• Title/Summary/Keyword: catalytic reactivity

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Inhibition Effects of Toxic Solvent Mixture in Catalytic Oxidation Process (유독성 유기용매의 촉매산화공정에서 혼합조성에 따른 간섭효과)

  • 이승범;김원일;홍인권;김형진
    • Journal of environmental and Sanitary engineering
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    • v.16 no.3
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    • pp.72-79
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    • 2001
  • The selective catalytic oxidation of toxic aromatic solvents (benzene, toluene, ethylbenzene, and styrene) and their mixtures were studied on a $Pt/{\;}{\gamma}-Al_2O_3$ catalyst at temperature ranging from $160~350^{\circ}C$. The deep conversion of aromatic solvents was increased as the inlet concentration was decreased and the reaction temperature was increased. The reactivity increases in order benzene > toluene > ethylbenzene > styrene. In mixture, remarkable effects on reaction rate and selectivity have been evidence ; the strongest inhibition effect is shown by styrene and increase in a reverse order with respect to that of reactivity. The inhibition effect was increased in order styrene > ethylbenzene > toluzene > benzene. This trend is due to the competition adsorption between the two or three reactants on the oxidized catalyst. Also, the deep conversion change of benzene was a small in tertiary mixtures(including of benzene and styrene) comparing with conversion characteristics of binary mixture with styrene. This result was due to small concentration of styrene. which had very strong inhibition effect.

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Reactions of Aryl Halides with Phenoxides and Alkoxides by Phase Transfer Catalysis

  • Jo, Bong Rae;Park, Seong Dae
    • Bulletin of the Korean Chemical Society
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    • v.5 no.3
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    • pp.126-129
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    • 1984
  • The reaction of aryl halides with phenoxides and alkoxides were investigated under phase transfer catalytic conditions. 2,4-Dinitro- and 4-nitrohalobenzenes reacted readily with phenoxides in NaOH(aq)-benzene in the presence of Bu4N+Br, affording the products quantitatively. Although the aryl halides did not react with alkoxides under the same condition, the reactions were completed within 2 hours at room temperature when conducted under solid-liquid phase transfenr catalytic condition. The reactivity of aryl halides was in the order, Ar = 2,4-dinitrophenyl > 4-nitrophenyl, and X = F > Cl, consistent with the SNAr mechanism. The reactivity of oxyanions increased with the change of reaction condition from liquid-liquid to solid-liquid phase transfer catalysis. The results were explained with the concentration and the degree of hydration of the anion in benzene.

Support Effect of Catalytic Activity on 3-dimensional Au/Metal Oxide Nanocatalysts Synthesized by Arc Plasma Deposition

  • Jung, Chan Ho;Naik, B.;Kim, Sang Hoon;Park, Jeong Y.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.08a
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    • pp.140.2-140.2
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    • 2013
  • Strong metal-support interaction effect is an important issue in determining the catalytic activity for heterogeneous catalysis. In this work, we report the catalytic activity of $Au/TiO_2$, $Au/Al_2O_3$, and $Au/Al_2O_3-CeO_2$ nanocatalysts under CO oxidation fabricated by arc plasma deposition (APD), which is a facile dry process with no organic materials involved. These catalytic materials were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and $N_2$-physisorption. Catalytic activity of the materials has measured by CO oxidation using oxygen, as a model reaction, in a micro-flow reactor at atmospheric pressure. Using APD, the catalyst nanoparticles were well dispersed on metal oxide powder with an average particle size (3~10 nm). As for catalytic reactivity, the result shows $Au/Al_2O_3-CeO_2$ nanocatalyst has the highest catalytic activity among three samples in CO oxidation, and $Au/TiO_2$, and $Au/Al_2O_3$ in sequence. We discuss the effects of structure and metal-oxide interactions of the catalysts on catalytic activity.

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Preparation and Application of ACFs Derived from the Petroleum Pitch and the Organometallic Compounds

  • Hong, Ik-Pyo;Ha, Baik-Hyon
    • Carbon letters
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    • v.3 no.3
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    • pp.146-151
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    • 2002
  • Activated carbon fibers were prepared from the petroleum isotropic pitch and organometallic compounds. The metalsvwere dispersed uniformly in the ACFs. The specific surface area and pore size distributions of metal containing ACFsvwere measured. The mesopores of ACFs were developed by Co, Ni, and Mn metals addition and the catalytic reactivityvof ACFs'SOx removal was increased by adding Ni and Pd metals. It was found that the mesopores did not work forvthe improvement of catalytic reactivity of ACFs' SOx removal with the blank experiment using the metal removedvACFs.

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Reactivity of SO2 Catalytic Reduction over Sn-Zr Based Catalyst under High Pressure Condition (고압조건에서 Sn-Zr계 촉매상에서 SO2 촉매환원 반응특성)

  • Park, Jung Yun;Park, No-Kuk;Lee, Tae Jin;Baek, Jeom-In;Ryu, Chong Kul
    • Korean Chemical Engineering Research
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    • v.48 no.3
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    • pp.316-321
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    • 2010
  • The $SO_2$ catalytic reduction was carried out under the condition of high pressure in this study. Sn-Zr based oxide and CO were used as the catalyst and reducing agent for the reduction of $SO_2$ to element sulfur, respectively. In order to compare the reactivity with the pressure on the catalytic process, the reactivity tests were performed under the conditions of atmospheric pressure and 20 atm. $SO_2$ conversion, the element sulfur yield and COS selectivity were also compared with changing the reaction temperature, $CO/SO_2$ mole ratio and the space velocity(GHSV). $SO_2$ conversion increased with increasing temperature and $CO/SO_2$ mole ratio under the condition of atmospheric pressure and element sulfur yield decreased due to the production of COS by the series reaction of CO and the produced sulfur. However, high $SO_2$ conversion and high element sulfur were obtained under the condition of 20 atm. It was concluded that COS decreased due to the condensation of the produced element sulfur under the condition of high pressure. Therefore, the high sulfur yield for $SO_2$ catalytic reduction could be profitably obtained under the condition of high pressure.

A Study on Remanufacturing of Deactivated Commercial Diesel Oxidation Catalyst by CVS-75 mode in Light Duty Diesel Engine (비활성화된 상용 디젤 산화 촉매의 소형 디젤 기관에서 CVS-75 모드를 이용한 재제조에 관한 연구)

  • Lee, Chang-Hee;Park, Hea-Kyung
    • Journal of Powder Materials
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    • v.18 no.6
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    • pp.517-525
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    • 2011
  • In this study, the used DOCs, which could remove the air pollutants such as CO and HC in the exhaust gas from diesel vehicle, were remanufactured by various conditions. Their catalytic performances and characterization were also investigated. The remanufacturing process of the deactivated DOCs includes high temperature cleaning of incineration, ultrasonic cleaning for washing with acid/base solutions to remove deactivating materials deposited to the surface of the catalysts, and active component reimpregnation for reactivating catalytic activity of them. The catalytic performance tests of the remanufactured DOCs were carried out by the diesel engine dynamo systems and chassi dynamo systems in CVS-75 mode. All prepared catalysts were characterized by the optical microscopes, SEM, EDX, porosimeter and BET to investigate correlations between catalytic reactivity and surface characteristics of them. The remanufactured DOCs at various conditions showed the improved catalytic performances reaching to 90% of fresh DOC, which is attributed to remove the deactivating materials from the surface of the used DOC through the analysis of catalytic performance test and their characterization.

The First-principles View of Nanometal Alloy Catalysts

  • Ham, Hyung Chul;Hwang, Gyeong S.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2013.02a
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    • pp.129-129
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    • 2013
  • Nanometal alloy catalysts have been found to significantly increase catalytic efficiency, compared to the monometallic counterparts. This enhancement can be attributed to various alloying effects: i) the existence of uniquemixed-metal surface sites [the so called ensemble (geometric) effect]; ii) electronic state changes due to metal-metal interactions [the so called ligand (electronic) effect]; and iii) strain caused by lattice mismatch between the alloy components [the socalled strain effect]. In addition, the presence of low-coordination surface atoms and preferential exposure of specific facets [(111), (100), (110)] in association with the size and shape of nanoparticle catalysts [the so called shape-size-facet effect] can be another important factor for modifying the catalytic activity. However, mechanisms underlying the alloying effect still remain unclear owing to the difficulty of direct characterization. Computational approaches, particularly the prediction using first-principles density functional theory (DFT), can be a powerful and flexible alternative for unraveling the role of alloying effects in catalysis since those can give us quantitative insights into the catalytic systems. In this talk, I will present the underlying principles (such as atomic arrangement, facet, local strain, ligand interaction, and effective atomic coordination number at the surface) that govern catalytic reactions occurring on Pd-based alloys using the first-principles calculations. This work highlights the importance of knowing how to properly tailor the surface reactivity of alloy catalysts for achieving high catalytic performance.

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Electronic structure and catalytic reactivity of model oxide catalysts

  • Kim, Yu-Gwon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.02a
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    • pp.35-35
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    • 2010
  • Understanding the mechanistic details of heterogeneous catalytic reactions will provide a way to tune the selectivity between various competing reaction channels. In this regard, catalytic decomposition of alcohols over the rutile $TiO_2$(110) surface as a model oxide catalyst has been studied to understand the reaction mechanism employing the temperature-programmed desorption (TPD) technique. The $TiO_2$(110) model catalyst is found to be active toward alcohol dehydration. We find that the active sites are bridge-bonded oxygen vacancies where RO-H heterolytically dissociates and binds to the vacancy to produce alkoxy (RO-) and hydroxyl (HO-). Two protons adsorbed onto the bridge-bonded oxygen atoms (-OH) readily react with each other to form a water molecule at ~500 K and desorb from the surface. The alkoxy (RO-) undergoes decomposition at higher temperatures into the corresponding alkene. Here, the overall desorption kinetics is limited by a first-order decomposition of intermediate alkoxy (RO-) species bound to the vacancy. We show that detailed analysis on the yield and the desorption temperatures as a function of the alkyl substituents provides valuable insights into the reaction mechanism. After the catalytic role of the oxygen vacancies has been established, we employed x-ray photoelectron spectroscopy to further study the surface electronic structure related to the catalytically active defective sites. The defect-related state in valence band has been related to the chemically reduced $Ti^{3+}$ defects near the surface region and are found to be closely related to the catalytic activity of the $TiO_2$(110) surface.

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The Effect of Catalytic Metal Work Functions and Interface States on the High Temperature SiC-based Gas Sensors (금속 (Pt)과 4H-SiC의 계면상태에 따른 실리콘 카바이드 기반 고온 가스센서 특성 분석)

  • Jung, Ji-Chul;Koo, Sang-Mo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.24 no.4
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    • pp.280-284
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    • 2011
  • Silicon carbide (SiC)-based gas sensors can be operated at very high temperatures. So far, catalytic metal-schottky diodes respond fast to a change between a reducing and an oxidizing atmosphere. Therefore SiC diodes have been suggested for high temperature gas sensor applications. In this work, the effect of reactivity of the catalytic surface on the 4H-SiC sensor-structures in 375 K~775 K have been studied and some fundamental simulations have also been performed.

Catalytic Cyclopolymerization and Copolymerization of Diethyl Dipropargylmalonate by (toluene)Mo$(CO)_3

  • Jeon, Sang Jin;Sim, Sang Cheol;Jo, Chan Sik;Kim, Tae Jeong;Gal, Yeong Sun
    • Bulletin of the Korean Chemical Society
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    • v.21 no.10
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    • pp.1044-1046
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    • 2000
  • Catalytic copolymerization of diethyl dipropargylmalonate (DEDPM) and phenylacetylene (PA) by Mo(CO)6 and (toluene) Mo(CO)3/chloranil has resulted in the expected copolymer consiting of a polyene backbone with five-and/or six-membered rings and th e PPA structure. Both complexes exhibited not only varying degree of catalytic activity depending upon the relative mole ratio of two monomers but also characterize the types of coploymers. The former yields the polyene backbone containing only five-membered rings as well as PA while the latter produces the polymers consisting of both five-and six-membered ring structure. Comparative studies show that Mo(CO)6 exhibits reactivity toward DEDPM alone, thus catalyzing initially metathesis cyclopoly-merization of DEDPM followed by copolymerization with PA while the (toluene)Mo(CO)3/chloranil system shows affinity for both PA and DEDPM.