• Title/Summary/Keyword: Heterogeneous catalyst

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Decomposition Studies of DFP Using Transition Metal Catalysts (전이금속촉매를 사용한 DFP 분해 성능 연구)

  • Kye, Young-Sik;Jeong, Keunhong;Chung, Woo Young
    • Applied Chemistry for Engineering
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    • v.21 no.1
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    • pp.1-5
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    • 2010
  • Cu(II)-organic complexes were synthesized with Lewis base organic ligands including diamine, aminothiol, and dithiol to determine the reactivity for DFP hydrolysis. Results show that the aminothiol catalyst enhances the hydrolysis of DFP in three folds compared to diamine type because aminothiol has higher basicity than diamine. Due to low solubility of Cu(II)(1,2-ethane dithiol)$(NO_3)_2$, it is impossible to compare directly the rates in homogeneous condition. However, the rate of dithol complex is even 1.6 times faster than that of the diamine type. The reactivity of zeolite for DFP hydrolysis is also evaluated. NaY type does not promote the hydrolysis, but RuNaY shows relatively lower reactivity than those of Cu(II)-organic ligands complexes.

Asymmetric Catalytic Activity of Mesoporous Mordenite containing Polymeric Chiral Salen Complexes in the Mesopore System (폴리머 키랄 살렌을 함유한 메조세공 모더나이트의 비대칭 촉매 활성)

  • Guo, Xiao-Feng;Kim, Yong-Suk;Kawthekar, Rahul B.;Kim, Geon-Joong
    • Applied Chemistry for Engineering
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    • v.20 no.3
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    • pp.279-284
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    • 2009
  • The formation of mesoporous pores in the microporous mordenite crystals was performed by controlled silica extraction on alkaline treatment. Inner tunable mesopore size could be controlled by changing the concentration of alkaline solution. The pore structure of mordenite zeolite was studied by instrumental analysis after alkaline-treatment. To obtain the cage type mesopores, Ti-coating on the ourside mordenite crystals before alkaline treatment was investigated to be the most effective. Polymeric chiral salen Co (III) complexes were successfully encapsulated in mesoporous mordenite zeolite by "ship-in-a-bottle" method. The heterogeneous catalyst could be applied in asymmetric ring opening of epichlorohydrine by water. It showed very excellent enantioselectivity with a high yield in the catalysis.

A study on production of dry oxidant by decomposition of H2O2 on K-Mn/Fe2O3 catalyst and NO oxidation process according to simulated flue gas flow (K-Mn/Fe2O3 촉매 상 H2O2 분해에 의한 건식산화제 생성 및 모사 배가스 유량에 따른 NO 산화공정)

  • Choi, Hee Young;Shin, Woo Jin;Jang, Jung Hee;Han, Gi Bo
    • Journal of the Korean Applied Science and Technology
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    • v.34 no.2
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    • pp.367-375
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    • 2017
  • In this study, NO oxidation process was studied to increase the NO treatment efficiency of pollutant present in exhaust gas. $H_2O_2$ catalytic cracking was introduced as a method of producing dry oxidizing agents with strong oxidizing power. The $K-Mn/Fe_2O_3$ heterogeneous catalysts applicable to the $H_2O_2$ decomposition process were prepared and their physico-chemical properties were investigated. The prepared dry oxidant was applied to the NO oxidation process to treat the simulated exhaust gas containing NO, NO conversion rates close to 100% were confirmed at various flow rates (5, 10, 20 L/min) of the simulated flue gas.

Production of Ethylbenzene from 4-Vinylcyclohexene (4-비닐시클로헥센을 이용한 에틸벤젠의 제조)

  • Joo, Young J.;Won, Jeong-Im;Kim, Chang-Min;Park, Kwang-Chun;Lee, Sang-Ok;Kim, Hong-Seok
    • Applied Chemistry for Engineering
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    • v.7 no.2
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    • pp.326-333
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    • 1996
  • Dehydrogenation of 4-vinylcyclohexene(4-VCH) to ethylbenzene is elucidated via catalytic transfer hydrogenation with the heterogeneous catalyst of Pd/C. Hydrogen-donor solvent is ethanol or water. Oxidizers of the catalytic dehydrogenation reaction are mono- or dinitro compounds, $H_2O_2$, NaClOn (n=1~4), or oxygen at $70{\sim}110^{\circ}C$. The ratio of 4-VCH/Nitro compounds is 1:0.02 to 1:0.5 and 4-VCH vs. $H_2O_2$ or NaClOn (n=1~4) is 1:0.1 to 1:3.

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X-ray absorption spectroscopic study of MgFe2O4 nanoparticles

  • Singh, Jitendra Pal;Lim, Weon Cheol;Song, Jonghan;Kim, Joon Kon;Chae, Keun Hwa
    • Proceedings of the Korean Vacuum Society Conference
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    • 2015.08a
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    • pp.230.2-230.2
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    • 2015
  • Nanoparticles of magnesium ferrite are used as a heterogeneous catalyst, humidity sensor, oxygen sensor and cure of local hyperthermia. These applications usually utilize the magnetic behavior of these nanoparticles. Moreover, magnetic properties of nanoferrites exhibit rather complex behavior compared to bulk ferrite. The magnetic properties of ferrites are complicated by spins at vortices, surface spins. Reports till date indicate strong dependency on the structural parameters, oxidation state of metal ions and their presence in octahedral and tetrahedral environment. Thus we have carried out investigation on magnesium ferrite nanoparticles in order to study coordination, oxidation state and structural distortion. For present work, magnesium ferrite nanoparticles were synthesized using nitrates of metal ions and citric acid. Fe L-edge spectra measured for these nanoparticles shows attributes of $Fe^{3+}$ in high spin state. Moreover O K-edge spectra for these nanoparticles exhibit spectral features that arises due to unoccupied states of O 2p character hybridized with metal ions. Mg K-edge spectra shows spectral features at 1304, 1307, 1311 and 1324 eV for nanoparticles obtained after annealing at 400, 500, 600, 800, 1000, and $1200^{\circ}C$. Apart from this, spectra for precursor and nanoparticles obtained at $300^{\circ}C$ exhibit a broad peak centered around 1305 eV. A shoulde rlike structure is present at 1301 eV in spectra for precursor. This feature does not appear after annealing. After annealing a small kink appear at ~1297 eV in Mg K-edge spectra for all nanoparticles. This indicates changes in local electronic structure during annealing of precursor. Observed behavior of change in local electronic structure will be discussed on the basis of existing theories.

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Density Functional Theory Study of Separated Adsorption of O2 and CO on Pt@X(X = Pd, Ru, Rh, Au, or Ag) Bimetallic Nanoparticles (Pt 기반 이원계 나노입자의 산소 및 일산화탄소 흡착 특성에 대한 전자밀도함수이론 연구)

  • An, Hyesung;Ha, Hyunwoo;Yoo, Mi;Choi, Hyuck;Kim, Hyun You
    • Korean Journal of Materials Research
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    • v.28 no.6
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    • pp.365-369
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    • 2018
  • We perform density functional theory calculations to study the CO and $O_2$ adsorption chemistry of Pt@X core@shell bimetallic nanoparticles (X = Pd, Rh, Ru, Au, or Ag). To prevent CO-poisoning of Pt nanoparticles, we introduce a Pt@X core-shell nanoparticle model that is composed of exposed surface sites of Pt and facets of X alloying element. We find that Pt@Pd, Pt@Rh, Pt@Ru, and Pt@Ag nanoparticles spatially bind CO and $O_2$, separately, on Pt and X, respectively. Particularly, Pt@Ag nanoparticles show the most well-balanced CO and $O_2$ binding energy values, which are required for facile CO oxidation. On the other hand, the $O_2$ binding energies of Pt@Pd, Pt@Ru, and Pt@Rh nanoparticles are too strong to catalyze further CO oxidation because of the strong oxygen affinity of Pd, Ru, and Rh. The Au shell of Pt@Au nanoparticles preferentially bond CO rather than $O_2$. From a catalysis design perspective, we believe that Pt@Ag is a better-performing Pt-based CO-tolerant CO oxidation catalyst.

Phase Transfer Catalytic Effects for Thiocyanate Displacement on Benzyl Chloride (티오시안산 염에 의한 염화벤질의 치환반응에 미치는 상이동 촉매효과)

  • Seung Hyun Chang;Mu Hong Yoon;Chang Su Kim;Kwang Bo Chung;Jae Hu Shim
    • Journal of the Korean Chemical Society
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    • v.33 no.6
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    • pp.651-656
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    • 1989
  • The catalytic effects of several phase-transfer catalysts (PTC) on the liquid-liquid heterogeneous nucleophilic displacement reaction of thiocyanate on benzyl chloride have been determined. Reactions followed a pseudo-first order dependency on the benzyl chloride concentration and the observed rate constant $(k_{obsd})$ were linearly related to the concentration of catalyst and varied with variables such as reaction temperature and solvent. The sequences of catalytic activity of the displacement were $NH_4Cl$ < BTMAC < 18-crown-6 < BTEAC < PEG < TBAC < CTMAB. Enthalpies and entropies of activation associated with the displacement were 15∼20 Kcal$mo^{l-1}$, -12∼-29 eu. respectively and the reaction occurs in the interphase comprising of microemulsion.

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Catalytic Activity of Au/$TiO_2$ and Pt/$TiO_2$ Nanocatalysts Synthesized by Arc Plasma Deposition

  • Jung, Chan-Ho;Kim, Sang-Hoon;Reddy, A.S.;Ha, H.;Park, Jeong-Y.
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.245-245
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    • 2012
  • Syntheses of oxide supported metal catalysts by wet-chemical routes have been well known for their use in heterogeneous catalysis. However, uniform deposition of metal nanoparticles with controlled size and shape on the support with high reproducibility is still a challenge for catalyst preparation. Among various synthesis methods, arc plasma deposition (APD) of metal nanoparticles or thin films on oxide supports has received great interest recently, due to its high reproducibility and large-scale production, and used for their application in catalysis. In this work, Au and Pt nanoparticles with size of 1-2 nm have been deposited on titania powder by APD. The size of metal nanoparticles was controlled by number of shots of metal deposition and APD conditions. These catalytic materials were characterized by x-ray diffraction (XRD), inductively coupled plasma (ICP-AES), CO-chemisorption and transmission electron microscopy (TEM). Catalytic activity of the materials was measured by CO oxidation using oxygen, as a model reaction, in a micro-flow reactor at atmospheric pressure. We found that Au/$TiO_2$ is reactive, showing 100% conversion at $110^{\circ}C$, while Pt/$TiO_2$ shows 100% conversion at $200^{\circ}C$. High activity of metal nanoparticles suggests that APD can be used for large scale synthesis of active nanocatalysts. We will discuss the effect of the structure and metal-oxide interactions of the catalysts on catalytic activity.

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Facile synthesis of ZnBi2O4-graphite composites as highly active visible-light photocatalyst for the mineralization of rhodamine B

  • Nguyen, Thi Mai Tho;Bui, The Huy;Dang, Nguyen Nha Khanh;Ho, Nguyen Nhat Ha;Vu, Quang Huy;Ngo, Thi Tuong Vy;Do, Manh Huy;Duong, Phuoc Dat;Nguyen, Thi Kim Phuong
    • Korean Journal of Chemical Engineering
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    • v.35 no.12
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    • pp.2442-2451
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    • 2018
  • Novel highly active visible-light photocatalysts in the form of zinc bismuth oxide ($ZnBi_2O_4$) and graphite hybrid composites were prepared by coupling via a co-precipitation method followed by calcination at $450^{\circ}C$. The asprepared $ZnBi_2O_4$-graphite hybrid composites were tested for the degradation of rhodamine B (RhB) solutions under visible-light irradiation. The existence of strong electronic coupling between the two components within the $ZnBi_2O_4$-graphite heterostructure suppressed the photogenerated recombination of electrons and holes to a remarkable extent. The prepared composite exhibited excellent photocatalytic activity, leading to more than 93% of RhB degradation at an initial concentration of $50mg{\cdot}L^{-1}$ with 1.0 g catalyst per liter in 150 min. The excellent visible-light photocatalytic mineralization of $ZnBi_2O_4-1.0graphite$ in comparison with pristine $ZnBi_2O_4$ could be attributed to synergetic effects, charge transfer between $ZnBi_2O_4$ and graphite, and the separation efficiency of the photogenerated electrons and holes. The photo-induced $h^+$ and the superoxide anion were the major active species responsible for the photodegradation process. The results demonstrate the feasibility of $ZnBi_2O_4-1.0graphite$ as a potential heterogeneous photocatalyst for environmental remediation.

Photocatalytic Generated Oxygen Species Properties by Fullerene Modified Two-Dimensional MoS2 and Degradation of Ammonia Under Visible Light

  • Zou, Cong-Yang;Meng, Ze-Da;Zhao, Wei;Oh, Won-Chun
    • Korean Journal of Materials Research
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    • v.31 no.6
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    • pp.353-366
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    • 2021
  • In this study, photocatalytic degradation of ammonia in petrochemical wastewater is investigated by solar light photocatalysis. Two-dimensional ultra-thin atomic layer structured MoS2 are synthesized via a simple hydrothermal method. We examine all prepared samples by means of physical techniques, such as SEM-EDX, HRTEM, FT-IR, BET, XRD, XPS, DRS and PL. And, we use fullerene modified MoS2 nanosheets to enhance the activity of photochemically generated oxygen (PGO) species. Surface area and pore volumes of the MoS2-fullerene samples significantly increase due to the existence of MoS2. And, PGO oxidation of MB, TBA and TMST, causing its concentration in aqueous solution to decrease, is confirmed by the results of PL. The generation of reactive oxygen species is detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). It is found that the photocurrent density and the PGO effect increase in the case with modified fullerene. The experimental results show that this heterogeneous catalyst has a degradation of 88.43% achieved through visible light irradiation. The product for the degradation of NH3 is identified as N2, but not NO2- or NO3-.