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Catalytic Properties of Ti-HMS with High Titanium Loadings
안화승,M. J. Kim,J. R. Ko,S. H. Jang 대한화학회 2005 Bulletin of the Korean Chemical Society Vol.26 No.8
Ti-HMS samples in which titanium species exist in various forms of isolated tetrahedral state, finely dispersed TiO2 cluster, and some in extra-framework anatase phase were prepared via a direct synthesis route using dodecylamine (DDS) as a structure directing agent by systematically varying the titanium loadings between 2 and 50 mol% Ti/(Ti+Si) in substrate composition. Physicochemical properties of the materials were evaluated using XRD, SEM/TEM, N2 adsorption, UV-vis and XANES spectroscopies. Catalytic properties of Ti-HMS in cyclohexene and 2,6-di-tert-butyl phenol (2,6-DTBP) oxidation using aqueous H2O2, and vapor phase photocatalytic degradation of acetaldehyde were evaluated. High H2O2 selectivity was obtained in cyclohexene oxidation, and cyclohexene conversion was found primarily dependent on the amount of tetrahedrally coordinated Ti sites. For bulky 2,6-DTBP oxidation and photocatalytic oxidation of acetaldehyde, on the other hand, conversions were found dependent on the total amount of Ti sites and maintaining an uniform mesoporous structure in the catalysts was not critical for efficient catalysis.
Hydrothermal synthesis of zeolite L in a Na+/K+ mixed alkali system
안화승,Yong Sig Ko 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.6
Zeolite L was prepared from the substrate system of Na2O-K2O-Al2O3-SiO2-H2O at temperatures of 373- 443 K by hydrothermal crystallization. The influence of various synthesis parameters such as the concentration ratios of the components, starting raw materials, synthesis temperature, gel aging, and stirring on the crystallization was investigated. Investigations revealed that the crystallinity of zeolite L crystals depends on molar ratios of the components such as SiO2/Al2O3, (K2O+Na2O)/SiO2, Na2O/(K2O+Na2O), and H2O/(K2O+Na2O). Pure and highly crystalline zeolite L could be obtained from a gel with the molar composition 5.4K2O-5.7Na2O-Al2O3-30SiO2-500H2O after 24 h at 443 K. It was found that the silica source affected the crystal size of zeolite L, and as the synthesis temperature increased, the average crystal size became larger. The crystal size could be decreased significantly by stirring the gel or subjecting the substrate mixture to an aging treatment at room temperature prior to the hydrothermal treatment. Thermal stability of the zeolite L crystals obtained was also briefly investigated.
고용식,안화승 ( Yong Sig Ko,Wha Seung Ahn ) 한국화학공학회 1993 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.31 No.6
A study was conducted to make activated carbon adsorbents using local rice hull ashes. As the carbonization temperature of the rice hull was increased, the specific surface area of the char increased steadily. The specific surface area of the char was enhanced either by boiling water washing, or by silica leaching using sodium hydroxide. When sodium hydroxide was used to leach out silica from the char, the specific surface area and the amount of silica removed increased most when the sodium hydroxide leaching was conducted in several stages. Activated carbon was also prepared from the rice hull by chemical activation method using phosphoric acid. The adsorption characteristics of phenol onto the activated carbons prepared were measured in a batch reactor. These results showed that as the specific surface areas of the activated carbons increased, better adsorptivities to phenol were obtained. The relationship between the amount of phenol adsorbed and equilibrium concentration was found to be well represented by the Freundlich isotherm. The adsorption capacity of the activated carbon prepared through chemical activation method was slightly better than that of the commercial product of Calgon F300.
티타늄 실리카라이트 1 촉매상에서 Cyclohexanone 의 Ammoximation 반응
김정규,고용식,안화승 ( J . K . Kim,Y . S . Ko,W . S . Ann ) 한국공업화학회 1995 공업화학 Vol.6 No.4
티타늄 실리카라이트 1 (TS-1) 촉매를 수열합성하고 X선 회절분석, 적외선 분광분석 및 주사전자현미경 관찰을 수행하여, 촉매의 구조 및 형상과 제올라이트 구조내로 티타늄이 치환된 정도를 검토하였다. TS-1 촉매상에서 cyclohexanone의 ammoximation 반응을 수행하여 촉매반응에 미치는 제반 인자들의 영향을 살펴보았다. TS-1 촉매의 활성은 결정크기, 티타늄 함량, 반응온도, 반응시간, 과산화수소의 주입방법에 의존하였고, 제올라이트 구조내로 도입된 티타늄이 cyclohexanone의 ammoximation 반응에 활성종임을 알 수 있었다. Titanium-silicalite 1 (TS-1) catalyst was prepared using the hydrothermal method. The structure of catalyst, morphology, and the extent of titanium incorporation into the zeolite framework were examined by XRD, FT-IR, and SEM analysis. The influence of the various reaction parameters on cyclohexanone ammoximation over TS-1 catalyst was investigated. The ammoximation activities of TS-1 catalysts were found to be dependent on the crystal size, titanium content, reaction temperature, reaction time, and the method of hydrogen peroxide addition. Furthermore, titanium in the zeolite framework was found to be the active site for the cyclohexanone ammoximation.
Hydrothermal synthesis and characterization of Fe(III)-substituted mordenites
Yong Sig Ko,장현태,안화승 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.6
Fe-substituted mordenites were synthesized hydrothermally, partially substituting iron atoms for the framework aluminum of mordenite. XRD, SEM, IR, UV-VIS DRS, ESR, XAS, and catalytic activity studies provided the evidence of Fe3+ present in the zeolite framework. The framework IR bands were shifted to lower frequencies as Fe3+ ions incorporated into the lattice, and a new Si-O-Fe bond vibration was located near 668 cm−1. The presence of a signal at g=4.3 in the ESR spectra was assigned to Fe3+ isomorphously substituted in the tetrahedral position. EXAFS at the Fe K-edge revealed that the Fe3+ ions were present in the zeolite framework in a four-fold coordination with an average Fe-O distance of 1.86 Å. In the UV-vis spectra, an absorption was observed at 375.7 nm which was assigned to the presence of Fe3+ in the zeolite framework. A toluene alkylation study reflected that the acidity strength of mordenite is weakened due to the presence of lattice iron species.