasma and metal-supported catalyst. Adsorption-desorption characteristics of toluene was performed using 4A type (Zeolite) filled in a concentration reactor. Through this test, it was found that the concentration reactor has 0.020 g/g of adsorption capacity (at ambient temperature and pressure) and 3,600 ppm of desorption property at $150^{\circ}C$ (with in 20 min). In case of developed catalyst, toluene decomposition rate of Pd-AO (Pd coated catalyst) was better than Pd/Cu-AO and Pd/Ag-AO (Pd/Ag composite metal catalyst). Developed non-thermal plasma system was obtained flame amplification effect using injection process of desorbed tolune, and 98% of removal efficiency.

A review on reactivity and stability of heterogeneous metal catalysts for deoxygenation of bio-oil model compounds

  • Lup, Andrew Ng Kay;Abnisa, Faisal;Daud, Wan Mohd Ashri Wan;Aroua, Mohamed Kheireddine
    • Journal of Industrial and Engineering Chemistry
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    • v.56
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    • pp.1-34
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    • 2017
  • Catalytic deoxygenation is a fundamental process for bio-oil upgrading due to its high oxygen content which will result in lower heating value, corrosion and instability issues. The discovery of an excellent heterogeneous deoxygenation metal catalyst with high deoxygenation activity is a necessary breakthrough for an optimized bio-oil catalytic deoxygenation. For an effective deoxygenation supported metal catalyst, properties such as high $H_2$ sticking coefficient, optimal metal-oxygen bond strength and suitable acid strength from support are needed to ensure facile scission of C-O bonds and activation of $H_2$ and O-containing compounds. Metals such as Fe, Ru, Sn, W, Zr and supports such as C, $TiO_2$, $ZrO_2$ which are oxophilic were also observed to enhance direct removal of oxygen from O-containing compounds due to their high C-O and C=O bond affinities. The choice of support is important to ensure it has optimal physicochemical properties for facile deoxygenation and the optimal acid strength to enhance C-O hydrogenolysis activity while minimizing coke formation. The choice of metal is dependent on the type of model compound since different metals catalyze different reaction pathways of the deoxygenation of model compounds. This review presents on the use of heterogeneous metal catalysts in the deoxygenation of bio-oil model compounds through several perspectives which are catalytic properties, reaction conditions, deactivation and regeneration of metal catalysts. In addition, several outlooks on the feasible range of reaction condition for catalytic deoxygenation and criteria of excellent deoxygenation supported metal catalysts were also expressed in this article based on the studies on the literatures.

Synthesis and Characterization of Non-precious Metal Co-PANI-C Catalysts for Polymer Electrolyte Membrane Fuel Cell Cathodes (고분자 전해질 연료전지 캐소드용 코발트-폴리아닐린-탄소로 구성된 비귀금속 촉매의 제조 및 특성 평가)

  • Choi, Jong-Ho
    • Journal of the Korean Electrochemical Society
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    • v.16 no.1
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    • pp.52-58
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    • 2013
  • In order to overcome the cost issue for commercialization of polymer electrolyte membrane fuel cell (PEMFC), this research was conducted for replacing platinum cathode catalyst with non-precious metal catalyst. The non-precious metal catalyst (Co-PANI-C) was synthesized by the simple reduction method with polyaniline (PANI), carbon black, and cobalt precursor without any heat treatment. Characterization of new Co-PANI-C composite catalysts was done by the measurement of X-ray diffraction (XRD) and thermogravimetric analysis (TGA) for structure analysis and performed by rotating disk electrode (RDE) and rotating ring disk electrode (RRDE) for electrochemical analysis. As a result, Co-PANI-C catalyst showed 60 mV lower on-set potential for oxygen reduction reaction (ORR) than Pt/C catalyst, but the overall reduction current of Co-PANI-C catalysts by ORR was still smaller than that of Pt/C. In addition, the ORR behavior of Co-PANI-C catalysts depending on the rotation speed of electrode and the stability of Co-PANI-C catalyst under potential cycling and the performance of fuel cell conditions are also discussed.

A study on the recovery of chromium from metal-plating wastewater with spent catalyst (폐산화철촉매에 의한 도금폐수중 크롬이온 회수에 관한 기초연구)

  • Lee Hyo Sook;Oh Yeung Soon;Lee Woo Chul
    • Journal of the Korean Institute of Resources Recycling
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    • v.13 no.2
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    • pp.9-15
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    • 2004
  • A large tons of spent iron oxide catalyst come from the Styrene Monomer(SM) production company. It is caused to pollute the land and underground water due to the high alkali contents in the catalyst by burying them in the landfill. In order to recycle the spent catalyst, a basic study on the recovery of chromium ion from metal plating wastewater with the spent catalyst was carried out. The iron oxide catalyst adsorbed physically $Cr^{+6}$ in the lower pH 3.0, that is the isoelectric point of the spent catalyst. It was found that the iron oxide catalyst reduced the $Cr^{+6}$ into Cr+3 by the oxidation of ferrous ion into ferric ion on the surface of catalyst, and precipitated as $Cr(OH)_3$ in the higher than pH 3.0. The $Cr^{+6}$ was recovered 2.0∼2.3g/L catalyst in the range of pH 0.5∼2.0, but it was recovered 1.5 g/L catalyst at pH 3.0 of wastewater. The recovery of Cr was increased as the higher concentration in the continuous process, but the flowrates were nearly affected on the Cr recovery.

Modification of Poly(methylsilene) Catalyzed by Group 4 and 6 Transition Metal Complexes and Its Pyrolysis

  • 양수연;박종목;우희권;김환기;김동표;황택성
    • Bulletin of the Korean Chemical Society
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    • v.18 no.12
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    • pp.1264-1268
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    • 1997
  • The poly(methylsilene) (1) was modified with the group 4 metallocene Cp2MCl2/Red-Al (M = Ti, Zr, Hf) combination catalyst and with the group 6 metal carbonyl M(CO)6 (M = Cr, Mo, W) catalyst, producing the highly cross-linked isoluble polymer and the lowly cross-linked soluble polymer, respectively. An interrelationship between molecular weight and percent ceramic residue yield with metal within the respective group was not found. The polymers modified with the group 4 metallocene combination catalysts have higher molecular weight and lower percent ceramic residue yield than the polymers modified with the group 6 metal carbonyl catalysts do. The catalytic activity of group 4 metallocene combinations appears to be higher at ∼100 ℃, but to be lower at very high temperature than those of group 6 metal carbonyls. The pyrolysis of the modified 1 yielded SiC ceramic.

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Synthesis of potassium glyceroxide catalyst for sustainable green fuel (biodiesel) production

  • Pradhan, Subhalaxmi;Shen, Jianheng;Emami, Shahram;Mohanty, Pravakar;Naik, S.N.;Dalai, Ajay K.;Reaney, Martin J.T.
    • Journal of Industrial and Engineering Chemistry
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    • v.46
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    • pp.266-272
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    • 2017
  • Metal hydroxides and alkoxides are used as base catalysts for biodiesel production. When metal hydroxides are dissolved in alcohol, they produce water, which can react with triglycerides (TGs) and produce free fatty acids (FFAs) rather than the desired fatty acid alkyl esters. Metal alkoxides are more expensive to produce and their transportation is hazardous. In this study, potassium alkoxide catalysts were synthesized from potassium hydroxide (KOH) solution and glycerol, which is by-product of biodiesel production process, by heating 50% KOH solution and glycerol at different mole ratios, temperatures and vacuum pressures. These operating parameters were optimized and their interactive effect on catalyst synthesis was studied by using response surface methodology (RSM). This study also focused on the development of a correlation relating the effects of these variables with drying behavior of reagents during catalyst synthesis. The results indicated that KOH to glycerol mole ratio and vacuum pressure had the most significant effects (P < 0.0001) on free water mass loss during catalyst synthesis. The optimum reaction condition was KOH to glycerol mole ratio of 2:1, reaction temperature $130^{\circ}C$ and vacuum pressure 113 mbar. X-ray powder diffraction showed that glycerol derived alkoxide compounds were predominantly mono-potassium substituted alkoxides that occur as adducts with potassium hydroxide. The glyceroxide catalyst prepared at 3:1 mole ratio of KOH:glycerol has improved biodiesel yield to that of conventional potassium methoxide ($KOCH_3$) catalyst.