• Korean Journal of Materials Research
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• v.17 no.7
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• pp.382-385
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• 2007

[ $LaFeO_3$ ] powders were prepared as the oxidation catalyst materials to reduce the emission of particulate matters from diesel engine and their catalytic effects on the oxidation of carbon were investigated. Solution combustion method was employed for the powder synthesis, which uses highly exothermic and selfsustaining reactions. In this study $LaFeO_3$ powders were synthesized at $400^{\circ}C$ as varying the ratio ($\Phi$) of fuel (citric acid) and oxidizer (metal nitrate), and their phase and carbon ignition property were examined. As $\Phi$ decreases, the crystallinity of synthesized $LaFeO_3$ powders enhanced. By calcining at $700^{\circ}C$, all the powders synthesized at various $\Phi$ fully crystallized. The calcined $LaFeO_3$ powders showed carbon ignition temperature as low as $501{\sim}530^{\circ}C$, which implied the decrease of the ignition temperature by $120{\sim}150^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.6039-6046
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• 2013

Cr(VI)-heterocyclic complex[Cr(VI)-2-methylpyrazine] was synthesized by the reaction between of heterocyclic compound(2-methylpyrazine) and chromium trioxide, and characterized by IR and ICP analysis. The oxidation of benzyl alcohol using Cr(VI)-2-methylpyrazine in various solvents showed that the reactivity increased with the increase of the dielectric constant(${\varepsilon}$), in the order : cyclohexene${\rho}$) was Cr(VI)-2-methylpyrazine= -0.65(308K). The observed experimental data have been ratiolized. The hydride ion transfer causes the prior formation of a chromate ester in the rate-determining step.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.245-245
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• 2012

Syntheses of oxide supported metal catalysts by wet-chemical routes have been well known for their use in heterogeneous catalysis. However, uniform deposition of metal nanoparticles with controlled size and shape on the support with high reproducibility is still a challenge for catalyst preparation. Among various synthesis methods, arc plasma deposition (APD) of metal nanoparticles or thin films on oxide supports has received great interest recently, due to its high reproducibility and large-scale production, and used for their application in catalysis. In this work, Au and Pt nanoparticles with size of 1-2 nm have been deposited on titania powder by APD. The size of metal nanoparticles was controlled by number of shots of metal deposition and APD conditions. These catalytic materials were characterized by x-ray diffraction (XRD), inductively coupled plasma (ICP-AES), CO-chemisorption and transmission electron microscopy (TEM). Catalytic activity of the materials was measured by CO oxidation using oxygen, as a model reaction, in a micro-flow reactor at atmospheric pressure. We found that Au/$TiO_2$ is reactive, showing 100% conversion at $110^{\circ}C$, while Pt/$TiO_2$ shows 100% conversion at $200^{\circ}C$. High activity of metal nanoparticles suggests that APD can be used for large scale synthesis of active nanocatalysts. We will discuss the effect of the structure and metal-oxide interactions of the catalysts on catalytic activity.

• Applied Chemistry for Engineering
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• v.18 no.6
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• pp.552-556
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• 2007

In this study, noble metals (Pd, Ru, Ir) were supported to $TiO_2$ catalyst. In order to distribute metals uniformly, $H_2O-H_2$ pretreatment technique was used. Xylene, toluene, and MEK were used as reactants. The monometallic or bimetallic catalysts were prepared by the excess wetness impregnation method and were characterized by XRD, and XPS analysis. Pd-Ru, Pd-Ir bimetallic catalysts had multipoint active sites which improved the range of Pd metal state. Bimetallic catalysts had a higher conversion of VOCs than that of monometallic one. The effect of $H_2O-H_2$ pretreatment technique was the enhancement of uniform distribution of Pd particles and promotion of catalytic efficiency. In this study, addition of Ru and Ir metals to Pd promoted oxidation conversion of VOCs. In addition, $H_2O-H_2$ pretreatment promoted removal efficiency of VOCs on the $TiO_2$ support.

• Applied Chemistry for Engineering
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• v.19 no.2
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• pp.242-248
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• 2008

The iron incorporation method according to addition steps during the synthesis of iron incorporated MCM-41 was examined systematically. Iron addition during pH adjustment was more effective than the other addition steps which were addition to template agent solution or addition after mixing of template agent and sodium silicate solution. In case of iron addition after extraction of template agent from as-synthesized silica MCM-41, most of the iron was on the surface of pores not the frame work structure. Although the amount of iron addition was increased, there was a limit to the amount of iron incorporated into framework structure of MCM-41. The synthesized FeMCM-41 catalyst showed catalytic activities for propylene oxidation. Otherwise, there might be no attractive differences of catalytic activity among the addition steps of iron.

• Applied Chemistry for Engineering
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• v.25 no.6
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• pp.648-653
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• 2014

Cr(VI)-heterocyclic complex (2,4'-bipyridinium chlorochromate) was synthesized by the reaction between heterocyclic compound(2,4'-bipyridine) and chromium trioxide, and characterized by IR and ICP analysis. The oxidation of benzyl alcohol using 2,4'-bipyridinium chlorochromate in various solvents showed that the reactivity increased with the increase of the dielectric constant (${\varepsilon}$), in the order : N,N-dimet-hylformamide (DMF) > acetone > chloroform > cyclohexene. In the presence of DMF solvent with acidic catalyst such as hydrochloric acid (HCl solution), 2,4'-bipyridinium chlorochromate oxidized benzyl alcohol (H) and its derivatives (p-$CH_3$, m-Br, m-$NO_2$). Electron-donating substituents accelerated the reaction rate, whereas electron acceptor groups retarded the reaction rate. The Hammett reaction constant (${\rho}$) was -0.67 (303 K). The observed experimental data have been rationalize the proton transfer occurred followed the formation of a chromate ester in the rate-determining step.

• Applied Chemistry for Engineering
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• v.5 no.4
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• pp.609-615
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• 1994

Partial oxidation of ethylene over 10wt% $Ag/{\alpha}-Al_2O_3$ catalyst was studied with a pulse reactor which was connected directly to a G. C. When ethylene was injected after oxygen injection at the temperature where molecular adsorption of oxygen is difficult ethylene oxide was evolved. From the results, it is suggested that adsorbed atomic oxygen is related with the evolution of ethylene oxide. The selectivity to ethylene oxide decreased with the decrease of the amounts of adsorbed oxygen and bulk oxygen. Ethylene oxide was either decomposed to ethylene and adsorbed oxygen or isomerized to acetaldehyde. However, the isomerization of ethylene oxide to acetaldehyde was strongly suppressed by the preadsorbed oxygen.

• Journal of the Korean Chemical Society
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• v.20 no.5
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• pp.431-437
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• 1976

On the condition of adequate air supply, complete removal of carbon monoxide,occurred above $650^{\circ}C$. Using catalysts, the oxidation of carbon monoxide occurred at lower temperatures; on both $MnO_2 \;and\;30%\;MnO_2-70%\;CuO\;at\;250{\circ}C,\;on\;CuO\;at\;450{\circ}C,\;on\;50%\;MnO_2-50%\;CuO\;at\;200{\circ}C,\;and\;on\;70%\;MnO_2-30%\;CuO\;at\;180{\circ}C$. Manganese dioxide (p-type) showed higher activity than cupric oxide (n-type) and a catalyst consisting of 60% $MnO_2-40%$ CuO had the highest activity of all the $MnO_2$-CuO mixture. Over the range of transitional temperature, carbon monoxide removal efficiency decreased linearly with increasing inlet carbon monoxide concentration while temperature was fixed. Residence time of gases in the catalytic reactor, in the range of 0.9 to 1.8 seconds, gave no effect on carbon monoxide conversion.

• Journal of the Korean Chemical Society
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• v.50 no.1
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• pp.53-59
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• 2006

.FAPO-5 molecular sieves were synthesized starting from the same reactant gel at 170 oC using microwave irradiation technique and conventional hydrothermal reaction. The FAPO-5 molecular sieves were characterized by several techniques such as SEM, FTIR, UV/Vis, and ESR. Moreover, the oxidation of styrene over FAPO-5s was carried out, and compared to check the oxidation and epoxidation ability of the two FAPO-5s. FAPO-5 can be obtained easily by microwave irradiation within 15 min at 170oC, whereas FAPO-5 synthesis is completed in 6 h by conventional electric heating, confirming the acceleration about 20 times by microwave technique. There are no appreciable differences between two FAPO-5s in surface area and coordination state of iron. The FAPO-5 synthesized by microwave irradiation shows higher epoxide selectivity in the styrene epoxidation, which may be explained by the higher hydrophobicity of the catalyst.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.317.2-317.2
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• 2013

Ultrathin oxide encapsulated metal-oxide hybrid nanocatalysts have been fabricated by a soft chemical and facile route. First, SiO2 nanoparticles of 25~30 nm size have been synthesized by modified Stobber's method followed by amine functionalization. Metal nanoparticles (Ru, Rh, Pt) capped with polymer/citrate have been deposited on functionalized SiO2 and finally an ultrathin layer of TiO2 coated on surface which prevents sintering and provides high thermal stability while maximizing the metal-oxide interface for higher catalytic activity. TEM studies confirmed that 2.5 nm sized metal nanoparticles are well dispersed and distributed throughout the surface of 25 nm SiO2 nanoparticles with a 3-4 nm TiO2 ultrathin layer. The metal nanoparticles are still well exposed to outer surface, being enabled for surface characterization and catalytic activity. Even after calcination at $600^{\circ}C$, the structure and morphology of hybrid nanocatalysts remain intact confirm the high thermal stability. XPS spectra of hybrid nanocatalyst suggest the metallic states as well as their corresponding oxide states. The catalytic activity has been evaluated for high temperature CO oxidation reaction as well as photocatalytic H2 generation under solar simulation. The design of hybrid structure, high thermal stability, and better exposure of metal active sites are the key parameters for the high catalytic activity. The maximization of metal-TiO2 interface interaction has the great role in photocatalytic H2 production.