• Journal of the Korean Chemical Society
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• v.59 no.6
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• pp.493-498
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• 2015

The reductive amination of cyclohexanone with ammonia over Cu-Cr-a/γ-Al₂O₃ was investigated. It was found that a proper solvent with high solubility of ammonia and 4Å molecular sieves for the elimination of generated water contributed to the formation of cyclohexylamine in the premixing process. In addition, the addition of ammonia in the fixedbed reactor could obviously improve the conversion of cyclohexanone to cyclohexylamine. Finally, reaction conditions including reaction temperature, hydrogen pressure and charging rate of the premix were optimized. Under the optimized conditions, cyclohexylamine was obtained in 83.06% yield.

• Journal of Life Science
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• v.15 no.3 s.70
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• pp.359-364
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• 2005

Spatial autocorrelation was applied to microgeographic variations of Sasa borealis populations in Korea. Separate counts of each type of join (combination of genotypes at a single locus) for each allele, and for each distance class of separation, were tested for significant deviation from random expectations by calculating the Standard Normal Deviation. Moran's I was significantly different from the expected value in 25 of 150 cases $(16.7\%)$. Seven of these values $(4.7\%)$ were negative, indicating genetic dissimilarity among pairs of individuals in the ten distance classes. Populations of S. borealis are small in Korea, and are distributed with occasional cutting of seed-bearing stems used for sieves. Thus, artificial disturbance may contribute to the fact that the S. borealis population of Jirisan is unusual in lacking spatial genetic structure.

• Bulletin of the Korean Chemical Society
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• v.34 no.10
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• pp.3065-3072
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• 2013

Direct synthesis of $H_2O_2$ and in situ oxidative desulfurization of model fuel over Au/Ti-HMS and Au/TS-1 catalysts has been comparatively investigated in water or methanol. Maximum amount (82%) of active $Au^0$ species for $H_2O_2$ synthesis was obtained. Au/Ti-HMS and Au/TS-1 exhibited the contrary performances in $H_2O_2$ synthesis as $CH_3OH/H_2O$ ratio of solvent changed. $H_2O_2$ decomposition and hydrogenation in water was inhibited by the introduction of methanol. Effect of $O_2/H_2$ ratio on $H_2O_2$ concentration, $H_2$ conversion and $H_2O_2$ selectivity revealed a relationship between $H_2O_2$ generation and $H_2$ consumption. The highest dibenzothiophene removal rate (83.2%) was obtained over Au/Ti-HMS in methanol at 1.5 of $O_2/H_2$ ratio and $60^{\circ}C$. But removal of thiophene over Au/TS-1 should be performed in water without heating to obtain a high removal rate (61.3%). Meanwhile, $H_2$ conversion and oxidative desulfurization selectivity of $H_2$ were presented.

• Korean Chemical Engineering Research
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• v.43 no.6
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• pp.675-682
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• 2005

Al containing mesoporous molecular sieve (Al-MMS) was synthesized by hydrolysis of $H_2SiF_6$ and $Al(NO_3)_3{\cdot}9H_2O$. The material obtained was characterized by XRD, $N_2$-physisorption. The specific surface area was $981m^2/g$, and the average pore size was uniformity $39{\AA}$. It was confirmed that the acidity of Al-MMS was milder than that of zeolite Y based on the results of $NH_3$-TPD. Active materials, Pt and Pd, were loaded on Al-MMS in order to examine the feasibility of using Al-MMS as a catalyst support in the hydrogenation of aromatic compounds included in the residue oil of a naphtha cracker. The hydrogenation activity of PtPd/Al-MMS has been studied by following the kinetics of the hydrogenation of naphthalene, and by comparing the kinetic parameters obtained with Pt and Pd catalysts supported on the other mesoporous material support and commercial conventional support materials. PtPd/Al-MMS catalyst shows the highest activity of hydrogenation and sulfur resistance. The high activity of PtPd/Al-MMS was confirmed again in the hydrogenation of PGO (pyrolized gas oil), which is residue oil obtained from a naphtha cracker. Therefore, PtPd/Al-MMS can be applied to the hydrogenation of aromatic compounds included in the residue oil of a commercial naphtha cracker commericially.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.317-321
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• 1998

X-type Zeolite for the gas separation was prepared by hydrothermal methods and the zeolite was ion-exchanged with KCl, $CaCl_2$, $YCl_3$ and $InCl_3$ in order to investigate the effect of ions on the properties of molecular sieves. Adsorption isotherms of $CO_2$ on ion exchanged X-type zeolites and those of $O_2$ and $N_2$ on the synthesized zeolite were measured at $25^{\circ}C$ using a volumetric method and the adsorption characteristics were compared with each other. Model parameters for the Langmuir, Freundlich and Toth equations were regressed for the measured adsorption isotherms. In order to confirm the applicability of the zeolite on $CO_2-PSA$ processes, breakthrough tests and process simulation were undertaken. It was found that the X-type zeolite could be a potential adsorbent in recovering $CO_2$ from flue gas.

• Journal of Environmental Science International
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• v.23 no.5
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• pp.943-962
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• 2014

Industrial gas drying, dilute gas mixtures purification, air fractionation, hydrogen production from steam reformers and petroleum refinery off-gases, etc are conducted by using adsorptive separation technology. The pressure swing adsorption (PSA) has certain advantages over the other methods, such as absorption and membrane, that are a low energy requirement and cost-effectiveness. A key component of PSA systems is adsorbents that should be highly selective to a gas being separated from its mixture streams and have isotherms suitable for the operation principle. The six standard types of isotherms have been examined in this review, and among them the best behavior in the adsorption of $CO_2$ as a function of pressure was proposed in aspects of maximizing a working capacity upon excursion between adsorption and desorption cycles. Zeolites and molecular sieves are historically typical adsorbents for such PSA applications in gas and related industries, and their physicochemical features, e.g., framework, channel structure, pore size, Si-to-Al ratio (SAR), and specific surface area, are strongly associated with the extent of $CO_2$ adsorption at given conditions and those points have been extensively described with literature data. A great body of data of $CO_2$ adsorption on the nanoporous zeolitic materials have been collected according to pressure ranges adsorbed, and these isotherms have been discussed to get an insight into a better $CO_2$ adsorbent for PSA processes.

• Journal of the Korean Magnetic Resonance Society
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• v.6 no.1
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• pp.20-37
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• 2002

MnAPSO-34 and Mn-impregnated SAPO-34(Mn-SAPO-34) sample were prepared with various manganese contents and studied by electron spin resonance(ESR) and electron spin echo modulation(ESEM). Electron spin echo modulation analysis of 0.07mo1 ％ Mn(relative to p) in MnAPSO-34 with adsorbed D$_{2}$O shows two deuteriums at 0.26 nm and two at 0.36 nm from Mn. This suggests that two waters hydrate an MnO$_{4}$ configuration with a D-O bond orientation for the waters as expect for a negatively charged site at low manganese content (0.1 mol％), the ESR spectra of MnAPSO-34 and MnH-SAPO-34 exhibit the same parameters(g 2.01 and A 89 G), but the spectra obtained from MnAPSO-34 samples are better resolved. The decomposition temperature of as-synthesized MnAPSO-34 were in the range of 200-600 $^{\circ}C$ of the morpholine which is 12 $^{\circ}C$ higher than that in as-synthesized MnH-SAPO-34. Infrared spectra showed that the position of a band at 3450 $cm^{-1}$ / shifted about 15 $cm^{-1}$ / toward higher energy in MnAPSO-34 versus MnH-SAPO-34. The modulation depth of the two-pulse ESE of MnAPSO-34 with adsorbed D$_{2}$O is deeper than that of MnH-SAPO-34 with adsorbed D$_{2}$O. Three-pulse ESEM of MnAPSO-34 and MnH-SAPO-34 with adsorbed deuterium oxide shows that the local environments of manganese in the hydrated samples are different, suggesting that Mn(II) is framework substituted in MnAPSO-34 since it obviously occupies an extraframework position in MnH-SAPO-34.

• Proceedings of the Korean Magnetic Resonance Society Conference
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• 2002.08a
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• pp.80-80
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• 2002

MnPSO-34 and Mn-impregnated SAPO-34 (Mn-SAPO-34) sample were prepared with various manganese contents and studied by electron spin resonance (ESR) and electron spin-echo modulation (ESEM). Electron spin-echo modulation analysis of 0.07mol ％ Mn(relative to p) in MnAPSO-34 with adsorbed D$_2$O shows two deuteriums at 0.25 nm and two at 0.36 nm from Mn. This suggests that two waters hydrate an MnO4 configuration with a D-O bond orientation for the waters as expect for a negatively charged site at low manganese content (0.07 mol％), the ESR spectra of MnAPSO-34 and MnH-SAPO-34 exhibit the same parameters (g 2.02 and A 87 G), but the spectra obtained from MnAPSO-34 samples are better resolved. TGA of as-synthesized MnAPSO-34 shows that the decomposition temperature in the range 200-$600^{\circ}C$ of the morpholine is 12$^{\circ}C$ higher than that in as-synthesized MnH-SAPO-34. Infrared spectra shows that the position of a band at about 15 cm-1 toward higher energy in MnAPSO-34 versus MnH-SAPO-34. The modulation depth of the two-pulse ESE of MnAPSO-34 with absorbed D$_2$O is deeper than that of MnH-SAPO-34 with absorbed D$_2$O. Three-pulse ESEM of MnAPSO-34 and MnH-SAPO-34 with absorbed deuterium oxide shows that the local environments of manganese in the hydrated samples are different, suggesting that Mn(II) is framework substituted in MnAPSO-34 since it obviously occupies an extra-framework position in MnH-SAPO-34

• Clean Technology
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• v.13 no.1 s.36
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• pp.64-71
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• 2007

The selection of a suitable adsorbent for removing organic sulfur compounds tetrahydrothiophene (THT) and t-butylmercaptan (TBM) from natural gas has been carried out. The saturation adsorption capacity for the sulfur compounds were determined by pulse adsorption method for a group of nanoporous materials, including Na-Y, Na-ZSM-5, Na,K-ET(A)S-10, Na-Mordenite, Na,K-Clinoptitolite, Ti/MCM-41, Ti/SBA-15 and amorphous titanosilicates. Among the materials tested, Na-Y and Na,K-ET(A)S-10 zeolites showed high adsorptive capacities for THT and TBM. The saturation capacity for THT on Na,K-ETS-10 was comparable with that on Na-Y zeolite, which is well known as an effective adsorbent. The capacity and adsorptivity for THT and TBM on Na,K-ETAS-10 were improved by an increase in crystallinity of Na,K-ETAS-10. An investigation of the competitive adsorption between THT and TBM from the breakthrough test using a simulated natural gas indicates that Na,K-ETS-10 selectively adsorbs THT. The breakthrough capacity for THT on Na,K-ETS-10 was 1.19 mmol/g. The results show that the high adsorption performance of Na.K-ETS-10 and Na,K-ETAS-10 is due to the highly exchanged cations in the zeolitic structure which exhibit the strong electrostatic interactions with organic sulfur compounds and their wide pore nature.

• Membrane Journal
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• v.27 no.1
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• pp.1-42
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• 2017

Metal-organic frameworks (MOFs) are nanoporous materials that consist of organic and inorganic moieties, with well-defined crystalline lattices and pore structures. With a judicious choice of organic linkers present in the MOFs with different sizes and chemical groups, MOFs exhibit a wide variety of pore sizes and chemical/physical properties. This makes MOFs extremely attractive as novel membrane materials for gas separation applications. However, the synthesis of high-quality MOF thin films and membranes is quite challenging due to difficulties in controlling the heterogeneous nucleation/growth and achieving strong attachment of films on porous supports. Microwave-based synthesis technology has made tremendous progress in the last two decades and has been utilized to overcome some of these challenges associated with MOF membrane fabrication. The advantages of microwaves as opposed to conventional synthesis techniques for MOFs include shorter synthesis times, ability to achieve unique and complex structures and crystal size reductions. Here, we review the recent progress on the synthesis of MOF thin films and membranes with an emphasis on how microwaves have been utilized in the synthesis, improved properties achieved and gas separation performance of these films and membranes.