• Polymer(Korea)
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• v.35 no.4
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• pp.284-288
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• 2011

For the purpose of the pre-industry production of poly(L-lactide) (PLLA) and full understanding of the supercritical polymerization system, large scale polymerization of L-iactide initiated by 1-dodecano/stannous 2-ethyl-hexanoate (DoOH/Sn(Oct)$_2$) was carried out in supercritical chlorodifluoromethane under various reaction conditions (time, temperature and pressure)and reactants (monomer and supercritical solvent) concentrations. A 3 L sized-reactor system was used throughout this study. The monomer conversion increased to 72% on increasing reaction time to 5 h. The molecular weight of PLLA product also increased to 68000 g/moi over the same period. An increase in monomer concentration resulted in a higher molecular weight, up to 144000 g/mol and 97% of monomer conversion. Raising the reaction pressure from 130 to 240 bar also resulted in an increased monomer conversion and molecular weight. To increase heat resistivity of PLLA, methanol treatment and heat-vacuum methods were evaluated. Both of them successfully improved the heat resistivity property of PLLA.

• Korean Journal of Medicinal Crop Science
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• v.11 no.1
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• pp.19-23
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• 2003

The optimum extraction condition of pungent component from Zanthoxylum piperitum D.C pericarps by using supercritical fluid extraction(SFE) was investigated. The optimum condition of SFE was $300kg/cm^2$ of pressure, $60\;^{\circ}C$ of extraction temperature, 80% of $CO_2$ fluid, 20% of modifier(methanol) volume and 20 min of extraction time. The extraction efficiency between the classical solvent extraction method and SFE was studied. About 40% of extraction efficiency was improved when SFE was applied.

• Food Science and Preservation
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• v.7 no.2
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• pp.177-183
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• 2000

A supercritical fluid extraction was performed for the extraction of phenolics from grape seeds which up to now have been discarded. The optimum condition for extraction process was predicted through response surface methodology using central composit experimental design. The extraction amount of grape seed phenolics was increased by increasing extraction temperature, pressure, and concentration of co-solvent (ethanol). The optimum extraction conditions were 84.83$^{\circ}$C, 51.50MPa and 1.27% ethanol. The yield of phenolics using SFE was higher with 3 folds than ethanol and 4 folds than hexane but less than 80% methanol. In the respects of food poisoning, the approved solvents were restricted to ethanol and hexane. So, SFE for extraction of phenolics could be powerful alternative method for solvent extraction.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.2
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• pp.27-32
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• 2020

Robust and hydrophobic tetraethoxysilane (TEOS) based silica aerogel was synthesized by supercritical alcohol drying with surface modification using the phenyl based silica co-precursor (PTMS). The aerogels were synthesized by hydrolysis and polycondensation reaction in which TEOS and PTMS in methanol were reacted together in presence of oxalic acid and ammonium hydroxide as the catalysts. Supercritical alcohol dried PTMS/TEOS composite silica aerogel were examined for the hydrophobicity, chemical interaction, surface morphology, and textural characteristics. The hydrophobic silica-based aerogels were characterized by Fourier transform infrared spectroscopy to investigate the presence of functional groups and chemical bonds. The prepared silica demonstrates hydrophobicity (76°-149°), a high specific surface area (398 ㎡/g to 739 ㎡/g). The present investigation provides a simple approach to synthesize hydrophobic and thermally stable silica aerogels.

• Korean Journal of Food Science and Technology
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• v.37 no.2
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• pp.183-188
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• 2005

Effects of co-solvent polarity, citric acid, pressure, temperature, run time, and co-solvent ratio on extraction of major flavonoids from Lonicera Flos were investigated using supercritical fluid $CO_{2}(SF-CO_{2})$. HPLC analysis revealed addition of pure methanol resulted in low extraction yield of major flavonoids, luteoloin (Lu), Quercetin (Qu), Apigenin (Ap). Under same condition, as co-solvent polarity increased, yields of major flavonoids increased gradually, At optimum co-solvent extraction condirion of 60% aqueous methanol (10%, v/v), yields of Lu, Qu, and Ap were 42.09, 28.18, and 3.49 mg/100 g, respectively. Addition of citric acid to 60% aqueous methanol gave higher, with addition of 1% citrie acid resulting in highest yields of 63.2 (Lu), 39.35 (Qu), and 5.79 (Ap) mg/100 g. Optimum extraction conditions of major flavonoids were 200 bar, $50^{\circ}C$, 60 min, and $CO_{2}$-methanol-water(20: 1.8: 1.2).

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.205-210
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• 2015

In this paper, microalgae lipid extractions were performed using conventional organic solvent and supercritical carbon dioxide (SC-$CO_2$) for biodiesel-convertible lipid fractions. The highest levels (58.31%) of fatty acid methyl ester (FAME) content in the lipid extracted by SC-$CO_2$ was obtained, and 18.0 wt.% crude lipid yield was achieved for Bligh-Dyer method. In the SC-$CO_2$ extraction, methanol as a co-solvent was applied to increase the polarity of extract. The experimental results indicated that crude lipid yield, FAME content and yield extracted by combination of SC-$CO_2$ with methanol were 12.5 wt.%, 56.32% and 7.04 wt.%, respectively, and this method could reduce the extraction time from 2 hour to 30 min when compared to SC-$CO_2$ extraction. Therefore, SC-$CO_2$ extraction is proven to be an environmentally-friendly and an effective method for lipid extraction from microalgae.

• KSBB Journal
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• v.21 no.3
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• pp.194-198
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• 2006

Dried raw Ascidians(Halocynthia roretzi) shells harvested from fish farms in southern coast area in Korea were used to extract ${\beta}$-carotene using supercritical carbon dioxide($SCO_2$) and with ethanol as a co-solvent at the range of temperatures and pressures, from 25 to $65^{\circ}C$ and 100 to 350 bar respectively. The size of the dried Ascidians shells was around $850{\mu}m$. The system used this study was a semi-batch flow type high pressure unit. The efficiency of ${\beta}$-carotene extraction using $SCO_2$ with and without co-solvent, ethanol, influenced to pressure and temperature changes. The highest solubility of ${\beta}$-carotene in $SCO_2$ was 1.35 mg/g for ${\beta}$-carotene at $35^{\circ}C$ and 350 bar. With addition of 2(v/v%) ethanol the recovery of ${\beta}$-carotene was 93%. As a result of using n-hexane and methanol for rinse, at $35^{\circ}C$ and 350 bar the amount of ${\beta}$-carotene by methanol rinse was 5 times higher than that of n-hexane rinse.

• Applied Biological Chemistry
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• v.44 no.3
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• pp.197-201
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• 2001

Extraction efficiency of ${\beta}-ecdysone$ in Achyranthis radix was investigated using the methods of solvent extraction and supercritical fluid extraction (SFE). The optimum SFE conditions for the analysis of ${\beta}-ecdysone$ in A. radix were 300 atm, $80^{\circ}C$, 100 ml of extraction volume, and 20% ratio of modifier(methanol). As revealed through SFE, detection limit of ${\beta}-ecdysone$ in A. radix was 5 ng and recoveries of ${\beta}-ecdysone$ in A. radix shoots and root were $90.7{\sim}93.5%$ and $77.8{\sim}81.9%$, respectively. Recoveries of ${\beta}-ecdysone$ in A. radix shoots and root through solvent extraction were $76.4{\sim}93.0%$ and $80.6{\sim}93.1%$, respectively. ${\beta}-Ecdysone$ content was determined to be highest at 654.9 ppm in the first year A. radix roots harvested in August.

• Clean Technology
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• v.18 no.3
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• pp.280-286
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• 2012

The dry etching of sacrificial $SiO_2$ was performed in supercritical carbon dioxide. The etching of boron phosphor silica glass (BPSG), tetraethyl orthosilicate (TEOS), thermal $SiO_2$, and Si-nitride (SiN) was investigated by using a two chamber system with HF/py etchant and alcohol additives. The etch rate of sacrificial $SiO_2$ increased upon the addition of methanol. The etch selectivity of BPSG with respect to SiN was highest with IPA although the highest etch rate was resulted from methanol except BPSG. The etch rate increased with the temperature in HF/py/MeOH system. Especially the increase of the etch rate was much higher for BPSG with an increase in the reaction temperature. The etch residue was not reduced apparently upon the addition of alcohol cosolvents to HF/py. While the etch rate in HF/$H_2O$ was higher than HF/py/alcohol system, the rate decreased with the addition of alcohols to HF/$H_2O$. The cantilever beam structure of high aspect ratios was released by the dry ething in supercritical carbon dioxide without damage.

• Clean Technology
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• v.14 no.4
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• pp.287-292
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• 2008

In this study, computer simulation works have been performed for the capture process of the $CO_2$ and $H_{2}S$ gases contained in the effluent stream using methanol aqueous solution. In order to increase the solubilities of the $CO_2$ and $H_{2}S$ in the methanol aqueous stream, the operating pressure of the absorber was raised to 30 bar and the feeding temperature of the solvent was lowered to $-20^{\circ}C$ by using refrigeration cycle. NRTL liquid activity coefficient model was used to estimate the liquid phase nonidealities for methanol and water. Soave-Redlich-Kwong equation of state was used for the vapor phase nonidealities. Henry's law option was also used to calculate the solubilities of the supercritical noncondensible gases into the methanol aqueous solvent stream.