• Journal of Environmental Science International
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• v.22 no.8
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• pp.945-951
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• 2013

Alumina-supported catalysts containing different transition metals such as Cu, Cr, Mn, Zn, Co, W were investigated for their activity in the selective oxidation of toluene. Catalytic oxidation of toluene was investigated at atmospheric pressure in a fixed bed flow reactor system over transition metals with $Al_2O_3$ catalyst. The result showed the order of catalytic activities for the complete oxidation of toluene was Mn > Cu> Cr> Co> W> Zn for 5wt.% transition $metals/Al_2O_3$. $Mn/Al_2O_3$ catalysts containing different amount of Mn were characterized by X-ray diffraction spectroscopy for decision of loading amount of metal to alumina. 5 wt.%$Mn/Al_2O_3$ catalyst exhibits the highest catalytic activity, over which the toluene conversion was up to 90% at a temperature of $289^{\circ}C$.

• Journal of the Korean Institute of Gas
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• v.19 no.5
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• pp.20-28
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• 2015

This work investigated the size and shape effect of ${\gamma}$-alumina-supported metal oxides on the hydrocarbon selective catalytic reduction of nitrogen oxides. Several metal oxides including Ag, Cu and Ru were used as the catalysts, and n-heptane as the reducing agent. For the Ag/${\gamma}$-alumina catalyst, the $NO_x$ reduction efficiency in the range of $250{\sim}400^{\circ}C$ increased as the size of Ag decreased (20 nm>50 nm>80 nm). The shape effect of metal oxides on the $NO_x$ reduction was examined with spherical- and wire-shape nanoparticles. Under identical condition, higher catalytic activity for $NO_x$ reduction was observed with Ag and Cu wires than with the spheres, while spherical- and wire-shape Ru exhibited similar $NO_x$ reduction efficiency to each other. Among the metal oxides examined, the best catalytic activity for $NO_x$ reduction was obtained with Ag wire, showing almost complete $NO_x$ removal at a temperature of $300^{\circ}C$. For Cu and Ru catalysts, considerable amount of NO was oxidized to $NO_2$, rather than reduced to $N_2$, leading to lower $NO_x$ reduction efficiency.

• Journal of the Korean Society of Combustion
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• v.8 no.2
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• pp.50-55
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• 2003

Synthesis of carbon nanofibers on a metal substrate by an ethylene fueled inverse diffusion flame was observed. Stainless steel plates were used for the catalytic metal substrate. The effects of radial distance and residence time of the substrate were investigated. The role of hydrocarbon composition in the fuel was also viewed. Nanofibers with a diameter range of 30-70nm were found on the substrate. The carbon nanofibers were formed and grown in the region from 4 to 5.5mm from the central axis of a flame outside of the visible flame front in the radial direction. The minimum residence time required for the formation of carbon nanofibers were about 20 seconds, and over 60 seconds were required for the full-scale growth. The characteristic time of the formation of carbon nanofibers was much shorter than that of the substrate temperature growth. In this study, the variation in hydrocarbon composition had no significant effect on the formation and growth of the carbon nanofibers.

• Journal of the Korean Applied Science and Technology
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• v.7 no.1
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• pp.71-76
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• 1990

Transesterification reactions (methyl methacrylate with monoethanolamine, methyl methacrylate with n-butyl alcohol, dimethylphthalate with ethylene glycol, dimethyl phthalate with monoethanolamine) were kinetically investigated in the presense of various metal acetate catalysts at $110^{\circ}C$. The amount of reactants was measured by gas and liquid chromatography, and the reaction rates also measured from the amount of reaction products and reactants upon each catalyst. The transesterification reactions were carried out under the first order conditions respect to the concentration of reactants, respectively. The overall reaction order was 2nd, Maximum reaction rates were appeared at the range of 1.4 to 1.6 in electronegativity of metal ions and maximum catalytic activities were obserbed at the range of 1.5 to 1,8 in instability constant of metal acetates.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1378-1379
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• 2006

Carbon nanotubes (CNTs) with few defects and very small amount of amorphous carbon coating have been synthesized by catalytic decomposition of acetylene in $H_2$ over well-dispersed metal particles supported on MgO. The yield, quality and diameters of CNTs were obtained by control of catalyst metal compositions to be used. The optimization condition of carbon nanotubes with high yield is when Co and Mo are in a 1:1 ratio and Fe metal contents to Co is increased on magnesium oxide support. It is also found that the diameter of the as-prepared CNTs can be controlled mainly by adjusting the molar ratio of Fe-Mo, Co-Fe, and Co-Mo versus the MgO support. Our results indicated that desired diameter distribution of CNTs is obtained by choosing or combining the catalyst to be employed.

• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.258-266
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• 2020

The chemical fixation of CO₂ into cyclic carbonates is considered to be one of the most promising way to alleviate global warming and produce fine chemicals. In this work, the catalytic applicability of metal-organic frameworks (MOFs) as porous crystalline materials for the synthesis of five-membered cyclic carbonate from CO₂ and epoxides was reviewed. In addition, we have briefly classified the materials based on their different structural features and compositions. The studies revealed that MOFs exhibited good catalytic performance towards cyclic carbonate synthesis because of the synergistic effect between the acid sites of MOFs and nucleophile. Moreover, the effect of structure of designed MOFs and mechanism for the cycloaddition of CO₂ were suggested.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.211-211
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• 2011

Nanostructures, with a diversity of shapes, built on substrates have been developed within many research areas. Lithography is one powerful, but complex, technique to make structures at the nanometer scale, such as platinum nanowires for studying CO catalytic reactions [1], or aluminum nanodisks for studying the plasmon effect [2]. In this work, we approach a facile method to construct nanostructures using noble metals on a titania thin film by using self-assembled structures as a pattern. Here, a large-scale silica monolayer is transferred to the titania thin film substrates using a Langmuir-Blodgett trough, followed by the deposition of a thin transition metal layer. Owing to the hexagonal close-packed structure of the silica monolayer, we would obtain a metal nanostructure that includes separated metallic triangles (islands) after removing the patterning silica beads. This nanostructure can be employed to investigate the role of metal-oxide interfaces in CO catalytic reactions by changing the patterning silica particles with different sizes or by replacing the oxide support. The morphology and chemical composition of the structure can be characterized by scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. In addition, we modify these islands to a connected island structure by reducing the silica size of the patterning monolayer, which is utilized to generating hot electron flow based on the localized surface plasmon resonance effect of the metal nanostructures.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.556-556
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• 2012

Transition metal-based organometallic complexes have shown great talents as a catalyst in various reactions. Designing organic molecules and coordinating them to such active centers have been a promising route to control the catalytic natures. Metallocene, which has transition metal atoms sandwiched by aromatic rings, is one of the representative systems for organometallic catalysts. Group 4-based metallocene catalysts have been most commonly used for the production of polyolefins, which have great world-wide markets in the real life. Graphenes and carbon nanotubes (CNTs) were composed of extended $sp^2$ carbon networks, showing high electron mobility as well as have extremely large steric bulkiness relative to metal centers. We were inspired by these characteristics of such carbon-based nano-materials and assumed that they could intimately interact with active centers of metallocene catalysts. We examined this hypothesis and, recently, reported that CNTs dramatically changed catalytic natures of group 4-based catalysts when they formed hybrid systems with such catalysts. In conclusion, we produced hybrid materials composed of group-4 based metallocenes, $Cp_2ZrCl_2$ and $Cp_2TiCl_2$, and carbon-based nano-materials such as RGO and MWCNT. Such hybrids were generated via simple adsorption between Cp rings of metallocenes and graphitic surfaces of graphene/CNT. The hybrids showed interesting catalytic behaviors for ethylene polymerizations. Resulting PEs had significantly increased Mw relative to those produced from free metallocene-based catalytic systems, which are not adsorbed on carbon-based nano-materials. UHMWPEs with extremely high Mw were obtained at low Tp.

• Journal of Environmental Science International
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• v.13 no.7
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• pp.619-626
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• 2004

We have studied the catalytic combustion of soot particulates over perovskite-type oxides prepared by malic acid method, The catalysts were modified to enhance the activity by substitution of metal into A or B site of perovskite oxide. In addition, the reaction conditions such as temperature and $O_2$ concentration were investigated. The partial substitution of alkali metals into A site in the $LaMnO_3$ catalyst, enhanced the catalytic activity in the combustion of carbon particulate and the activity was shown in the order: Cs > K > Na. For the $La_{1-x}Cs_{x}MnO_{3}$ catalysts, the catalytic activity showed the maximum value with x=0.3 but no more increase on the catalytic activity was shown with x > 0.3. For the $La_{0.8}Cs_{0.2}MnO_{3}$ catalyst, the substitution of Fe or Ni increased the ignition temperature. The ignition temperature decreased with an increase of $O_2$ concentration, however, no more increase in the catalytic activity was shown with $O_2$ concentration > 0.2. The introduction of NO into reactants showed no effect on the catalytic activity.

• Proceedings of the Korean Vacuum Society Conference
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• 2008.08a
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• pp.238-238
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• 2008