• Applied Chemistry for Engineering
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• v.9 no.7
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• pp.1018-1022
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• 1998

Characteristics and catalytic activities of 12-molybdophosphoricacid catalysts modified by ring opening polymerization of tetrahydrofuran (THF) were studied in this work. 12-Molybdophosphoricacid catalysts modified by THF showed higher conversions and product yields than the mother acid in the vapor-phase ethanol conversion. It was believed that the enhanced catalytic activities of modified 12-molybdophosphoricacids were due to structural flexibility of heteropolyanions and weakened hydrogen bond around heteropolyanions. THF interacted with protons and crystalline water molecules of heteropolyacids. The interaction between THF and heteropolyanoins, which crystalline water molecules act as intermediary, was the dominant factor deciding the catalytic activities of modified 12-molybophosphoricacids.

• Applied Chemistry for Engineering
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• v.2 no.4
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• pp.363-371
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• 1991

The catalytic performance and availability of heteropoly compounds for the conversion of methanol to hydrocarbons have been studied. The effects of reaction conditions such as reaction temperature, methanol partial pressure and residence time and the effects of ion-exchange of the catalysts were examined for enhancing the yield of hydrocarbons and the selectivity of low olefins. Their acid strength depended on the kind of countercation, and the yield of hydrocarbons and the selectivity for propylene to propane were closely related to the electronegativity of the corresponding countercations. In contrast to the other heteropoly compounds, the ammonium salt showed a considerably high catalytic activity and a high selectivity for paraffins to low olefins.

• Journal of the Korean Institute of Gas
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• v.3 no.2 s.7
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• pp.70-76
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• 1999

Because of the tight pollution control of $SO_2$ emission, sulfuric acid manufacturers have been interested in the operation with the highest possible conversion efficiency. In this work, the design criteria and operating conditions of the catalytic converter were investigated for maximum conversion efficiency and minimum $SO_2$ emission by parametric analysis and process optimization for the existing acid plants. The Double Converter/Double Absorber(DC/DA) process was investigated by varying $SO_2$ compositions of feed gas, pressures and temperatures of layers of the converter and the depth of the catalyst beds. In order to evaluate the process, a computer simulator for sulfuric acid plants has been developed. The results by process optimization could be used for the converter design and operating conditions with highest conversion efficiency.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.8
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• pp.859-869
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• 2005

The commercial $V_2O_5-WO_3/TiO_2$ catalysts which had been exposed to the off gas from incinerator for a long time were regenerated by physical and chemical treatment. The catalytic properties and NOx conversion reactivity of those catalysts were examined by analysis equipment and NOx conversion experiment. The characterization of the catalysts were performed by XRD(x-ray diffractometer), BET, POROSIMETER, EDX(energy dispersive x-ray spectrometer), ICP(inductively coupled plasma), TGA(thermogravimetric analyzer) and SEM (scanning electron microscopy). NOx conversion experiment were performed with simulated off gas of the incinerator and $NH_3$ was used as a reductant of SCR reaction. Among the regeneration treatment methods which were applied to regenerate the aged catalysts in this study, it showed that the heat treatment method had excellent regeneration effect on the catalytic performance for NOx conversion. The catalytic performance of the regenerated catalysts with heat treatment method were recovered over than 95% of that of fresh catalyst. For the regenerated catalysts with the acid solution(pH 5) and the alkali solution(pH 12), the catalytic performance were recovered over than 90% of that of fresh catalyst. From the characterization results of the regenerated catalysts, the specific surface area was recovered in the range of $85{\sim}95%$ of that of fresh catalyst. S and Ca element, which are well known as the deactivation materials for the SCR catalysts, accumulated on the aged catalyst surface were removed up to maximum 99%. Among the P, Cr, Zn and Pb elements accumulated on the aged catalyst surface, P, Cr and Zn element were removed up to 95%. But the Pb element were removed in the range of $10{\sim}30%$ of that of fresh catalyst.

• Clean Technology
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• v.15 no.1
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• pp.42-46
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• 2009

Solvent-free direct preparation of dichloropropanol (DCP) from glycerol (by-product of bio-diesel production) and hydrochloric acid gas was carried out over acetin catalyst in a gas-liquid batch reactor. For this purpose, acetin mixture and triacetin were used as a homogeneous acetin catalyst. Performance in the acetin-catalyzed reaction was compared to that in the non-catalytic reaction under the same reaction conditions ($110^{\circ}C$, 3 bar, 3 h). Conversion of glycerol in the acetin-catalyzed reactions was ca. 3% higher than that in the non-catalytic reaction, and selectivity for dichloropropanol in the acetin-catalyzed reactions was ca. 50% higher than that in the non-catalytic reaction. It was also revealed that the catalytic performance of triacetin was ca. 2% higher than that of acetic mixture.

• Journal of the Korean Electrochemical Society
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• v.24 no.4
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• pp.113-119
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• 2021

In this study, impurity free V^3.5+ electrolytes were prepared using formic acid as a reducing agent and PtD/C as a catalyst and it was applied to VRFB. The well-oriented 3D dendrite structure of the PtD/C catalyst showed high catalytic activity in formic acid oxidation reaction and vanadium reduction reaction. As a result, the conversion ratio of electrolyte using the PtD/C was 2.73 mol g^-1 h^-1, which was higher than that of 1.67 mol g^-1 h^-1 of Pt/C prepared by the polyol method. In addition, in the VRFB charging and discharging experiment, the V^3.5+ electrolyte produced by the catalytic reaction showed the same performance as the standard V^3.5+ electrolyte prepared by the electrolytic method, thus proving that it can be used as an electrolyte for VRFB.

• Clean Technology
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• v.29 no.2
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• pp.126-134
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• 2023

Direct catalytic decomposition is a promising method for controlling the emission of nitrous oxide (N₂O) from the semiconductor and display industries. In this study, a γ-Al₂O₃ catalyst was developed to reduce N₂O emissions by a catalytic decomposition reaction. The γ-Al₂O₃ catalyst was prepared by an extrusion method using boehmite powder, and a N₂O decomposition test was performed using a catalyst reactor that was approximately 25.4 mm (1 in) in diameter packed with approximately 5 mm of catalysts. The N₂O decomposition tests were carried out with approximately 1% N₂O at 550 to 750 ℃, an ambient pressure, and a GHSV=1800-2000 h^-1. To confirm the N₂O decomposition properties and the effect of O₂ and steam on the N₂O decomposition, nitrogen, air, and air and steam were used as atmospheric gases. The catalytic decomposition tests showed that the 1% N₂O had almost completely disappeared at 700 ℃ in an N₂ atmosphere. However, air and steam decreased the conversion rate drastically. The long term stability test carried out under an N₂ atmosphere at 700 ℃ for 350 h showed that the N₂O conversion rate remained very stable, confirming no catalytic activity changes. From the results of the N₂O decomposition tests and long-term stability test, it is expected that the prepared γ-Al₂O₃ catalyst can be used to reduce N₂O emissions from several industries including the semiconductor, display, and nitric acid manufacturing industry.

• Journal of Microbiology and Biotechnology
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• v.26 no.12
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• pp.2076-2086
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• 2016

Fungal cytochrome P450 (CYP) enzymes catalyze versatile monooxygenase reactions and play a major role in fungal adaptations owing to their essential roles in the production avoid metabolites critical for pathogenesis, detoxification of xenobiotics, and exploitation avoid substrates. Although fungal CYP-dependent biotransformation for the selective oxidation avoid organic compounds in yeast system is advantageous, it often suffers from a shortage avoid intracellular NADPH. In this study, we aimed to investigate the use of bacterial glucose dehydrogenase (GDH) for the intracellular electron regeneration of fungal CYP monooxygenase in a yeast reconstituted system. The benzoate hydroxylase FoCYP53A19 and its homologous redox partner FoCPR from Fusarium oxysporum were co-expressed with the BsGDH from Bacillus subtilis in Saccharomyces cerevisiae for heterologous expression and biotransformations. We attempted to optimize several bottlenecks concerning the efficiency of fungal CYP-mediated whole-cell-biotransformation to enhance the conversion. The catalytic performance of the intracellular NADPH regeneration system facilitated the hydroxylation of benzoic acid to 4-hydroxybenzoic acid with high conversion in the resting-cell reaction. The FoCYP53A19+FoCPR+BsGDH reconstituted system produced 0.47 mM 4-hydroxybenzoic acid (94% conversion) in the resting-cell biotransformations performed in 50 mM phosphate buffer (pH 6.0) containing 0.5 mM benzoic acid and 0.25% glucose for 24 h at $30^{\circ}C$. The "coupled-enzyme" system can certainly improve the overall performance of NADPH-dependent whole-cell biotransformations in a yeast system.

• International Journal of Computer Science & Network Security
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• v.22 no.6
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• pp.91-96
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• 2022

The photocatalytic degradation of salicylic acid takes place in several stages involving coupled phenomena, such as the transport of molecules and the chemical reaction. The systems of transport equations and the photocatalytic reaction are numerically solved using COMSOL Mutiphysics (CM) simulation software. CM will make it possible to couple the phenomena of flow, the transport of pollutants (salicylic acid) by convection and diffusion, and the chemical reaction to the catalytic area (bauxite or TiO2 doped by nanoparticles). The simulation of the conversion rate allows to correctly fit the experimental results. The temporal simulation shows that the reaction reaches equilibrium after a transitional stage lasting over one minute. The outcomes of the study highlight the importance of diffusion in the boundary layer and the usefulness of injecting micro-agitation into the microchannel flow. Under such conditions, salicylic acid degrades completely.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.28.2-28.2
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• 2011

The selective catalytic reduction (SCR) of NOx by $NH_3$ is well known as one of the most convenient, efficient, and economical method to prevent NOx emission in flue gas from stationary sources. The degradation of the reactivity is the obstacle for its real application, since high concentrations of sulfur dioxide and thermal factor would deactivate the catalyst. It is necessary to develop high stability of catalysts for low-temperature SCR. Among the transition metal oxides, $WO_3$ is known to exhibit high SCR activity and good thermal stability. The $MnOx-WO_3-TiO_2$ catalysts prepared by sol-gel method with various $WO_3$ contents were investigated for low-temperature SCR. These catalysts were observed in terms of micro-structure and spectroscopy analyses. The $WO_3$ catalyst as a promoter is used to enhance the thermal stability of catalyst since it increases the phase transition temperature of $TiO_2$ support. It was found that the addition of tungsten oxides not only maintained the temperature window of NO conversion but also increased the acid sites of catalyst.