• 한국환경과학회지
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• 제15권7호
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• pp.635-642
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• 2006

Present study evaluated the low-temperature destruction of n-hexane and benzene using mesh-type transition-metal platinum(Pt)/stainless steel(SS) catalyst. The parameters tested for the evaluation of catalytic destruction efficiencies of the two volatile organic compounds(VOC) included input concentration, reaction time, reaction temperature, and surface area of catalyst. It was found that the input concentration affected the destruction efficiencies of n-hexane and benzene, but that this input-concentration effect depended upon VOC type. The destruction efficiencies increased as the reaction time increased, but they were similar between two reaction times for benzene(50 and 60 sec), thereby suggesting that high temperatures are not always proper for thermal destruction of VOCs, when considering the destruction efficiency and operation costs of thermal catalytic system together. Similar to the effects of the input concentration on destruction efficiency of VOCs, the reaction temperature influenced the destruction efficiencies of n-hexane and benzene, but this temperature effect depended upon VOC type. As expected, the destruction efficiencies of n-hexane increased as the surface area of catalyst, but for benzene, the increase rate was not significant, thereby suggesting that similar to the effects of the re- action temperature on destruction efficiency of VOCs, high catalyst surface areas are not always proper for economical thermal destruction of VOCs. Depending upon the inlet concentrations and reaction temperatures, almost 100% of both n-hexane and benzene could be destructed, The current results also suggested that when applying the mesh type transition Metal Pt/SS catalyst for the better catalytic pyrolysis of VOC, VOC type should be considered, along with reaction temperature, surface area of catalyst, reaction time and input concentration.

• 한국연소학회지
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• 제5권1호
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• pp.1-6
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• 2000

Surface reaction occurs at a certain surface temperature when a catalyst is heated up in a reactive mixture. If homogeneous ignition does not occur, a steady state is observed because the heat produced by the surface reaction is balanced with the heat loss caused by convection, conduction and radiation. The present paper treats the effects of pressure on the surface temperature at the steady state. Hydrogen and oxygen are used as reactants and nitrogen as an inert gas. A spherical platinum catalyst of 1.5 mm in diameter is sustained in the chamber with two wires of 0.1 mm in diameter. As results, there exists a maximum steady temperature at a certain relative hydrogen concentration which increases with total pressure. At the steady state, it can be approximated that the heat release is estimated by the mass transfer considering the effect of natural convection. The experimental results are explained qualitatively by the approximation.

• 대한화학회지
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• 제67권1호
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• pp.28-32
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• 2023

The reaction conditions optimization, including the temperature of the reaction, amount of catalyst required, and reaction time for the linoleic acids (LAs) and conjugated linoleic acids (CLAs) production by catalytic dehydration of castor oil via saponification was investigated by response surface methodology (RSM). It was confirmed that all three parameters (temperature, time, and amount of catalyst) were influential factors in isolating LAs and CLAs. When the temperature was increased, the iodine value increased, and the reaction time and catalyst amount increased. The optimal reaction conditions were: 240 ℃, 2.2 h reaction time, and 7 wt% catalyst amount. The maximum iodine value reached 156.25 with 91.69% conversion to the essential fatty acids.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.287-298
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• 2003

A numerical investigation of a catalytically stabilized thermal (CST) combustor was conducted for a multi-channel catalyst bed, and both the catalyst bed and thermal combustor were simultaneously modeled. The numerical model handled the coupling of the surface and gas reaction in the catalyst bed as well as the gas reaction in the thermal combustor. The behavior of the catalyst bed was investigated at a variety of operating conditions, and location of the flame in the CST combustor was investigated via an analysis of the distribution of CO concentration. Through parametric analyses of the flame position, it was possible to derive a criterion to determine whether the flame is present in the catalyst bed or the thermal combustor for a given inlet condition. The results showed that the maximum inlet temperature at which the flame is located in the thermal combustor increased with increasing inlet velocity.

• 에너지공학
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• 제2권1호
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• pp.114-122
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• 1993

A model describing the reaction rate and catalyst deactivation in a simplified reaction system was developed to investigate the significance of catalyst pore structure in terms of porosities, porosity ratios, and size ratios of reactants to pores. The model showed that the unimodal catalyst could give a better performance than the bimodal in certain circumstances and the crossover found in the reactivity curves resulted from a trade-off between surface area and diffusivity. Under the assumption of uniform coke buildup, the bimodal catalyst appeared to provide better resistance to deactation than unimodal catalyst.

• 신재생에너지
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• 제2권4호
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• pp.70-77
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• 2006

The butane decomposition over the catalyst is an attractive method for the hydrogen production. The objective of the work was investigated the catalysis of carbon black in butane decomposition reaction. The Butane decomposition was performed over carbon black catalyst in a range of $500-1100^{\circ}C$. The butane conversion of thermal decomposition and catalytic decomposition were increased with increasing the reaction temperature The butane conversion of the thermal decomposition was higher than the butane conversion of the catalytic decomposition. Hydrogen and methane were mostly observed in the butane decomposition over $1000^{\circ}C$. Especially, the hydrogen yield was steadily increased with raising the reaction temperature, It could be known that the hydrogen yield of the catalytic decomposition was higher than one of the thermal cracking because the hydrogen productivity was improved by the catalyst. The deactivation of the catalyst was not observed in the reactivity test. The surface and crystalline of the fresh and used catalysts were characterized by TEM, BET surface area and XRD analysis, respectively. The fresh carbon black particles had mostly smoothly round-shaped surfaces. In the surface of the carbon black after the reaction, the deposited carbon was formed as the protrusion-shaped carbon and the cone-shaped. The proper peaks of carbon black appeared in XRD analysis.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1998년도 제17회 KOSCI SYMPOSIUM 논문집
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• pp.59-67
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• 1998

The aim of this study is to investigate advantages that the catalytically supported combustor can have. For this purpose, the catalytic combustor was prepared which consisted of the catalyst bed and the thermal combustor at the downstream of the catalyst bed. The catalyst bed consisted of two-stage. Pd catalyst was installed in the first stage of the catalyst bed, and Pt catalyst was placed in the second stage. Results showed that the catalytically supported combustion had some advantages. One was that auto-ignition occurred in the thermal combustor. This can give merit that an igniter is not necessary to start flame ignition. Other was that the catalytically supported combustion was stable for lean mixture. When combustion of lean mixture was not supported by surface reaction it became unstable so that big combustion noise was created. Therefore, it is desirable to support flame by catalytic surface reaction to obtain the stable combustion of lean mixture.

• 한국응용과학기술학회지
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• 제22권4호
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• pp.349-354
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• 2005

It is interesting to discover the reaction kinetics of the newly developed molybdenum containing catalysts. The dissociation/adsorption of nitrogen on molybdenum surface is known to be structure sensitive, which is similar to that of nitrogen on iron surface. The rates over molybdenum nitride catalysts are increased with the increase of total pressure. This tendency is the same as that for iron catalyst, but is quite different from that for ruthenium catalyst. The activation energies of the molybdenum nitride catalysts are almost on the same level, although the activity is changed by the addition of the second component. The reaction rate is expressed as a function of the concentration of reactants and products. The surface nature of $CO_3Mo_3N$ is drastically changed by the addition of alkali, changing the main adsorbed species from $NH_2$ to NH on the surface. The strength of $NH_x$ adsorption is found to be changed by alkali dopping.

• Bulletin of the Korean Chemical Society
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• 제28권4호
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• pp.529-532
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• 2007

Combined temperature programmed reaction (TPR) and infrared (IR) spectroscopic studies for Fischer- Tropsch reaction have been performed over Ru/SiO2 and Ru-Ag/SiO2 supported catalysts. Reaction of linearly absorbed CO with hydrogen starts at 375 K over Ru/SiO2 catalyst and reaches maximum at 420 K accompanied with an intensity decrease of linear CO absorption. The reaction with bridged absorbed CO peaks around 510-535 K. Addition of Ag yields mixed Ru-Ag bimetallic sites while it suppresses the formation of bridged bonded CO. Formation of methane on this modified surface occurs at 390 K and reaches maximum at 444 K. Suppression of hydrogen on the Ag-doped surface also occurs resulting in the formation of unsaturated hydrocarbons and of CHx intermediates not observed with Ru/SiO2 catalyst. Such intermediates are believed to be the building blocks of higher hydrocarbons during the Fischer-Tropsch synthesis. Linearly absorbed CO is found to be more reactive as compared to bridged CO. The Ag-modified surface also produces CO2 and carbon. On this surface, hydrogenation of CO begins at 390 K and reaches maximum at 494 K. The high temperature for hydrogenation of absorbed CO and C over Ru-Ag/SiO2 catalyst as compared to Ru/SiO2 catalyst is due to the formation of Ru-Ag bimetallic surfaces impeding hydrogen adsorption.

• 한국수소및신에너지학회논문집
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• 제22권6호
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• pp.905-912
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• 2011

In this study, the novel concept catalytic reactor was designed for water-gas shift reaction (WGS) under high pressure. The novel concept catalytic reactor was composed of an autoclave, the catalyst, and liquid water. Cu-ZnO/$Al_2O_3$ as the low temperature shift catalyst was used for WGS reaction. WGS in the novel concept catalytic reactor was carried out at the ranges of 150~$250^{\circ}C$ and 30~50 atm. The liquid water was filled at the bottom of the autoclave catalytic reactor and the catalyst of pellet type was located at the gas-liquid water interface. It was concluded that WGS reaction occurred over the surface of catalysts partially wetted with liquid water. The conversion of CO for WGS was also controlled with changing content of Cu and ZnO used as the catalytic active components. Meanwhile, the catalyst of honey comb type coated with Cu-ZnO/$Al_2O_3$ was used in order to increase the contact area between wet-surface of catalyst and the reactants of gas phase. It was confirmed from these experiments that $H_2$/CO ratio of the simulated coal gas increased from 0.5 to 0.8 by WGS at gas-liquid water interface over the wet surface of honey comb type catalyst at $250^{\circ}C$ and 50 atm.