• Title/Summary/Keyword: Catalyst dispersion

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Effects of Catalyst Dispersion for Reaction Energy Control on Eco-AZ91 MgH2 (Eco-AZ91 MgH2의 반응열 제어에 미치는 촉매 분산 효과)

  • SOOSUN LEE;SONG SEOK;TAE-WHAN HONG
    • Transactions of the Korean hydrogen and new energy society
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    • v.34 no.6
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    • pp.631-640
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    • 2023
  • This study selected Eco-AZ91 MgH2, which shows high enthalpy as a material for this purpose, as the basic material, and analyzed the change in characteristics by synthesizing TiNi as a catalyst to control the thermodynamic behavior of MgH2. In addition, the catalyst dispersion technology using graphene oxide (GO) was studied to improve the high-temperature aggregation phenomenon of Ni catalyst and to secure a source technology that can properly disperse the catalyst. XRD, SEM, and BET analysis were conducted to analyze the metallurgical properties of the material, and TGA and DSC analysis were conducted to analyze the dehydrogenation temperature and calorific value, and the correlation between MgH2, TiNi catalyst, and GO reforming catalyst was analyzed. As a result, the MgH2-5 wt% TiNi at GO composite could lower the dehydrogenation temperature to 478-492 K due to the reduction of the catalyst aggregation phenomenon and the increase in the reaction specific surface area, and an experimental result for the catalyst dispersion technology by GO could be ensured.

Preparation of Highly Dispersed Ru/$\alpha-Al_2O_3$ Catalyst for Preferential CO Oxidation (선택적 CO 산화 반응을 위한 Ru/$\alpha-Al_2O_3$ 촉매 고분산 제조 방법에 관한 연구)

  • Eom, Hyun-Ji;Koo, Kee-Young;Jung, Un-Ho;Rhee, Young-Woo;Yoon, Wang-Lai
    • Transactions of the Korean hydrogen and new energy society
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    • v.21 no.5
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    • pp.390-397
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    • 2010
  • 0.5wt% Ru/$\alpha-Al_2O_3$ catalysts are prepared by deposition-precipitation method for the preferential CO oxidation In order to investigate the effect of pH on the Ru dispersion and particle size, the pH of precursor solution is adjusted to between 5.5 and 9.5. 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared at the pH of 6.5 has high Ru dispersion of 17.9% and small particle size of 7.7nm. In addition, 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared at the pH 6.5 is easily reduced at low temperatures below $150^{\circ}C$ due to high dispersion of $RuO_2$ particle and shows high CO conversion over 90% in the wide temperature range between $100^{\circ}C$ and $160^{\circ}C$. Moreover, the deposition-precipitation is a feasible method to improve the Ru dispersion as compared to the impregnation method. The 0.5wt% Ru/$\alpha-Al_2O_3$ catalyst prepared by deposition-precipitation exhibits higher CO conversion than 0.5wt% Ru/$\alpha-Al_2O_3$ catalysts prepared by impregnation due to higher metal dispersion and better reducibility at low temperature.

Strength and conversion characteristics of DeNOx catalysts with the addition of dispersion agent (분산제 첨가에 따른 탈질촉매의 강도세기 및 전환특성)

  • Lee, Hyun Hee;Park, Kwang Hee;Cha, Wang Seog
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.14 no.12
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    • pp.6575-6580
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    • 2013
  • Various modified SCR catalysts were prepared and tested to improve the strength of catalysts for use under severe conditions. The SCR catalysts were modified with a binder and dispersion agent, and tested at the fixed bed reactor. FT-IR and $H_2$-TPR were used to analyze the degree of hydrogen use and ammonia adsorption by the modified catalysts. In the case of the SCR catalysts coated with 2.3g of the binder, 4.7g of ethanol, and 0.1g of dispersion agent, the strength of catalyst was increased by approximately 12%. On the other hand, despite the enhancement of strength, the activities of the SCR catalysts were decreased by 2-10%. When the mixed solution composed of binder, dispersion agent and $SiO_2$ solution was precipitated on the catalyst, the $NO_x$ conversion of the catalyst was decreased slightly. The Bronsted acid site and Lewis acid site worked as the activators for the SCR reaction, and were decreased by $SiO_2$.

Hydrogen Production Through Catalytic Dehydrogenation of Decalin over Pt/C Catalyst Using Activated Carbon Aerogel

  • Lee, Gihoon;Kang, Ji Yeon;Jeong, Yeojin;Jung, Ji Chul
    • Korean Journal of Materials Research
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    • v.25 no.4
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    • pp.191-195
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    • 2015
  • To improve its textural properties as a support for platinum catalyst, carbon aerogel was chemically activated with KOH as a chemical agent. Carbon-supported platinum catalyst was subsequently prepared using the prepared carbon supports(carbon aerogel(CA), activated carbon aerogel(ACA), and commercial activated carbon(AC)) by an incipient wetness impregnation. The prepared carbon-supported platinum catalysts were applied to decalin dehydrogenation for hydrogen production. Both initial hydrogen evolution rate and total hydrogen evolution amount were increased in the order of Pt/CA < Pt/AC < Pt/ACA. This means that the chemical activation process served to improve the catalytic activity of carbon-supported platinum catalyst in this reaction. The high surface area and the well-developed mesoporous structure of activated carbon aerogel obtained from the activation process facilitated the high dispersion of platinum in the Pt/ACA catalyst. Therefore, it is concluded that the enhanced catalytic activity of Pt/ACA catalyst in decalin dehydrogenation was due to the high platinum surface area that originated from the high dispersion of platinum.

Hydrophobic Catalyst Mixture for the Isotopic Exchange Reaction between Hydrogen and Water

  • Paek S.;Ahn D.H.;Choi H.J.;Kim K.R.;LEE M.;YIM S.P.;CHUNG H.
    • Proceedings of the Korean Radioactive Waste Society Conference
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    • 2005.11b
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    • pp.141-148
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    • 2005
  • Pt/SDBC catalyst, which is used for the hydrogen-water isotopic exchange reaction, was prepared. The various properties of the catalyst, such as the thermal stability, pore structure and the platinum dispersion, were investigated. A hydrophobic Pt/SDBC catalyst which has been developed for the LPCE column of the WTRF (Wolsong Tritium Removal Facility) was tested in a trickle bed reactor. An experimental apparatus was built for the test of the catalyst at various temperatures and gas velocities.

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Electrochemical Behavior of Cathode Catalyst Layers Prepared with Propylene Glycol-based Nafion Ionomer Dispersion for PEMFC (프로필렌글리콜에 분산된 나피온 이오노머로 제조된 공기극 촉매층의 연료전지 성능 특성 연구)

  • Woo, Seunghee;Yang, Tae-Hyun;Park, Seok-Hee;Yim, Sung-Dae
    • Korean Chemical Engineering Research
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    • v.57 no.4
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    • pp.512-518
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    • 2019
  • To develop a membrane electrode assembly (MEA) with lower Pt loading and higher performance in proton exchange membrane fuel cells (PEMFCs), it is an important research issue to understand interfacial structure of Pt/C catalyst and ionomer and design the catalyst layer structure. In this study, we prepared short-side-chain Nafion-based ionomer dispersion using propylene glycol (PG) as a solvent instead of water which is commonly used as a solvent for commercially available ionomers. Cathode catalyst layers with different ionomer content from 20 to 35 wt% were prepared using the ionomer dispersion for the fabrication of four different MEAs, and their fuel cell performance was evaluated. As the ionomer content increased to 35 wt%, the performance of the prepared MEAs increased proportionally, unlike the commercially available water-based ionomer, which exhibited an optimum at about 25 wt%. Small size micelles and slow evaporation of PG in the ionomer dispersion were effective in proton transfer by inducing the formation of a uniformly structured catalyst layer, but the low oxygen permeability problem of the PG-based ionomer film should be resolved to improve the MEA performance.

Synthesis of Pd-Ag on Charcoal Catalyst for Aerobic Benzyl Alcohol Oxidation Using [Hmim][PF6] ([Hmim][PF6]를 사용한 벤질 알코올의 호기성 산화반응용 팔라듐-은 차콜 촉매 제조)

  • Choo, Yunjun;Yoo, Kye Sang
    • Applied Chemistry for Engineering
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    • v.25 no.4
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    • pp.425-429
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    • 2014
  • Pd on charcoal particles were prepared by wet impregnation to develop commercial catalyst for aerobic benzyl alcohol oxidation. Especially, one of room temperature ionic liquids, [Hmim][$PF_6$], was used as an effective solvent in the synthesis to improve the metal dispersion of the catalysts. Among the Pd/Charcoal with various Pd concentrations, 7.5 wt% catalyst showed the higher catalytic activity and stability. Moreover, Ag was used as a promoter with various ratios in catalyst preparation. Under identical reaction conditions, the catalyst with 9 : 1 of Pd and Ag weight ratios was most active due to higher metal dispersion.

A Study on Preferential CO Oxidation over Supported Pt Catalysts to Produce High Purity Hydrogen (고순도 수소 생산을 위한 CO 선택적 산화 반응용 Pt 촉매 연구)

  • Jeon, Kyung-Won;Jeong, Dae-Woon;Jang, Won-Jun;Na, Hyun-Suk;Roh, Hyun-Seog
    • Transactions of the Korean hydrogen and new energy society
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    • v.24 no.5
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    • pp.353-358
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    • 2013
  • To develop preferential CO oxidation reaction (PROX) catalyst for small scale hydrogen generation system, supported Pt catalysts have been applied for the target reaction. The supports were systematically changed to optimize supported Pt catalysts. $Pt/Al_2O_3$ catalyst showed the highest CO conversion among the catalysts tested in this study. This is due to easier reducibility, the highest dispersion, and smallest particle diameter of $Pt/Al_2O_3$. It has been found that the catalytic performance of supported Pt catalysts for PROX depends strongly on the reduction property and depends partly on the Pt dispersion of supported Pt catalysts. Thus, $Pt/Al_2O_3$ can be a promising catalyst for PROX for small scale hydrogen generation system.

Production of Hydrogen and Carbon Nanotubes from Catalytic Decomposition of Methane over Ni:Cu/Alumina Modified Supported Catalysts

  • Hussain, Tajammul;Mazhar, Mohammed;Iqbal, Sarwat;Gul, Sheraz;Hussain, Muzammil;Larachi, Faical
    • Bulletin of the Korean Chemical Society
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    • v.28 no.7
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    • pp.1119-1126
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    • 2007
  • Hydrogen gas and carbon nanotubes along with nanocarbon were produced from commercial natural gas using fixed bed catalyst reactor system. The maximum amount of carbon (491 g/g of catalyst) formation was achieved on 25% Ni, 3% Cu supported catalyst without formation of CO/CO2. Pure carbon nanotubes with length of 308 nm having balloon and horn type shapes were also formed at 673 K. Three sets of catalysts were prepared by varying the concentration of Ni in the first set, Cu concentration in the second set and doping with K in the third set to investigate the effect on stabilization of the catalyst and production of carbon nanotubes and hydrogen by copper and potassium doping. Particle size analysis revealed that most of the catalyst particles are in the range of 20-35 nm. All the catalysts were characterized using powder XRD, SEM/EDX, TPR, CHN, BET and CO-chemisorption. These studies indicate that surface geometry is modified electronically with the formation of different Ni, Cu and K phases, consequently, increasing the surface reactivity of the catalyst and in turn the Carbon nanotubes/H2 production. The addition of Cu and K enhances the catalyst dispersion with the increase in Ni loadings and maximum dispersion is achieved on 25% Ni: 3% Cu/Al catalyst. Clearly, the effect of particle size coupled with specific surface geometry on the production of hydrogen gas and carbon nanotubes prevails. Addition of K increases the catalyst stability with decrease in carbon formation, due to its interaction with Cu and Ni, masking Ni and Ni:Cu active sites.

Catalyst Enhanced by Controlling Structure and Shape of Nanocrystals, Support Materials, and Hybrid System in DMFCs (나노입자의 구조와 모양, 담지체 및 하이브리드 시스템 제어를 통한 직접메탄올 연료전지의 촉매 개발)

  • Lee, Young Wook;Shin, Tae Ho
    • Ceramist
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    • v.22 no.2
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    • pp.189-197
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    • 2019
  • Direct methanol fuel cells (DMFCs) have found a wide variety of commercial applications such as portable computer and mobile phone. In a fuel cell, the catalysts have an important role and durability and efficiency are determined by the ability of the catalyst. The activity of the catalyst is determined by the structure and shape control of the nanoparticles and the dispersion of the nanoparticles and application system. The surface energy of nanoparticles determines the activity by shape control and the nanostructure is determined by the ratio of bi- and tri-metals in the alloy and core-shell. The dispersion of nanoparticles depends on the type of support such as carbon, graphen and metal oxide. In addition, a hybrid system using both optical and electrochemical device has been developed recently.