• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.119-124
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• 2018

The production of methyl N-phenyl carbamate by an oxidative carbonylation method of aniline and methanol is of great interest as an environmentally friendly process that can replace the monomer production process of a polymer produce using conventional phosgene. In this study, heterogeneous catalysts were prepared by using Y-zeolite, $SiO_2$, $Al_2O_3$ as support, and oxidative carbonylation continuous operation from aniline and methanol was attempted using the prepared heterogeneous catalyst. Batch reactor was used to determine the support, and various reaction conditions such as reaction temperature, reaction pressure, and effect of promoter were established using palladium catalyst. A reaction kinetics study was conducted under optimum reaction conditions. The basic data for carbamate process development were obtained by performing continuous operation for a long time under established reaction condition.

• 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.

• Applied Chemistry for Engineering
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• v.25 no.2
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• pp.215-221
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• 2014

A simple heterogeneous system has been developed by using base treated manganese dioxide (B-$MnO_2$) for the aerobic oxidation of amines under mild reaction conditions of 1 atm of air and $50^{\circ}C$ in hexane. This system was highly efficient to oxidize various kinds of primary or secondary amines including aliphatic, aromatic, and hetero-atomic ones under the applied reaction conditions. Amines were oxidized to nitriles or diimines by the self-condensation or oxidative dehydrogenation through imine intermediate. The B-$MnO_2$ was reused for at least 5 times without any loss of its catalytic performance and showed its cost effectiveness, easy workup, and easy separation of the products for achieving the protocol of green chemistry.

• Korean Chemical Engineering Research
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• v.43 no.2
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• pp.206-214
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• 2005

Heterogeneously-catalyzed oxidation of aqueous phase trichloroethylene (TCE) over supported metal oxides has been conducted to establish an approach to eliminate ppm levels of organic compounds in water. A continuous flow reactor system was designed to effect predominant reaction parameters in determining catalytic activity of the catalysts for wet TCE decomposition as a model reaction. 5 wt.% $CoO_x/TiO_2$ catalyst exhibited a transient period in activity vs. on-stream time behavior, suggesting that the surface structure of the $CoO_x$ might be altered with on-stream hours; regardless, it is probable to be the most promising catalyst. Not only could the bare support be inactive for the wet decomposition reaction at $36^{\circ}C$, but no TCE removal also occurred by the process of adsorption on $TiO_2$ surface. The catalytic activity was independent of all particle sizes used, thereby representing no mass transfer limitation in intraparticle diffusion. Very low TCE conversion appeared for $TiO_2$-supported $NiO_x$ and $CrO_x$ catalysts. Wet oxidation performance of supported Cu and Fe catalysts, obtained through an incipient wetness and ion exchange technique, was dependent primarily on the kinds of the metal oxides, in addition to the acidic solid supports and the preparation routes. 5 wt.% $FeO_x/TiO_2$ catalyst gave no activity in the oxidation reaction at $36^{\circ}C$, while 1.2 wt.% Fe-MFI was active for the wet decomposition depending on time on-stream. The noticeable difference in activity of the both catalysts suggests that the Fe oxidation states involved to catalytic redox cycle during the course of reaction play a significant role in catalyzing the wet decomposition as well as in maintaining the time on-stream activity. Based on the results of different $CoO_x$ loadings and reaction temperatures for the decomposition reaction at $36^{\circ}C$ with $CoO_x/TiO_2$, the catalyst possessed an optimal $CoO_x$ amount at which higher reaction temperatures facilitated the catalytic TCE conversion. Small amounts of the active ingredient could be dissolved by acidic leaching but such a process gave no appreciable activity loss of the $CoO_x$ catalyst.

• 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.

• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.258-266
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• 2020

The chemical fixation of CO₂ into cyclic carbonates is considered to be one of the most promising way to alleviate global warming and produce fine chemicals. In this work, the catalytic applicability of metal-organic frameworks (MOFs) as porous crystalline materials for the synthesis of five-membered cyclic carbonate from CO₂ and epoxides was reviewed. In addition, we have briefly classified the materials based on their different structural features and compositions. The studies revealed that MOFs exhibited good catalytic performance towards cyclic carbonate synthesis because of the synergistic effect between the acid sites of MOFs and nucleophile. Moreover, the effect of structure of designed MOFs and mechanism for the cycloaddition of CO₂ were suggested.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.168-174
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• 2023

In commercial production processes of methyl methacrylate, there is a methacryl aldehyde as an intermediate or impurities. The existence of impurities is critical factor because of significant decrease of the conversion rate and selectivity of the entire chemical reaction. This study found that an acid was the main cause of the decrease in reactivity among various impurities because an acid rapidly lowers the activity of a catalyst and promotes a side reaction, the hetero Diels-Alder reaction. Therefore, the pretreatment methods with the removal of acid were comparatively evaluated by the selective hydrogenation reaction of the carbonyl group of the reactants. Based on several experimental conditions, we believe that proposed effective pretreatment improves productivity with appropriate economical process.

• Applied Chemistry for Engineering
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• v.24 no.1
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• pp.55-61
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• 2013

Heterogeneous metallocene catalysts supported on montmorillonite (MMT), [$Cp_2ZrCl_2$/MMT, $Cp_2ZrCl_2$/MAO/MMT, and $Cp_2ZrCl_2$ + MAO/MMT], were prepared with three different methods of immobilization and tested for ethylene polymerization. The heterogeneous catalysts immobilized on organo clay (30B-MMT) showed the higher metal loading and polymerization activity than those immobilized on natural clay $Na^+-MMT$. These results suggest that the hydroxyl groups of organo clay interlayers react with the MAO and catalyst through the chemical bond. The metallocene catalyst supported directly on MMT showed lower activity for ethylene polymerization compared to the homogeneous systems, while MMT/MAO/$Cp_2ZrCl_2$, catalysts treated with MAO before impregnation, showed a higher activity. The polymers obtained from MMT-supported catalysts have higher melting point, molecular weight and molecular weight distributions than those of homogeneous catalysts. The polymer particles with increasing significant size. Ethylene polymerization over 30B-MMT/MAO/$Cp_2ZrCl_2$ catalyst was also performed varying the process variables to optimize the process conditions.

• Applied Chemistry for Engineering
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• v.3 no.1
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• pp.35-45
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• 1992

The interest in photocatalysis, which is a new branch of catalysis, is steadily increasing. Recently photocatalysis is attracting considerable attention as new methods and processes for obtaining cheap and renewable sources of energy and for syntheses of chemically useful products. In this review article, the principles and some examples of heterogeneous and homogeneous photocatalyses are described. In addition, the problems yet to resolve and the prospect of application of photocatalysis are discussed.

• Clean Technology
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• v.21 no.1
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• pp.68-75
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• 2015

In this study, we investigated the structure and properties of a highly heat conductive metal-ceramic core-shell CoAl₂O₄@Al micro-composite for heterogeneous catalysts support. The CoAl₂O₄@Al was prepared by hydrothermal surface oxidation of Al metal powder, which resulted in the structure with a high heat conductive Al metal core encapsulated by a high surface area CoAl₂O₄ shell. For comparison, CoAl₂O₄ was also prepared by co-precipitation method and also utilized for a catalyst support. Rh catalysts supported on CoAl₂O₄@Al and CoAl₂O₄ were prepared by incipient wetness impregnation and characterized by N₂ adsorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), CO chemisorption, and temperature-programmed reduction (TPR). The properties of catalysts were investigated for glycerol steam reforming reaction for hydrogen production at 550 ℃. Rh/CoAl₂O₄@Al exhibited about 2.8 times higher glycerol conversion turnover frequency (TOF) than Rh/CoAl₂O₄ due to facilitated heat transport through the core-shell structure. The CoAl₂O₄@Al and CoAl₂O₄ also showed some catalytic activities due to a partial reduction of Co on the support, and a higher catalytic activity was also found on the CoAl₂O₄@Al core-shell than CoAl₂O₄. These catalysts, however, displayed deactivation on the reaction stream due to carbon deposition on the catalysts surface.