• Title, Summary, Keyword: perovskite-type oxides

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Catalytic Combustion of Methane over Perovskite-Type Oxides

  • Hong, Seong-Soo;Sun, Chang-Bong;Lee, Gun-Dae;Ju, Chang-Sik;Lee, Min-Gyu
    • Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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    • v.4 no.2
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    • pp.95-102
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    • 2000
  • Methane combustion over perovskite-type oxides prepared using the malic acid method was investigated. To enhance the catalytic activity, the perovskite oxides were modified by the substitution of metal into their A or B site. In addition, the reaction conditions, such as the temperature, space velocity, and partial pressure of the methane were varied to understand their effect on the catalytic performance. With the LaCoO3-type catalyst, the partial substitution of Sr or Ba into site A enhanced the catalytic activity in the methane combustion. With the LaBO3(B=Co, Fe, Mn, Cu)-type catalyst, the catalytic activities were exhibited in the order of Co>Fe Mn>Cu. Futhermore, the partial substitution of Co into site B enhanced the catalytic activity, whereas an excess amount of Co decreased the activity. The surface area and catalytic activity of the perovskite catalysts prepared using the malic acid method showed higher values than those prepared using the solid reaction method. The catalytic activity was enhanced with decreased methane concentration and with a decrease in the space velocity.

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The Sensor Response for CO Gas of LaMO$_3$ and $LaFe_{1-$\chi$}CO_ $\chi$O$_3$$ in Perovskite Type Oxides (Perovskite형 산화물 LaMO$_3$$LaFe_{1-$\chi$}CO_ $\chi$O$_3$$의 일산화탄소가스에 대한 센서 응답 특성)

  • 임병오;손태원;권동혁
    • Journal of the Korean Society of Safety
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    • v.3 no.1
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    • pp.7-13
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    • 1988
  • The oxides in perovskite type, LaMO$_3$ (M=Ni, Cr, Fe, Co), compared with gas sensors which have been used, were synthesised and then examined sensor response comparatively in order to make a thick film gas sensor having a good gas selectivity, durability and simple manufacturing. The oxides in perovskite type, LaFe$_{l-x}$O$_3$(x=0.2, 0.4, 0.6, 0.8), which a part of Fe was replaced with Co, were examined with regard to their electric resistance with variable temperature and sensor response for carbon monoxide gas.s.

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Catalytic Combustion of Benzene over Perovskite-type Oxides Prepared Using Malic Acid Method (능금산법으로 제조된 페롭스카이트형 산화물에서 벤젠의 촉매연소반응)

  • Jung, Won-Young;Hong, Seong-Soo
    • Clean Technology
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    • v.18 no.3
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    • pp.259-264
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    • 2012
  • Perovskite-type oxides were successfully prepared using malic acid method, characterized by TG/DTA, XRD, XPS, TEM and $H_2$-TPR and their catalytic activities for the combustion of benzene were determined. Almost of catalyst showed perovskite crystalline phase and 15-70 nm particle size. The $LaMnO_3$ catalysts showed the highest activity and the conversion reaches almost 100% at $350^{\circ}C$. The catalysts were modified to enhance the activity through substitution of metal into the A or B site of the perovskite oxides. In the $LaMnO_3$-type catalyst, the partial substitution of Sr into site the A-site enhanced the catalytic activity in the benzene combustion. In addition, the partial substitution of Co or Cu into site the B-site also enhanced the catalytic activity and the catalytic activity was in the order of Co > Cu > Fe in the $LaMn_{1-x}B_xO_3$ (B = Co, Fe, Cu) type catalyst.

An Experimental Study on the Reduction of Nitric Oxides from the Diesel Engine Exhaust Gas with Metal Supported Oxides Catalysts (디젤엔진 배기가스중 질소산화물 저감을 위한 금속 산화물 촉매를 이용한 실험적 연구)

  • Chae, Jae-Ou;Hwang, Jae-Won;Jung, Jee-Yong;Han, Jung-Hee;Hwang, Hwa-Ja;Kim, Seok;Eduard, Mikholap
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.3
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    • pp.68-75
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    • 2001
  • In this paper, a number of supported metal oxides and perovskite type catalysts were investigated for the NOx reduction from the diesel engine exhaust gas. All catalysts were made into pellets type with diameter of 3-4 mm alumina(Al$_2$O$_3$) as a supporter. These samples were tested by real diesel exhaust gas which contains CO, hydrocarbons and soot in the temperature range of 150~55$0^{\circ}C$ with the $3300h^{-1}$ space velocity (SV). Among the results, several promising catalysts showed NOx conversion above 50% in the temperature range of 150-35$0^{\circ}C$. From these results supported metal oxides catalysts and perovskite type could be recommended for the practical application to the automobile exhaust treatments.

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A Stud on the Catalytic Removal of Nitric Oxide (질소산화물의 촉매반응에 의한 저감기술에 관한 연구)

  • 홍성수;박종원;정덕영;박대원;조경목;오광중
    • Journal of Korean Society for Atmospheric Environment
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    • v.14 no.1
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    • pp.25-33
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    • 1998
  • We have studied the reduction of NO by propane over perovskite-type oxides prepared by malic acid method. The catalysts were modified to enhance the activity by substitution by substitution of metal into A or B site of perovskite oxides. In addition, the reaction conditions, such as temperature, $O_2$ concentration, space velocity have been studed. In the $LaCoO_3$ type catalyst, the partial substitution of Ba, Sr into A site enhanced the catalytic activity in the reduction of NO. In the $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3(x=0 \sim 1.9)$ catalyst, the partial substitution of Fe into B site enhanced the conversion of NO, but excess amount of Fe decreased the conversion of NO. The surface area and catalytic activity of perovskite catalysts prepared by malic acid method showed higher values than those of solid reaction method. In the $La_{0.6}Sr_{0.4}Co_{1-x}Fe_xO_3$ catalyst, the conversion of NO increased with increasing $O_2$ concentration and contact time. The introduction of water into reactant feed decreased the catalytic activity.

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Synthesis and Characterisation of Mixed Conducting Perovskite Type Oxide and Its Electrochemical Application to Electrode Material for Solid Oxide Fuel Cell

  • Kim, Yu-Mi;Pyun, Su-Il;Lee, Gyoung-Ja;Kim, Ju-Sik
    • Journal of the Korean Electrochemical Society
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    • v.10 no.2
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    • pp.116-125
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    • 2007
  • This article is concerned with synthesis, characterisation and electrochemical application of the mixed conducting perovskite type oxide to electrode materials for solid oxide fuel cell. First, this review provides a comprehensive survey of the various synthetic methods such as solid state reaction, Pechini, glycine nitrate process and sol-gel methods for the preparation of perovskite type oxide powders. Subsequently, the electrical and microstructural properties of the mixed conducting oxides were discussed in detail. Finally, as electrochemical applications of the mixed conducting perovskite type oxides to electrode materials for solid oxide fuel cell, fundamentals of theoretical ac-impedance model for porous mixed conducting electrodes were introduced. Furthermore, the ac-impedance behaviour of porous and dense mixed conducting electrodes prepared by various synthetic methods was discussed.

Catalytic Characteristics of Perovskite-type Oxides under Mixed Methane and Oxygen Gases (메탄-산소 혼합가스 조건에서의 페롭스카이트계 산화물의 촉매특성 평가)

  • Ahn, Ki-Yong;Kim, Hyoung-Chul;Chung, Yong-Chae;Son, Ji-Won;Lee, Hae-Won;Lee, Jong-Ho
    • Journal of the Korean Ceramic Society
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    • v.45 no.4
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    • pp.232-237
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    • 2008
  • As the single chamber SOFC(SC-SOFC) showed higher prospect on reducing the operation temperature as well as offering higher design flexibility of SOFCs, lots of concerns have been given to investigate the catalytic activity of perovskite-type oxide in mixed fuel and oxidant conditions. Hence we thoroughly investigated the catalytic property of various perovskite-type oxides such as $La_{0.8}Sr_{0.2}MnO_3(LSM),\;La_{0.6}Sr_{0.4}CoO_3(LSC),\;La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3(LSCF),\;Sm_{0.5}Sr_{0.5}CoO_3(SSC),\;and\;Ba_{0.5}Sr_{0.5}Co_{0.8}Fe_{0.2}(BSCF)$ under the partial oxidation condition of methane which used to be given for SC-SOFC operation. In this study, powder form of each perovskite oxides whose surface areas were controlled to be equal, were investigated as functions of methane to oxygen ratios and reactor temperature. XRD, BET and SEM were employed to characterize the crystalline phase, surface area and microstructure of prepared powders before and after the catalytic oxidation. According to the gas phase analysis with flow-through type reactor and gas chromatography system, LSC, SSC, and LSCF showed higher catalytic activity at fairly lower temperature around $400^{\circ}C{\sim}450^{\circ}C$ whereas LSM and BSCF could be activated at much higher temperature above $600^{\circ}C$.

Development of Perovskite-type Cobaltates and Manganates for Thermoelectric Oxide Modules

  • Weidenkaff, A.;Aguirre, M.H.;Bocher, L.;Trottmann, M.;Tomes, P.;Robert, R.
    • Journal of the Korean Ceramic Society
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    • v.47 no.1
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    • pp.47-53
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    • 2010
  • Ceramics with perovskite-type structure are interesting functional materials for several energy conversion processes due to their flexible structure and a variety of properties. Prominent examples are electrode materials in fuel cells and batteries, thermoelectric converters, piezoelectrics, and photocatalysts. The very attractive physical-chemical properties of perovskite-type phases can be modified in a controlled way by changing the composition and crystallographic structure in tailor-made soft chemistry synthesis processes. Improved thermoelectric materials such as cobaltates with p-type conductivity and n-type manganates are developed by following theoretical predictions and tested to be applied in oxidic thermoelectric converters.

Catalytic Combustion of Carbon Particulate over LaMnO3 Perovskite-Type Oxides (LaMnO3형 페롭스카이트 산화물에서 입자상물질의 촉매연소반응)

  • Lee, Yong Hwa;Lee, Geun Dae;Park, Seong Su;Hong, Seong Su
    • Journal of Environmental Science International
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    • v.13 no.7
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    • pp.619-626
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    • 2004
  • We have studied the catalytic combustion of soot particulates over perovskite-type oxides prepared by malic acid method, The catalysts were modified to enhance the activity by substitution of metal into A or B site of perovskite oxide. In addition, the reaction conditions such as temperature and $O_2$ concentration were investigated. The partial substitution of alkali metals into A site in the $LaMnO_3$ catalyst, enhanced the catalytic activity in the combustion of carbon particulate and the activity was shown in the order: Cs > K > Na. For the $La_{1-x}Cs_{x}MnO_{3}$ catalysts, the catalytic activity showed the maximum value with x=0.3 but no more increase on the catalytic activity was shown with x > 0.3. For the $La_{0.8}Cs_{0.2}MnO_{3}$ catalyst, the substitution of Fe or Ni increased the ignition temperature. The ignition temperature decreased with an increase of $O_2$ concentration, however, no more increase in the catalytic activity was shown with $O_2$ concentration > 0.2. The introduction of NO into reactants showed no effect on the catalytic activity.