• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.678-687
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• 2014

The catalytic performance of silicon carbide supported nickel catalysts modified with or without second metal (Co, Cu and Zn) for the methanation of CO has been investigated in a fixed-bed reactor using a feed consisting of 25% CO and 75% $H_2$ without any diluent gas. It has been found that the introduction of Co species can clearly improve the catalytic activity of Ni/SiC catalyst, whereas the addition of Cu or Zn can result in a significant decrease in the catalytic activity. The characterizations by means of XRD, TEM, XPS, CO-TPD and $H_2$-TPR indicate that the addition of Co could decrease the particle size of active metal, increase active sites on the surface of methanation catalyst, improve the chemisorption of CO and enhance the reducibility of methanation catalysts. Additionally, the special interaction between Co species and Ni species is likely favorable for the dissociation of adsorbed CO on the surface of catalyst, and this may also contribute to the high activity of 5Co-Ni/SiC catalyst for CO methanation reaction. For 5Cu-Ni/SiC catalyst and 5Zn-Ni/SiC catalyst, Cu and Zn species could cover partial nickel particles and decrease the chemisorption amount of CO. These could be responsible for the low methanation activity. In addition, a 150h stability test under 2 MPa and $300^{\circ}C$ showed that 5Co-Ni/SiC catalyst was very stable for CO methanation reaction.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.415-418
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• 2010

Highly ordered mesoporous silver material was successfully synthesized from a mesoporous silica template (KIT-6) with 3-D channel structure using the nano-replication method. The effects of $H_2$ or $O_2$ pretreatments on the catalytic performance of the mesoporous silver were investigated using a temperature programmed CO oxidation technique in a fixed bed reactor. The mesoporous silver material that was pretreated with $H_2$ exhibited an excellent catalytic activity compared to the as-prepared and $O_2$-pretreated catalysts. Moreover, this present mesoporous silver material showed good catalytic stability. For the CO oxidation, the apparent activation energy of the $H_2$-pretreated mesoporous silver catalyst was $61{\pm}0.5\;kJ\;mol^{-1}$, which was also much lower than the as-prepared ($132{\pm}1.5\;kJ\;mol^{-1}$) and $O_2$-pretreated ($124{\pm}1.4\;kJ\;mol^{-1}$) catalysts.

• Applied Chemistry for Engineering
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• v.10 no.1
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• pp.85-92
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• 1999

The complete catalytic oxidation of vinyl chloride was investigated over chromium oxide supported ${\gamma}$-alumina using a fixed bed micro-reactor at temperature between 240 and $300^{\circ}C$ and concentration between 600 and 3500 ppm. The oxidation of vinyl chloride was nonlinear in the concentration of vinyl chloride and zeroth order in the concentration of oxygen. The addition of HCl and $H_2O$ as products to the feed stream didn't influence the conversion of vinyl chloride. Several kinetic rate model were tested to describe the data over the range of condition investigated, and developed a model which provide the best correlation of experimental data. The resulting model of kinetic rate was derived by assuming that the reacting occurred via adsorption and subsequent decomposition of the vinyl chloride onto the oxygen covered chromium oxide surface, with the reaction being inhibited by the adsorption of vinyl chloride. The percent standard deviation between the predicted and experimental was about 5.2%, and the activation energy was 18.9 kcal/mol.

• Clean Technology
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• v.20 no.3
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• pp.256-262
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• 2014

Catalytic oxidation characteristics of benzene as a VOC was investigated in a fixed bed flow reactor using $Cu/{\gamma}-Al_2O_3$ catalyst. The parametric tests were conducted at the reaction temperature range of $200{\sim}500^{\circ}C$, benzene concentration of 400~650 ppm, gas flow rate of 50~100 cc/min, and space velocity range of $7,500{\sim}22,500hr^{-1}$. The property analyses by using the BET, SEM, TGA and the conversion of catalytic oxidation of benzene were examined. The experimental results showed that the conversion was increased with decreasing benzene concentration, gas flow rate and space velocity. Benzene oxidation reaction over $Cu/{\gamma}-Al_2O_3$ catalyst could be expressed as the first order homogeneous reaction of which the activation energy was 17.2 kcal/mol and frequency factor was $1.33{\times}10^6sec^{-1}$.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.4
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• pp.444-451
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• 2007

Catalytic oxidation characteristics of benzene as a VOC was investigated using a fixed bed reactor system over transition $metals/\gamma-Al_2O_3$ catalysts. As transition metals, eight metals including copper, nickel, manganese, iron etc. were adopted. The parametric tests were conducted at the reaction temperature range of $200\sim500^{\circ}C$, benzene concentration of $1,000\sim3,000$ ppm, and space velocity range of $5,000\sim60,000\;hr^{-l}$. The property analyses such as BET, SEM, XRD and the conversions of catalytic oxidation of VOC were examined. The experimental results showed that the conversion was increased with decreasing VOC concentration and space velocity. It was also found that $Cu/\gamma-Al_2O_3$ catalyst calcinated at $500^{\circ}C$ showed the highest activity for the oxidation of benzene and 15% metal loading was the optimum impregnation level.

• Bulletin of the Korean Chemical Society
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• v.31 no.4
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• pp.808-814
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• 2010

Activities of nanostructure HZSM-5 and Co-ZSM-5 catalysts (with different Co-loading) for catalytic conversion of ethyl acetate and toluene were studied. The catalysts were prepared by wet impregnation method and were characterized by XRD, BET, SEM, TEM and ICP-AES techniques. Catalytic studies were carried out inside a U-shaped fixed bed reactor under atmospheric pressure and different temperatures. Toluene showed lower reactivity than ethyl acetate for conversion on Co-ZSM-5 catalysts. The effect of Co loading on conversion was prominent at temperatures below $400^{\circ}C$ and $450^{\circ}C$ for ethyl acetate and toluene respectively. In a binary mixture of organic compounds, toluene and ethyl acetate showed an inhibition and promotional behaviors respectively, in which the conversion of toluene was decreased at temperatures above $350^{\circ}C$. Inhibition effect of water vapor was negligible at temperatures above $400^{\circ}C$. An artificial neural networks model was developed to predict the conversion efficiency of ethyl acetate on Co-ZSM-5 catalysts based on experimental data. Predicted results showed a good agreement with experimental results. ANN modeling predicted the order of studied variable effects on ethyl acetate conversion, which was as follows: reaction temperature (50%) > ethyl acetate inlet concentration (25.085%) > content of Co loading (24.915%).

• Clean Technology
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• v.20 no.3
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• pp.218-225
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• 2014

Catalytic gasification of raw coals at mild condition is not realized yet mainly due to deactivation of catalysts via their irreversible interaction with mineral matters in coal. In this work, the gasification behavior of ash-free coal (AFC) was compared with that of the parent raw coal. In order to modify the gasification conditions, the raw coal gasified with fixed variables (water supply, space velocity, temperature, catalysts) in a fixed bed reactor. When catalysts are added by physical mixing method with coal, $K_2CO_3$ was the most effective additives for steam gasification of coal. However, the activity of ash-free coal (AFC) was much less reactive than raw coal due to high temperature extraction in a 1-methylnaphthalene under 30bar at $370^{\circ}C$ for 1 h, almost removed oxygen functional groups, and increased carbonization. The addition of $K_2CO_3$ in AFC achieved higher conversion rate at low temperature ($700^{\circ}C$). At that time, the molar ratio of gases ($H_2/CO$ and $CO_2/CO$) was increased because of water-gas shift reaction (WGSR) by addition of catalysts. This shows that catalytic steam gasification of AFCs is achievable for economic improvement of gasification process at mild temperature.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.33-36
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• 2014

Gasification of biomass produces syngas containing CO, $H_2$ and/or $CH_4$, which can then be converted into energy or value-added fuels. One of key issues for efficient gasification is to minimize tar concentration in the syngas for use in a final conversion device such as gas engine. This study investigated the decomposition of primary tar by catalytic cracking using char as catalyst, of which the feature can be integrated into a fixed bed gasifier design. The pyrolysis vapor containing tar from pyrolysis of wood at $500^{\circ}C$ was passed through a reactor filled with or without char at $800^{\circ}C$ for a residence time of 1, 3 or 5 sec. Then, the condensable vapor (water and tar) and gases were analyzed for the yields and elemental composition. Four types of char particles with different microscopic surface area and pore size distribution: wood, paddy straw, palm kernel shell and activated carbon. The results were analyzed for the mass and carbon yields of tar and the composition of product gases to conclude the effects of char types and residence time.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.1
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• pp.135-141
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• 2014

$NH_3$-SCR has high NOx removal efficiency approximately 80~90%. Recently, the copper or iron ion-exchanged zeolite catalysts are widely used as automobile SCR catalysts. In this paper, the effect of the space velocity, temperature of reaction and $NO_2$ addition on the $NH_3$-SCR reaction were studied using various zeolite SCR catalysts. The test was conducted with small sized fresh catalysts in a laboratory fixed-bed flow reactor system using simulated gases. It is found that the activity of the BEA is better than MFI. It seems that three-dimensional framework and a wide pore entrance of BEA enhances the SCR activity. It is also found that low temperature activity of Cu-zeolites was better than Fe-zeolites. Once $NO_2$ was added, the NOx conversion activity of the Cu-zeolite was slightly enhanced, whereas remarkable improvement was achieved by Fe-zeolite.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.525-530
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• 2014

Titanium dioxide nanotube supported ZSM-5 zeolite composite catalyst was fabricated by decorating ZSM-5 zeolite on the hydrothermally synthesized titanium dioxide via hydrothermal process and subsequent annealing. The catalyst was characterized by X-ray powder diffraction (XRD), Transmission electron microscopy (TEM) and Nitrogen adsorption-desorption (BET). The surface acidity of the catalyst was measured by means of Fourier transform infrared (FT-IR) spectrum of pyridine adsorption. And the catalytic activity for ethanol dehydration to ethylene was evaluated in a continuous flow fixed-bed reactor. Attributed to the increase of the effective surface acid sites caused by titanium dioxide nanotube as electron acceptor, titanium dioxide nanotube supported ZSM-5 zeolite composite catalyst exhibits strongly enhanced activity for ethanol dehydration to ethylene.