• Applied Chemistry for Engineering
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• v.24 no.3
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• pp.333-336
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• 2013

Experimental investigation to estimate the feasibility of fast selective catalytic reduction (SCR) or oxidation catalyst combined ammonia SCR system to abate NOx in low temperature condition ($150{\sim}250^{\circ}C$) is reported. Because the conversion of NO to $NO_2$ is pre-requisite of the fast SCR process, the effect of the amount of oxidation catalyst to NO conversion to $NO_2$ was tested. 37, 45 and 51% of conversion rates were obtained for the OCV of 563000, 375000 and 281000 h, respectively. $De-NO_x$ performance in the case of $NO_2/NO_x$ ratio of 45% showed the best result in all tested temperature conditions. Comparison of the fast SCR and standard SCR with the condition of $NO_2/NO_x$ ratio of 45%, $200{\sim}250^{\circ}C$ and space velocity of 10000~30000 h showed that the fast SCR does not show much difference according to the variance of space velocity. Also it was shown that using the fast SCR, the volume of SCR catalyst can be reduced less than half of the standard SCR condition by increasing space velocity without the loss of $De-NO_x$ performance.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.646-652
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• 2020

In this study, an NH3-selective catalytic reduction (SCR) experiment was performed to control NOx in the temperature range of 200~500 ℃. The reaction activity experiment was conducted by varying the firing temperature of Sb/TiO2 when using V/Sb/TiO2 composite as a catalyst. As a result, when the sintering temperature of Sb/TiO2 was 600 ℃, the efficiency was the best, and it was confirmed that the NOx conversion rate was close to 80% at the reaction temperature of 250 ℃. H2-temperature programmed reduction (TPR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses were employed to derive the cause of the activity enhancement when prepared at different firing temperatures as described above. As a result, when the sintering temperature of Sb/TiO2, which showed an excellent activity, was prepared at 600 ℃, it was confirmed that VSbO4 was generated. This indicates that the non-stoichiometric species of V increased, resulting in the excellent NOx conversion rate of V/Sb/TiO2.

• Resources Recycling
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• v.32 no.3
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• pp.45-56
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• 2023

This study analyzed the economic and environmental effect of recycling rhodium used in the non-catalytic field. As an analysis methodology, economic effect analysis applied cost-benefit analysis and resource-saving effect analysis and the environmental effect analysis applied life cycle assessment (LCA). The results show that from an economic point of view, the cost-benefit ratio was 1.28, which was feasible, and the cost reduction was 237,000 won based on 1 g of rhodium recycled and the amount of rhodium recycled was 7.17 billion won in 2025. As for the environmental effect, the greenhouse gas(GHG) emissions were compared between the case of recycling based on rhodium 1 kg and the case of overseas sales. The calculation results show that based on rhodium 1 kg, greenhouse gas emissions were reduced by 99.8%, from 65 kg CO₂eq./kg-Rh when recycling to 28,800 kg CO₂eq. when sold overseas. The results obtained from this study could suggest that rhodium recycling is necessary in Korea where resources are scarce by analyzing the economic and environmental effect of recycling rhodium used in the non-catalytic field.

• The Journal of Natural Sciences
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• v.17 no.1
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• pp.13-29
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• 2006

Most redox-active proteins have thiol-bearing cysteine residues that are sensitive to oxidation. Cysteine thiols oxidized to sulfenic acid are generally unstable, either forming a disulfide with a nearby thiol or being further oxidized to a stable sulfinic acid, which have been viewed as an irreversible protein modification. However, recent studies showed that cysteine residues of certain thiol peroxidases (Prxs) undergo reversible oxidation to sulfinic acid and the reduction reaction is catalyzed by sulfiredoxin (Srx1). Specific Cys residues of various other proteins are also oxidized to sulfinic acid ($Cys-So_2H$). Srxl is considered one of the oxidant proteins with a role in signaling through catalytic reduction of oxidative modification like in the reduction of glutathionylation, a post-translational, oxidative modification that occurs on numerous proteins. In this study, the role of sulfiredoxin in cellular processes, was investigated by studying its interaction with other proteins. Through the yeast two-hybrid system (Y2HS) technique, we have found that Ams1 is a potential and novel interacting protein partner of Srxl. $\alpha$-mannosidase (Ams1) is a resident vacuolar hydrolase which aids in recycling macromolecular components of the cell through hydrolysis of terminal, non-reducing $\alpha$-D-mannose residues. It forms an oligomer in the cytoplasm and under nutrient rich condition and is delivered to the vacuole by the Cytoplasm to Vacuole (Cvt) pathway. Aside from the role of Srxl as a catalyst in the reduction of cysteine sulfenic acid groups, it may play a completely new function in the cellular process as indicated by its interaction with Ams1 of the yeast Saccharomyces cerevisiae.

• Journal of Korean Society for Atmospheric Environment
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• v.31 no.6
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• pp.562-572
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• 2015

$NO_x$ emissions from diesel vehicles have been regarded as a main cause of high $NO_2$ concentration in metropolitan area. Recent studies have shown that the on-road $NO_x$ emissions of diesel vehicles are quite higher than the emission limits specified with the pre-defined test method for emission certification. To reduce air pollutants effectively, the discrepancy of emissions in certification and real-driving conditions should be tackled. In this study, the real-driving emissions have been estimated with portable emission measurement system (PEMS). The results of this study have shown that the on-road $NO_x$ emissions from diesel vehicles have been decreased as the introduction of stricter emission regulation, EURO-6, but additional reduction should be still required and robust technologies should be applied to control $NO_x$ in real-driving conditions. RDE-LDV (Real Driving Emission - Light Duty Vehicles) test method being developed in the European Union can represent excessive on-road $NO_x$ emissions of diesel vehicles as applied emission technologies and can be a solution to remove discrepant $NO_x$ emissions between certification and Korean real-driving conditions. Among the $NO_x$ reduction technologies for EURO-6 diesel vehicles, selective catalytic reduction (SCR) system has shown the better performance than lean $NO_x$ trap (LNT) system to control on-road $NO_x$ emissions. Implementing RDE-LDV will require vehicle manufacturers to adopt the more effective $NO_x$ reduction technology in real driving conditions.

• Journal of Powder Materials
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• v.8 no.3
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• pp.151-156
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• 2001

MgO based nanocomposite powder including ferromagnetic iron particle dispersions, which can be available for the magnetic and catalytic applications, was fabricated by the spray pyrolysis process using ultra-sonic atomizer and reduction processes. Liquid source was prepared from iron (Fe)-nitrate, as a source of Fe nano-dispersion, and magnesium (Mg)-nitrate, as a source of MgO materials, with pure water solvent. After the chamber were heated to given temperatures (500~$^800{\circ}C$), the mist of liquid droplets generated by ultrasonic atomizer carried into the chamber by a carrier gas of air, and the ist was decomposed into Fe-oxide and MgO nano-powder. The obtained powders were reduced by hydrogen atmosphere at 600~$^800{\circ}C$. The reduction behavior was investigated by thermal gravity and hygrometry. After reduction, the aggregated sub-micron Fe/MgO powders were obtained, and each aggregated powder composed of nano-sized Fe/MgO materials. By the difference of the chamber temperature, the particle size of Fe and MgO was changed in a few 10 nm levels. Also, the nano-porous Fe-MgO sub-micron powders were obtained. Through this preparation process and the evaluation of phase and microstructure, it was concluded that the Fe/MgO nanocomposite powders with high surface area and the higher coercive force were successfully fabricated.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1161-1168
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• 1999

The redox property of oxide materials of the 3rd period transition metals(Cr~Zn), V, Mo, and W was studied with temperature-programmed reduction/temperature-programmed oxidation(TPR/TPO) experiment. The peak temperatures of TPO spectra were equal to or lower than those of TPR spectra. And the peak shapes of TPO spectra were broader than those of TPR ones. The activation energies of TPR/TPO for the oxides of the 3rd period transition metals showed in the range of 33~149 kJ/mol, while for the oxides of V, Mo, and W, they showed relatively higher values. The change of activation energies of TPR/TPO with various metal oxides showed a similar trend to the change of their metal-oxygen bond strengths. The change of activation energies of o-xylene oxidation for various metal oxides was proportional to the difference (${\Delta}E_a$) between the activation energy of TPR and that of TPO. From these results, we concluded that the oxidation of o-xylene over various metal oxide catalysts follows the Mars-van Krevelen mechanism including the surface reduction-oxidation of the metal oxide itself.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.154-161
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• 2009

This study is a part of project of urea-SCR system development for an in-use medium duty diesel engine. This study shows the effect of ammonia oxidation catalyst and SCR volume on $NO_X$ reduction performance. When AOC(Ammonia Oxidation Catalyst) is not used, the urea injection should be controlled accurately to prevent $NH_3$ slip. However, it is found that the accurate $NH_3$ slip control is not easy without AOC in real engine operating conditions, because $NH_3$ and $NO_X$ reaction characteristics change with many factors such as exhaust gas temperature and $NH_3$ absorbance on SCR. SCR volume is also one of important design parameters. This study shows that $NO_X$ reduction efficiency increases with increase of SCR volume especially at high space velocity and low exhaust gas temperature conditions. Additionally, this paper shows the emissions of EURO-2 medium duty diesel engine can be improved to the level of EURO-5 with a DPF and urea-SCR system.

• Transactions of the Korean hydrogen and new energy society
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• v.29 no.5
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• pp.450-457
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• 2018

To design the practical core-shell electrocatalysts, combination of core and shell materials is important to meet catalytic activity and durability target. In general, Pd is considered as a good core material due to its best activity caused by strain/ligand effect. Preparing Pd nanoparticles can be a starting point in fabricating core-shell type electrocatalysts, much simplified Pd preparing process is suggested by using carbon monoxide (CO) as a reducing agent and/or capping agent. The solvent composition and reaction temperature can control to nanosheet, tetrahedron, and sphere without using additional stabilizer. Among them, Pd nanosheet which has mainly (111) plane showed about 3 times higher electrocatalytic activity for oxygen reduction reaction (ORR) to the spherical Pd nanoparticles. The enhanced ORR activity of Pd nanosheets can be attributed to the exposure of Pd (111) surface and the high electrochemical surface area. Therefore, we demonstrated that the shape of Pd nanomaterials is easily controlled via a facile reduction method using CO, and (111) plane-oriented Pd nanosheets can be a promising ORR catalysts and core material for polymer electrolyte fuel cells (PEFCs).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.1017-1026
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• 2014

A multi-perforated tube is generally installed between the muffler inlet and in front of selective catalytic reduction (SCR) catalysts in the integrated urea-SCR muffler system in order to disperse the urea-water solution spray uniformly and to make better use of the SCR catalyst, which would result in an increase nitrogen oxide ($NO_x$) reduction efficiency and a decrease in the ammonia slip. The effects of the multi-perforated tube orifice area ratios on the internal flow characteristics were investigated analytically by using a general-purpose commercial software package. From the results, it was clarified that the multi-perforated tube geometry sensitively affected the generation of the bulk swirling motion inside the plenum chamber set in front of the SCR catalyst and to the uniformity index of the velocity distribution produced at the inlet of the catalyst. To verify the analytical results, engine tests were carried out in the ESC and ETC modes. Results of these tests indicated that the larger flow model in the longitudinal direction showed the highest NOx reduction efficiency, which was a good agreement with the analytical results.