• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.587-593
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• 2011

As a result of increasing environmental concerns related to air quality and maintenance of automobiles, the alkylation of isobutane with olefins has become an even more important process for production of high quality gasoline. However, the widespread use of the alkylation process is limited by the polluting and corrosive liquid acid catalysts (HF and $H_2SO_4$) currently used in industry. For the reason, a large number of solid catalysts, especially zeolites, have been studied as an environmental friendly catalyst in this process. Recently, mesoporous solid acids and ionic liquids have been investigated as a green catalyst. In this review, the research of environmental friendly catalysts for an isobutane alkylation is summarized.

• Clean Technology
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• v.28 no.4
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• pp.269-277
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• 2022

With the recent development of the biological enzymatic reaction industry, lactic acid (LA) can be mass-produced from biomass sources. In particular, a catalytic process that converts LA into acrylic acid (AA) is receiving much attention because AA is used widely in the petrochemical industry as a monomer for superabsorbent polymers (SAP) and as an adhesive for displays. In the LA conversion process, NaY zeolites have been previously shown to be a high-activity catalyst, which improves AA selectivity and long-term stability. However, NaY zeolites suffer from fast deactivation due to severe coking. Therefore, the aim of this study is to modify the acid-base properties of the NaY zeolite to address this shortcoming. First, base promoters, Ca ions, were introduced to the NaY zeolites to tune their acidity and basicity via ion exchange (IE) and incipient wetness impregnation (IWI). The IWI method showed superior catalyst selectivity and stability compared to the IE method, maintaining a high AA yield of approximately 40% during the 16 h reaction. Based on the NH₃- and CO₂-TPD results, the calcium salts that impregnated into the NaY zeolites were proposed to exit as an oxide form mainly at the exterior surface of NaY and act as additional base sites to promote the dehydration of LA to AA. The NaY zeolites were further treated with KOH before calcium impregnation to reduce the total acidity and improve the dispersion of calcium through the mesopores formed by KOH-induced desilication. However, this KOH treatment did not lead to enhanced AA selectivity. Finally, calcium loading was increased from 1wt% to 5wt% to maximize the amount of base sites. The increased basicity improved the AA selectivity substantially to 65% at 100% conversion while maintaining high activity during a 24 h reaction. Our results suggest that controlling the basicity of the catalyst is key to obtaining high AA selectivity and high catalyst stability.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.2
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• pp.10-15
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• 2014

For hypersonic aircraft, increase of flight speeds causes heat loads that are from aerodynamic heat and engine heat. The heat loads could lead structural change of aircraft's component and malfunctioning. Endothermic fuels are liquid hydrocarbon fuels which are able to absorb the heat loads by undergoing endothermic reactions, such as thermal and catalytic cracking. In this study, methylcyclohexane was selected as a model endothermic fuel and experiments on endothermic properties were implemented. To improve heat of endothermic reaction, we applied zeolites and confirmed that HZSM-5 was the best catalyst for the catalytic performance. The objective is to investigate catalytic effects for heat sink improvement. The catalyst could be applied to system that use kerosene fuel as endothermic fuel.

• Applied Chemistry for Engineering
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• v.8 no.3
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• pp.543-549
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• 1997

The direct reaction of carbon dioxide($CO_2$) with butane($C_4H_{10}$) to obtain synthesis gas and hydrocarbon compounds have been studied on nickel loaded catalysts. In the reaction of $CO_2$ with $C_4H_{10}$, Ni loaded catalysts showed similar activity with Pt catalyst and Coke deposition on the catalyst was severe by dehydrogenation of butane. The main products were carbon monoxide and hydrogen, when alumina and Y type zeolite were used as a support. Instead, a great deal of aromatic hydrocarbons were obtained on the Ni loaded ZSM-5 catalyst. The conversion of $CO_2$ increased with the increasing molar ratio of $CO_2$/$C_4H_{10}$ on Ni/ZSM-5, Ni/NaY and Ni/alumina catalyst, but the conversion decreased again from the ratio of 2. The value of $CO_2$ conversion was the highest at the 5wt% of Ni loading on ZSM-5 catalyst. A part of cokes deposited on the catalysts diminished when only $CO_2$ gas or water steam flowed into the reactor. The coke deposited on the catalysts was very reactive and it may be an important intermediate for the carbon dioxide reforming reaction.

• Applied Chemistry for Engineering
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• v.28 no.1
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• pp.50-56
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• 2017

Formaldehyde is one of the toxic substances without any color and smell. Several methods to remove formaldehyde has been investigated up to now. Here, both the enzymatic and chemisorptive/catalytic liquid phase formaldehyde removal were investigated, and their catalytic activities in terms of specific activities were compared. Firstly, formaldehyde dehydrogenase (FDH) enzyme from Escherichia coli K12 was cloned, and expressed in Escherichia coli BL21(DE3). And the catalytic activity was characterized as $2.49{\times}10^3sec^{-1}mM^{-1}$ of $k_{cat}/K_m$ with 8.69 U/mg of the specific activity. Secondly, the chemisorptive and oxidative catalytic removals were investigated simultaneously. Activated carbons and zeolites treated with heat, KI, and KOH were used as chemisorption medium. And $Pd/TiO_2$ was used as an oxidative catalyst for the formaldehyde removal. All of the tested chemicals showed similar formaldehyde removal efficiencies of around 50%. However, the specific activity of FDH dependent formaldehyde removal was absolutely higher than that of using chemisorptive and catalytic removal processes with the ranges of 0.01 to 0.26 U/g.

• Applied Chemistry for Engineering
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• v.4 no.1
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• pp.162-170
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• 1993

Vapor-phase ETBE(ethyl tert-butyl ether) synthesis from TBA(tert-butyl alcohol) and ethanol was carried over solid acid catalysts such as heteropoly acids and proton type zeolites. Heteropoly acids were more active than proton type zeolites and $H_4SiW_{12}O_{40}$ catalyst showed about the same activity as Amberlyst-15 ion exchange resin catalyst used as an industrial catalyst in ETBE synthesis. The catalytic activity of transition metal exchanged heteropoly acids was greatly enhanced, because new acid site was generated with hydrogen reduction. This effect of hydrogen reduction was related to the reduction characteristics of catalysts and the order of reducibility was $Ag^+$>$Cu^{2+}$>$Fe^{2+}$.

• Applied Chemistry for Engineering
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• v.7 no.4
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• pp.661-669
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• 1996

Pt-Rh/NaY catalysts with various Pt/Rh ratios were prepared by an ion-exchange method and their characteristics were investigated by $^{129}Xe$-NMR and EXAFS. Both the $^{129}Xe$-NMR and EXAFS data indicate that the surface of PtRh bimetallic clusters was enriched with Rh atoms. The catalytic activities of these catalysts for conversion of CO, HC and $NO_x$ were measured by using simulated automobile engine exhausts under lean, rich and stoichiometric conditions. The Pt-Rh/NaY(Pt/Rh=1) catalyst exhibited the greatest reactive activity among the catalysts used in this study.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.521-529
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• 2011

Methanol-to-olefin (MTO) reaction was studied over MWW zeolite with independently developed two pores (circular and straight) and MFI zeolite with intercrossed sinusoidal and straight pores in order to investigate the effect of pore structure on their catalytic behavior. MWW and MFI zeolites with similar acidity exhibited commonly high conversion and slow deactivation in the MTO reaction, but their product selectivities were considerably different: linear hydrocarbons of $C_3-C_9$ were mainly produced on MWW, while the yield of $C_2{^=}$ and aromatics were high on MFI. Polyaroamatic hydrocarbons (PAHs) were accumulated on MWW, but a small amount of benzene and aromatics on MFI. The impregnation of phosphorous on MWW caused significant decreases in the catalytic activity and toluene adsorption, but the decreases were relatively small on MFI. Although the straight pores of MWW were inactive in the MTO reaction due to the accumulation of PAHs, its circular pores which suppressed the formation of PAHs sustained catalytic activity for the production of linear hydrocarbons. Therefore, the impregnation of phosphorous on the circular pores of MWW caused a significant decrease in catalytic activity. The phosphorous impregnation on the cross sections of MFI altered the product selectivity due to the neutralization of strong acid sites, but catalytic deactivation was negligible. The difference of MWW and MFI zeolites in the MTO reaction was explained by their difference in pore structure.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.291-300
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• 2008

Catalytic cracking of n-octane was carried out over H-ZSM-5 zeolite catalysts after calcination with air and steaming with 100% steam in the temperature range of $550-750^{\circ}C$ for 24 h and compared with the results of thermal cracking. The increase of calcination and steaming temperature resulted in the decrease of surface area, pore volume, and strong acid sites, which was mainly caused by the dealumination of H-ZSM-5 framework. It was found by $^{27}Al$ and $^{29}Si$ MAS NMR that the dealumination was proceeded through the transformation process of tetrahedral framework Al${\rightarrow}$penta-cordinated Al ${\rightarrow}$ octahedral framework Al and the phenomena was much more severe in steaming conditions than that of calcination. In the catalytic cracking of n-octane, as the temperatures of calcination and steaming were increased, the conversion of n-octane, the selectivity of light olefins and ethylene to propylene ratio were decreased due to the dealumination of framework aluminum resulting the loss of acidic strengths. The conversion, selectivity of light olefins and ethylene to propylene ratio reached almost to the level of thermal cracking after steaming at $750^{\circ}C$ for 24 h.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.155-160
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• 2011

Dimethyl ether draws an attention as a green fuel in recent years. In this study, we investigated dehydration of methanol to produce DME using solid-acid catalysts, a series of zeolite. We found that ceria took a role of promoting the reaction conversion as well as selectivity of DME formation as a cocatalyst to the zeolite catalyst. We varied Si/Al ratio and ceria percentage on the surface of the catalyst to get high performance catalyst. ZSM5-30 with 5 wt% ceria on the surface was found to have excellent DME selectivity and to be little influenced by water content in methanol feed. We proposed a reaction model and obtained kinetic parameters for the DME formation using the catalyst based on experimental results using a microreactor.