• Journal of Korean Society of Environmental Engineers
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• v.31 no.8
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• pp.679-689
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• 2009

Light olefins are very important hydrocarbons widely used as the raw materials of the most petrochemicals including plastics and medicines. In addition, the nation's olefin production capacity is regarded as one of the key indicators to predict the nation's economic scale and growth. Steam cracking of naphtha (or called "NCC (Naphtha Cracking Center) technology"), the traditional process to produce light olefins, is one of the most consuming energy processes among the chemical industries. Therefore, this process causes tremendous $CO_2$ emission. To reduce the energy consumption and $CO_2$ emission from NCC process, the present paper, firstly, investigates and analyses some alternative technologies which can be potentially substituted for traditional process. Secondly, applying the alternative technologies to NCC process, their effects such as energy savings, $CO_2$ emission reduction and CER (Certified Emission Reduction) were estimated. It is found that the advanced NCC process can reduce approximately 35% of SEC (Specific Energy Consumption) of traditional NCC process. This effect can lead to the reduction of 3.3 million tons of $CO_2$ and the acquisition of the 128 billion won of CER per year. Catalytic cracking of naphtha technology, which is other alternative processes, can save up to approximately 40% of SEC of traditional NCC process. This value equates to the 3.8 million tons of $CO_2$ mitigation and 147 billion won of CER per year.

• Applied Biological Chemistry
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• v.38 no.5
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• pp.455-462
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• 1995

The new six herbicidal N-[(pyrimidin-2-yl)aminocarbonyl]-2-substituted-6-(1-hydroxy-2-fluoroethyl)benzenesulfonamide derivatives(S) were synthesized and rate constants for the hydrolysis of thier in the range of pH $1.0{\sim}10.0$ have been studied in 15%(v/v) aqueous acetonitrile solution at $45^{\circ}C$. From the basis of the results, pH-effect, solvent effect, ortho-substituent effect, thermodynamic parameters(${\Delta}H^{\neq}$ & ${\Delta}S^{\neq}$), pKa constant(4.80), rate equation, analysis of hydrolysis products(2-(1-hydroxy-2-fluoroethyl)benzenesulfonamide & 4,6-dimethoxyaminopyrimidine), it may be concluded that the general acid catalyzed hydrolysis through $A-S_E2$ mechanism and specific acid catalyzed hydrolysis through A-2 type(or $A_{AC}2$) mechanism proceeds via conjugate acid($SH^+$) and tetrahedral intermediate(I) below pH 8.0, whereas, above pH 9.0, the general base catalyzed hydrolysis by water molecules(B) through $(E_1)_{anion}$ mechanism proceeds via conjugate base(CB). In the range between $pH\;7.0{\sim}pH\;9.0$, these two reactions occur competitively.

• Korean Chemical Engineering Research
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• v.54 no.6
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• pp.854-862
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• 2016

As the demand for a clean energy to replace fossil fuel being depleted increases, hydrogen energy is considered as a promising candidate for future energy source. Water electrolysis which produces hydrogen has high energy efficiency and stability but still has a large overpotential for oxygen evolution reaction (OER). In this study, $Co_3O_4$ catalysts with different morphology were prepared by spray pyrolysis from solutions which contain Co precursor and various organic additives (urea, sucrose, and citric acid), followed by post heat treatment. For the catalysts synthesized, X-ray diffraction (XRD) measurements were performed to identify their crystal structure. Morphology and surface shape of the catalysts were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Surface area and pore volume were examined by nitrogen adsortpion & desorption tests and X-ray photoelectron spectroscopy (XPS) was conducted to confirm nitrogen doping. Linear sweep voltammetry (LSV) was carried out to investigate OER activity of $Co_3O_4$ catalysts. As a result, bare-$Co_3O_4$ which has high surface area and small particle size determined by spray pyrolysis showed high activity toward OER.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.224-228
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• 2015

The carbon precursor pitch from pyrolyzed fuel oil (PFO), by-product of Naphta cracking process (NCC), was prepared through heat and UV irradiation treatments with various concentrations of $AlCl_3$, which is a new pitch preparation method. The reformed pitches were characterized by measuring their elemental composition, chemical structure of components, molecular weight distribution, and softening point. The oxygen contents of reformed pitch increased as increasing $AlCl_3$ amounts on the other hand, the carbon and hydrogen contents were not nearly changed. UV irradiated reformed pitches were composed of more aromatic carbon compounds than that of using only heat-treatment without any UV irradiation. The addition of $AlCl_3$ catalyst was ineffective on the aromaticity of reformed pitches. The softening point of prepared pitches was in the range of $103.3{\sim}168.9^{\circ}C$. Also the yield of prepared pitch increased from 48% to 80% when 5 wt% of $AlCl_3$ was added during the heat and UV irradiation reforming. It is expected that the UV irradiation reforming method can be practical and helpful to produce high yields of pitches with diverse properties.

• Elastomers and Composites
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• v.48 no.2
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• pp.133-140
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• 2013

Carbon fiber reinforced polymer (CFRP) composites consist of carbon fibers in a polymer matrix. Recently, CFRP composites having high thermal stability and low outgassing are finding their use in high performance materials for aerospace and electronics applications under high temperature and high vacuum conditions. Cyanate ester resin is one of the most suitable matrix resins for this purpose. In this study, proper combination of cyanate ester and catalyst, curing behavior, and cure cycle were determined by chemorheology. Optimum condition was found to be catalyst content of 100 ppm and curing temperature of $150^{\circ}C$. Thermal stability and outgassing of cured resin composition were analyzed and the results showed thermal decomposition temperature of $385^{\circ}C$ and total mass loss of 0.29%. The CFRP prepregs and subsequent composites were fabricated by predetermined resin composition and the cure condition. Tensile moduli of the composites were compared with theoretical models and the results were very consistent.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.749-757
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• 2019

Methyltrimethoxysilane (MTMS) and trimethylethoxysilane (TMES) as starting materials were dissolved in various types of solvents, and hydrolysis with water and polycondensation reaction were carried out using various types of catalysts to prepare non-fluorinated water-repellent coating solutions. The coating solutions were spin-coated on cold-rolled steel sheets, and thermally cured to prepare water-repellent coating films. The effect of types of catalysts and solvents on the water repellency of the resulting coating films was investigated during this process. When hydrochloric acid and nitric acid, which are strong acids, were used as catalysts, the solutions showed a white opaque state due to the aggregation of siloxane polymers. On the other hand, when acetic acid, phosphoric acid, and oxalic acid, which are weak acids, were used, they were in a stable and transparent state without precipitation. As a result, the contact angles of the coated films, prepared from hydrochloric acid and nitric acid, were $58^{\circ}$ and $92^{\circ}$, respectively, showing low water repellency. On the other hand, when acetic acid, phosphoric acid, and oxalic acid were used, the contact angles of the coated films were $101^{\circ}$, $103^{\circ}$ and $116^{\circ}$, respectively, showing high water repellency. In addition, when isopropanol and ethanol were used as solvents, phase separation occurred in the solutions due to the aggregation of siloxane polymers. On the other hand, when methanol, ethyl acetate, and methyl ethyl ketone were used as solvents, the solutions were transparent and showed a stable state without sedimentation.

• Clean Technology
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• v.23 no.2
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• pp.181-187
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• 2017

The perfluorocompounds (PFCs) emitted from the semiconductor and display manufacture is treated by abatement systems which use various technologies, such as combustion, thermal, plasma, catalyst. However, it is required that the system should overcome their drawbacks with excess energy consumption and low removal efficiency. The new technology using combination of pressure swing adsorption and excess enthalpy combustion for the reduction of PFCs emissions were developed and analyzed its characteristics. PFCs concentration ratio and PFCs loss factor were calculated from measuring concentration of PFCs at the calculated by comparing concentration of PFCs at the combustor's inlet and outlet. There were performance evaluations with various gas flow for comparing energy consumption and removal efficiency with existing equipments. The concentration ratio and the loss factor of PFCs were 1.65, 8.2%, respectively, when the total gas flow of the pressure swing absorption (PSA) inlet was 204 liter per minute (LPM) and $CF_4$ concentration was 1412 ppm. In comparison with existing system at constant condition, $CF_4$ removal efficiency for a porous media combustion (PMC) showed the improvement more than 16% and the consumed energy was also reduced up to approximately 41%. Then, the total gas flow introduced into PMC and $CF_4$ concentration were 91-LPM and 2335 ppm, respectively, and the destruction and removal efficiency of $CF_4$ was about 96% at 19-LPM $CH_4$, and 40-LPM $O_2$.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.1-8
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• 2023

Research, such as developing alternative energy in the transportation field, including aviation, is being actively conducted to solve the issue of current climate change. Interest in ammonia fuel as a carbon free energy (CFE) source is increasing due to the ease of liquefaction and transportation and similarity in energy density to that of methanol. However, explosiveness and toxicity of ammonia make it difficult to handle. Therefore, in this study, stable ammonia production was attempted using relatively easy-to-handle urea water solution (UWS). High temperature steam was used to promote the hydrolysis of ammonia. In order to determine the causes for ammonia production below the theoretical equivalent ratio, it was suggested that there were not enough collisions to promote the hydrolysis based on the kinetic theory of gases. The hydrolysis of unreacted isocyanic acid (HNCO) was tested according to the change in water supply. As a result, an increased amount of ammonia produced was confirmed. The increased amount of ammonia produced in a certain section was dependent on the steam temperature and the flow rate of water supplied.

• Journal of the Korean Chemical Society
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• v.25 no.4
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• pp.207-213
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• 1981

Conformations of thioacetamide (TAA) and its protonated form were determined using the CNDO/2 method, and the intermolecular interaction energies between the protonated TAA and water were calculated. It was found that: (1) protonation occurs preferentially on the N rather than on the S atom, (2) the stabilization energy of intermolecular perturbation between the protonated TAA and water was also large for the N-protonated TAA. This causes preferential CS bond cleavage due to large antibonding nature of the CS bond in the LUMO, and leads to an orbital controlled reaction.

• Journal of Environmental Science International
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• v.22 no.9
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• pp.1097-1103
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• 2013

Tetrafluoromethane($CF_4$) have been widely used as etching and chemical vapor deposition gases for semiconductor manufacturing processes. $CF_4$ decomposition efficiency using microwave system was carried out as a function of the microwave power, the reaction temperature, and the quantity of $Al_2O_3$ addition. High reaction temperature and addition of $Al_2O_3$ increased the $CF_4$ removal efficiencies and the $CO_2/CF_4$ ratio. When the SA30 (SiC+30wt%$Al_2O_3$) and SA50 (SiC+50wt%$Al_2O_3$) were used, complete $CF_4$ removal was achieved at $1000^{\circ}C$. The $CF_4$ was reacted with $Al_2O_3$ and by-products such as $CO_2/CF_4$ and $AlF_3$ were produced. Significant amount of by-product such as $AlF_3$ was identified by X-ray powder diffraction analysis. It also showed that the ${\gamma}-Al_2O_3$ was transformed to ${\alpha}-Al_2O_3$ after microwave thermal reaction.