• Bulletin of the Korean Chemical Society
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• v.27 no.4
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• pp.489-494
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• 2006

Goethite, hematite, magnetite and synthesized iron oxide are used as catalysts for Fenton-type oxidation of phenol. The synthesized iron oxides were characterized by X-ray diffraction (XRD), BET, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR). The catalytic activity of these materials is classified according to the observed rate of phenol oxidation. The effectiveness of the catalysts followed the sequence: ferrous ion > synthesized iron oxide >> magnetite hematite > goethite. According to these results, the most effective iron oxide catalyst had the structure similar to natural hematite. The surface oxidation state of the catalyst was between magnetite and hematite (+2.5 ~ +3.0). Phenol degraded completely in 40 min at neutral pH (pH = 7). Soluble ferric and ferrous ions were not detected in the filtrate from Fenton reaction solution by AAS. The formation of hydroxyl radicals was confirmed by EPR.

• Bulletin of the Korean Chemical Society
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• v.34 no.1
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• pp.221-224
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• 2013

Three different kinds of hydroxyapatites (HAPs) having different sizes and compositions are prepared by hydrothermal and molten salt syntheses. Using the ion exchange reactions, ruthenium ions are incorporated on the surface of HAPs. The crystallinity, morphology and ruthenium contents are investigated by XRD, SEM, TEM and ICP. We found that smaller size of HAP having large amounts of ruthenium under ion exchange reaction shows higher catalytic activity for aerobic oxidation of alcohols.

• Prospectives of Industrial Chemistry
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• v.24 no.2
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• pp.1-9
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• 2021

플라스틱은 가볍고 물성이 뛰어나며 가공이 용이하면서도 낮은 가격 때문에 우리의 실생활에서 매일 사용되고 있다. 동시에 썩지 않는 특성 탓에 폐플라스틱에 의한 환경오염의 문제가 심해짐에 따라 전 세계적으로 일회용 포장재 및 용기에 사용되는 플라스틱의 사용을 금지하는 규제 및 폐플라스틱을 재활용하려는 시도가 늘어나고 있다. 하지만 인류가 지난 수십 년간 생산한 플라스틱은 약 83억 톤이지만 이중 약 10%정도만 재활용 되었을 정도로 폐플라스틱의 재활용 비율은 미비하다. 특히, 최근 코로나 팬데믹으로 인해 택배 및 배달음식 주문량이 늘어남에 따라 플라스틱의 사용량이 급증하여 폐플라스틱의 재활용 필요성은 더욱더 커지고 있다. 본 기고문에서는 불균일 촉매를 이용한 수소첨가 폐플라스틱의 분해에 관한 최신 연구동향을 다루고자 한다. 안정적이고 반응성 및 선택성이 뛰어난 촉매 개발은 폐플라스틱의 효과적인 분해를 위해서 매우 중요하다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2001.11a
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• pp.163-166
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• 2001

• Nanomaterials
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• v.11 no.2
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• pp.310-322
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• 2021

Fine control of morphology and exposed crystal facets of porous γ-Al₂O₃ is of significant importance in many application areas such as functional nanomaterials and heterogeneous catalysts. Herein, a morphology controlled in situ synthesis of Al@Al₂O₃ core-shell architecture consisting of an Al metal core and a porous γ-Al₂O₃ shell is explored based on interfacial hydrothermal reactions of an Al metal substrate in aqueous solutions of inorganic anions. It was found that the morphology and structure of boehmite (γ-AlOOH) nano-crystallites grown at the Al-metal/solution interface exhibit significant dependence on temperature, type of inorganic anions (Cl^-, NO₃^-, and SO₄^2-), and acid-base environment of the synthesis solution. Different extents of the electrostatic interactions between the protonated hydroxyl groups on (010) and (001) facets of γ-AlOOH and the inorganic anions (Cl^-, NO₃^-, SO₄^2-) appear to result in the preferential growth of γ-AlOOH toward specific crystallographic directions due to the selective capping of the facets by adsorption of the anions. It is hypothesized that the unique Al@Al₂O₃ core-shell architecture with controlled morphology and exposed crystal-facets of the γ-Al₂O₃ shell can provide significant intrinsic catalytic properties with enhanced heat and mass transport to heterogeneous catalysts for applications in many thermochemical reaction processes. The direct fabrication of γ-Al₂O₃ nano-crystallites from Al metal substrate with in-situ modulation of their morphologies and structures into 1D, 2D, and 3D nano-architectures explored in this work is unique and can offer significant opportunities over the conventional methods.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.275-280
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• 2018

Methyl ester derived from coconut oil is very interesting to study since it contains free-fatty acid with chemical structure of medium carbon chain ($C_{12}-C_{14}$), so the methyl ester obtained from its part can be a biodiesel and another partially into biokerosene. The use of heterogeneous catalysts in the production of methyl ester requires severe conditions (high pressure and high temperature), while at low temperature and atmospheric conditions, yield of methyl ester is relatively very low. By using microwave irradiation trans-esterification reaction with heterogeneous catalysts, it is expected to be much faster and can give higher yields. Therefore, we studied the production of methyl ester from coconut oil using CaO catalyst assisted by microwave. Our aim was to find a kinetic model of methyl ester production through a transesterification process from coconut oil assisted by microwave using heterogeneous CaO catalyst. The experimental apparatus consisted of a batch reactor placed in a microwave oven equipped with a condenser, stirrer and temperature controllers. Batch process was conducted at atmospheric pressure with a variation of CaO catalyst concentration (0.5; 1.0; 1.5; 2.0, 2.5%) and microwave power (100, 264 and 400 W). In general, the production process of methyl esters by heterogeneous catalyst will obtain three layers, wherein the first layer is the product of methyl ester, the second layer is glycerol and the third layer is the catalyst. The experimental results show that the yield of methyl ester increases along with the increase of microwave power, catalyst concentration and reaction time. Kinetic model of methyl ester production can be represented by the following equation: $-r_{TG}=1.7{\cdot}10^6{_e}{\frac{-43.86}{RT}}C_{TG}$.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.225-228
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• 2011

Poly(4-vinylpyridine)-supported $Br{\phi}nsted$ acids (P4VP-HX) were prepared by wet impregnation technique. These supported acids were found as efficient heterogeneous green catalysts for acetylation of alcohol, amine and phenol with different catalytic activities. The wide application of P4VP-HX as reusable solid acid catalyst in organic reactions is possible because of its simple preparation and handling, stability, simple work up procedure.

• Journal of the Korean Chemical Society
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• v.38 no.9
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• pp.695-700
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• 1994

Hydrogenolysis reactions of CFC-113a catalyzed by various heterogeneous catalysts $(Rh/Al_2O_3,\;Pd/C,\;Ni,\;Al_2O_3,\;Active\;carbon)$ were investigated in the liquid and gas phases. In the liquid phase reaction, different catalysts showed different activities, but all catalysts used gave high selectivities toward HCFC-123 over 95%. It was noticeable that the neutral $Al_2O_3$ showed both a high activity and a selectivity in the liquid phase reaction. In the gas phase reaction, transition metals on carbon(Pd/C, Pt/C) were so active for hydrogenolysis of CFC-113a that they even catalyzed the production reaction of overhydrogenated compounds such as $HCFC-133a(CF_3CH_2Cl)\;and\;HFC-143a(CF_3CH_3)$. $Al_2O_3$, which showed the high activity in the liquid phase reaction, did not show a remarkable activity. When $Al_2O_3$ was used in the liquid phase reaction, the hydrogenolysis of CFC-113a proceeded without any side products in THF. However, the same reaction in MeOH produced side products, such as $CH_3OCH_3\;and\;CH_3CH_2OCH_3$ from solvent. Based on this result, including heterogeneous catalysts, it was concluded that the solvent played an important role in the liquid phase reaction.

• Korean Journal of Chemical Engineering
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• v.39
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• pp.20-37
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• 2022

Liquid organic hydrogen carriers (LOHC) are recently recognized as an attractive solution for H₂ storage and transportation. Among several challenging tasks for practical application, the most stringent limitations stem from the dehydrogenation reaction requiring high temperatures thermodynamically. Unlike previous reviews focusing on the LOHC concept, LOHC molecules, and process integration, this review highlights the state-of-the-art catalysts reported for the dehydrogenation of homocyclic and heterocyclic LOHC molecules. In the conversion of heterocyclic LOHC, Pd-based catalysts overnumbered Pt-based ones owing to preferential adsorption of heteroatoms onto the Pd surface. However, because of low stability of C-heteroatom bonds, catalyst development needs to concentrate on inhibiting the generation of byproducts while maintaining superior performance under mild conditions. In the case of homocyclic LOHC, Pt is overwhelmed in single metal and bimetallic catalysts owing to pronounced C-H bond cleavage. Nevertheless, the ability of Pt in C-C bond cleavage should be diminished for higher H2 selectivity, better catalyst stability, and steady LOHC recyclability, which is possible by tuning electronic and geometric effects of main active metals, as well as adding metal promoters. Consequently, great efforts will be diversely devoted to achieving an active and stable dehydrogenation catalyst for future LOHC demonstration.

• Applied Chemistry for Engineering
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• v.2 no.1
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• pp.1-11
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• 1991

Xenon-129 NMR technique has been developed since 1980 as a new method for the characterization of microporous materials such as zeolites, activated carbons and alumina by using chemical shift and linewidth variations in $^{129}Xe$ NMR of adsorbed xenon gas. This NMR technique has been known to be very effective to probe the locational and the chemical changes of the supported metallic species as well as the physicochemical change of the support material. Recently, this method has been successfully applied for the characterization of amorphous materials such as activated carbons, silica and alumina. Basic principles, experimental techniques and recent applications of the $^{129}Xe$ NMR method for the study of heterogeneous catalysts are introduced in this paper.