• Membrane Journal
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• v.30 no.4
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• pp.260-268
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• 2020

Mixed-matrix carbon molecular sieve membranes containing conventional and hierarchically structured 5A were synthesized for application in oxygen (O₂)/nitrogen (N₂) separation. In general, incorporating 5A fillers into porous carbon matrices dramatically increased the permeability of the membrane with a marginal decrease in selectivity, resulting in very attractive O₂/N₂ separation performances. Hierarchical zeolite 5A, which contains both microporous and mesoporous domains, improved the separation performance further, indicating that the mesopores in the zeolite can serve as an additional path for rapid gas diffusion without sacrificing O₂/N₂ selectivity substantially. This facile strategy successfully and cost-effectively pushed the performance close to the Robeson upper bound. It produced high performance membranes based on Matrimid^® 5218 polyimide and zeolite 5A, which are inexpensive commercial products.

• Proceedings of the KAIS Fall Conference
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• 2012.05a
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• pp.431-435
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• 2012

Aluminum containing mesoporous molecular sieves Al-SBA-1 ($n_{Si}/n_{Al}$= 2, 5, 10, 15) was synthesized with a one-step method, and the catalyst was characterized with powder X-ray diffraction (XRD), nitrogen adsorption-desorption, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Finally, we studied the catalytic activities of Al-SBA-1 molecular sieves in Pechmann reaction of 3-methoxyphenol and Ethyl acetoacetate to get 7-methoxy-4-methyl coumarin. Four parameters reaction temperature, time, catalyst weight and reactants ratio were optimized.

• Journal of the Korean Chemical Society
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• v.55 no.4
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• pp.691-696
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• 2011

CTAB or CTAB-Nafion catalyst were successfully supported on siliceous hollow tubular MCM-41 which synthesized by hydrothermal method using CTAB as a single template or CTAB and Nafion-Na as mixed templates. The properties of two kinds of catalysts were characterized with XRD, SEM and adsorption and desorption isotherms of nitrogen and pore diameter distribution, respectively. Then they were applied to catalyze brominating reaction of 1,7-heptanediol, moreover the rate of brominating reaction with different catalysts was compared. The results showed that catalytic activities of CTAB/MCM-41 and CTAB-Nafion/MCM-41 are better than CTAB, and that of CTAB-Nafion/MCM-41 is the best because of its phase-transfer and strong acidity function. The two kinds of catalysts can be separated from the reactive products and recycled.

• Bulletin of the Korean Chemical Society
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• v.18 no.4
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• pp.379-384
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• 1997

High quality MCM-41 is prepared from a gel of molar composition SiO2:0.20 CTACl:0.18 TMAOH:25 H2O aged at 20 ℃ for 24 hours before crystallization lasting for 48 hours. The (110) and (200) peaks of XRD pattern of high quality MCM-41 are unusually well resolved and the FWHM (full-width-at-half-maximum) of the (100) peak is 0.13° for as-prepared MCM-41 and 0.21° for calcined one, which indicate well-developed crystals. The properties of the crystal depend on the source and concentration of the reactants and the gel aging time. There is no induction period in the course of the synthesis, which is conveniently monitored by pH measurement. Gel aging, during which a spatial distribution of silicate polyanions and micellar cations is established, is essential for preparing high quality MCM-41. Surfactants with the same cationic organic group but different counteranions change the crystallization behavior. Highly basic gel (pH=12.6) favours the lamellar product; the quality of MCM-41 is lower as insufficient TMAOH is available to dissolve the silica.

• Korean Membrane Journal
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• v.6 no.1
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• pp.16-23
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• 2004

The silica containing carbon (C-SiO$_2$) membranes were fabricated using poly(imide siloxane) (PIS) having -CO- swivel group. The characteristics of porous C-SiO$_2$ structures prepared by the pyrolysis of poly(imide siloxane) were related with the micro-phase separation between the imide block and the siloxane block. Furthermore, the nitrogen adsorption isotherms of the CMS and the C-SiO$_2$ membranes were investigated to define the characteristics of porous structures. The C-SiO$_2$ membranes derived from PIS showed the type IV isotherm and possessed the hysteresis loop, which was associated with the mesoporous carbon structures, while the CMS membranes derived from PI showed the type I isotherm. For the molecular sieving probe, the C-SiO$_2$ membranes pyrolyzed at 550, 600, and 700$^{\circ}C$ showed the O$_2$ permeability of 924, 1076, and 367 Barrer (1 ${\times}$ 10$\^$-10/㎤(STP)cm/$\textrm{cm}^2$$.$s$.$cmHg) and O$_2$/N$_2$ selectivity of 9, 8, and 12.

• Journal of the Korean Magnetic Resonance Society
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• v.10 no.2
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• pp.141-154
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• 2006

A solid-state reaction of $V_2O_5$ with AlMCM-41 followed by calcinations generated $V^{5+}$ species in the mesoporous materials. Dehydration results in the formation of a vanadyl species, $VO^{2+}$, that can be characterized by electron spin resonance (ESR). The chemical environment of the vanadium centers in V-AlMCM-41 was investigated by XRD, EDX, diffuse reflectance UV-VIS, ESR, $^{29}Si,\;^{27}Al,\;and\;^{51}V$ NMR. It was found that the vanadium species on the wall surface and inside the wall of the hexagonal tubular wall of the V-AlMCM-41 were completely oxidized to tetrahedral $V^{5+}$ and transformed to square pyramidal by additional coordination to water molecules upon hydration. The oxidized $V^{5+}$ species on the wall surfaces and inside the wall were also reversibly reduced to $VO^{2+}$ species or lower valences by thermal process.

• Bulletin of the Korean Chemical Society
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• v.25 no.5
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• pp.634-638
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• 2004

Titanium silicalite-1 (TS-1) molecular sieve was produced by microwave heating of amorphous titanium-containing solid precursors after impregnation with aqueous TPAOH solution. $SiO_2-TiO_2$ xerogel, sub-micron sized $SiO_2-TiO_2$ prepared by thermal plasma process, and Ti-containing mesoporous silica, Ti-HMS, were tested as the solid phase substrates. Highly crystalline product was obtained within 30 min. after microwave irradiation with yields over 90% using $SiO_2-TiO_2$ xerogel, which showed essentially identical physicochemical properties to TS-1 prepared by conventional hydrothermal method. Excellent catalytic activity was also obtained for 1-hexene epoxidation using $H_2O_2.\;SiO_2-TiO_2$ particles prepared by thermal plasma and Ti-HMS were found inferior as a substrate for TS-1, probably due to difficulties in wetting the surface uniformly with TPAOH.