• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.661-669
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• 1996

Pt-Rh/NaY catalysts with various Pt/Rh ratios were prepared by an ion-exchange method and their characteristics were investigated by $^{129}Xe$-NMR and EXAFS. Both the $^{129}Xe$-NMR and EXAFS data indicate that the surface of PtRh bimetallic clusters was enriched with Rh atoms. The catalytic activities of these catalysts for conversion of CO, HC and $NO_x$ were measured by using simulated automobile engine exhausts under lean, rich and stoichiometric conditions. The Pt-Rh/NaY(Pt/Rh=1) catalyst exhibited the greatest reactive activity among the catalysts used in this study.

• Bulletin of the Korean Chemical Society
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• v.23 no.4
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• pp.563-566
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• 2002

Copper complexes have been directly incorporated into cellulose acetate (CA) and the resulting light blue colored homogeneous films of 5-20 wt.% copper acetate complex concentrations are found to be thermally stable up to 200 $^{\circ}C$. The reaction chem istry of Cu in CA has been investigated by reacting them with small gas molecules such as CO, H2, D2, O2, NO, and olefins in the temperature range of 25-160 $^{\circ}C$, and various Cu-hydride, -carbonyl, -nitrosyl, and olefin species coordinated to Cu sites in CA are characterized by IR and UV/Vis spectroscopic study. The reduction of Cu(II) complexes by reacting with H2 gas at the described conditions results in the formation of Cu2O and copper metal nanoparticles in CA, and their sizes in 30-120 nm range are found to be controlled by adjusting metal complex concentration in CA and/or the reduction reaction conditions. These small copper metal particles show various catalytic reactivity in hydrogenation of olefins and CH3CN; CO oxidation; and NO reduction reactions under relatively mild conditions.

• Bulletin of the Korean Chemical Society
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• v.28 no.1
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• pp.17-28
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• 2007

Indium and gallium have emerged as useful metals in organic synthesis as a result of its intriguing chemical properties of reactivity, selectivity, and low toxicity. Although indium belongs to a main metal in group 13, its first ionization potential energy is very low and stable in H2O and O2. Therefore, indium-mediated organic reactions are of our current interest. On the basis of these properties of indium, many efficient indium-mediated organic reactions have been recently developed, such as the addition reactions of allylindium to carbonyl and iminium groups, the indium-mediated synthesis of 2-(2-hydroxyethyl)homoallenylsilanes, the indiummediated allylation of keto esters with allyl halides, sonochemical Reformatsky reaction using indium, the indium-mediated selective introduction of allenyl and propargyl groups at C-4 position of 2-azetidinones, the indium-mediated Michael addition and Hosomi-Sakurai reactions, the indium-mediated β-allylation, β- propargylation and β-allenylation onto α,β-unsaturated ketones, the highly efficient 1,4-addition of 1,3-diesters to conjugated enones by indium and TMSCl, and the intramolecular carboindation reactions. Also, we found gallium-mediated organic reactions such as addition reactions of propargylgallium to carbonyl group and regioselective allylgallation of terminal alkynes.

• Transactions of the Korean hydrogen and new energy society
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• v.30 no.1
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• pp.1-7
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• 2019

The preparation and catalytic activities of various transition metal carbide crystallites (VC, MoC, WC) were examined in this study. In particular, the effect of different kinds of transition metal crystallites were scrutinized on the ammonia decomposition reaction. The experimental results showed that BET surface areas ranged from $8.3m^2/g$ to $36.3m^2/g$ and oxygen uptake values varied from $9.1{\mu}mol/g$ to $25.4{\mu}mol/g$. Amongst prepared transition metal carbide crystallites, tungsten compounds (WC) were observed to be most active for ammonia decomposition reaction. The main reason for these results were considered to be related to the extent of electronegativity between these materials. Most of transition metal carbide crystallites were exceeded by Pt/C crystallite. However, the steady state reactivities for some of transition metal carbide crystallites (WC) were comparable to or even higher than that determined for the Pt/C crystallite.

• Bulletin of the Korean Chemical Society
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• v.15 no.2
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• pp.161-167
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• 1994

Rate constants have been measured spectrophotometrically for the nucleophilic substitution reactions of aryl substituted benzenesulfonates (3) with alkali metal ethoxides ($EtO^-M^+$) and butane-2,3-dione monoximates ($Ox^-M^+$) in ethanol at $25^{\circ}C$. The reactivity of the alkali metal ethoxides decreases in the order $EtO^-K^+> EtO^- > EtO^-Li^+$, indicating that $K^+$ ion behaves as a catalyst and $Li^+$ ion acts as an inhibitor for all the substrates studied. For the corresponding reactions of 3 with Ox^-M^+$, $Li^+$ ion also exhibits inhibitory effect for all the substrates, while, $K^+$ ion shows catalytic or inhibitory effects depending on the nature of substituents on the acyl and phenyl moieties. A study of substituent effect on rate has revealed that both EtO^- $and Ox^-$ systems have the same reaction mechanism. The different behavior shown by $K^+$ ion for the reaction of 3 with $EtO^-$ and $Ox^-$ would be attributed to a difference in charge polarization of S=O bond in the transition state between the two systems and/or a change in conformation of Ox^-K^+$.

• Journal of Energy Engineering
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• v.23 no.3
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• pp.150-156
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• 2014

In this study, we implemented a research for improving performance of redox flow battery (RFB) via enhancing reaction rate of vanadium reaction ($[VO]^{2+}/[VO_2]^+$) that was a rate determining step. For doing that, porous catalyst, CMK3 was employed and its perfoamance was compared with that of Vulcan(XC-72) and commercial Pt/C (Johnson-Matthey Pt 20wt.%). Cyclic voltammetry (CV) was used for inspecting reactivity, while its structural feature was measured by TEM and BET&BJH. Also, Charge-discharge trend was evaluated by single cell tests. As result, CMK3 showed 6 times better catalytic activity and twice better reversibility than Vulcan(XC-72), while it showed larger surface area than Vulcan XR due to its porous structure. Furthermore, CMK3 indicated 85% of reactivity and reversibility of commercial Pt/C despite its Pt-less situation. In single cell tests, when RFB adopted CMK3 as catalyst for positive electrode, its charge-discharge curve result was better than that adopted commercial Pt/C.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.141-148
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• 1998

Reactivity of Pt catalysts(0.2, 0.5 wt% Pt) supported on solid super acid, $ZrO_2$ $SO_4{^{2-}}$ for low-temperature oxidation was investigated for complete oxidation of cyclohexane. Catalytic activity measured as reactant conversion in a packed-bed tubular reactor increased in accordance with the acidity and specific surface area of the catalyst activity and specific surface area of $Pt/ZrO_2$ $SO_4{^{2-}}$ catalyst were diminished by adding potassium during catalyst preparation. the catalyst activity decreased in accordance with the amount of potassium added. In addition, $Pt/ZrO_2$ $SO_4{^{2-}}$ catalyst exhibited an activity greater than that of a $Pt/SiO_2$ or $Pt/Al_2O_3$ catalyst possessing much larger specific surface area at $250^{\circ}C$ for the reactant stream of 15.000 ppm cyclohexane concentration and $18,000hr^{-1}$ space velocity, a cyclohexane conversion as high as 96% was obtained over 0.2 wt% $Pt/ZrO_2$ $SO_4{^{2-}}$, whereas cyclohexane conversions over 0.2 wt% $Pt/SiO_2$ and 0.2 wt% $Pt/Al_2O_3$ were 83 and 79%, respectively.

• Applied Chemistry for Engineering
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• v.17 no.3
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• pp.235-242
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• 2006

Liquid phase alkylation of biphenyl (BP) was studied over large pore zeolites. Selective formation of the least bulky products, 4,4'-diisopropylbiphenyl (4,4'-DIPB) occurred only in the isopropylation of BP over some large pore molecular sieves. H-mordenites (MOR) gave the highest selectivity among them. The dealumination of MOR enhanced catalytic activity and the selectivity of 4,4'-DIPB because of the decrease of coke-deposition. Non-selective catalysis occurs on external acid sites over MOR with the low $SiO_2/Al_2O_3$ ratio because severe coke-deposition deactivates the acid sites inside the pores by blocking pore openings. The selectivity of DIPB isomers was changed with reaction temperature. Selective formation of 4,4'-DIPB was observed at moderate temperatures such as $250^{\circ}C$, whereas the decrease of the selectivity of 4,4'-DIPB occurred at higher temperatures as $300^{\circ}C$. However, 4,4'-DIPB was almost exclusive isomer in the encapsulated DIPB isomers inside the pores even at high temperatures. These decreases of the selectivity of 4,4'-DIPB are due to the isomerization of 4,4'-DIPB on the external acid sites. Some 12-membered molecular sieves, such as SSZ-24, MAPO-5 (M:Mg, Zn, Si), SSZ-31, and ZSM-12, which have straight channels, gave 4,4'-DIPB with moderate to high selectivity; however; SSZ-55, SSZ-42, and MAPO-36 (M: Mg, Zn) gave lower selectivity because of cages in 12-membered one dimensional channels. Three dimensional H-Y and Beta zeolites also yield 4,4'-DIPB in low yield because of their wide circumstances for the isopropylation of BP. The increasing the size of alkylating agent enhanced the shape-selective alkylaiton even for the zeolites, such as UTD-1. The ethylation of BP to ethylbiphenyls (EBPs) and diethylbiphenyls (DEBPs) over MOR was non-selective. The ethylation of BP to EBPs was controlled kinetically. However, there was difference in reactivity of EBPs and DEBPs for their further ethylation. 4-EBP was ethylated preferentially among the isomers, although the formation of 4,4'-DEBP was less selective. The least bulky 4-EBP and 4,4'-DEBP have the highest reactivity among EBPs and DEBPs for the ethylation to polyethylbiphenyls (PEBPs). These results show that the environments of MOR pores are too loose for shape selective formation of the least bulky isomers, 4-EBP and 4,4'-DEBP in the ethylation of BP, and that MOR pores have enough space for the further ethylation of 4,4'-DEBP.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.217-222
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• 2012

The synthesis of dimethyl carbonate(DMC) is a promising reaction for the use of naturally abundant carbon dioxide. DMC has gained considerable interest owing to its versatile chemical reactivity and unique properties such as high oxygen content, low toxicity, and excellent biodegradability. In this study, the synthesis of DMC through the transesterification of ethylene carbonate(EC) with methanol was investigated by using ionic liquid and metal oxide catalysts. The screening test of different catalysts revealed that choline hydroxide ([Choline][OH]) and 1-n-butyl-3-methyl imidazolium hydroxide([BMIm][OH]) had better catalytic performance than metal salts catalysts such as MgO, ZnO and CaO. The effects of reaction parameters such as reaction temperature, MeOH/EC mole ratio, and carbon dioxide pressure on the reactivity of [Choline][OH] catalyst were discussed. High temperature and high MeOH/EC mole ratio were favorable for high conversion of EC. However, the yield of DMC showed a maximum when carbon dioxide pressure was 1.34 MPa, and then it decreased for higher carbon dioxide pressure. Zinc chloride($ZnCl_2$) was used as co-catalyst with the ionic liquid catalyst. The mixed catalyst showed a synergy effect on the EC conversion and DMC yield probably due to the acid-base properties of the catalysts.

• Korean Chemical Engineering Research
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• v.53 no.5
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• pp.653-662
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• 2015

In general, the coal gasification has to be operated under high temperature ($1300{\sim}1400^{\circ}C$) and pressure (30~40 bar). However, to keep this conditions, it needs unnecessary and excessive energy. In this work, to reduce the temperature of process, alkali catalysts such as $K_2CO_3$ and $Na_2CO_3$ were added into Cyprus coal. We investigated the kinetic of Cyprus char-$CO_2$ gasification. To determine the gasification conditions, the coal (with and without catalysts) gasified with fixed variables (catalyst loading, catalytic effects of $Na_2CO_3$ and $K_2CO_3$, temperatures) by using TGA. When catalysts are added by physical mixing method into Cyprus coal the reaction rate of coal added 7 wt% $Na_2CO_3$ is faster than raw coal for Cyprus char-$CO_2$ gasification. The activation energy of coal added 7 wt% $Na_2CO_3$ was calculated as 63 kJ/mol which was lower than raw char. It indicates that $Na_2CO_3$ can improve the reactivity of char-$CO_2$ gasification.