Chieh-Ming J. Chang

Densities and P-x-y diagrams for carbon dioxide dissolution in methanol, ethanol, and acetone mixtures

Abstract Densities and P-x-y diagrams for carbon dioxide + methanol, carbon dioxide + ethanol, and carbon dioxide + acetone were determined by a novel technique of density measurement at 291, 298, 303, 308, 313 K, and pressures up to 8 MPa. Solubilities of carbon dioxide in methanol, ethanol, and acetone were found to increase with applied pressure, but to decrease with increasing temperature. Carbon dioxide has the highest solubility in acetone for the whole pressure range. The Patel-Teja and Peng-Robinson equations of state with the van der Waals one-fluid mixing rules were able to correlate successfully equilibrium data for these three systems.

Separation of catechins from green tea using carbon dioxide extraction

This study presents a novel packed-column extractor coupled with an absorption system to improve the quality of green tea essential oils, extracted by using high-pressure carbon dioxide. The effects of various co-solvents on the extract are also examined. In addition, gravimetric measurement and HPLC chromatographic analyses individually determine the amount of essential oil and the concentration of four major catechins. Results show that the mean contents in the extract are 4.4-fold higher by addition of 95% ethanol than by addition of water. The ratio of polyphenols to caffeine is highest in the Soxhlet ethanol extraction.

Supercritical fluids extraction of Ginkgo ginkgolides and flavonoids

Abstract This study investigated the feasibility of extracting three major terpene lactones and flavonoids from Ginkgo leaves by using supercritical carbon dioxide, nitrous oxide and R134a. A semi-batch extraction and absorption process was employed to collect and sequentially dissolve solutes precipitated from supercritical fluids. The extraction conditions ranged from 24.2 to 31.2 MPa and from 333 to 393 K. A reverse-phase HPLC system coupled with RI and UV detectors was also used to individually quantify the level of terpene lactones and flavonoid aglycones in the extracts. Experimental data showed that Soxhlet ethanol extraction had the best performance on total yield and the amount of terpene lactones and flavonoids. Our results further indicated that three dry supercritical fluids, individually at the density of 0.84, 0.83 and 1.13 g/ml, could not extract terpene lactones and flavonoids. However, when ethanol was added to supercritical fluid extraction, the extracted amount of terpene lactones increased with the mole fraction of ethanol addition. In doing so, supercritical carbon-dioxide (SC-CO2) could extract more terpene lactones than the other two fluids.

Carbon dioxide extraction of ginseng root hair oil and ginsenosides

Abstract This investigation developed a semi-continuous flow process to extract crude oil from ginseng root hair. The extraction conditions were 308–333 K, 10.4–31.2 MPa, with the addition of ethyl alcohol as a co-solvent. Analysis of the content of the extracted crude oil and ginsenosides revealed that carbon dioxide extraction at 31.2 MPa, 333 K, 660 litres CO2, with 6 mole% preload addition of ethanol achieved the closest result to hot water extraction, but remained inferior to ethanol extraction. Analytical results further demonstrated that the amount of crude oil extracted increased with pressure at constant temperature, and only increased with temperature when pressure exceeded 24.2 MPa. Furthermore, the maximum levels of crude oil and ginsenosides, extracted by supercritical carbon dioxide, were 0.1 g per gram of Panax ginseng and 1141 mg per kilogram absorbent, respectively.

High-pressure densities and P–T–x–y diagrams for carbon dioxide+linalool and carbon dioxide+limonene

Abstract Liquid and vapor densities for carbon dioxide+linalool, and carbon dioxide+limonene were measured by using a system consisting of two vibrating tube densimeters. The P–T–x–y diagrams and saturated liquid and vapor densities for these two binary mixtures were determined at 313, 323 and 333 K, respectively, as well as at pressures up to 11 MPa. The density of the saturated CO2 phase increased with increasing pressure. At higher pressure, the density of the liquid phase decreased with increasing pressure, corresponding to an increasing amount of carbon dioxide.

Optimization of lipase-catalyzed biodiesel by isopropanolysis in a continuous packed-bed reactor using response surface methodology

Isopropanolysis reactions were performed using triglycerides with immobilized lipase in a solvent-free environment. This study modeled the degree of isopropanolysis of soybean oil in a continuous packed-bed reactor when Novozym 435 was used as the biocatalyst. Response surface methodology (RSM) and three-level-three-factor Box-Behnken design were employed to evaluate the effects of synthesis parameters, reaction temperature ( degrees C), flow rate (mL/min) and substrate molar ratio of isopropanol to soybean oil, on the percentage molar conversion of biodiesel by transesterification. The results show that flow rate and temperature have a significant effect on the percentage of molar conversion. On the basis of ridge max analysis, the optimum conditions for synthesis were as follows: flow rate 0.1 mL/min, temperature 51.5 degrees C and substrate molar ratio 1:4.14. The predicted value was 76.62+/-1.52% and actual experimental value was 75.62+/-0.81% molar conversion. Moreover, continuous enzymatic process for seven days did not show any appreciable decrease in the percent of molar conversion (75%). This work demonstrates the applicability of lipase catalysis to prepare isopropyl esters by transesterification in solvent-free system with a continuous packed-bed reactor for industrial production.

Designing supercritical carbon dioxide extraction of rice bran oil that contain oryzanols using response surface methodology

This study examines the supercritical carbon dioxide (SC-CO(2)) extraction of oryzanols contained rice bran oil from powdered rice bran. The extraction efficiencies and concentration factors of oryzanols, free fatty acids and triglycerides in the SC-CO(2) extracts were determined. With top-flow type SC-CO(2) extraction the total oil yield was 18.1% and the extraction efficiencies of oryzanols and triglycerides were 88.5 and 91.3% respectively, when 2750 g CO(2 )was consumed during the extraction of 35 g rice bran powder. The concentration factors of oryzanols and triglycerides in SC-CO(2)-extracted oil were higher than in the Soxhlet n-hexane extracted oil. SC-CO(2) extractions indicated that pressure can be used more effectively than temperature to enhance the extraction efficiency and concentration factor of oryzanols. A two-factor central composite scheme of response surface methodology was employed to determine the optimal pressure (300 bar) and temperature (313 K) for increasing the concentration of oryzanols in the SC-CO(2) extracted oil.

Optimized enzymatic synthesis of caffeic acid phenethyl ester by RSM.

In this study, optimization of enzymatic synthesis of caffeic acid phenethyl ester (CAPE), catalyzed by immobilized lipase (Novozym 435) from Candida antarctica was investigated. Novozym 435 was used to catalyze caffeic acid and 2-phenylethanol in an isooctane system. Response surface methodology (RSM) and 5-level-4-factor central-composite rotatable design (CCRD) were employed to evaluate the effects of synthesis parameters, such as reaction temperature (30-70 degrees C), reaction time (24-72 hours), substrate molar ratio of caffeic acid to 2-phenylethanol (1:10-1:90) and enzyme amounts (100-500 PLU) on percentage conversion of CAPE by direct esterification. Reaction temperature and time had significant effects on percent conversion. On the basis of ridge max analysis, the optimum conditions for synthesis were: reaction time 59 hours, reaction temperature 69 degrees C, substrate molar ratio 1:72 and enzyme amount 351 PLU. The molar conversion of predicted values and actual experimental values were 91.86+/-5.35% and 91.65+/-0.66%, respectively.

The solubility of carbon dioxide in organic solvents at elevated pressures

Abstract Chang C.J., 1992. The solubility of carbon dioxide in organic solvents at elevated pressures. Fluid Phase Equilibria, 74: 235-242. The solubility of carbon dioxide in toluene, n-butanol and cyclohexane has been measured by the high-pressure densitometer method. The solubility is found to increase with increase of pressure at constant temperature; and the mixture becomes miscible in the liquid phase up to the point where carbon dioxide approaches liquefaction. The Peng-Robinson equation of state with two adjustable parameters is proposed for calculating the solubility of carbon dioxide dissolved in the solution.

Optimized ultrasound-assisted extraction of phenolic compounds from Polygonum cuspidatum.

In this study the phenolic compounds piceid, resveratrol and emodin were extracted from P. cuspidatum roots using ultrasound-assisted extraction. Multiple response surface methodology was used to optimize the extraction conditions of these phenolic compounds. A three-factor and three-level Box-Behnken experimental design was employed to evaluate the effects of the operation parameters, including extraction temperature (30–70 °C), ethanol concentration (40%–80%), and ultrasonic power (90–150 W), on the extraction yields of piceid, resveratrol, and emodin. The statistical models built from multiple response surface methodology were developed for the estimation of the extraction yields of multi-phenolic components. Based on the model, the extraction yields of piceid, resveratrol, and emodin can be improved by controlling the extraction parameters. Under the optimum conditions, the extraction yields of piceid, resveratrol and emodin were 10.77 mg/g, 3.82 mg/g and 11.72 mg/g, respectively.