Solubility model of arachis hypogea skin oil by modified supercritical carbon dioxide

The main objective of this study was to determine the solubility of peanut (Arachis Hypogea) skin oil using modified supercritical carbon dioxide (SCCO₂). The solubility was measured at pressure ranging from 100 to 300 Bar, temperature of 313 to 328 K, and rate of modifier from 0.075 to 0.225 mL/min. The solubility of extraction was ranging from 1.12 to 7.73 mg/min. The Chrastil, modified Chrastil, Del Valle Aguilera (DVA), Adachi-Lu, and Gordillo as empirical models were tested to fit the experimental data. Solubilities from these models followed the average absolute relative deviations (AARD) from experimental data: Chrastil, modified Chrastil, DVA, Adachi-Lu, and Gordillo with AARD of 8.54%, 8.26%, 19.41%, 9.24%, and 20.62%, respectively. Modified Chrastil model provide the best fit.     

Characterization and supercritical carbon dioxide extraction of walnut oil

Walnut (Juglans regia L.) oil was extracted with compressed carbon dioxide (CO₂) in the temperature range of 308 to 321 K and in the pressure range of 18 to 23.4 MPa. The influence of particle size was also studied at a superficial velocity of 0.068 cm/s, within a tubular extractor of 0.2 L capacity (cross-sectional area of 16.4 cm²). FFA, sterol, TAG, and tocopherol compositions were not different from those of oil obtained with n-hexane. The main FA was linoleic acid (56.5%), followed by oleic acid (21.2%) and linolenic acid (13.2%). The main TAG was LLL (linoleic, linoleic, linoleic) (24.4%), followed by OLL (oleic, linoleic, linoleic) (19.6%) and LLLn (linoleic, linoleic, linolenic) (18.4%). The main component of sterols was β-sitosterol (85.16%), followed by campesterol (5.06%). The amount of cholesterol was low (0.31 and 0.16% for oils extracted by n-hexane and supercritical fluid extraction, respectively. The CO₂-extracted oil presented a larger amount of tocopherols (405.7 μg/g oil) when compared with 303.2 μg/g oil obtained with n-hexane. Oxidative stability determined by PV and the Rancimat method revealed that walnut oil was readily oxidized. Oil extracted by supercritical CO₂ was clearer than that extracted by n-hexane, showing some refining. A central composite, nonfactorial design was used to optimize the extraction conditions using the software Statistica, Version 5. The best results were found at 22 MPa, 308 K, and particle diameter (Dp) −0.1 mm.     

Equilibrium distributions of key components of spearmint oil in sub/supercritical carbon dioxide

Effects of temperature (at 35, 45 or 55°C) and pressure (10–110 atm) on the relative distribution coefficients of the twelve key components of spearmint oil (essential oil ofMentha cardiaca; Scotch spearmint) at equilibrium in dense CO₂ were investigated under conditions ranging from subcritical to supercritical regions. Effects of vapor pressure, molecular weight and polarity of the key components on their equilibrium distributions in sub/supercritical CO₂ are discussed. At 35°C, all key components of spearmint oil are equally soluble in dense CO₂ within the 12–102 atm pressure region. At 45 and 55°C, the key components are equally soluble for pressures greater than about 60 atm. However, around either 45°C/27 atm or 55°C/35 atm conditions, the relative distribution coefficients of all monoterpene hydrocarbons and of isomenthone (an oxygenated monoterpene) exhibit maxima, which are due to significantly higher vapor pressures of these components and significantly lower solvating power of the dense-gas solvent at these particular temperatures and pressures. Vapor-pressure effects, coupled with the decrease in solvating power, dominate the effects of polarity and molecular mass of the key components. Deterpenation of spearmint oil with dense CO₂ is possible around either 45°C/27 atm or 55°C/35 atm, where the monoterpene hydrocarbons tend to concentrate in the CO₂-rich phase.     

Synthesis of PCL/clay masterbatches in supercritical carbon dioxide

Pre-exfoliated nanoclays were prepared through a masterbatch process using supercritical carbon dioxide as solvent and poly(?-caprolactone) as organic matrix. In situ polymerization of ?-caprolactone in the presence of large amount of clay was conducted to obtain these easily dispersible nanoclays, collected as a dry and fine powder after reaction. Dispersion of these pre-exfoliated nanoclays in chlorinated polyethylene was also investigated. All the results confirm the specific advantages of supercritical CO₂ towards conventional solvents for filler modification.     

Quantitative extraction of hamster liver lipid and cholesterol with supercritical carbon dioxide

A quantitative method for liver lipid and cholesterol extraction with supercritical CO₂ and ethanol entrainer (SCE) is reported and compared with the Folch (chloroform/methanol) procedure. Mean values for lipid and cholesterol in hamster livers (n=48) were similar between the SCE and Folch methods. Correlation coefficients between the two methods were 0.9866 for total lipid and 0.9546 for cholesterol. Similar mean values and high correlations between the two methods validate the SCE procedure as a precise alternative method for quantitative liver lipid extractions. The SCE method also reduces the use of hazardous solvents.     

Continuous enzymatic production of biodiesel from virgin and waste sunflower oil in supercritical carbon dioxide

A continuous process for biodiesel production in supercritical carbon dioxide was implemented. In the transesterification of virgin sunflower oil with methanol, Lipozyme TL IM led to fatty acid methyl esters yields (FAME) that exceeded 98% at 20 MPa and 40 °C, for a residence time of 20 s and an oil to methanol molar ratio of 1:24. Even for moderate reaction conversions, a fractionation stage based on two separators afforded FAME with >96% purity. Lipozyme TL IM was less efficient with waste cooking sunflower oil. In this case, a combination of Lipozyme TL IM and Novozym 435 afforded FAME yields nearing 99%.     

Oxidative stability of sunflower oil extracted with supercritical carbon dioxide

Extraction of oilseeds with supercritical carbon dioxide (SC−CO₂) is a promising technique to obtain vegetable oils. However, instability of such oils has been associated in the past with SC−CO₂ extraction. The reasons underlying such instability were unclear. Results presented here suggest that oil instability may be related to the oxygen content of CO₂. In fact, oil stability decreases sharply when refined oil (additive-free) is re-extracted with SC−CO₂ and can be related to the oxygen content in the CO₂. Never-theless, oil stability could be improved to the level of conventionally extracted oil by adding trace amounts of ascorbic acid.     

Interfacial tension of linear and branched PP in supercritical carbon dioxide

In this study, sessile drops are imaged in a high-pressure and high-temperature view chamber to determine the density and interfacial tension of linear polypropylene (LPP) and branched polypropylene (BPP) melts in supercritical carbon dioxide (CO₂). The pressure-volume-temperature (PVT) data of polyprophylene (PP)-CO₂ is investigated by monitoring the swelling changes of the polymer melt in supercritical CO₂. The density difference between the polymer/CO₂ mixture and the CO₂ is determined by combining the swelling results with the CO₂ solubility information in the polymer melt. Both the Sanchez-Lacombe (SL) and the Simha-Somcynsky (SS) equations-of-state (EOS) are applied to predict the density of the PP-CO₂ mixture, which is then compared to the density data obtained experimentally. The dependence of interfacial tension on the temperature and pressure of PP in supercritical CO₂ is investigated at temperatures from 180 °C to 220 °C and pressures up to 31 MPa. Effects of long-chain branching on the density and interfacial tension of PP-CO₂ mixtures are discussed.     

Extraction of metal ions with non-fluorous bipyridine derivatives as chelating ligands in supercritical carbon dioxide

Three new non-fluorous bipyridine derivatives, bis(2-(2-butoxyethoxy)ethyl)-2,2′-bipyridine-4,4′-dicarboxylate (ligand 1), bis(2-(2-ethoxyethoxy)ethyl)-2,2′-bipyridine-4,4′-dicarboxylate (ligand 2), and bis(2-butoxyethyl)-2,2′-bipyridine-4,4′-dicarboxylate (ligand 3), were synthesized as chelating ligands to remove metal ions from solid matrix into supercritical CO₂ (scCO₂). These produced compounds 1-3 showed considerable solubilities in scCO₂ (8.0 g/l, 4.8 g/l, 7.8 g/l for ligands 1-3 at 313 K, respectively) and the tested solubility data were then calculated and correlated with semiempirical model at different pressures and temperatures, which showed satisfactory agreement with each other and the average absolute relative deviation were in the range of 0.1-28.3%. The effects of pressure, temperature, time, and ligand to metal ratio (5:1 to 75:1) on the extraction efficiency of metal ions were also systematically investigated. The extraction efficiency was 100% for Ni²⁺ and 95.9% for Cu²⁺ in scCO₂ with the system of ligand 1, ultrapure water, and perfluoro-1-octanesulfonic acid tetraethylammonium salt (PFOAT) under the optimized conditions (25 MPa, 313 K, 90 min, and ligand to metal ratio of 10). Although all ligands exhibited good efficiency for Ni²⁺ (>85%) and Cu²⁺ (>70%) extraction, the extraction of mixed metal ions indicated that the bipyridine derivatives had low selectivity. Finally, the detailed calculation results exhibited that the extraction constants (K_ex) of the metal ions increased with the increase of the extraction efficiency in the same extraction system for each same metal ion.     

Influence of pretreatments for extraction of lipids from yeast by using supercritical carbon dioxide and ethanol as cosolvent

Saccharomyces cerevisiae is one of the most studied and industrially exploited yeast. It is a non-oleaginous yeast whose lipids are mainly phospholipids. In this work, the extraction of yeast lipids by supercritical carbon dioxide (SCCO₂) and ethanol as a co-solvent was studied. In particular our attention was focused on the selectivity toward triglycerides, and in a subsequent extraction of the phospholipids present in the yeast. Indeed CO₂ is a non-polar solvent and is not an efficient solvent for the extraction of phospholipids. However, SCCO₂ can be used to extract neutral lipids, as triglycerides, and the addition of polar co-solvents like ethanol, at different compositions, allows a more efficient extraction of triglycerides, and also an extraction-fractionation of phospholipids. In this work SCCO₂ extractions of a specific membrane complex of S. cerevisiae, obtained from an industrial provider, were carried out at 20 MPa and 40 °C, using ethanol as a co-solvent (9%, w/w). It was shown that different pretreatments are necessary to obtain good extraction yields and have a great impact on the extraction. The kinetic of the extractions were successfully modeled using Sovova's model. From the fitting of the main parameters of the model it was possible to compare the effects of the pretreatments over the yeast material, and to better understand the extraction process. Among the seven tested pretreatments the more appropriate was found to be an acid hydrolysis followed by a methanol maceration.     

Study on elution ability of salicylic acid on ion exchange resins in supercritical carbon dioxide

The elution ability of salicylic acid on ion exchange resins in supercritical carbon dioxide has been studied. Some factors influencing elution recovery, including entrainer, temperature, pressure and the flow rate of supercritical fluid CO₂ are discussed in this work. The addition of a small amount of entrainer, such as ethanol, triethanolamine and their mixture to supercritical CO₂ can cause dramatic effects on the elution ability. The results show that the salicylic acid can be only slightly eluted from the resin with supercritical CO₂ alone with temperatures ranging from 307.15 to 323.15 K and pressures ranging from 10 to 30 MPa. Meanwhile, with the same T, P conditions, 40.58% and 73.08% salicylic acid can be eluted from the ion exchange resin with ethanol and ethanol + triethanolamine as the entrainer, respectively. An improved PR equation of state with VDW1 mixing rules is used to calculate the elution recovery of salicylic acid in supercritical CO₂ and the results agree well with the experimental data.     

Form coke reaction processes in carbon dioxide

Uncertainty in metallurgical coke supplies has prompted development of form coke from low quality coals and fines. Reaction rates have been measured and mechanisms identified that control carbonaceous briquette reaction rate in CO₂. Three briquette formulations were prepared, characterized and coked in an inert atmosphere at high temperature. A given weight of each formulation was then reacted in a packed bed with CO₂ at 1373 K for 0.5–2 h. Partially reacted briquettes contained a solid core with some internal reaction surrounded by a loosely adhering layer of carbon-containing ash. The reaction rate of briquettes with CO₂ was affected by diffusion of CO₂ through the bulk gas and the ash-carbon layer to the core surface, as well as CO₂–carbon reaction. Key variables governing briquette reaction rate included CO₂ mole fraction and briquette void fraction.     

Extraction of wheat germ oil by supercritical CO<Subscript>2</Subscript>: Oil and defatted cake characterization

In this paper the working conditions for the extraction of wheat germ oil in a supercritical CO₂ pilot plant of 1-L-extraction capacity were studied. The best conditions were: pressure, 38 MPa; temperature, 55°C; wheat germ particle size, about 0.35 mm; CO₂ flow rate, 1.5 L min⁻¹. These conditions gave yields of about 92% of total oil after 3 h of processing. The obtained oils and the partially defatted cake were investigated with regard to their FA, tocol (tocopherol and tocotrienol), carotenoid, and sterol compositions and to their quality characteristics (FFA, PV, para-anisidine value, and color of the by product). Moreover, the oil quality was evaluated in relation to the progress of the supercritical extraction.     

Extraction of rice brain oil using supercritical carbon dioxide and propane

Extraction of rice bran lipids was performed using supercritical carbon dioxide (SC−CO₂) and liquid propane. To provide a basis for extraction efficiency, accelerated solvent extraction with hexane was performed at 100°C and 10.34 MPa. Extraction pressure was varied for propane and SC−CO₂ extractions. Also, the role of temperature in SC−CO₂ extraction efficiency was investigated at 45,65, and 85°C. For the SC−CO₂ experiments, extraction efficiencies were proportional to pressure and inversely proportional to temperature, and the maximal yield of oil achieved using SC−CO₂ was 0.222±0.013 kg of oil extracted per kg of rice bran for conditions of 45°C and 35 MPa. The maximal yield achieved with propane was 0.224±0.016 kg of oil per kg of rice bran at 0.76 MPa and ambient temperature. The maximum extraction efficiencies of both SC−CO₂ and propane were found to be significantly different from the hexane extraction baseline yield, which was 0.261±0.005 kg oil extracted per kg of rice bran. A simulated economic analysis was performed on the possibility of using SC−CO₂ and propane extraction technologies to remove oil from rice bran generated in Mississippi. Although the economic analysis was based on the maximal extraction efficiency for each technology, neither process resulted in a positive rate of return on investment.     

Analysis on the dyeing of polypropylene fibers in supercritical carbon dioxide

Polypropylene fibers were dyed in supercritical carbon dioxide system and the results were compared with those of fiber dyed in water system. Dye uptake value calculated by a UV spectrum indicated that polypropylene fiber dyeing was much better in carbon dioxide than in water. Optical microscopical analysis showed that dye molecules had diffused thoroughly into fiber in CO₂ because of the excellent compatibility between the dye and the CO₂. X-ray and birefrigence analysis demonstrated that plastification caused by the implementation of CO₂ made molecular chain more mobile and led to an increase in the dyeing of polypropylene fibers. Moreover a mechanical test and DSC analysis indicated that the fiber structure was not damaged when the fabric was dyed at 100 °C. Hence dyeing polypropylene using CO₂ as a transport medium was very feasible and worthy of further development.     

超临界CO_2萃取水冬瓜油

研究了用超临界ＣＯ２流体从水冬瓜果实中提取油品的工艺,探索了操作压力、温度、流量及时间对水冬瓜油的萃取率的影响。分析了萃取条件与油品质量的关系,并综合得出了超临界ＣＯ２萃取水冬瓜油的最佳萃取条件。     

Supercritical carbon dioxide extraction of Baizhu: Experiments and modeling

In this work, supercritical CO₂ extraction has been carried out on a traditional Chinese herb of Baizhu under pressure of 15-45 MPa, temperature of 40-60 °C, mean powder size of 0.167-0.675 mm, and extraction time of up to 180 min. The maximum extraction yield obtained in 5 h is about 6.76 × 10⁻² g per gram raw materials at 60 °C and 45 MPa. The extraction process is correlated by means of five different mathematical models. The evaluation of these models against experimental data shows that among these models the Sovová model performs the best with an overall average absolute relative deviation of 1.62%, followed by Crank and Naik models, finally the Barton and Martínez models. From the Sovová model, the mass transfer coefficient in solid or fluid are obtained and they are varying in the ranges of 4.02-6.14 × 10⁻⁸ m/s and 0.88-2.87 × 10⁻⁹ m/s, respectively. These results suggest that solute diffusion in solid matrices and solute mass transfer in fluid are both important in affecting the supercritical CO₂ extraction process of Baizhu.     

Extraction of lipid-grown bacterial cells by supercritical fluid and organic solvent to obtain pure medium chain-length polyhydroxyalkanoates

A simple two-step process was developed to extract and purify medium chain-length polyhydroxyalkanoates (MCL-PHA) from bacterial cells (Pseudomonas resinovorans) grown on lard and tallow. The process consists of supercritical fluid extraction (SFE) of the lyophilized cells with carbon dioxide to remove lipid impurities, followed by chloroform extraction of the cells to recover the MCL-PHA. SFE conditions were varied as to temperature (40–100°C), pressure (2000–9000 psi), and carbon dioxide flow rate (0.5–1.5 L/min, expanded gas). Lipid material, usually 2–4%, but in some cases as high as 11%, was extracted from the dried cells by SFE. A pressure range (5000–9000 psi, increased stepwise), a temperature of 60°C, and a carbon dioxide flow of 1.5 L/min were routinely used to extract the bacterial cells (4–5 g) after 3 h. Higher flow rates could shorten the extraction time even more. SFE did not extract MCL-PHA from the cells. Yield of MCL-PHA after chloroform extraction at room temperature was a maximum of 42.4% based on dry cell weight. The results show that the two-step process saves time, uses much less organic solvent, and produces a purer MCL-PHA biopolymer than previous extraction and purification methods. A more environmentally friendly clean-up procedure based on SFE and organic solvent recovery was developed to remove contaminating lipid materials from the fermentation biomass, allowing for the recovery of higher purity MCL-PHA that are suitable for more demanding applications.     

Effects of supercritical carbon dioxide on waste banana peels for heavy metal removal

The effects of supercritical carbon dioxide (CO₂) on waste banana peels for copper adsorption were evaluated. Supercritical CO₂ was employed both in a solvent extraction for antioxidant compound recovery and in an emerging biomass treatment to increase the subsequent heavy metal-removal step; the latter is termed “explosion with supercritical CO₂”. This lignocellulosic biomass was analyzed before and after being subjected to both processes by scanning electron microscopy and X-ray patterning. Thermal gravimetric and differential scanning calorimetry analyses were performed to understand the different effects of supercritical carbon dioxide employed in these two processes on banana peels. The explosion with supercritical CO₂ process resulted in a more pronounced effect on the vegetable structure. Nevertheless, no increase in the copper-removal capacity was achieved. The adsorption studies showed similar behaviors for fresh and extracted samples, demonstrating that banana peels previously extracted with supercritical CO₂ retained their adsorption capacity for subsequent heavy metal removal.