• Clean Technology
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• v.17 no.1
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• pp.37-40
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• 2011

Some ionic liquids are suitable for catalysts and solvents which are applicable to $CO_2$ fixation reaction converting $CO_2$ to carbonate. Using the ionic liquids, the synthesis process will become greener and simpler because of easy catalyst recycling and unnecessary use of volatile and harmful organic solvents. In this work, the synthesis of propylene carbonate from propylene oxide using carbon dioxide and ionic liquids were measured at high pressures up to ~140 bar and at temperatures between $60^{\circ}C$ and $80^{\circ}C$. As a results, we found the optimum condition and obtained the maximum yield under that condition.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.3
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• pp.500-508
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• 2004

The heat transfer coefficients during gas cooling process of carbon dioxide in a horizontal tube were investigated. The experiments are conducted without oil in the refrigerant loop. The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter, a pre-heater, and a gas cooler(test section). The water loop consists of a variable-speed pump, an isothermal tank, and a flow meter. The gas cooler is a counterflow heat exchanger by cooled water flowing in the annulus. The $CO_2$ flows in the horizontal stainless steel tube. which is 9.53mm in O.D. and 7.75mm in I.D. The gas cooler is 6 [m] in length. which is divided into 12 subsections, respectively. The experimental conditions considered in the study are following range of variables : refrigerant temperature is between 20 and $100^{\circ}C$. mass fluxes ranged from 200 to 400kg/($m^2$.s), average pressure varied from 7.5 to 10.0MPa. The main results were summarized as follows : The friction factors of $CO_2$ in the gas cooler show a relatively good agreement with those predicted by Blasius' correlation. The local heat transfer coefficient in the gas cooler has compared with most of correlations, which are the famous ones for forced convection heat transfer of turbulent flow. The results show that the local heat transfer coefficient of gas cooler agrees well with the correlation by Bringer-Smith except that at the region near pseudo critical temperature. while that at the near pseudo critical temperature is higher than the correlation.

• Bulletin of the Korean Chemical Society
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• v.32 no.7
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• pp.2178-2182
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• 2011

Recently, the synthesis of ordered macroporous materials has received much attention due to its potential use as photonic band gap materials.$^1$ In this study, we have used the three-dimensional (3D) latex array template impregnated with benzenesulfonic acid (BSA), which is capable of catalyzing the reaction using tetraethyl orthosilicate (TEOS) as a precursor and distilled water. The polystyrene (PS) templates were reacted with TEOS in $scCO_2$ at 40 $^{\circ}C$ and at 80 bar. In the reactor, TEOS was filtrated into the PS particle lattice. After the reaction, porous silica materials were obtained by calcinations of the template. The stability test of the PS template in pure $CO_2$ was conducted before the main experiment. Scanning electron microscopy (SEM) images showed that the reaction in $scCO_2$ takes place only on the particle surface. This new method using $scCO_2$ has advantages over conventional sol-gel processes in its capability to control the fluid properties such as viscosity and interfacial tension. It has been found that the reaction in $scCO_2$ occurs only on the particle surface, making the proposed technique as more rapid and sustainable method of synthesizing inverse opal materials than conventional coating processes in the liquid phase and in the vapor phase.

• Journal of the Korean Applied Science and Technology
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• v.26 no.3
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• pp.279-287
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• 2009

Fisher-Tropsch synthesis for the production of hydrocarbon from syngas was investigated on 20% cobalt-based catalysts (20% Co/HSA, 20% Co/Si-MMS), which were prepared by home-made supports with high surface areas such as high surface alumina (HSA) and silica mesopores molecular sieve (Si-MMS). In the gas phase reaction by syngas only, 20% Co/Si-MMS catalyst was shown in higher CO conversion and lower carbon dioxide formation than 20% Co/HSA, whereas the olefin selectivity was higher in 20% Co/HSA than in 20% Co/Si-MMS. In the effect of n-hexane added in syngas, the selectivities of $C_{5+}$ and olefin were increased by comparing the supercritical phase reaction with the gas phase reaction in addition to reduce unexpected methane and carbon dioxide.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.403-410
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• 2020

This paper focuses on the design of a 12-kW small-scale supercritical CO₂ test loop. A theoretical study, stabilization, and optimization of carbon dioxide were carried out with the application of a solar heat source based on solar thermal data in Pohang. The thermodynamic cycle of the test facility is a Rankine cycle (transcritical cycle), which contains liquid, gas, and supercritical CO₂. The system is designed to achieve 6.98% efficiency at a maximum pressure of 12 MPa and a maximum temperature of 70℃. In addition, the optimum turbine inlet temperature and pressure were calculated to increase the cycle efficiency, and the application of an internal heat exchanger (IHX) was simulated. It was found that the maximum efficiency increases to 18.75%. The simulation confirmed that the efficiency of the cycle is 6.7% in May and 6.26% in June.

• Clean Technology
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• v.10 no.4
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• pp.221-228
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• 2004

Ethoxylated Nonyl Phenol Series (NP-series), nonionic surfactants, were applied for forming microemulsions in supercritical $CO_2$. Measurement results of the solubility in supercritical $CO_2$ are in the following; NP-series were high soluble in carbon dioxide in spite of the fact that those were not $CO_2$-philic surfactants traditionally well known. Water in $CO_2$ microemulsions were also formed stably. A complexation of hydrophilic lengths for $CO_2$-philic parts of NP-Series surfactants was optimized by NP-4 surfactant(N=4) for forming the microemulsions through the experiments. Formation of microemulsions was confirmed by measuring the UV-Visible spectrum through a spectroscopic method and existence of water in the microemulsions was confirmed as well. In order to apply it for a metal surface treatment or electroplating, an experiment for forming acid(organic, inorganic) solution in $CO_2$ microemulsions was carried out. Ionic surfactant in the reaction to an acid solution became unstable to form microemulsions, however, nonionic surfactant was formed stably in the reaction. Results of the study will be utilized for expanding the application scope of supercritical $CO_2$ which is an environmental-friendly solvent.

• Clean Technology
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• v.23 no.4
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• pp.441-447
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• 2017

The economic analysis for the power plant developed in the conceptual design phase is becoming more important and, research on process optimization for process development that meets the target economic is actively carried out. In the filed of power generation systems, economic assessment methods to predict the levelized cost of electricity (LCOE) has been widely applied for comparing economic effect quantitatively. In this paper, the platform that design criteria of key component required to optimize economic of power cycle can be calculated reversely was established roughly and design criteria of the key equipment (Compressor, turbine, heat exchanger) required to meet the target LCOE (the LCOE of supercritical steam Rankine cycle) was derived when the supercritical $CO_2$ power cycle is applied to the coal-fired power plant.

• Clean Technology
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• v.14 no.1
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• pp.1-6
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• 2008

Removal of paraffin wax from a ceramic injection mold using supercritical $CO_2$ has been studied. The paraffin wax is used as a binder in the ceramic injection molding process. The effects of pressure, temperature and flow rate of supercritical $CO_2$ on the removal of the paraffin wax were investigated. The removal rates were measured with various flow rates of $CO_2$ in the range of 328.15 - 348.15 K and 15 - 30 MPa. The removal rate of paraffin wax increased as the pressure increased. In the effect of temperature, the paraffin wax was effectively removed over 329.15K (melting point of paraffin wax), however, the efffct of temperature was not significant when the temperature was further increased. The increase of $CO_2$ flow rate also affected the removal of paraffin wax. However, the effect of flow rate was not observed when the flow rate reached a certain value. Propane was used as a co solvent in order to remove the paraffin wax effectively. When the propane was added to the $CO_2$, the removal efficiency was improved. The paraffin wax was completely removed from the ceramic injection mold without any change in their shape and the structure.

• KSBB Journal
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• v.15 no.1
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• pp.80-83
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• 2000

Polyacetylenes were extracted from Korean ginseng using supercritical $CO_2$ Yield of extraction of panaxydol and panaxynol was increased as the pressure of supercritical $CO_2$ increased at the range from 200 to 300 bar. The optimal yields of panaxydol and panaxynol was achieved at 65 and $55^{\circ}C$, respectively. Methanol was applied as a modifier. The highest yield of panaxydol and panaxynol were 0.230 and 0.054 mg/g-dry weight at modifier concentration of 10%(w/w), 300 bar, and $65^{\circ}C$. When these results were compared to that of methanol-extraction, the recoveries of panaxydol and panaxynol by supercritical $CO_2$ extraction in SFE were 37.8 and 55.1%, respectively.

• Journal of Life Science
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• v.13 no.5
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• pp.569-575
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• 2003

Supercritical $CO_2$ extraction was applied to extraction of the valuable compound for benign prostatic hyperplasia from saw palmitto. Three levels of parameters, temperature $(35^{\circ}C,\; 60^<\circ}C)$, pressure 22∼30 Mpa and ethanol modified solvent concentration, were used as the independent variables of central composite to rotate the design. The extracting pressure and temperature interaction was significantly affected the extraction of valuable compounds. The ethanol was an efficient modifier to extract valuable compound by supercritical carbon dioxide. The optimal processing conditions were extracting pressure, 30 Mpa, extracting temperature, $60^<\circ}C$, ethanol modifier, 15% for extracts of the valuable compounds from saw palmitto. In conclusion, it was found that supercritical $CO_2$ extraction can successfully be applied to extract high quality extracts from saw palmitto.