• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.323-327
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• 2020

The reaction characteristics of Ni/CeO_2-X which is highly efficient at a low temperature was investigated for an application to carbon dioxide methanation process. The CeO_2-X support was obtained by the heat treatment of Ce(NO₃)₃ at 400 ℃ and the catalyst was prepared by impregnation process. The operating parameters of the experiment were the internal pressure of the reactor, the composition of oxygen, methane, and hydrogen sulfide in the inlet gas and the reaction temperature. When Ni/CeO_2-X was used for the carbon dioxide methanation reaction, the CO₂ conversion rate increased by more than 25% as the pressure increased from 1 to 3 bar. The increase was large at a low reaction temperature. When both oxygen and methane were in the inlet gas, the CO₂ conversion rate of the catalyst decreased by up to 16 and 4%, respectively. As the concentration of oxygen and methane increased, the reduction rate of the CO₂ conversion rate tended to increase. In addition, the hydrogen sulfide in the inlet gas reduced the CO₂ conversion rate by up to 7% and caused catalyst deactivation. The results of this study will be useful as basic data for the carbon dioxide methanation process.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.137-145
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• 2009

The steady-state kinetics of the selective catalytic reduction (SCR) of $NO_X$ with $NH_3$ has been investigated over a commercial ${V_2}{O_5}/TiO_2$ catalyst. In order to account for the influence of transport effects the kinetics are coupled with a fully transient two-phase 1D+1D monolith channel model. The Langmuir-Hinshelwood (L-H) mechanism is adopted to describe the steady-state kinetic behavior of the ${V_2}{O_5}/TiO_2$ catalyst. The reaction rate expressions are based on previously reported papers and are modified to fit the experimental data. The steady-state chemical reaction scheme used in the present mathematical model has been validated extensively with experimental data of selective $NO_X$ reduction efficiency for a wide range of inlet conditions such as space velocity, oxygen concentrations, water concentration, and $NO_2/NO$ ratio. The parametric investigations are performed to examine how the $NH_3$ slip from a SCR $DeNO_X$ catalyst and the conversion of $NO_X$ are affected by the reaction temperature, $NH_3/NO_X$ feed ratio, and space velocity for feed gas compositions with $NO_2/NO_X$ ratios of 0 and 0.5.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.112-119
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• 2022

Molten carbonate fuel cells (MCFCs) are environmentally friendly, large-capacity power generation devices operated at approximately 650℃. If MCFCs are to be commercialized by improving their competitiveness, their cell life should be increased by operating them at lower temperatures. However, a decrease in the operating temperature causes a reduction in the cell performance because of the reduction in the electrochemical reaction rate. The cell performance can be improved by introducing a coating on the cathode of the cell. A coating with a high surface area expands the triple phase boundaries (TPBs) where the gas and electrolyte meet on the electrode surface. And the expansion of TPBs enhances the oxygen reduction reaction of the cathode. Therefore, the cell performance can be improved by increasing the reaction area, which can be achieved by coating nanosized LiCoO₂ particles on the cathode. However, although a coating improves the cell performance, a thick coating makes gas difficult to diffuse into the pore of the coating and thus reduces the cell performance. In addition, LiCoO₂-coated cathode cell exhibits stable cell performance because the coating layer maintains a uniform thickness under MCFC operating conditions. Therefore, the performance and stability of MCFCs can be improved by applying a LiCoO₂ coating with an appropriate thickness on the cathode.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5610-5614
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• 2012

Performance of catalyst was studied with various operating conditions for selective catalytic reduction of $NO_x$ with $NH_3$. It is confirmed that catalysts containing Mn and Cu have a good efficiency in the usage of oxygen by the $H_2$-TPR analysis. In the case of catalyst #1, $NO_x$ conversion was decrease with the increase of reaction temperature. But in the case of catalyst #2, $NO_x$ conversion was increased and then remained constant with the increase of reaction temperature. This phenomenon is due to the difference of the $NH_3$ oxidation of both catalysts.

• Journal of Environmental Health Sciences
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• v.24 no.1
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• pp.104-111
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• 1998

The utilization of food garbage as composting was investigated by using the batch reactor and by varying the initial temperature of the fermentation reactors. As the straw controlled under 50 to 55% of moisture content and mixed 5% of EM(Effective Micro-organisms) microbial agent. An agitator continuously operated 1 rpm, supplying the amount of air(2l/kg.min). Reactor temperature changed three type of 40$\circ$C, 50$\circ$C, 60$\circ$C. In the case of 50$\circ$C operated 72 hr after organic contents showed lowest 48%, and weight reduction rate of showed 77%. The reaction gas was showed 30 min after 19. 9% of the lowest level at 20.9% concentration of oxygen and CO$_2$ gas was produced 0.9% due to organic disintegration on initial react time. NH$_4$, H$_2$ and CH$_4$ gas concentration showed 589 ppm lhr after, 83 ppm and 0.3%, but 8hr after gas product was complete. As using the straw of bulking agent, the Reduction by disintegration should be more effectively than composting.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.3
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• pp.383-388
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• 2006

SBR is one of the most general sewage/wastewater treatment processes and, particularly, has an advantage in high concentration wastewater treatment like sewage wastewater. A Kernel PCA based fault diagnosis system for biological reaction in full-scale wastewater treatment plant was proposed using only common bio-chemical sensors such as ORP(Oxidation-Reduction Potential) and DO(Dissolved Oxygen). During the SBR operation, the operation status could be divided into normal status and abnormal status such as controller malfunction, influent disturbance and instrumental trouble. For the classification and diagnosis of these statuses, a series of preprocessing, dimension reduction using PCA, LDA, K-PCA and feature reduction was performed. Also, the diagnosis result using differential data was superior to that of raw data, and the fusion data show better results than other data. Also, the results of combination of K-PCA and LDA were better than those of LDA or (PCA+LDA). Finally, the fault recognition rate in case of using only ORP or DO was around maximum 97.03% and the fusion method showed better result of maximum 98.02%.

• Korean Journal of Materials Research
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• v.11 no.7
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• pp.609-614
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• 2001

This study was carried out to obtain a basic data on the production of the Nd-Fe-B system rare earth anisotropic bonded magnet by R-D & HDDR process. The reduction reaction of Nd$_2$O$_3$by metallic Ca and the diffusion reaction of Nd into Fe-B alloy powder were investigated for the production the Nd-Fe-B alloy powder. We concluded that a proper quantity of metallic Ca was about 1.3 times of theoretical equivalent from the yields of Nd and B after the R-D reaction at 100$0^{\circ}C$ for 1h. In the XRD analysis the diffusion reaction of Nd into the center of Fe-B alloy powder for the completed homogenization was required through about 45min at 110$0^{\circ}C$ for the R-D reaction, and also the maximum efficiency on the yield of Nd was obtained with such a condition. Residual Ca and oxygen contents of the final powder sample after washing were detected in 0.17wt% and 0.42wt% by ICP and oxygen analyzer, respectively.

• Journal of Powder Materials
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• v.27 no.1
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• pp.63-71
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• 2020

It is necessary to fabricate uniformly dispersed nanoscale catalyst materials with high activity and long-term stability for polymer electrolyte membrane fuel cells with excellent electrochemical characteristics of the oxygen reduction reaction and hydrogen oxidation reaction. Platinum is known as the best noble metal catalyst for polymer electrolyte membrane fuel cells because of its excellent catalytic activity. However, given that Pt is expensive, considerable efforts have been made to reduce the amount of Pt loading for both anode and cathode catalysts. Meanwhile, the atomic layer deposition (ALD) method shows excellent uniformity and precise particle size controllability over the three-dimensional structure. The research progress on noble metal ALD, such as Pt, Ru, Pd, and various metal alloys, is presented in this review. ALD technology enables the development of polymer electrolyte membrane fuel cells with excellent reactivity and durability.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.715-720
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• 2014

A Cu(II) complex with an three nitrogens and one sulfur coordination environment was synthesized and characterized. Its redox potential was observed at 0.483 V vs. NHE, very similar to that of a Cu-containing fungal enzyme, galactose oxidase, which catalyzes the oxidation of alcohols to corresponding aldehydes with the concomitant reduction of molecular oxygen to water. The Cu(II) complex selectively oxidizes the benzylic alcohols using TEMPO/$O_2$ under mild reaction conditions to corresponding aldehydes without forming any over-oxidation product. Moreover, the catalyst can be recovered and reused multiple times for further oxidation reactions, thus minimizing the waste generation.

• Applied Chemistry for Engineering
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• v.30 no.4
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• pp.493-498
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• 2019

In polymer exchange membrane fuel cells, it is crucial to fabricate a highly active and thin Pt catalyst layer for the smooth mass transport of dissolved oxygen and water. Although a highly loaded platinum (Pt) catalyst based on the hydrothermal synthesis has been reported in several studies, its growing behaviors and kinetics were yet to be understood. In this study, we investigated the growth of Pt crystal in suspension after the reduction step depending on a stirring time and evaluated the electrochemical activity. For only a couple of hours in the early stage, Pt colloids were adsorbed on the Pt-carbon catalyst and the Pt crystal was grown. After that, the small Pt colloid was formed by another nucleation step, which did not involve the growth of Pt crystal. We reveal that the Pt-Carbon catalyst with stirring for 6 h showed a high activity toward the oxygen reduction reaction.