• 산업기술연구
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• 제39권1호
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• pp.1-5
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• 2019

In this study, we examined the effect of NO addition on the ozone-induced soot oxidation activity of $LaMnO_3$ perovskite catalysts. The addition of 10~20% NO ($NO_2$) with respect to the concentration of ozone effectively enhanced the rate of ozone-induced soot oxidation rate over $LaMnO_3$. However, the excessive addition of NO ($NO_2$) was detrimental to ozone-induced soot oxidation activity. It is supposed nitrogen oxides would adsorb on the catalyst and then react with carbon-oxygen species developed on soot surface, but an excessive addition of nitrogen oxide would inhibit the formation of carbon-oxygen species, which is a key intermediate in the reaction, and consequently suppress the oxidation rate of soot.

• 한국수소및신에너지학회논문집
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• 제18권2호
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• pp.116-123
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• 2007

[ $La_{0.5}Ce_{0.5}Co_{1-x}Cu_xO_{3-{\alpha}}$ ](X=0, 0.1, 0.3, 0.5) perovskites were prepared by coprecipitation method at pH 7 or pH 11 and its catalytic activity of selective CO oxidation was investigated. The characteristics of these catalysts were analyzed by $N_2$ adsorption, X-ray diffraction(XRD), SEM, $O_2$-temperature programmed desorption(TPD). The pH value at a preparation step made effect on particle morphology. The smaller particle was obtained with a condition of pH 7. The better catalytic activity was observed using catalysts prepared at pH 7 than pH 11. The maximum CO conversion of 98% was observed over $La_{0.5}Ce_{0.5}Co_{0.7}Cu_{0.3}O_{3-{\alpha}}$ at $320^{\circ}C$. Below $200^{\circ}C$, the most active catalyst was $La_{0.5}Ce_{0.5}Co_{0.9}Cu_{0.1}O_{3-{\alpha}}$, of which conversion was 92% at $200^{\circ}C$. By the substitution of Cu, the evolution of ${\alpha}$-oxygen was remarkably enhanced regardless of pH value at preparation step according to $O_2$-TPD. Among the different ${\alpha}$-oxygen species, the oxygen species evolved between $400^{\circ}C$ and $500^{\circ}C$, gave the better catalytic performance for selective CO oxidation including $La_{0.5}Ce_{0.5}CoO_3$ in which Cu was absent.

• 세라미스트
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• 제23권2호
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• pp.211-230
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• 2020

Perovskite-type oxides with the nominal composition of ABO₃ can exsolve the B-site transition metal upon the controlled reduction. In this exsolution process, the transition metal emerges from the oxide lattice and migrates to the surface at which it forms catalytically active nanoparticles. The exsolved nanoparticles can recover back to the bulk lattice under oxidation treatment. This unique regeneration character by the redox treatment provides uniformly dispersed noble metal nanoparticles. Therefore, the conventional problem of traditional impregnated metal/support, i.e., sintering during reaction, can be effectively avoided by using the exsolution phenomenon. In this regard, the catalysts using the exsolution strategy have been well studied for a wide range of applications in energy conversion and storage devices such as solid oxide fuel cells and electrolysis cells (SOFCs and SOECs) because of its high thermal and chemical stability. On the other hand, although this exsolution strategy can also be applied to gas phase reaction catalysts, it has seldomly been reviewed. Here, we thus review recent applications of the exsolution catalysts to the gas phase reactions from the aspects of experimental measurements, where various functions of the exsolved particles were utilized. We also review non-perovskite type metal oxides that might have exolution phenomenon to provide more possibilities to develop higher efficient catalysts.

• Korean Chemical Engineering Research
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• 제51권4호
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• pp.513-517
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• 2013

본 연구는 광 촉매로써 널리 사용되어 온 perovskite 결정인 $SrTiO_3$ 골격에 형광능력이 우수한 Nb을 일부 삽입한 $Nb_xSrTi_{1-x}O_3$를 합성하였고, Nb와 Ti의 몰 비율에 따른 물 분해로부터 수소제조 성능을 비교하고자 하였다. 제조한 $SrTiO_3$ 및 $Nb_xSrTi_{1-x}O_3$ 분말에 대한 물성평가는 X-선 회절분석법(XRD), 에너지 분산형 X-선 분광계(EDS), 자외선/가시선 분광계(UV/Vis-spectrometer)를 통해 분석하였다. 메탄올:물(1:1) 광분해 수소제조 실험 결과, $SrTiO_3$ 광 촉매보다 Nb이 0.05 mol% 첨가된 $Nb_{0.05}SrTi_{0.95}O_3$ 광 촉매에서 촉매활성이 가장 뛰어났으며, 특히 염기성 용액에서 더 많은 양의 수소가 발생하였으며 8시간 반응 후 수소의 발생 누적 량은 4.9 mL였다.

• 대한기계학회논문집B
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• 제28권1호
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• pp.24-30
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• 2004

Analysis model for the two-phase catalytic reactor is presented. With the progress in development of micro thermofluidic devices, needs fur understanding of the phenomena in two phase reaction in cm scale has been arisen. To investigate thermal and reactive performance of down scaled two phase reactor simple analysis model that is a kind of lumped flow model is proposed. Analysis model presented is based on the experiment on mm scale model reactor. Target experiment is catalytic decomposition of 70wt％ hydrogen peroxide with existence of perovskite L $a_{0.8}$S $r_{0.2}$Co $O_3$ catalyst. It is composed of balance equations of mass and energy. Each phase is considered to be a species fur the simplicity. Axial diffusion and transversal distribution of properties are neglected. Two phase catalytic reaction is modeled as successive gasification of liquid lump around catalyst and reaction in gas phase. Heat transfer is modeled by model function ofNu number. Modeled Nu is expressed as Nu=N $u_{0}$ (1＋ $a_1$( $a_2$ $T^{-}$ $a_3$)exp( $a_4$ $T^{-1}$)exp( $a_{5}$ z). Transfer coefficients are determined by the comparison of experimental results. With the model, heat transfer characteristics are investigated. Also by the mass transfer coefficient, characteristics in mass transfer is investigated. With the result basic understanding on design and analysis of mm scale two-phase reactive device is obtained. Also it can be further applied to micro scale reactive device fabricated by micromachining.ing..

• Korean Chemical Engineering Research
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• 제49권6호
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• pp.715-719
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• 2011

$LaCrO_{3}$를 기본으로 하는 perovskite형 재료인 $La_{0.7}Sr_{0.3}Cr_{1-x}Ni_{x}O_{3}$(0.1 ${\leq}$ x ${\leq}$ 0.5)를 citric acid와 EDTA를 이용한 졸-겔법(sol-gel method)으로 합성하였다. 제조한 촉매의 특성분석은 BET, XRD, SEM, $H_2$-TPR, EA 그리고 TEM을 이용하였고, 프로판 수증기 개질 반응을 통하여 촉매 활성을 평가하였다. Perovskite 산화물의 A-site에는 Sr을 30 ml% 고정치환하고, B-site에 Ni 치환양을 증가시키면서 프로판 수증기 개질 반응 실험을 수행한 결과 Ni 치환양과 S/C의 비(steam to carbon ratio)가 증가할수록 프로판 전환율과 수소 수율이 향상되었다. $La_{0.7}Sr_{0.3}Cr_{0.5}Ni_{0.5}O_{3}$(LSCN-0.5)촉매가 S/C의 비가 1.7이고, $800^{\circ}C$의 반응온도 조건에서 100%의 프로판 전환율과 95.9%의 높은 수소 수율을 나타내어 가장 좋은 촉매 활성을 보였다. 반응 후의 촉매에서는 filamentous cabon형태의 탄소 침적형태가 나타나며, Ni 치환양이 증가할수록 침적되는 탄소의 양이 증가하는 것을 확인하였다.

• 대한환경공학회지
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• 제22권1호
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• pp.169-178
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• 2000

알루미나 상에 페롭스카이트 산화물 촉매를 구연산 용액에서 제조하였다. 고온 배가스 처리에 페롭스카이트 촉매의 적용가능성을 평가하기 위해 충진 촉매 반응기내에서 조업온도와 $CO/NO_x$ 몰비를 변화시키면서 CO에 의한 $NO_x$의 환원특성을 실험하였다. 본 연구에서 제조한 촉매를 분석한 결과 알루미나 상에 $La_{0.5}Sr_{0.5}CoO_3$, $SrAl_{12}O_{19}$, $LaAl_{11}O_{18}$의 복합산화물이 균일하게 분포되어 있음을 확인하였다. $CO/NO_x$ 몰비가 1보다 높은 조건에서 $NO_x$의 전환율은 온도가 높아짐에 따라 $700^{\circ}C$ 근방까지는 급격히 증가하였고, 그 이상에서는 100%에 근접하였다. 또한 조업온도 $800^{\circ}C$, 공간속도 $10700hr^{-1}$에서 23시간 연속조업한 결과 $NO_x$의 전환율은 98% 이상으로 유지됨을 확인할 수 있었다.

• 한국세라믹학회지
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• 제28권11호
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• pp.859-864
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• 1991

High quality lead titanate thin films were fabricated by spin coating on a silicon substrate. The resulting dried gel layers were uniform in thickness through 2$\times$2 $\textrm{cm}^2$ area, and polycrystalline perovskite structures developed almost crack free with a heat treatment above 50$0^{\circ}C$ in films with thickness above 360 nm. Metastable pyrochlore structures were observed in films with thickness of 160 nm when heat treated at 500 and $600^{\circ}C$, but these structure did not appear in films with thickness of 360 nm. The thickness dependence in crystal structure of films was studied. by varying the substrate condition and analyzing the interface between the film and substrate. In native oxide films on silicon stbstrates, amorphous dried gel layers were heterogeneously nucleated. Metastable cubic pyrochlore structure could be crystallized in amorphous native oxide.

• 공업화학
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• 제34권3호
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• pp.226-240
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• 2023

This paper provides an overview of the trends and future directions in the development of anode materials for solid oxide fuel cells (SOFCs) using hydrocarbons as fuel, with the aim of enabling a decentralized energy supply. Hydrocarbons (such as natural gas and biogas) offer promising alternatives to traditional energy sources, as their use in SOFCs can help meet the growing demands for energy. We cover several types of materials, including perovskite structures, high-entropy alloys, proton-conducting ceramic materials, anode on-cell catalyst reforming layers, and anode functional layers. In addition, we review the performance and long-term stability of cells based on these anode materials and assess their potential for commercial manufacturing processes. Finally, we present a model for enhancing the applicability of fuel cell-based power generation systems to assist in the realization of the H₂ economy as the best practice for enabling distributed energy. Overall, this study highlights the potential of SOFCs to make significant progress toward a sustainable and efficient energy future.

• 한국수소및신에너지학회논문집
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• 제27권6호
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• pp.677-684
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• 2016

Various commercially available gas diffusion layers (GDLs) from different manufacturers were used to prepare an air electrode using $La_{0.8}Sr_{0.2}CoO_3$ perovskite (LSCP) as the catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in an alkaline solution. Various GDLs have different physical properties, such as porosity, conductivity, hydrophobicity, etc. The ORR and OER of the resulting cathode were electrochemically evaluated in an alkaline solution. The electrochemical properties of the resulting cathodes were slightly different when compared to the physical properties of GDLs. Pore structure and conductivity of GDLs had a prominent effect and their hydrophobicities had a minor effect on the electrochemical performances of cathodes for ORR and OER.