• 제목, 요약, 키워드: metal catalyst

검색결과 747건 처리시간 0.053초

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

  • 오정근;주병권;김남수
    • 한국전기전자재료학회논문지
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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.

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

  • 오정근;주병권;김남수
    • 한국전기전자재료학회:학술대회논문집
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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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금속담지 활성알루미나 촉매의 암모니아 저온연소반응 (Catalytic Oxidation of Ammonia over Metal Supported on Alumina at Low Temperature)

  • 임윤희;이주열;박병현
    • 한국응용과학기술학회지
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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.

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

  • 임윤희;이주열;신재란;최진식;박병현
    • 한국응용과학기술학회지
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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.

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

  • 최종호
    • 전기화학회지
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    • v.16 no.1
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    • pp.52-58
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    • 2013
  • 고분자 전해질 연료전지(Polymer Electrolyte Membrane Fuel Cell, PEMFC) 상용화를 위해 해결해야 할 과제 중의 하나인 가격 저감을 이루기 위한 방법으로 백금 촉매를 대신할 비귀금속(non-precious metal) 촉매 제조에 관한 연구를 수행하였다. 비귀금속 촉매의 합성은 산소환원반응(oxygen reduction reaction, ORR)의 활성점으로 알려져 있는 코발트-질소(Co-N) 결합을 형성하기 위해 질소를 포함하는 폴리아닐린(PANI)과 코발트염(Co precursor), 그리고 카본 블랙(C)을 일정한 비율대로 혼합한 후 특별한 열처리 과정 없이 단순한 화학적 환원법에 제조되었다. 제조된 Co-PANI-C 복합 촉매의 구조 분석을 위해 X-선 회절분석(X-ray diffraction, XRD)과 열중량분석(thermogravimetric analysis, TGA)을 실시하였고, ORR에 대한 활성을 평가하기 위해 rotating disk electrode(RDE) 및 rotating ring disk electrode(RRDE) 측정을 수행하였다. 그 결과 Co-PANI-C 복합 촉매는 ORR반응에 대한 개시 전압은 백금 촉매보다 60 mV 밖에 낮지 않은 값을 보였지만, 반응에 의해 발생되는 환원 전류는 여전히 백금 촉매보다 낮은 값을 보였다. 이 밖에도 전극 회전 속도에 따른 ORR 특성 변화, 전압 사이클 회수에 따른 내구성 변화, 연료전지 적용 시 성능 변화에 대해 논의할 것이다.

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

  • 이효숙;오영순;이우철
    • 자원리싸이클링
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    • v.13 no.2
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    • pp.9-15
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    • 2004
  • 석유화학공정으로부터 폐기되는 폐산화철촉매를 이용하여 도금합성폐수중 크롬회수에 관한 연구를 회분식과 연속식으로 실시하였다. 도금합성제수 중 $CrO _{4}^{-2}$ 형태의 음이온으로 존재하는 6가 크롬은 폐산화철촉매의 등전점(pH 3.0)이하에서 폐촉매와 물리적 흡착을 한다. 한편, 6가 크롬은 pH 3.0 이상에서도 폐촉매의 수산화철과 산화환원반응에 의해 일부 환원되어 $Cr(OH)_3$로 침전한다. 컬럼을 이용한 크롬 연속회수실험에서 크롬합성폐수의 pH가 0.5∼2.0일 때 폐촉매의 크롬흡착량은 2.0∼2.3g/L이며, pH가 3.0에서는 1.5g/L이었다. 폐수 중 크롬농도가 50∼500mg/L로 높아질수록 폐촉매에 흡착한 크롬누적량은 1.29∼8.56g/L로 증가하지만, 유속이 30∼80 ml/mm으로 증가하여도 크롬 흡착누적량은 2.21∼2.49 mg/L로 거의 유사하였다.

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.