• Title/Summary/Keyword: Heterogeneous catalyst

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Synthesis and Characterization of Zn(1-x)NixAl2O4 Spinels as a New Heterogeneous Catalyst of Biginelli's Reaction

  • Akika, Fatima-Zohra;Kihal, Nadjib;Habila, Tahir;Avramova, Ivalina;Suzer, Sefik;Pirotte, Bernard;Khelili, Smail
    • Bulletin of the Korean Chemical Society
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    • v.34 no.5
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    • pp.1445-1453
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    • 2013
  • $Zn_{(1-x)}Ni_xAl_2O_4$ (x = 0.0-1.0) spinels were prepared at $800^{\circ}C$ by co-precipitation method and characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The specific surface area was determined by BET. SEM image showed nano sized spherical particles. XPS confirmed the valence states of the metals, showing moderate Lewis character for the surface of materials. The powders were successfully used as new heterogeneous catalysts of Biginelli's reaction, a one-pot three-component reaction, leading to some dihydropyrimidinones (DHPMs). These new catalysts that produced good yields of DHPMs, were easily recovered by simple filtration and subsequently reused with persistent activity, and they are non-toxic and environmentally friendly. The optimum amount of catalyst is 20% by weight of benzaldehyde derivatives, while the doping amount has been found optimal for x = 0.1.

Electrochemical Characteristics of Solid Polymer Electrode Fabricated with Low IrO2 Loading for Water Electrolysis

  • Ban, Hee-Jung;Kim, Min Young;Kim, Dahye;Lim, Jinsub;Kim, Tae Won;Jeong, Chaehwan;Kim, Yoong-Ahm;Kim, Ho-Sung
    • Journal of Electrochemical Science and Technology
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    • v.10 no.1
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    • pp.22-28
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    • 2019
  • To maximize the oxygen evolution reaction (OER) in the electrolysis of water, nano-grade $IrO_2$ powder with a low specific surface was prepared as a catalyst for a solid polymer electrolyte (SPE) system, and a membrane electrode assembly (MEA) was prepared with a catalyst loading as low as $2mg\;cm^{-2}$ or less. The $IrO_2$ catalyst was composed of heterogeneous particles with particle sizes ranging from 20 to 70 nm, having a specific surface area of $3.8m^2g^{-1}$. The anode catalyst layer of about $5{\mu}m$ thickness was coated on the membrane (Nafion 117) for the MEA by the decal method. Scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) confirmed strong adhesion at the interface between the membrane and the catalyst electrode. Although the loading of the $IrO_2$ catalyst was as low as $1.1-1.7mg\;cm^{-2}$, the SPE cell delivered a voltage of 1.88-1.93 V at a current density of $1A\;cm^{-2}$ and operating temperature of $80^{\circ}C$. That is, it was observed that the over-potential of the cell for the oxygen evolution reaction (OER) decreased with increasing $IrO_2$ catalyst loading. The electrochemical stability of the MEA was investigated in the electrolysis of water at a current density of $1A\;cm^{-2}$ for a short time. A voltage of ~2.0 V was maintained without any remarkable deterioration of the MEA characteristics.

Nanosulfated Silica as a Potential Heterogeneous Catalyst for the Synthesis of Nitrobenzene

  • Khairul Amri;Aan Sabilladin;Remi Ayu Pratika;Ari Sudarmanto;Hilda Ismail;Budhijanto;Mega Fia Lestari;Won-Chun Oh;Karna Wijaya
    • Korean Journal of Materials Research
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    • v.33 no.7
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    • pp.265-272
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    • 2023
  • In this study, the synthesis of nitrobenzene was carried out using sulfated silica catalyst. The study delved into H2SO4/SiO2 as a solid acid catalyst and the effect of its weight variation, as well as the use of a microwave batch reactor in the synthesis of nitrobenzene. SiO2 was prepared using the sol-gel method from TEOS precursor. The formed gel was then refluxed with methanol and calcined at a temperature of 600 ℃. SiO2 with a 200-mesh size was impregnated with 98 % H2SO4 by mixing for 1 h. The resulting 33 % (w/w) H2SO4/SiO2 catalyst was separated by centrifugation, dried, and calcined at 600 ℃. The catalyst was then used as a solid acid catalyst in the synthesis of nitrobenzene. The weights of catalyst used were 0.5; 1; and 1.5 grams. The synthesis of nitrobenzene was carried out with a 1:3 ratio of benzene to nitric acid in a microwave batch reactor at 60 ℃ for 5 h. The resulting nitrobenzene liquid was analyzed using GC-MS to determine the selectivity of the catalyst. Likewise, the use of a microwave batch reactor was found to be appropriate and successful for the synthesis of nitrobenzene. The thermal energy produced by the microwave batch reactor was efficient enough to be used for the nitration reaction. Reactivity and selectivity tests demonstrated that 1 g of H2SO4/SiO2 could generate an average benzene conversion of 40.33 %.

Decomposition of Sulfamethoxazole by Catalytic Wet Peroxide Oxidation (촉매습식과산화(CWPO)를 이용한 설파메톡사졸의 분해)

  • Kim, Dul Sun;Lee, Dong-Keun;Kim, Jin Sol
    • Clean Technology
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    • v.24 no.4
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    • pp.293-300
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    • 2018
  • Sulfamethoxazole (SMX) is sulfaamide-based synthetic antibiotics, which are widely prescribed pharmaceutical compound to treat bacterial infections in both human and animals. Most of them are not completely decomposed as refractory substances. The environmental impact of pharmaceuticals as emerging contaminants has generated severe concerns. In this study, catalytic wet peroxide oxidation (CWPO) of SMX was carried out with $Cu/Al_2O_3$ catalyst and investigated the optimum reaction conditions of temperature, dosage of catalyst and concentration of $H_2O_2$ to completely decompose the SMX. It was observed that SMX was completely decomposed within 20 min using 0.79 mM $H_2O_2$ and 6 g $Cu/Al_2O_3$ catalyst at 1 atm and $40^{\circ}C$, but SMX was not fully mineralized and converted to intermediates as hydroylated-SMX, sulfanilic acid, 4-aminobenzenesulfinic acid and nitrobenzene. After that these are completely mineralized through organic acid. We proposed the decomposition reaction path ways of SMX by analyzing the behavior of these intermediates. To investigate the durability of heterogeneous catalyst, decomposition of SMX was observed by continuously recycling catalysts. When the heterogeneous catalyst of 10 wt% $Cu/Al_2O_3$ was continuously reused 5 times, decomposition of SMX was a little lowered, but the activity of catalyst was overall very stable.

Chiral Mesoporous Silica for Asymmetric Metal-free Catalysis: Enhancement of Chirality thorough Confinement Space by Plug Effect

  • Jeong, Eun-Yeong;Im, Cheong-Rae;Park, Sang-Eon
    • Proceedings of the Korean Vacuum Society Conference
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    • 2011.08a
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    • pp.199-199
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    • 2011
  • The addition of a carbanion to ${\yen}{\acute{a}}{\yen}{\hat{a}}$-unsaturated carbonyl compounds is of importance in the C-C bond formation reactions for modern pharmaceuticals and organic synthesis. Recently, heterogeneous asymmetric catalysis became more attractive area of research because of the easy recovery and separation of the catalyst from the reaction system. Most of synthetic methods for heterogeneous catalysts were grafting or immobilization of homogeneous catalyst onto the solid supports. Trans-1,2-Diaminocyclohexane(DACH) and L-proline ligands have been enormously used as chiral ligands in several catalytic transformation under homogenous conditions. Our group prepared l-proline functionalized mesoporous silica was synthesized under acidic condition using a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer template (EO20PO70EO20, Pluronic P-123, BASF). Furthermore, we successfully directly synthesized trans-1,2 diaminocyclohexane functionalized mesoporous silica by using microwave method. The direct functionalization of chiral ligand into the framework of mesoporous materials is expected to be useful for the heterogeneous asymmetric catalysis. So, we adopt the direct synthesis of chiral ligand functionalized mesoporous silica by using thermal and microwave irradiation. Then, chiral ligand functionalized mesoporous silicas were applied to enantioselective asymmetric catalytic reactions.

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Heterogeneous SnCl2/SiO2 versus Homogeneous SnCl2 Acid Catalysis in the Benzo[N,N]-heterocyclic Condensation

  • Darabi, Hossein Reza;Aghapoor, Kioumars;Mohsenzadeh, Farshid;Jalali, Mohammad Reza;Talebian, Shiva;Ebadi-Nia, Leila;Khatamifar, Ehsan;Aghaee, Ali
    • Bulletin of the Korean Chemical Society
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    • v.32 no.1
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    • pp.213-218
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    • 2011
  • The scope of homogeneous Lewis acid-catalyzed benzo[N,N]-heterocyclic condensation was expanded to include the use of various metal salts not reported in the literature and $SnCl_2{\cdot}2H_2O$ was finally selected. Among various solid supports activated with $SnCl_2$, heterogeneous $SnCl_2/SiO_2$ proved to be the most effective and significantly higher conversions were achieved compared to $SnCl_2{\cdot}2H_2O$ itself. The results of TG-DTA and BET indicated that dispersed $SnCl_2$ coordinates with surface hydroxyl groups of silica leading to formation of stable Lewis acid sites. Low catalyst loading, operational simplicity, practicability and applicability to various substrates render this eco-friendly approach as an interesting alternative to previously applied procedures.

The Influence of the Internal Donors in the Heterogenous Olefin Polymerization Catalyst on the Molecular Structure of Linear Low Density Polyethylene (불균일계 올레핀 중합촉매내 내부전자공여체가 선형 저밀도폴리에틸렌 분자구조에 미치는 영향)

  • Ko, Young Soo
    • Korean Chemical Engineering Research
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    • v.45 no.4
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    • pp.410-413
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    • 2007
  • The effect of internal donor(ID) in the heterogeneous Ziegler-Natta catalyst on the ethylene-1-butene copolymerization and the molecular structure of the resulting copolymer was investigated. $SiO_2$-supported $TiCl_4$ catalysts having ID/Ti molar ratio of 0.5 were prepared with ethyaluminium dichloride, magnesium alkyl, 2-ethyl-1-hexanol and $TiCl_4$. Three different IDs were employed such as ethylbenzoate(EB), diisobuylphthalate(DIBP) and dioctylphthalate(DOP). ID-added catalyst showed a larger fraction of Ti(+3) compared to that of no ID-added catalyst. The EB-added catalyst showed the highest activity in copolymerization. Xylene soluble value decreased by more than 50 % with ID-added catalysts compared to that of no ID-added catalyst. Crystaf analysis showed the chemical compositional distribution of PE copolymer was improved in the case of DIBP-added catalyst significantly. It could be explained that the presence of ID could make more even active sites and block the non-stereospecific active sites.

Development of Solid Base Catalyst K2CO3/γ-Al2O3 for the Production of Biodiesel (바이오디젤 생산을 위한 K2CO3/γ-Al2O3 고체염기촉매의 개발)

  • Sim, Yeon Ju;Kim, Jong Hoon;Kim, Eui Yong
    • Korean Chemical Engineering Research
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    • v.54 no.1
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    • pp.64-69
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    • 2016
  • The applications of heterogeneous catalyst have been relatively active area of research in the biodiesel process. These catalysts have the benefit of easy recovery and reusability of the catalyst. The objective of this study is to find out significant effect of calcination temperature on $K_2CO_3/{\gamma}-Al_2O_3$ catalytic activity in the biodiesel formation reaction. As a results, the temperature at which a catalyst was calcined had very important influence on the catalytic activity. The catalytic activity increased up to $600^{\circ}C$, but it severely decreased above the temperature. The reduction of catalyst activity at high temperature would be due to the deduction of the active sites of Al-O-K and $Al-O_2-K$.

Polymerization of Ethylene over $Cp_2ZrCl_2$ Catalyst Supported on Montmorillonite (Montmorillonite에 담지된 $Cp_2ZrCl_2$ 촉매를 이용한 에틸렌 중합특성 연구)

  • Ahn, Sung-Hyun;Lee, Sung-Ho;Choi, Moo-Seok;Im, Jun-Seop;Sheikh, Rizwan;Cho, Deug-Hee;Park, Yeung-Ho
    • Applied Chemistry for Engineering
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    • v.24 no.1
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    • pp.55-61
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    • 2013
  • Heterogeneous metallocene catalysts supported on montmorillonite (MMT), [$Cp_2ZrCl_2$/MMT, $Cp_2ZrCl_2$/MAO/MMT, and $Cp_2ZrCl_2$ + MAO/MMT], were prepared with three different methods of immobilization and tested for ethylene polymerization. The heterogeneous catalysts immobilized on organo clay (30B-MMT) showed the higher metal loading and polymerization activity than those immobilized on natural clay $Na^+-MMT$. These results suggest that the hydroxyl groups of organo clay interlayers react with the MAO and catalyst through the chemical bond. The metallocene catalyst supported directly on MMT showed lower activity for ethylene polymerization compared to the homogeneous systems, while MMT/MAO/$Cp_2ZrCl_2$, catalysts treated with MAO before impregnation, showed a higher activity. The polymers obtained from MMT-supported catalysts have higher melting point, molecular weight and molecular weight distributions than those of homogeneous catalysts. The polymer particles with increasing significant size. Ethylene polymerization over 30B-MMT/MAO/$Cp_2ZrCl_2$ catalyst was also performed varying the process variables to optimize the process conditions.

Scale-up Study of Heterogeneous Catalysts for Biodiesel Production from Nepalese Jatropha Oil (네팔산 자트로파 오일로부터 바이오디젤 제조를 위한 불균일계 촉매 Scale-up 연구)

  • Sim, Minseok;Lee, Seunghee;Kim, Youngbin;Ku, Huiji;Woo, Jaegyu;Joshi, Rajendra;Jeon, Jong-Ki
    • Clean Technology
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    • v.27 no.2
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    • pp.198-204
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    • 2021
  • This study focused on a two-step process using heterogeneous catalysts to produce biodiesel using Nepalese jatropha oil as a raw material. As a first step, the effect of the repetitive regeneration number of Amberlyst-15 on the esterification reaction of FFA in jatropha oil was investigated. Second, the possibility of a transesterification reaction scale-up using a dolomite bead catalyst was tested. Using 120 kg of jatropha seeds from Nepal, 30 L (27 kg) of jatropha oil was obtained, and the jatropha oil yield from the seeds was about 25.0 wt%. The acid value and FFA content of jatropha oil were measured to be 11.3 mgKOH g-1 and 5.65%, respectively. As a result of the esterification reaction of jatropha oil using the Amberlyst-15 catalyst in the form of beads, the acid value of the reaction product could be lowered to 0.26 mgKOH g-1 when the fresh Amberlyst-15 catalyst was used. As the regeneration of the Amberlyst-15 catalyst is repeated, the catalyst has been deactivated, and the esterification reaction performance has deteriorated. The cause of the deactivation seems to be due to the catalyst being broken and impurities being deposited. It was confirmed that the Amberlyst-15 catalyst could be reused up to 5 times for the esterification reaction of jatropha oil. In the second step, the transesterification reaction, a dolomite catalyst, was mass-produced and used in the form of beads. By transesterifying the pretreated jatropha oil in a spinning catalyst basket reactor equipped with 90 g of dolomite bead catalyst, 89.1 wt% of biodiesel yield was obtained in 2 hours after the start of the reaction, which was similar to the transesterification of soybean oil under the same conditions.