• 대한기계학회논문집
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• 제17권12호
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• pp.3187-3195
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• 1993

Combustion of liquid-fuelled combustion in a high-temperature vitiated-air stream was studied. The mathematical formulation comprise the application of Eulerian conservation equation to the gas phase and Lagrangian equation of droplet motion. The latter is coupled with a droplet-tracking technique (PSI-CELL Model) which regard the droplet phase as a source of mass, momentum, and energy to the gaseous phase. Reaction rate is determined by taking into account the Arrhenius reaction rate based on a single-step reaction mechanism. The calculated profiles show somewhat uncertainess at the upstream, but bases data for designing the combustor followed by 2-phase flow were obtained.

• 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.

• 한국수소및신에너지학회논문집
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• 제15권2호
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• pp.119-128
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• 2004

DME(Dimethyl Ether) was directly produced from the synthesis gas using the slurry phase reactor. The catalyst for DME production prepared two types (A type; Cu:Zn:Al=57:33:10, B type; Cu:Zn:Al=40:45:15, molar ratio). It was evaluated for the effect of the reaction medium oil using the small size slurry phase reactor. DME production yield and the methanol selectivity decreased in the order: n-hexadecane oil> mineral oil> therminol oil. The long-term test of DME production was carried out using A and B type catalyst, and n-hexadecane oil and mineral oil, respectively. It was confirmed that the use of A type for the catalyst and n-hexadecane for the reaction medium oil was very useful for the viewpoint of the DME production form the synthesis gas.

• 대한화학회지
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• 제57권6호
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• pp.684-690
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• 2013

Since a glycerol molecule has three active sites, two ${\alpha}$ and one ${\beta}$ hydroxyl groups; it undergoes condensation by releasing water molecules to produce linear, nonlinear and heterocyclic oligomers. The Gibbs free energy (G), enthalpy (H) and internal energy (E) of 7 diglycerol, 15 triglycerol and 23 tetraglycerol isomers were calculated at B3LYP level of theory using 6-311++G(d, p) basis set, in both gas and aqueous phases. Linear oligomers, ${\alpha}{\alpha}$-diglycerol, ${\alpha}{\alpha}$, ${\alpha}{\alpha}$-triglycerol and ${\alpha}{\alpha}$, ${\alpha}{\alpha}$, ${\alpha}{\alpha}$-tetraglycerol, were found to be the most stable oligomers in aqueous phase. It was found that the stability of cyclic oligomers decreases as the size of their rings increases. Cyclic oligomers are produced by dehydration of the acyclic ones which is an endothermic reaction while its ${\Delta}G$ is negative. The dehydration reaction is less endothermic in aqueous phase.

• Bulletin of the Korean Chemical Society
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• 제10권3호
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• pp.273-278
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• 1989

The gas-phase reactions of methyl formate with anions, $-NH_2,\;-OH,\;-CH_2CN$, are studied theoretically using the AM1 method. Stationary points are located by the reaction coordinate method, refined by the gradient norm minimization and characterized by the determination of Hessian matrix. Potential energy profiles and the stationary point structures are presented for all conceivable processes. Four reaction paths are found to be possible: formyl proton and methyl proton abstractions, carbonyl addition, and $S_N2$ process. For the most basic anion $-NH_2$ the proton abstraction path is favored, while in other case, $OH\;and\;-CH_2CN$, the carbonyl addition paths are favored. In all cases the $S_N2$ process is the most exothermic, but due to the relatively high activation barrier the process can be ruled out.

• 한국환경과학회지
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• 제1권2호
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• pp.105.1-113
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• 1992

The present study was performed to develop the removal system of the offensive gases, including hydrogen sulfide of acid gas, ammonia or amice of base gas, from the nightsoil treatment plant. In order to remove the offensive gases, the Fe-EDTA system liquid phase catalytic oxidation method with the bubble lift column reactor was employed. From the results obtained, it was confirmed that the offensive gases can be deodorized simultaneously and also hydrogen sulfide of acid gas, ammonia of base gas completely removed at pH 6.45. In addition, as input gases feed rate the efficiency of acid gas did not change but the efficiency of base gases decreased to approximately 90 % at pH 6, 0. From the result of particle size analyzer, it was found that the particle sizes including sulfur and other impurites grew up to $21{\mu}m$ over 72hour reaction time.

• 한국연소학회지
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• 제3권2호
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• pp.51-63
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• 1998

Air-assisted atomizer flames are investigated numerically to study spray structures in nonburning and burning conditions based on experimental data. A PDA is used to measure droplet size, velocity, and number density for both nonburning and burning spray. Computations utilize time-averaged gas-phase equations and $k-{\varepsilon}$ turbulence model for simplicity. The major features of the liquid-phase model are that a SSF approach is used to represent the effect of gas-phase turbulence on droplet trajectories and vaporization, an infinite-diffusion model is employed to represent the transient liquid-phase process. Computation and experiment results show that the droplet acceleration and evaporation proceed quickly in near the atomizer, characterizing high number densities and a strong convective effect. The primary combustion zone, however, is dorminated by the gas phase reaction and exhibits a sheath combustion.

• The Korean Journal of Ceramics
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• 제4권3호
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• pp.235-239
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• 1998

Ultrafine $SnO_2$ powder was prepared by the diffusion mixing gas-phase reaction of $SnCl_4$(g) and water vapor. The effects of reaction variables, such as the chloride partial pressure, the reaction temperature, and the residence time is the reactor, on the powder size were examined systematically. Calculated concentration and distribution of chemical species, using the Burke-Schumann diffusion mixing model, were compared with the experimetal results. The effects of the reaction variables on the powder size were also discussed qualitatively.

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2003년도 봄 학술발표회 발표논문집
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• pp.135-136
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• 2003

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 2003년도 정기총회 및 학술발표회
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• pp.73-73
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• 2003

We report here the results on N-acetyl-N'-methylamide of alanine (Ac-Ala-NHMe) calculated using the ab initio molecular orbital method with the self-consistent reaction field (SCRF) theory at the HF level with the 6-3l+G(d) basis set to investigate the conformational preference of alanine depending on the backbone torsion angles $\square$ and$\square$ in the gas phase, chloroform, and water. There are seven local minima (LM) in the gas phase and two additional LM are found in chloroform and water. These two additional LM A (an $\square$-helical structure) and F (a polyproline structure) are stabilized only in solutions. In the gas phase, the lowest LM is the conformation C with a C$\sub$7/ intramolecular hydrogen bond and the relative conformational energies range from 0.3 to 6.0 ㎉/mol. In chloroform, the lowest LM is the conformation E (an extended structure) and the relative conformational energies range from 0.7 to 4.9 ㎉/mol. In particular, we identified 14 possible transition states connecting between seven LM in the gas phase. The search for transition states probable in chloroform and water is now in progress.