• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.666-673
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• 2015

In this paper the selective reduction catalyst (SCR) for controlling the NOx at high temperature range was studied. XRD and FT-IR BET analysis was also performed to determine the structural properties and adsorption/desorption characteristics of the catalyst. In the case of anatase $TiO_2$ support, a negligible NOx conversion was observed, but the $W/TiO_2$ catalyst made using W as a active metal showed an excellent ability to remove NOx. In particular, the $W/TiO_2$ exhibited a rapid increase in the catalytic activity due to the presence of W for the NOx conversion compared to that of using the pure $TiO_2$ at a high temperature range over $400^{\circ}C$. In addition, the phenomenon of reduced reaction activity due to the heat shock for a long time was found to be suppressed.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.4
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• pp.1-8
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• 2005

An experimental investigation of a microthruster that uses hydrogen peroxide as a monopropellant is described. The study comprises of preparation method of silver as a catalyst and performance evaluation of a mesoscale reactor. Reduction of silver in $H_2\;at\;500^{\circ}C$ resulted in the best reactivity of all the treatment method tested. A mesoscale reactor was built to find the optimum configuration for full decomposition of propellant. The catalyst bed was made of a glass wafer substrate sputtered with silver and had a length of 20 mm. We measured the conversion rate with varying feed rate of $H_2O_2$ and preheating temperature. With the feed rate of $H_2O_2$, the space time within the reactor varies as well. For the bed length of 20 mm, space time more than 480 s was required for full conversion.

• Journal of the Korean Chemical Society
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• v.56 no.5
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• pp.571-576
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• 2012

A sol-gel derived carbon composite electrodes (CCEs) were fabricated by mixing horseradish peroxidase (HRP), sol of tetraethoxysilane (TESO), and graphite powder. The HRP solution was added to the sol solution of TEOS, and then graphite powder was added to this mixture. The resulting carbon ceramic network effectively encapsulated HRP and shows a catalytic reduction starting at -0.2 V for $H_2O_2$. The optimum conditions for $H_2O_2$determination have been characterized with respect to the enzyme loading ratio and pH. The linear range and detection limit of $H_2O_2$ detection were from 0.2 mM to 2.2 mM and 0.035 mM, respectively. The common electroactive interferences such as ascorbic acid, acetaminophene, and uric acid were not affected upon the response to $H_2O_2$ at the HRP biosensor due to low detection potential.

• Transactions of the Korean hydrogen and new energy society
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• v.26 no.4
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• pp.339-346
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• 2015

The synthesis of Fischer-Tropsch (FT) oil is the catalytic hydrogenation of CO to give a range of products, which can be used for the production of high-quality diesel fuel, gasoline and linear chemicals. This studied catalyst was prepared Cobalt-supported alumina and silica by the incipient wet impregnation of the nitrates of cobalt, promoter and organic solvent with supports. Cobalt catalysts were calcined at $350^{\circ}C$ before being loaded into the FT reactors. After the reduction of catalyst has been carried out under $450^{\circ}C$ for 24h, FT reaction of the catalyst has been carried out at GHSV of 4,000/hr under $200^{\circ}C$ and 20atm. From these experimental results, we have obtained the results as following; In case of $SiO_2$ catalysts, the activity of 12wt% $Cobalt-SiO_2$ synthesized by organic solvent was about 2 or 3 times higher than the activity of 12wt% $Cobalt-SiO_2$ catalyst synthesized without organic solvent. In particular, the activity of the $Cobalt-SiO_2$ catalyst prepared in the presence of an organic solvent P was two to three times higher than that of the $Cobalt-SiO_2$ catalyst prepared without the organic solvent. Effect of Cr and Cu metal as a promoter was found little. 200 h long-term activity test was performed with a $Co/SiO_2$ catalyst prepared in the presence of an organic solvent of Glyoxal solution.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.2
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• pp.114-121
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• 2014

The synthesis of Fischer-Tropsch oil is the catalytic hydrogenation of CO to give a range of products, which can be used for the production of high-quality diesel fuel, gasoline and linear chemicals. Our cobalt catalyst was prepared Co/alumina, Co/silica and Co/titania by the incipient wetness impregnation of the nitrates of cobalt with supports. Co-based catalysts was calcined at $400^{\circ}C$ before being loaded into the FT reactors. After the reduction of catalyst has carried out under $450^{\circ}C$, FT reaction of the catalyst has carried out at GHSV of 4,000 under $200^{\circ}C$ and 20atm. From test results, the order of increasing activity for the catalyst was Co/alumina > Co/silica > Co/titania. When the content of Co metal such as 5, 12, 20 and 30wt% was changed, an CO conversion increased as the content of Co metal increased. The activity of catalyst has obtained the best value at 12wt% Co content.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.5
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• pp.71-80
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• 2012

To improve the $NO_X$ conversion over a SCR (selective catalytic reduction) catalyst, the DOC (diesel oxidation catalyst) is usually placed upstream of the SCR catalyst to enhance the fast SCR reaction ($4NH_3+2NO+2NO_2{\rightarrow}4N_2+6H_2O$) using equimolar amounts of NO and $NO_2$. Here, a ratio of $NO_2/NO_X$ above 50% should be avoided, because the reaction with $NO_2$ only ($4NH_3+4NO+O_2{\rightarrow}4N_2+6H_2O$) is slower than the standard SCR reaction ($4NH_3+4NO+O_2{\rightarrow}4N_2+6H_2O$). In order to accurately predict the performance characteristics of SCR catalysts, it is therefore desired to develop a more simple and reliable mathematical and kinetic models on the oxidation kinetics of nitric oxide over a DOC. In the present work, the prediction accuracy and limit of three different chemical reaction kinetics models are presented to describe the chemicophysical characteristics and conversion performance of DOCs. Steady-state experiments with DOCs mounted on a light-duty four-cylinder 2.0-L turbocharged diesel engine then are performed, using an engine-dynamometer system to calibrate the kinetic parameters such as activation energies and preexponential factors of heterogeneous reactions. The reaction kinetics for NO oxidation over Pt-based catalysts is determined in conjunction with a transient one-dimensional (1D) heterogeneous plug flow reactor (PFR) model with diesel exhaust gas temperatures in the range of 115~$525^{\circ}C$ and space velocities in the range of $(0.4{\sim}6.5){\times}10^5\;h^{-1}$.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.103-109
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• 2015

A heat recovery steam generator consists of inlet expansion duct and heat transfer tube bank modules. For the enhancement of heat transfer in the tube bank modules, the flow should be uniform before the 1st heat transfer tube bank module. The present study has been carried out to analyze the flow characteristics in the inlet expansion duct of a heat recovery steam generator by using numerical flow analysis. The aim of the present study is to establish the proper heat transfer mechanism in the heat transfer tube bank modules by the comparison of the heat transfer models, the case with the constant heat loss per unit volume and the case with heat loss by using inner and outer convective heat transfer coefficient of heat transfer tube. From the present research, it could be seen that the heat transfer mechanism with using inner and outer convective heat transfer coefficient derives more proper temperature distribution results and the acceptance criteria of the temperature distribution within ${\pm}10^{\circ}C$ before SCR is satisfied with using this heat transfer mechanism.

• Applied Chemistry for Engineering
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• v.10 no.2
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• pp.231-236
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• 1999

Several series of morphologically controlled $MoO_3$/$SiO_2$ catalysts were prepared, characterized, and tested for hydrodesulfurization (HDS) of dibenzothiophene (DBT) activity. Molybdenum surface loaded with 4.0 atoms $Mo/nm^2$ was prepared as sintered hexagonal and sintered orthorhombic, as well as a novel "well dispersed hexagonal" phase. Characterization by XRD, Raman, and $O_2$ chemisorption results reveals that the dispersion of $MoO_3$ over silica depends on the final $MoO_3$ phase in the order of; sintered hexagonal < sintered orthorhombic < dispersed hexagonal phase. Temperature programmed reduction (TPR) results show that both bulk and dispersed microcrystalline of $MoO_3$ reduce to $MoO_2$ at $650^{\circ}C$ and to Mo metal at $1000^{\circ}C$. HDS of DBT was performed in a differential reactor at 30 atm over the temperature range $350{\sim}500^{\circ}C$. Activity of $MoO_3$/$SiO_2$ toward HDS of DBT is proportional to dispersion.

• Applied Chemistry for Engineering
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• v.23 no.1
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• pp.119-123
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• 2012

This study presents the effect of oxygen on the $NH_3$ selective catalytic reduction (SCR) by Mn/$TiO_2$ catalyst. The lattice oxygen of catalysts is participate in the low temperature SCR, and the gaseous oxygen directly takes part in the rexoidtion of reduced catalyst. These redox properties of oxygen an play important role in SCR activity and the available capability of lattice oxygen depends on the manganese oxidation state of the catalyst surface. $MnO_2$ species has a higher redox property than that of $Mn_2O_3$ species on deposited $TiO_2$ surface and these manganese oxide states strongly depend on the $TiO_2$ surface area.

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.253-258
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• 2012

The effects of active sites and valence states were investigated over $Pd/TiO_2$ catalyst on simultaneous oxidation of $CH_4$ and CO. The Pd species (PdO) crystallite size increased with increasing Pd loadings, which results in enhancement of the activity of $CH_4$ oxidation. Different results from the activity of $CH_4$ and CO oxidation were shown to be dependent on the Pd valence state on the surface of the catalyst prepared through a thermal treatment. XRD and $H_2-TPR$ analysis confirmed that $Pd^{2+}$species was predominated in the calcination catalyst, while $Pd^0$species was predominated in the reduction catalyst. Additionally, it could be found that the valence state of Pd was a more important factor on the catalytic activity than that of factors as the surface area and pore volume. The reaction mechanism of $CH_4$ and CO followed by the valence state of Pd could be identified using FT-IR analysis.