• Title/Summary/Keyword: Pd-based Catalyst

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Fabrication of a Porous 3C-SiC Based Resistivity Hydrogen Sensor and Its Characteristics (다공성 3C-SiC 기반 저항식 수소센서의 제작과 그 특성)

  • Kim, Kang-San;Chung, Gwiy-Sang
    • Journal of Sensor Science and Technology
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    • v.20 no.3
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    • pp.168-171
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    • 2011
  • Porous 3C-SiC(pSiC) samples with different pore diameters were prepared from poly crystalline N-type 3C-SiC by electrochemical anodization. The pSiC surface was chemically modified by the sputtering of Pd and Pt nano-particles as a hydrogen catalyst. Changes in resistance were monitored with hydrogen concentrations in the range of 110 ppm - 410 ppm. The variations of the electrical resistance in the presence of hydrogen demonstrated that Pd and Pt-deposited pSiC samples have the ability to detect hydrogen at room temperature. Regardless of the catalyst, the 25 nm pore diameter samples showed good response and recovery properties. However, the 60 nm samples showed unstable and slow response. It was found that the pore size affects the catalyst reaction and consequently, results in changes of the sensitivity to hydrogen.

Characteristics of Catalytically Supported Combustion for Gas Turbine Catalytic Combustor;Effects of the inlet shape of catalytic burner (가스터빈용 촉매 연소기를 위한 촉매-화염 복합 연소 특성연구;촉매버너 입구 형상의 영향)

  • Lee, Kyung-Won;Chung, Nam-Jo;Ryu, In-Soo;Cho, Sung-June;Seo, Yong-Seog;Kang, Sung-Kyu;Song, Kwang-Sup;Chun, Kwang-Min
    • 한국연소학회:학술대회논문집
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    • 2002.11a
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    • pp.71-79
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    • 2002
  • The characteristics of the catalytically supported combustion with Pd and Pd/Pt based catalyst using the bench-scaled high pressure combustor have been investigated up to 5atm. This study aimed to investigate combustion characteristics of the stable flame attached to the exit of catalyst bed and NOx emissions with respect to the position of axial and radial direction in the combustor. NOx emissions were increased along the axial distance after the catalyst bed exit and radially decreased from the center to the wall of the combustor. At the higher pressure, the NOx emission decreased slightly due to the lower flame temperature in the combustor at the high pressure.

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Effect of Promoter with Ru and Pd on Hydrogen Production over Ni/CeO2-ZrO2 Catalyst in Steam Reforming of Methane (메탄의 수증기 개질 반응에서 Ni/CeO2-ZrO2 촉매의 수소 생산에 대한 Ru 및 Pd의 조촉매 효과)

  • In Ho Seong;Kyung Tae Cho;Jong Dae Lee
    • Applied Chemistry for Engineering
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    • v.35 no.2
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    • pp.134-139
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    • 2024
  • In the steam reforming of methane reactions, the effect of adding noble metals Ru and Pd to a Ni-based catalyst as promoters was analyzed in terms of catalytic activity and hydrogen production. The synthesized catalysts were coated on the surface of a honeycomb-structured metal monolith to perform steam methane reforming reactions. The catalysts were characterized by XRD, TPR, and SEM, and after the reforming reaction, the gas composition was analyzed by GC to measure methane conversion, hydrogen yield, and CO selectivity. The addition of 0.5 wt% Ru improved the reduction properties of the Ni catalyst and exhibited enhanced catalytic activity with a methane conversion of 99.91%. In addition, reaction characteristics were analyzed according to various process conditions. Methane conversion of over 90% and hydrogen yield of more than 3.3 were achieved at a reaction temperature of 800 ℃, a gas hourly space velocity (GHSV) of less than 10000 h-1, and a ratio of H2O to CH4 (S/C) higher than 3.

Composition Survey and Analysis of Non-Pt Oxygen Reduction Catalysts for Proton Exchange Membrane Fuel Cells (고체 고분자 연료전지용 비백금계 산소환원촉매 조성 조사 및 분석)

  • Kwon, Kyung-Jung
    • Journal of the Korean Electrochemical Society
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    • v.15 no.1
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    • pp.12-18
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    • 2012
  • The prohibitively high cost of Pt catalyst might be the biggest barrier for the commercialization of proton exchange membrane fuel cells (PEMFC) of which wide application is expected. Worldwide research efforts for the development of alternative to Pt oxygen reduction reaction (ORR) catalyst are made recently. One of the important considerations in the catalyst development is durability issue as well as economic aspect. From this point of view, platinum group metals (PGM) except Pt can be a candidate for replacing Pt catalyst because the material properties and the catalytic activity of PGM are expected to be similar to Pt. In contrast to Ir, Rh and Os to which not so much attention has been paid as an ORR catalyst, Pd that is most similar to Pt in terms of material properties and catalytic activity and Ru that is in the form of chalcogenide have been studied intensively. Activity comparison between non-Pt and Pt oxygen reduction catalysts by half cell test using RDE (rotating disk electrode) or PEMFC MEA (membrane electrode assembly) operation indicates that Pd-based catalysts show the most similar activity to Pt. In this paper we analyze the composition of PGM ORR catalyst in literature to promote the development of non-Pt ORR catalyst.

Characteristics of Catalysts System of NGOC-LNT-SCR for CNG Buses (CNG 버스용 NGOC+LNT+SCR 촉매시스템의 특성)

  • Seo, Choong-Kil
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.20 no.4
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    • pp.626-631
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    • 2019
  • The policy-making and technological development for the supply expansion of eco-friendly automobiles has been continuing, but the internal combustion engines still accounts for about 95%. Also, in order to meet the stricter emission regulations of internal combustion engines based on fossil fuels, the proportion of after-treatments for vehicles and (ocean going) vessels is gradually increasing. This study is a basic study for the post-Euro-VI exhaust response of CNG buses, and it is to investigate the basic characteristics according to Pd substitution transition metal effect, catalyst volume effect and space velocity. A catalysts was prepared and tested using a model gas reactor. The NGOC catalyst with 3Pd exhibited the highest catalytic activity with 22% at $300^{\circ}C$, 48% at $350^{\circ}C$ and about 75% at $500^{\circ}C$. 3Co NGOC containing 3wt% of transition metal was excellent in oxidation ability, and it was small in size of 2nm, and the degree of catalyst dispersion was improved and de-NO/CO conversion was high. The volume of the NGOC-LNT-SCR catalyst system was optimal in the combination of 1.5+0.5+0.5 with a total score of 165, considering $de-CH_4/NOx$ performance and catalyst cost. For SV $14,000h^{-1}$, the $CH_4$ reduction performance was the highest at about 20%, while the SV $56,000h^{-1}$ was the lowest at about 5%. If the space velocity is small, the flow velocity decreases and the time remaining in the catalyst volume become long, so that the harmful gas was reduced.

A optimization study on the preparation and coating conditions on honeycomb type of Pd/TiO2 catalysts to secure hydrogen utilization process safety (수소 활용공정 안전성 확보를 위한 Pd/TiO2 수소 상온산화 촉매의 제조 및 허니컴 구조의 코팅 조건 최적화 연구)

  • Jang, Young hee;Lee, Sang Moon;Kim, Sung Su
    • Journal of the Korea Organic Resources Recycling Association
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    • v.29 no.4
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    • pp.47-54
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    • 2021
  • In this study, the performance of a honeycomb-type hydrogen oxidation catalyst to remove hydrogen in a hydrogen economy society to secure leaking hydrogen. The Pd/TiO2 catalyst was prepared based on a liquid phase reduction method that is not exposed to a heat source, and it was showed through H2-chemisorption analysis that it existed as very small active particles of 2~4 nm. In addition, it was found that the metal dispersion decreased and the active particle size increased as the reduction reaction temperature increased. It was meant that the active metal particle size and the hydrogen oxidation performance were in a proportional correlation, so that it was consistent with the hydrogen oxidation performance reduction result. The prepared catalyst was coated on a support in the form of a honeycomb so that it could be applied to the hydrogen industrial process. When 20 wt% or more of the AS-40 binder was coated, oxidation performance of 90% or more was observed under low-concentration hydrogen conditions. It was showed through SEM analysis that long-term catalytic activity can be expected by enhancing the adhesion strength of the catalyst and preventing catalyst desorption. It is a basic research that can secure safety in a hydrogen society such as gasification, organic resource, and it can be utilized as a system that can respond to unexpected safety accidents in the future.

Pd-doped $SnO_2$-based oxide semiconductor thick-film gas sensors prepared by three different catalyst-addition processes

  • Lee, Kyu-Chung;Hur, Chang-Wu
    • Journal of information and communication convergence engineering
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    • v.7 no.1
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    • pp.72-77
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    • 2009
  • Three different procedures for adding Pd compounds to $SnO_2$ particles have been investigated. These processes are: (1) coprecipitation; (2) dried powder impregnation; and (3) calcined powder impregnation. The microstructures of $SnO_2$ particles have been analyzed by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). In the coprecipitaion method, the process does not restrain the growth of $SnO_2$ particles and it forms huge agglomerates. In the dried powder impregnation method, the process restrains the growth of $SnO_2$ particles and the surfaces of the agglomerates have many minute pores. In the calcined powder impregnation method, the process restrains the growth of $SnO_2$ particles further and the agglomerates have a lot more minute pores. The sensitivity ($S=R_{air}/R_{gas}$) of the $SnO_2$ gas sensor made by the calcined powder impregnation process shows the highest value (S = 21.5 at 5350 ppm of $C_3H_8$) and the sensor also indicates the lowest operating temperature of around $410^{\circ}C$. It is believed that the best result is caused by the plenty of minute pores at the surface of the microstructure and by the catalyst Pd that is dispersed at the surface rather than the inside of the agglomerate. Schematic models of Pd distribution in and on the three different $SnO_2$ particles are presented.

EVALUATION OF NOx REDUCTION CATALYST BY MODEL GAS FOR LEAN-BURN NATURAL GAS ENGINE

  • LEE C. H.;CHO B. C.
    • International Journal of Automotive Technology
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    • v.6 no.6
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    • pp.591-598
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    • 2005
  • A three-way catalyst system of a natural gas vehicle (NGV) has characteristics of higher fuel consumption and higher thermal load than a lean-bum catalyst system. To meet stringent emission standards in the future, NGV with the lean-bum engine may need a catalyst system to reduce the amounts of HC, CO and NOx emission, although natural gas system has low emission characteristics. We conducted experiments to evaluate the conversion efficiency of the NOx reduction catalyst for the lean-burn natural gas engine. The NOx reduction catalysts were prepared with the ${\gamma}-Al_{2}O_3$ washcoat including Ba based on Pt, Pd and Rh precious metal. In the experiments, effective parameters were space velocity, spike duration of the rich condition, and the temperature of flowing model gas. From the results of the experiments, we found that the temperature for maximum NOx reduction was around $450^{\circ}C$, and the space velocity for optimum NOx reduction was around $30,000\;h^{-1}$ And we developed an evaluation model of the NOx reduction catalyst to evaluate the conversion performance of each other catalysts.

REDUCTION CHARACTERISTICS OF NOx STORAGE CATALYST FOR LEAN-BURN NATURAL GAS VEHICLES

  • Lee, C.H.;Choi, B.C.
    • International Journal of Automotive Technology
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    • v.8 no.6
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    • pp.667-674
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    • 2007
  • Various types of NOx storage catalysts for NGV's were designed, manufactured, and tested in this work on a model gas test bench. As in most of other studies on NOx storage catalyst, alkaline earth metal barium(Ba) was used as the NOx adsorbing substance. The barium-based experimental catalysts were designed to contain different amounts of Ba and precious metals at various ratios. Reaction tests were performed to investigate the NOx storage capacity and the NOx conversion efficiency of the experimental catalysts. From the results, it was found that when Ba loading of a catalyst was increased, the quantity of NOx stored in the catalyst increased in the high temperature range over 350. With more Ba deposition, the NOx conversion efficiency as well as its peak value increased in the high temperature range, but decreased in the low temperature range. The best of de-NOx catalyst tested in this study was catalyst B, which was loaded with 42.8 g/L of Ba in addition to Pt, Pd and Rh in the ratio of 7:7:1. In the low temperature range under $450^{\circ}C$, the NOx conversion efficiencies of the catalysts were lower when $CH_4$, instead of either $C_3H_6$ or $C_3H_8$, was used as the reductant.