• Bulletin of the Korean Chemical Society
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• 제29권7호
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• pp.1364-1368
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• 2008

The activity of the catalytic system composed of Fe$(acetylacetonate)_3$ (Fe$(acac)_3$), triphenylphosphine, and diethylaluminum chloride for the dimerization of bicyclo[2.2.1]hepta-2,5-diene (2,5-norbornadiene, NBD) to produce hexacyclic endo-endo dimer (hexacyclo[$7.2.1.0^{2,8}.1^{3,7}.1^{5,13}.0^{4,6}$]tetradec-10-ene, Hnn) was significantly enhanced by the presence of $AlCl_3$, especially at the molar ratios of NBD/Fe$(acac)_3$ of 500. XPS analysis of the catalytic systems clearly demonstrates that $AlCl_3$ facilitates the reduction of Fe$(acac)_3$ to form active species, Fe(II) and Fe(0) species. The layer separation was observed when [BMIm]Cl was used along with $AlCl_3$, but catalyst recycle was not very successful.

• Journal of Electrochemical Science and Technology
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• 제2권3호
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• pp.131-135
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• 2011

It is, in general, believed that during the activation process, the proton conductivity increases due to wetting effect and the electrochemical resistance reduction, resulting in an increase in the fuel cell performance with time. However, until now, very scant information is available on the understanding of activation processes. In this study, dominant variables that effect on the performance increase of membrane electrode assemblies (MEAs) during the activation process were investigated. Wetting, pore restructuring and active metal utilization were analyzed systematically. Unexpectedly, the changes for both ohmic and reaction resistance characterized by the electrochemical impedance spectroscopy (EIS) after initial wetting process were much smaller when considering the degree of cell performance increases. However, the EIS spectra represents that the pore opening of electrode turns into gas transportable structure more easily. The increase in the performance with activation cycles was also investigated in a view of active metals. Though the particle size was grown, the number of effective active sites might be exposed more. The impurity removal and catalytic activity enhancement measured by cyclic voltammetry (CV) could be a strong evident. The results and analysis revealed that, not merely wetting of membrane but also restructuring of electrodeand catalytic activity increase are important factors for the fast and efficient activation of the polymer electrolyte fuel cells.

• Bulletin of the Korean Chemical Society
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• 제26권1호
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• pp.103-106
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• 2005

In order to investigate the catalytic mechanism for the growth of carbon nanotubes (CNTs), a comprehensive study was conducted using carbon materials synthesized at 680 ${^{\circ}C}$ with a gas mixture of CO-H$_2$ after reduction at 800 ${^{\circ}C}$ by H$_2$ gas from iron oxide, and metal Pt. The resulting material was observed by scanning electron microscopy (SEM) and X-ray diffraction patterns (XRD) after a variety of reaction times. The carbon materials synthesized by metal Pt were little affected by reaction time and the sintered particles did not form CNTs. Xray analysis revealed that metal Fe was completely converted to iron carbide (Fe$_3$C) without Fe peaks in the early stage. After 5 min, iron carbide (Fe$_3$C) and carbon (C) phases were observed at the beginning of CNTs growth. It was found that the intensity of the carbon(C) peak gradually increased with the continuous growth of CNTs as reaction time increases. It was also found that the catalyst of growth of CNTs was metal carbide.

• 한국산학기술학회논문지
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• 제16권11호
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• pp.7433-7438
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• 2015

암모니아를 환원제로 사용하는 선택적 촉매 환원법에서 $V_2O_5/TiO_2$ 촉매를 사용하여 황산화물에 대한 비활성화 특성을 연구하였다. 반응온도와 황산화물 농도를 변경시키면서 촉매의 활성변화를 측정하였다. 촉매의 활성은 황산화물의 농도와 반응시간이 증가할수록 감소하였다. 또한 황산화물에 대한 촉매의 활성감소 정도는 반응온도 $250{\sim}300^{\circ}C$의 범위에서 반응온도가 증가할수록 크게 감소하였다. BET, XRD, SEM, TPD분석을 통해 비활성화된 촉매의 물리화학적인 특성을 조사하였다. 분석결과, 비활성화현상은 황산화물이 존재하는 상태에서 미반응 암모니아, 수분 등이 반응하여 황산암모늄이 생성되기 때문이다. 황산암모늄은 촉매의 기공을 막으며 활성물질에 침적된다.

• 공업화학
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• 제23권6호
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• pp.604-607
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• 2012

본 연구에서는 표면적이 높은 제올라이트나 촤를 지지체로 이용해 알칼리금속을 담지시킴으로써 염기 세기를 증가시켜 전이에스테르화 반응에 있어 보다 좋은 활성을 가지는 고체촉매를 만들고자 하였다. 제올라이트는 KOH 수용액으로 담지하였고, 미역촤는 calcium nitrate를 담지하여 염기의 세기를 증가시켰다. Hammett 지시약과 $CO_2$-TPD를 통하여 촉매의 특성을 분석하였다. 대두유과 메탄올을 사용하여 바이오디젤을 합성한 후 지방산 메틸에스테르 함유량을 측정함으로서 촉매의 활성을 알아보았다. 일정량까지는 담지량과 활성이 비례하였으나, 과량 담지 시 오히려 활성이 감소하는 결과를 보였다.

• 공업화학
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• 제31권2호
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• pp.200-207
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• 2020

본 연구에서는, NH₃-SCO (selective catalytic oxidation) 반응에서 RuTi 촉매 제조 시 소성온도에 따른 영향을 확인하였다. RuTi 촉매는 습윤 함침법을 이용하여 제조되었고, 공기 분위기에서 400~600 ℃로 4 h 동안 소성되었다. 촉매는 RuTi x00로 표기되었으며, x00는 소성온도를 의미한다. XRD, TEM, H₂-TPR 분석에 따르면, RuTi x00 촉매는 소성온도가 증가할수록 활성금속의 분산도가 감소하는 것을 나타내었다. XPS, NH₃-TPD 분석을 통하여, 낮은 분산도를 갖는 촉매는 표면 흡착 산소 종(O_β) 및 NH₃ 흡착량이 감소하는 특성을 나타내었다. 따라서 RuTi 400 촉매는 TiO₂ 표면에 활성금속이 가장 잘 분산되었으며, NH₃ 제거 효율이 가장 우수하였다.

• Korean Chemical Engineering Research
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• 제57권3호
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• pp.425-431
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• 2019

As rechargeable metal-air batteries will be ideal energy storage devices in the future, an active cathode electrocatalyst is required with bi-functionality on both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) during discharge and charge, respectively. Here, a class of perovskite cathode catalyst with a micro-tubular structure has been developed by controlling bi-functionality from different Ru and Ni dopant ratios. A micro-tubular structure is achieved by the activated carbon fiber (ACF) templating method, which provides uniform size and shape. At the perovskite formula of $LaCrO_3$, the dual dopant system is successfully synthesized with a perfect incorporation into the single perovskite structure. The chemical oxidation states for each Ni and Ru also confirm the partial substitution to B-site of Cr without any changes in the major perovskite structure. From the electrochemical measurements, the micro-tubular feature reveals much more efficient catalytic activity on ORR and OER, comparing to the grain catalyst with same perovskite composition. By changing the Ru and Ni ratio, the $LaCr_{0.8}Ru_{0.1}Ni_{0.1}O_3$ micro-tubular catalyst exhibits great bi-functionality, especially on ORR, with low metal loading, which is comparable to the commercial catalyst of Pt and Ir. This advanced catalytic property on the micro-tubular structure and Ru/Ni synergy effect at the perovskite material may provide a new direction for the next-generation cathode catalyst in metal-air battery system.

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2172-2184
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• 2018

The production of isophthalic acid (IPA) from the oxidation of m-xylene (MX) by air is catalyzed by $H_3PW_{12}O_{40}$ (HPW) loaded on carbon and cobalt. We used $H_2O_2$ solution to oxidize the carbon to improve the catalytic activity of HPW@C catalyst. Experiments reveal that the best carbon sample is obtained by calcining the carbon at $700^{\circ}C$ for 4 h after being impregnated in the 3.75% $H_2O_2$ solution at $40^{\circ}C$ for 7 h. The surface characterization displays that the $H_2O_2$ modification leads to an increase in the acidic groups and a reduction in the basic groups on the carbon surface. The catalytic capability of the HPW@C catalyst depends on its surface chemical characteristics and physical property. The acidic groups play a more important part than the physical property. The MX conversion after 180 min reaction acquired by the HPW@C catalysts prepared from the activated carbon modified in the best condition is 3.81% over that obtained by the HPW@C catalysts prepared from the original carbon. The IPA produced by the former is 46.2% over that produced by the latter.

• Advances in Energy Research
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• 제8권4호
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• pp.223-231
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• 2022

An ex-situ gravitational fixed bed pyrolysis reactor was used over Al₂O₃ supported Ni₂P based catalyst with various Ni/P molar ratios (0.5-2.0) and constant nickel loading of 5.37 mmol/g Al₂O₃ to determine the hydrodeoxygenation of rubberwood sawdust (RWS) at atmospheric pressure. The 3D catalysts formed were characterized structurally as well as acidic properties were determined by hydrogen-temperature programmed reduction (TPR). The Ni₂P phase formed completely on Al₂O₃ for 1.5 Ni/P ratio, although lesser crystallite sizes of Ni₂P were seen at Ni/P ratios less than 1.5. Additionally, it was shown that when nickel loading level increased, acidity increased and specific surface area dropped, probably because nickel phosphate is not easily converted to Ni₂P. When Ni/P ratio was 1.5, Ni₂P phase fully formed on Al₂O₃. The catalytic activity was explained in terms of impacts of reaction temperature and Ni/P molar ratio. At relatively high temperature of 450℃, the high-value deoxygenated produce was predominantly composed of n-alkanes. Based on the findings, it was suggested that hydrogenolysis, hydrodeoxygenation, dehydration, decarbonylation, and hydrogenation are all part of mechanism underlying hydrotreatment of RWS. In conclusion, the synthesized Ni₂P/ Al₂O₃ catalyst was capable of deoxygenating RWS with ease at atmospheric pressure, primarily resulting in long chained (C₉-C₂₄) hydrocarbons and acetic acid.

• 공업화학
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• 제35권2호
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• pp.134-139
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• 2024

메탄의 수증기 개질 반응에서 Ni 기반 촉매에 귀금속 Ru 및 Pd을 조촉매로 첨가하여 촉매의 활성 및 수소 생산에 미치는 영향을 분석하였다. 합성된 촉매는 허니컴 구조의 금속 모노리스 구조체 표면에 코팅하여 수증기 메탄 개질 반응을 수행하였다. 촉매의 특성은 XRD, TPR 및 SEM으로 분석하였으며 개질 반응 후 가스를 포집하여 GC로 조성을 분석한 후 메탄의 전환율, 수소 수율 및 CO 선택도를 측정하였다. 0.5 wt%의 Ru 첨가는 Ni의 환원 특성을 개선하였고, 99.91%의 메탄 전환율로 향상된 촉매 활성을 나타내었다. 또한, 다양한 공정 조건에 따른 반응 특성을 분석하였으며, 800 ℃의 반응 온도, 10000 h^-1 이하의 공간속도(GHSV), 3 이상의 H₂O와 CH₄의 비(S/C)에서 90% 이상의 메탄 전환율과 3.3 이상의 수소 수율을 얻을 수 있었다.