• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.200-207
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• 2020

In this study, the effect of calcination temperature on the production of RuTi catalyst in NH₃-SCO (selective catalytic oxidation) was investigated. The RuTi catalyst was prepared using the wet impregnation method, and calcined at 400~600 ℃ for 4 h in air condition. The catalysts were named RuTi x00 where x00 means the calcination temperature. According to XRD (X-Ray diffraction), TEM (transmission electron microscope), H₂-TPR (H₂-temperature programmed reduction) analyses, RuTi x00 catalysts displayed that the dispersion of active metal decreased via increasing the calcination temperature. The catalysts with low dispersion showed a decrease in the surface adsorption oxygen species (O_β) and NH₃ adsorption amount via XPS, and NH₃-TPD analyses. Therefore, the RuTi 400 catalyst was well dispersed in the active metal on TiO₂ surface, and also, the NH₃ removal efficiency was excellent.

• Applied Chemistry for Engineering
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• v.31 no.5
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• pp.560-567
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• 2020

In this study, we investigated that the effect of alkali metals [Na(Sodium) and K(Potassium)], known as representative deactivating substances among exhaust gases of various industrial processes, on the NH₃-SCR (selective catalytic reduction) reaction of V/W/TiO₂ catalysts. NO, NH₃-TPD (temperature programmed desorption), DRIFT (diffuse reflectance infrared fourier transform spectroscopy analysis), and H₂-TPR analysis were performed to determine the cause of the decrease in activity. As a result, each alkali metal acts as a catalyst poisoning, reducing the amount of NH₃ adsorption, and Na and K reduce the SCR reaction by reducing the L and B acid points that contribute to the reaction activity of the catalyst. Through the H₂-TPR analysis, the alkali metal is considered to be the cause of the decrease in activity because the reduction temperature rises to a high temperature by affecting the reduction temperature of V-O-V (bridge oxygen bond) and V=O (terminal bond).

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.87-92
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• 2006

The steam reforming of methane over Ru-promoted $Ni/Al_2O_3$ was carried out. Compared with $Ni/Al_2O_3$, which needs pre-reduction by $H_2$, $Ru/Ni/Al_2O_3$ catalysts exhibited relatively higher activity than conventional $Ni/Al_2O_3$. According to $H_2-TPR$ of reduced or used catalysts and $CH_4-TPR$, it was revealed that the reduction of $RuO_x$ by $CH_4$ decomposition begins at a lower temperature ($220^{\circ}C$) and the reduced Ru facilitates the reduction of NiO, and leads to self-activation. To improve metal dispersion, the catalyst was soaked in 7 M aqueous $NH_4OH$ for 2 h at $45^{\circ}C$ while stirring. As a result, $Ru/Ni/Al_2O_3$ catalysts with aqueous $NH_4OH$ treatment have higher activity, larger metal surface area (by $H_2$-chemisorption), and small particle size (by XRD and XPS). It is noted that the amount of noble metal could be reduced by aqueous $NH_4OH$ treatment.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.49 no.3
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• pp.193-201
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• 2023

Hydrogen peroxide (H₂O₂) is a type of active oxygen species (ROS) that causes oxidative stress in cells and affects cell growth, proliferation, senescence, and death. The purpose of this study is to find active peptides that attenuate cytotoxicity of H₂O₂. A positional scanning synthetic tetrapeptide combinatorial library was screened to predict the sequence of potentially active peptides. As a result of comparing the effect of peptide pools on H₂O₂-induced death of human keratinocytes (HaCaT cells), various active peptide sequences were predicted. Especially, peptides containing cysteine (C) residue were predicted to be active. In follow-up experiments, the cytotoxicity and activity of cysteine-containing peptides of different lengths, such as C-NH₂, CC-NH₂, CCC-NH₂, and CCCC-NH₂ were examined. C-NH₂ and CC-NH₂ showed no significant cytotoxicity up to 1.0 mM, but CCC-NH₂, and CCCC-NH₂ showed relatively strong cytotoxicity. C-NH₂ and CC-NH₂ alleviated H₂O₂-induced cytotoxicity. CC-NH₂ was more cytoprotective compared to C-NH₂, C, N-acetyl cysteine (NAC), and glutathione (GSH). When intracellular ROS was measured by flow cytometry, H₂O₂ increased ROS production, and CC-NH₂ suppressed ROS production more effectively than C-NH₂, and it was as effective as C, NAC, and GSH. This study suggests that CC-NH₂ of the cysteine-containing peptides of different lengths has an antioxidant property that safely and effectively alleviates H₂O₂-induced cytotoxicity and ROS production.

• Korean Journal of Environmental Biology
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• v.40 no.3
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• pp.267-274
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• 2022

Excess nitrogen (N) flowing from livestock manure to water systems poses a serious threat to the natural environment. Thus, livestock wastewater management has recently drawn attention to this related field. This study first attempted to obtain the optimal conditions for the further volatilization of NH₃ gas generated from pig wastewater by adjusting the amount of injected magnesia (MgO). At 0.8 wt.% of MgO (by pig wastewater weight), the volatility rate of NH₃ increased to 75.5% after a day of aeration compared to untreated samples (pig wastewater itself). This phenomenon was attributed to increases in the pH of pig wastewater as MgO dissolved in it, increasing the volatilization efficiency of NH₃. The initial pH of pig wastewater was 8.4, and the pH was 9.2 when MgO was added up to 0.8 wt.%. Second, the residual ammonia nitrogen (NH₄⁺-N) in pig wastewater was removed by precipitation in the form of struvite (NH₄MgPO₄·6H₂O) by adjusting the pH after adding MgO and H₃PO₄. Struvite produced in the pig wastewater was identified by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analysis. White precipitates began to form at pH 6, and the higher the pH, the lower the concentration of NH₄⁺-N in pig wastewater. Of the total 86.1% of NH₄⁺-N removed, 62.4% was achieved at pH 6, which was the highest removal rate. Furthermore, how struvite changes with pH was investigated. Under conditions of pH 11 or higher, the synthesized struvite was completely decomposed. The yield of struvite in the precipitate was determined to be between 68% and 84% through a variety of analyses.

• Bulletin of the Korean Chemical Society
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• v.27 no.9
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• pp.1405-1417
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• 2006

The geometrical structures, potential energy surfaces, and energetics for the ligand exchange reactions of tetracoordinated platinum $(PtY_2L_2\;:\;Y,\;L=Cl^-,\;OH^-,\;OH_2,\;NH_3)$ complexes in the ligand-solvent interaction systems were investigated using the ab initio Hartree-Fock (HF) and Density Functional Theory (DFT) methods. The potential energy surfaces for the ligand exchange reactions used for the conversions of $(PtCl_4\;+\;H_2O)^{^\ast_\ast}\;to\;[PtCl_3(H_2O)\;+\;Cl^-]$ and $[Pt(NH_3)_2Cl_2\;+\;H_2O]$$[Pt(NH_3)_2Cl_2\;+\;H_2O]$ to $[Pt(NH_3)_2Cl(H_2O)\;+\;Cl^-] $ were investigated in detail. For these two exchange reactions, the transition states $([PtY_2L_2{\cdot}{\cdot}{\cdot}L^\prime])^{^\ast_\ast} $ correspond to complexes such as $(PtCl_4{\cdot}{\cdot}{\cdot}H_2O)^{^\ast_\ast}$ and $[Pt(NH_3)_2Cl_2{\cdot}{\cdot}{\cdot}H_2O]^{^\ast_\ast}$, respectively. In the transition state, $([PtCl_4{\cdot}{\cdot}{\cdot}H_2O]^{^\ast_\ast}$ and $[Pt(NH_3)_2Cl_2{\cdot}{\cdot}{\cdot}H_2O]]^{^\ast_\ast})$ have a kind of 6-membered $(Pt-Cl{\cdot}{\cdot}{\cdot}HOH{\cdot}{\cdot}{\cdot}Cl)$ and $(Pt-OH{\cdot}{\cdot}{\cdot}Cl{\cdot}{\cdot}{\cdot}HN)$ interactions, respectively, wherein a central Pt(II) metal directly combines with a leaving $Cl^-$ and an entering $H_2O$. Simultaneously, the entering $H_2O$ interacts with a leaving $Cl^-$. No vertical one metal-ligand interactions $([PtY_2L_2{\cdot}{\cdot}{\cdot}L^\prime]) $ are found at the axial positions of the square planar $(PtY_2L_2)$ complexes, which were formed via a vertically associative mechanism leading to $D_{3h}$ or $C_{2v}$-transition state symmetry. The geometrical structure variations, molecular orbital variations (HOMO and LUMO), and relative stabilities for the ligand exchange processes are also examined quantitatively. Schematic diagrams for the dissociation reactions of {PtCl4(H2O)n(n=2,4)} into {$PtCl_3(H_2O)_{(n-2)}\;+\;Cl^-(H_2O)_2$} and the binding energies {$PtCl_4(H_2O)_n$(n = 1-5)} of $PtCl_4$ with water molecules are drawn.

• Bulletin of the Korean Chemical Society
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• v.24 no.3
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• pp.369-376
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• 2003

Coulson (ZINDO), Mulliken $(MP2/6-31G^*)$ and Natural $(MP2/6-31G^*)$ population analyses of several large molecules were performed by the Fragment Reassociation (FR) method. The agreement between the conventional ZINDO (or conventional MP2) and FR-ZINDO (or FR-MP2) charges of these molecules was excellent. The standard deviations of the FR-ZINDO net atomic charges from the conventional ZINDO net atomic charges were 0.0008 for $C_{10}H_{22}$ (32 atoms), 0.0012 for $NH_2-C_{16}O_2H_{28}-COOH$ (53 atoms), 0.0014 for $NH_3^+-C_{16}O_2H_{28}-COOH$ (54 atoms), 0.0017 for $NH_2-C_{16}O_2H_{28}-COO^-$ (52 atoms), 0.0019 for $NH_3^+-C_{16}O_2H_{28}-COO^-$ (53 atoms), 0.0024 for a conjugated model $(O=CH-(CH=CH)_{15}-C=O-(CH=CH)_{12}-CH=CH_2)$, 118 atoms), 0.0038 for aglycoristocetin $(C_{60}N_7O_{19}H_{52}^+$, 138 atoms), 0.0023 for a polypropylene model complexed with a zirconocene catalyst $(C_{68}H-{121}Zr^+$, 190 atoms) and 0.0013 for magainin $(C_{112}N_{29}O_{28}SH_{177}$, 347 atoms), respectively. The standard deviations of the FR-MP2 Mulliken (or Natural) partial atomic charges from the conventional ones were 0.0016 (or 0.0016) for $C_{10}H_{22}$, 0.0019 (or 0.0018) for $NH_2-C_{16}O_2H_{28}-COOH$ and 0.0033 (or 0.0023) for $NH_3^+-C_{16}O_2H_{28}-COO^-$, respectively. These errors were attributed to the shape of molecules, the choice of fragments and the degree of ionic characters of molecules as well as the choice of methods. The CPU time of aglycoristocetin, conjugated model, polypropylene model complexed with zirconocene and magainin computed by the FR-ZINDO method was respectively 2, 4, 6 and 21 times faster than that by the normal ZINDO method. The CPU time of $NH_2-C_{16}O_2H_{28}-COOH\;and\;NH_3^+-C_{16}O_2H_{28}-COO^-$ computed by the FR-MP2 method was, respectively, 6 and 20 times faster than that by the normal MP2 method. The largest molecule calculated by the FR-ZINDO method was B-DNA (766 atoms). These results will enable us to compute atomic charges of huge molecules near future.

• Korean Journal of Materials Research
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• v.4 no.5
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• pp.541-549
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• 1994

The crystallization behavior and structural change of amorphous $PbTiO_{3}$ precursors prepared by coprecipitation method were investigated by XRD, Raman spectra, TEM, and RDF. The precursors were prepared at $45^{\circ}C$ and pH of 9 from a mixed solution of lead nitrate and titanium tetrachloride derived using $H_2O_2$ or $NH_4NO_3$ as an ion stabilizer. The activation energy and temperature for crystallization of the coprecipitate prepared using $NH_4NO_3$ as an ion stabilizer were lower than that derived from the solution containing $H_2O_2$ stabilizer. The amorphous coprecipitate transformed to transient phase and then to crystalline $PbTiO_{3}$. Average interatomic distances of amorphous states decreased with increasing heat-treatment temperature.

• Journal of the Korean Chemical Society
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• v.16 no.3
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• pp.157-165
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• 1972

Thermal decomposition of ammonium metavanadate has been investigated by using the quartz spring balance and differential thermal analysis. It showed that the decomposition of ammonium metavanadate is proceeded at two stages which correspond to $180^{\circ}C-220^{\circ}C$ and $310^{\circ}C-330^{\circ}C$ decomposition temperatures, respectively. Evolved ammonia gas in thermal decomposition has been analyzed quantitatively by titration. And the constituents of gases evolved have been evaluated by gas chromatography and omegatron spectrometer. From these results, it was concluded that the gases evolved in the first step decomposition were $NH_3$ and $H_2O$ with 2:1 ratio and the second step decomposition corresponded to the formation of $NH_3$, $H_2O$ and $N_2O$ which was produced in oxidation of $NH_3$ by $V_2O_5$. The decomposition products were identified by means of X-ray diffraction method. The decomposition product in air was V_2O_5 and the product in vacuum $V_3O_7.$ The kinetics of the thermal decomposition was studied, giving the values of the activation energy of 41.4 kcal/mole and 64.4 (kcal/mole) respectively.

• Journal of the Korean Magnetic Resonance Society
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• v.23 no.2
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• pp.40-45
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• 2019

The phase transition temperatures and thermodynamic properties of $(NH_4)_2MnCl_4{\cdot}2H_2O$ grown by the slow evaporation method were studied using differential scanning calorimetry and thermogravimetric analysis. A structural phase transition occurred at temperature $T_{C1}$ (=264 K), whereas the changes at $T_{C2}$ (=460 K) and $T_{C3}$ (=475 K) seemed to be chemical changes caused by thermal decomposition. In addition, the chemical shift and the spin-lattice relaxation time $T_{1{\rho}}$ were investigated using $^1H$ magic-angle spinning nuclear magnetic resonance (MAS NMR), in order to understand the role of $NH_4{^+}$ and $H_2O$. The rise in $T_{1{\rho}}$ with temperature was related to variations in the symmetry of the surrounding $H_2O$ and $NH_4{^+}$.