• Journal of the Korean Chemical Society
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• v.32 no.1
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• pp.22-29
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• 1988

The reaction of methanol-water mixture to $CO_2$ and $H_2$ on alkaline earth metal-copper-zinc oxide has been studied in the temperature range of 150 ${\sim}\;300^{\circ}C$. Generally the addition of the alkaline earth metal to Cu/ZnO resulted in an enhancement of selectivity for $CO_2$ formation and a reduction of catalytic activity. Measurable activities were found from 150$^{\circ}C$, 200$^{\circ}C$, and 250$^{\circ}C$ on Mg/Cu/ZnO, Ca/Cu/ZnO, and Ba/Cu/ZnO respectively. However, the highest selectivity for $CO_2$ formation was observed in Ba/Cu/ZnO catalyst at 250$^{\circ}C$. The effect of alkaline earth metal or ZnO on the reactivity was investigated using temperature programmed desorption of $CO_2$ or temperature programmed reduction with $H_2$ over catalysts respectively. It was found that $CO_2$ interacts more strongly in the sequence of MgO < CaO < BaO and ZnO decereases the reduction temperature of CuO. From the results, it was suggested that ZnO activates $H_2$ in the redox process of Cu component and alkaline earth metals adsorbs $CO_2$ in the catalytic process.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.891-897
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• 2019

In this study, heteropoly acid PVMo catalysts were supported on activated carbon with various composition of phosphoric acid ($H_3PO_4$), vanadium (V) pentoxide ($V_2O_5$) and molybdenum (VI) trioxide ($MoO_3$). Catalytic performance was examined at $140^{\circ}C$ for 1hour in vapor formaldehyde. XRD and BET analyses were carried with the catalysts before and after the reaction. Formaldehyde conversion was increased with decreasing Mo and $H_3PO_4$ content and increasing $V_2O_5$ content. Acidity of the catalysts was investigated with $NH_3-TPD$. Crystallinity of the catalysts was relatively low, and surface area was decreased after the reaction. In $NH_3-TPD$ result, the ratio of strong acid site corresponding to $NH_3$ desorption between $400^{\circ}C$ and $500^{\circ}C$ was increased by decreasing $MoO_3$ and $H_3PO_4$ content and increasing $V_2O_5$ content. Therefore, it was found that the strong acid site could affect the catalytic reactivity in vapor formaldehyde conversion.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.714-722
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• 2019

Catalysts were prepared by using incipient wetness impregnation method with 17 wt% Ni on a support ($SiO_2-Y_2O_3$, $Al_2O_3$, $SiO_2-ZrO_2$, $SiO_2$, $TiO_2$, MgO) and the catalytic activity in the reductive amination of ethanol with ammonia in the presence of hydrogen was compared and evaluated. The catalysts used before and after the reaction were characterized using X-ray diffraction, nitrogen adsorption, ethanol-temperature programmed desorption (EtOH-TPD), isopropanol-temperature programmed desorption (IPA-TPD), and hydrogen chemisorption etc. In the case of preparing $ZrO_2$ and $Y_2O_3$ supports, the small amount of Si dissolution from the Pyrex reactor surface provoked the formation of mixed oxides $SiO_2-ZrO_2$ and $SiO_2-Y_2O_3$. Among the catalysts used, $Ni/SiO_2-Y_2O_3$ catalyst showed the best activity, and this good activity was closely related to the highest nickel dispersion, and low desorption temperature in EtOH-TPD and IPA-TPD. The low catalytic activity on Ni/MgO catalysts showed low activity due to the formation of NiO-MgO solid-solutions. In the case of $Ni/TiO_2$, the reactivity was low due to the low nickel metal phase due to strong metal-support interaction. In the case of using a support as $SiO_2-Y_2O_3$, $Al_2O_3$, $SiO_2-ZrO_2$, and $SiO_2$, the selectivities of ethylamines and acetonitrile were not significantly different at similar ethanol conversion.

• Applied Chemistry for Engineering
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• v.18 no.3
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• pp.218-226
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• 2007

The stereoselective synthesis of chiral terminal epoxides is of immense academic and industrial interest due to their utility as versatile starting materials as well as chiral intermediates. In this study, new dinuclear chiral Co (salen) complexes bearing gallium-, indium- and tallium-chloride have been synthesized and characterized. The mass and EXAFS spectra provided the direct evidence of formation of dinuclear complex. Their catalytic activity and selectivity have been demonstrated for the asymmetric ring opening of various terminal epoxides having ether or ester groups by hydrolytic kinetic resolution technology. The easily prepared dimeric complexes exhibited very high enantioselectivity for the asymmetric ring opening of epoxides with $H_2O$ nucleophile, providing enantiomerically enriched terminal epoxides (> 99% ee). The dimeric structured chiral salen showed remarkably enhanced reactivity and may be employed substantially lower loadings than its monomeric analogues. The system described in this work is very efficient for the synthesis of chiral epoxide and 1,2-diol intermediates

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1517-1522
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• 2012

Anion effects on structures of $Cd^{II}$ complexes containing 2,2'-bipyridine (2,2'-bpy) ligands have been studied, and compared with $Zn^{II}$-(2,2'-bpy) complexes. For each anion, different structures have been obtained in both $Zn^{II}$-(2,2'-bpy) and $Cd^{II}$-(2,2'-bpy). Polymeric structures of $Cd^{II}$-2,2'-bpy complexes can be produced by hydrogen bonding interactions as shown in $Zn^{II}$-2,2'-bpy complexes. In addition, the bigger size of a $Cd^{II}$ ion gives higher coordination numbers forming variety of structures, and it makes that chlorides can act as bridging ligands to form a one-dimensional structure. The compound $\mathbf{5}$ catalyzed efficiently the transesterification of a variety of esters with methanol, while the rest of the compounds have displayed very slow conversions. In addition, the emission bands of complexes $\mathbf{1}$, $\mathbf{2}$, $\mathbf{4}$, and $\mathbf{6}$ are blue-shifted compared to the corresponding ligand 2,2'-bpy, whereas $\mathbf{3}$ and $\mathbf{5}$ showed the similar emission observed for the ligand.

• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.1079-1085
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• 1999

An investigation was made of the effect of various transition metal catalysts, ligands, and a promoter on the synthesis of N,N'-diphenylurea(DPU) from nitrobenzene, aniline, and carbon monoxide. Homogeneous Pd and Ni catalysts were found to be highly efficient, giving almost quantitative isolated DPU yields at 100% nitrobenzene conversion. Bidentate ligand, 1,3-bis(diphenylphosphino)proane(dppp) showed much improved activity and significantly different reactivity relative to the usual monodentate $PPh_3$ ligand in the presence of Ni and Pd catalysts. These results were inferred to the effect of the cis coordination of bidentate dppp ligand on the metal. The use of a promoter $Et_4NCl$ was indispensable in the case of $PPh_3$, yet inhibited the reaction if used with dppp. It was possible to reuse the Pd-dppp catalyst system, although the catalytic activity was reduced slowly.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.409-413
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• 2006

An experimental study on a combined $De-NO_x$ process of non-thermal plasma and $NH_{3}$ SCR, which can be operated under low temperature conditions, i.e. $150{\sim}200^{\circ}C$, has been conducted. The test results confirmed feasibility of fast SCR reaction, which shows faster reactivity compared with typical SCR reaction under the low temperature conditions. The test showed that pre-oxidation step to convert NO to $NO_2$ is necessary for the fast SCR reaction, and the appropriate ratio of $NO_{2}/NO_{x}$ ranges from 0.3 to 0.5. Ammonium salts produced under low temperature conditions, effects of hydrocarbons on the combined process, the operation power of the process are discussed in the present study.

• Journal of Korean Society for Atmospheric Environment
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• v.18 no.E1
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• pp.29-36
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• 2002

The selective catalytic reduction (SCR) reaction of promoter catalysts was investigated in this study. A pure anatase type of TiO$_2$ was used as support. Activation measurement of prepared catalysts was practiced on a fixed reactor packing by the glass bead after filling up catalysts in 1/4 inch stainless tube. The reaction temperature was measured by K-type thermocouple and catalyst was heated by electric furnace. The standard compositions of the simulated flue gas mixture in this study were as follows: NO 1,780ppm, NH$_3$1,780ppm, $O_2$1% and $N_2$ as balance gas. In this study, gas analyzer was used to measure the outgassing gas. Catalyst bed was handled for 1hr at 45$0^{\circ}C$, and the reactivity of the various catalyst was determined in a wide temperature range. Conversion of NH$_3$/NO ratio and of $O_2$ concentration was practiced at 1,1.5 and 2, respectively. The respective space velocity were as follows . 10,000, 15,000 and 17,000 hr-1. It was found that the maximum conversion temperature range was in a 5$0^{\circ}C$. It was also found toi be very sensitive at space velocity, $O_2$ concentration, and NH$_3$/NO ratio. We also noticed that the maximum conversion temperature of (W, Mo, Sn) -V$_2$O$_{5}$/TiO$_2$ catalysts was broad. Specially WO$_3$-V$_2$O$_{5}$TiO$_2$2 catalyst appeared nearly 100% conversion at not only above 30$0^{\circ}C$ ut also below 25$0^{\circ}C$. At over 30$0^{\circ}C$, NH$_3$ oxidation decreased with decrease of surface excess oxygen. In addition, WO$_3$-V$_2$O$_{5}$TiO$_2$ catalyst did not appear to affect space velocity, $O_2$ concentration, and NH$_3$/NO ratio.ratio.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.10
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• pp.575-580
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• 2017

Chlorinated hydrocarbons (TCE and PCE), petroleum hydrocarbons (BTEX, PAHs, and TPH), and explosive compounds (TNT, RDX, and HMX) have been detected in underground water countrywide. The overall objective of this study is to evaluate sono-catalytic degradation coupled with the use of PUV in order to understand the fate and transport of a representative selection of non-biodegradable contaminants (i.e., TCE, PCE, BTEX, PAHs, TPH, TNT, RDX, and HMX) in groundwater. Both ultraviolet (UV) and ultrasound (US) systems are used in degrading of organic contaminants and they can thus be applicable simultaneously as an UV/US hybrid system in attempts further to increase the degradation efficiency. Results indicate that synergistic effect of UV/US hybrid system is closely correlated to the enhancement of sono-chemical reactivity with the UV-US interaction of increasing the formation rate of OH by providing additional $H_2O_2$ production through the pyrolysis of water molecules during UV/US hybrid irradiation.

• Bulletin of the Korean Chemical Society
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• v.35 no.6
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• pp.1749-1753
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• 2014

Pseudo-first-order rate constants ($k_{obsd}$) have been measured spectrophotometrically for the nucleophilic substitution reaction of Y-substituted-phenyl picolinates (7a-f) with potassium ethoxide (EtOK) in anhydrous ethanol at $25.0{\pm}0.1^{\circ}C$. The plot of $k_{obsd}$ vs. [EtOK] curves upward while the plot of $k_{obsd}/[EtO^-]_{eq}$ vs. $[EtO^-]_{eq}$ is linear with a positive intercept in all cases. Dissection of $k_{obsd}$ into $k_{EtO^-}$ and $k_{EtOK}$ (i.e., the second-order rate constants for the reactions with the dissociated $EtO^-$ ion and ion-paired EtOK, respectively) has revealed that the ion-paired EtOK is more reactive than the dissociated $EtO^-$. The ${\sigma}^{\circ}$ constants result in a much better Hammett correlation than ${\sigma}^-$ constants, indicating that the reaction proceeds through a stepwise mechanism in which departure of the leaving group occurs after the rate-determining step (RDS). $K^+$ ion catalyzes the reaction by increasing the electrophilicity of the reaction center through formation of a cyclic transition state (TS). The catalytic effect decreases as the substituent Y becomes a stronger electron-withdrawing group (EWG). Development of a positive charge on the N atom of the picolinyl moiety through resonance interactions is responsible for the decreasing $K^+$ ion catalysis.