• Journal of Hydrogen and New Energy
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• v.29 no.1
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• pp.90-96
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• 2018

Reaction characteristics and kinetics of a oxygen carrier (OCN717-R1SU) for chemical looping combustion (CLC) have been investigated using TGA by changing gas concentration (10-30 vol.% $CH_4$) and reaction temperature ($825-900^{\circ}C$). Reaction rate of OCN717-R1SU increased as temperature increased and it was found that reaction is delayed at the initial reaction regime. Johnson-Mehl-Avrami (JMA) model was adopted to explain the reaction phenomenon. The activation energy (E) determined by JMA model in reduction reaction of OCN717-R1SU is $151.7{\pm}2.03kJ/mol$ and pre-exponential factor and JMA exponent were also obtained. The parameters calculated in this study will be applied in design of the reactor and operation conditions for CLC process.

• Journal of the Korean Chemical Society
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• v.39 no.4
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• pp.275-280
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• 1995

The electron transfer reactions between cis-[Co(en)2(NO2)2]+ and rac-[Co(Y)]2-(Y=EDTA, PDTA, CyDTA) have been investigated in the presence of hydrogen ion. From the kinetic data, it has been found that electron transfer reactions between cis-[Co(en)2(NO2)2]+ and rac-[Co(Y)]2- proceed via inner-sphere pathway by catalysis of hydogen ion. The stereoselectivity in the electron transfer reactions between optically active △-cis-[Co(en)2(NO2)2]+ and rac-[Co(Y)]2- produced 6.0, 2.9, 3.0% e.e.(e.e.=enantiomeric excess) of △-[Co(EDTA)]-, △-[Co(PDTA)]- and △-[Co(CyDTA)]-, respectively. Based upon this observation, it seems that △-cis-[Co(en)2(NO2)2]+ is associated with rac-[Co(Y)]2- at first, and followed by the electron transfer reaction. Therefore, it was suggested that stereoselective electron transfer reaction between △-cis-[Co(en)2(NO2)2]+ and rac-[Co(Y)]2- proceed through both inner-sphere by the proton catalysis and outer-sphere with ionic association.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.224.1-224.1
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• 2010

본 연구에서는 천연가스 수증기 개질반응에 니켈 촉매가 코팅된 금속 구조체 촉매를 적용하여 수소를 생산하였다. 금속구조체 촉매는 기존 펠릿 촉매가 충진 된 촉매반응기에 비해 열 및 물질 전달 특성이 우수하여 이를 여러 개질반응에 적용하고자하는 연구가 수행되어 왔다. 하지만, 기존 금속구조체 촉매의 개발에 있어 촉매와 금속 지지체간의 안정한 결합을 통한 열안정성 확보에 대한 문제는 여전히 해결과제로 남아 있다. 따라서, 본 연구에서는 니켈 촉매를 금속 지지체에 안정하게 부착하기 위한 금속 지지체 표면 처리 방법을 개발하였으며 금속 구조체의 형상에 상관없이 균일한 표면처리가 가능하였다. 개발된 표면 처리방법을 적용한 금속 구조체 촉매는 촉매와 금속지지체간의 결합력 향상으로 인해 120시간 이상 안정한 반응활성을 보였다. 또한, 빠른 공간속도에서도 펠릿촉매와 표면처리를 적용하지 않은 금속 구조체 촉매에 비해 높은 촉매 활성을 보였다. 뿐만 아니라, 본 연구에서 개발된 표면처리를 모노리스와 폼을 비롯한 다양한 형상의 금속구조체 촉매에 적용하여 기하학적 표면 특성에 따른 촉매의 활성 차이를 살펴보았다. 겉보기 표면적이 넓은 금속구조체일 수록 촉매의 고분산 코팅에 유리하여 높은 활성을 보였다.

• Membrane Journal
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• v.28 no.5
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• pp.297-306
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• 2018

This review focused carbon-free hydrogen productions from ammonia decomposition including inorganic membranes, catalysts and the presently studied reactor configurations. It also contains general information about hydrogen productions from hydrocarbons as hydrogen carriers. A Pd-based membrane (e.g. a porous ceramic or porous metallic support with a thin selective layer of Pd alloy) shows its efficiency to produce the high purity hydrogen. Ru-based catalysts consisted of Ru, support, and promoter are the efficient catalysts for ammonia decomposition. Packed bed membrane reactor (PBMR), Fluidized bed membrane reactor (FBMR), and membrane micro-reactor have been studied mainly for the optimization and the improvement of mass transfer limitation. Various types of reactors, which contain various combinations of hydrogen-selective membranes (i.e. Pd-based membranes) and catalysts (i.e. Ru-based catalysts) including catalytic membrane reactor, have been studied for carbon-free hydrogen production to achieve high ammonia conversion and high hydrogen flux and purity.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.225.1-225.1
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• 2010

Within recent years attention has been focused on the method of hydrogen storage using metal hydride reactor due to its high energy density, durability, safety and low operating pressure. In this paper, a numerical study is carried out to investigate the coupled heat and mass transfer process for absorption in a cylindrical metal hydride hydrogen storage reactor using a newly developed model. The simulation results demonstrate the evolution of temperature, equilibrium pressure, H/M atomic ratio and velocity distribution as time goes by. Initially, hydrogen is absorbed earlier from near the wall which sets the cooling boundary condition owing to that absorption process is exothermic reaction. Temperature increases rapidly in entire region at the beginning stage due to the initial low temperature and enough metal surface for hydrogen absorption. As time goes by, temperature decreases slowly from the wall region due to the better heat removal. Equilibrium pressure distribution appears similarly with temperature distribution for reasons of the function of temperature. This work provides a detailed insight into the mechanism and corresponding physicochemical phenomena in the reactor during the hydrogen absorption process.

• Journal of the Korean Electrochemical Society
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• v.7 no.1
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• pp.21-25
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• 2004

The electrochemical behaviors of dissolved hydrogen and hydrogen peroxide at a platinum disk electrode were investigated in boric acid solution by potentiostatic polarization method at the temperature of 25 and $200^{\circ}C$. The oxidation of dissolved hydrogen at $25^{\circ}C$ was kinetically controlled reaction, the rate of which depends upon the electron transfer on the electrode surface. As temperature was raised, however, the electrochemical characteristics of dissolved hydrogen were changed from a kinetically controlled reaction to a diffusion controlled one. One notable feature, with dissolved hydrogen at high temperature, is that an abnormal potential range was observed, where the oxidation rate of dissolved hydrogen rapidly decreased just before starting potential of water oxidation. We think it is caused by the deactivation of the electrode that results from the adsorption of hydroxyl ion on the surface of the platinum disk. On the contrary, a definite change with temperature was not identified in the case of the hydrogen peroxide except for the increase in current density that was due to the increasing diffusion coefcient with an increase of temperature.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.433-438
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• 1998

수소와 물 사이의 촉매교환공정은 중수 생산 및 삼중수소 분리를 위해 개발되어 왔다. 국산 소수성 촉매를 이용하여 새로운 튜브형 촉매탑을 고안하고, 수소와 물 사이의 수소 동위원소 분리를 실증하는 실험을 수행하였다. 국산 소수성 측매는 Styrene Divinyl Benzene Copolymer 담체에 백금을 담지한 촉매로써, 모양은 실린더형이며, 직경이 4mm이다. 촉매 작용을 하지 않는 충전물은 wire mesh ring(3mmx3mm)이고, 튜브는 PCI사 membrane(PVDF)이다. 촉매합의 직경은 2.5cm, 높이는 35cm였고, 온도는 333k, 압력은 0.1MPa였다. 기상 촉매반응만 시켰을 때 촉매탑이 정상상태에 도달되는데 약 3-5시간이 필요했으며, 액체 흐름이 있는 경우가 훨씬 짧았다. 촉매탑의 분리성능을 평가하기 위해 수소 동위원소 분리실험에서 얻은 기체 농도를 이용하여 물질전달계수(Kya)를 계산하였다. Kya는 0.2-0.5 sec$^{-1}$였으며, 액체와 기체 유속에 의해 크게 영향을 받았다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2002.05a
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• pp.115-119
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• 2002

고분자 전해질 연료전지는 전해질로 고체고분자막을 사용하는 연료전지로 고분자막은 수소 이온의 활발한 전달을 위해 일정량의 수분이 존재해야 한다. 따라서 연료전지의 운전 중에 고분자막은 항상 수화되어 있어야 하며 수분이 부족하게 되면 수소이온 전도도가 떨어지고, 막의 수축으로 인해 전극과 막 계면의 저항이 증가한다. 반대로 수분이 많이 존재하면 촉매 표면에 반응기체의 확산이 어려워져 전지 성능이 감소하게 된다.(중략)

• Journal of the Korean Chemical Society
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• v.53 no.5
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• pp.499-504
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• 2009

Metals have often played important roles to some enzymatic reactions that are essential to biological processes. Therefore many scientists have studied the reaction mechanisms of catalytic reactions in metaloenzymes for many years. Methane MonoOxygenase (MMO) is an enzyme that oxidize methane to methyl alcohol. Recently Tolman et al. studied a model reaction for MMO, which is a hydroxide transfer reaction in Bis-($\mu$-oxo)-dicopper complex, and suggested several possible mechanisms. Later a two-step mechanism, which is hydrogen transfer followed by hydroxide rebound, was proposed from theoretical studies. In this study we calculated the reactant, product, and the transition state structures, and energetics of the first hydrogen transfer reaction using various DFT methods including recently developed the MO6 family of DFT, namely, MO6, MO6L, and MO6-2X. We found that the M06/6-31G(d,p)/LANL2DZ method reproduce the experimental XRD structure of reactants very well. The TS structures, barrier heights, and reaction energies depend very much on the size of the basis sets.

• Applied Chemistry for Engineering
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• v.24 no.6
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• pp.650-655
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• 2013

In this study, the synthesis of succinic acid from hydrogenation of maleic anhydride over Pd/C were performed in aqueous solution at various reaction conditions. We confirmed that the distribution of product was different according to process parameters. When increasing the reaction pressure and agitation speed, the by-product decreased and the purity of succinic acid increased. From the result, we may conclude that the reaction pressure and agitation speed are important factors for promoting the mass transfer rate of gas-liquid interface by increasing gas-liquid solubility in liquid hydrogenation. When the reaction pressure increased from 5 bar to 10 bar, the reaction rate increased 2.14 times. When the agitation speed increased from 300 rpm to 700 rpm, the reaction rate increased 2.75 times.