Continuous production of fatty acid methyl esters from corn oil in a supercritical carbon dioxide bioreactor

Continuous production of fatty acid methyl esters (FAMEs) from corn oil was studied in a supercritical carbon dioxide (SC-CO₂) bioreactor using immobilized lipase (Novozym 435) as catalyst. Response surface methodology (RSM) based on central composite rotatable design (CCRD) was employed to investigate and optimize the reaction conditions: pressure (11-35 MPa), temperature (35-63 °C), substrate mole ratio (methanol:corn oil 1-9) and CO₂ flow rate (0.4-3.6 L/min, measured at ambient conditions). Increasing the substrate mole ratio increased the FAME content, whereas increasing pressure decreased the FAME content. Higher conversions were obtained at higher and lower temperatures and CO₂ flow rates compared to moderate temperatures and CO₂ flow rates. The optimal reaction conditions generated from the predictive model for the maximum FAME content were 19.4 MPa, 62.9 °C, 7.03 substrate mole ratio and 0.72 L/min CO₂ flow rate. The optimum predicted FAME content was 98.9% compared to an actual value of 93.3 ± 1.1% (w/w). The SC-CO₂ bioreactor packed with immobilized lipase shows great potential for biodiesel production.     

Separation of fatty acid esters from cholesterol in esterified natural and synthetic mixtures by supercritical carbon dioxide

The solubility of cholesterol in supercritical carbon dioxide was determined by a continuous flow method. The solubility of cholesterol increased with increasing pressure and exhibited retrograde behavior. The Chrastil equation was used to describe the relationship between solubility and the density of carbon dioxide. A model mixture was made by adding cholesterol and fatty acid esters together. Squid visceral oil was esterified as the feed material. Both the model mixture and esterified squid visceral oil were extracted by supercritical carbon dioxide. The experimental results showed that cholesterol could be removed from a model mixture and from esterified squid visceral oil at low pressure (1500 psig) and high temperature (328.2°K). Under these conditions, cholesterol content in the extract was reduced from 2867 mg/100 g to 14.1 mg/100 g.     

Extraction of essential oil from geranium (Pelargonium graveolens) with supercritical carbon dioxide

This study investigated the supercritical fluid extraction (SFE) of geranium essential oil from geranium (Pelargonium graveolens) using supercritical carbon dioxide solvent. The extraction yield was measured as a function of pressure, temperature and carbon dioxide flow rate. At low pressure (10 MPa) and high temperature (343 K), waxes were co‐extracted with the essential oil, resulting in artificially elevated essential oil extraction yields as no method was available with the SFE apparatus used to separate co‐extracted waxes and oil. At high pressure (30 MPa) and low temperature (313 K), the amount of wax co‐extracted decreased. Under these ‘optimum’ conditions, the extraction yield increased with decrease in flow rate giving a maximum extraction yield of 2.53%. All samples were analyzed by gas chromatography–mass spectrometry and the effect of pressure and extraction time on oil composition was studied. The percentage compositions of terpene hydrocarbons, terpenols, geraniol and geranyl esters were significantly affected by pressure and extraction time. The oil samples obtained by SFE were also compared with commercially obtained steam distilled samples. All major components of the commercially obtained oils were present in the SFE‐obtained oils; however, the percentage composition of the major components differed greatly between steam distilled and SFE oils. Copyright © 2005 Society of Chemical Industry     

Crystallinity development in cellular poly(lactic acid) in the presence of supercritical carbon dioxide

This article investigates the crystallinity development in cellular poly(lactic acid) (PLA) and the effect of the achieved crystalline content on its properties and microstructure. Carbon dioxide (CO₂) in its supercritical state was used as the expansion agent for three different grades of PLA that differed in terms of L‐lactic acid content. Cellular PLA was produced on a twin‐screw extrusion line using capillary dies of various diameters. The obtained crystalline contents were measured by differential scanning calorimetry and X‐ray diffraction techniques. The morphology of the cellular structures was examined using scanning electron microscopy. The crystallinity developed on expansion depended on L‐lactic acid content, on supercritical CO₂ concentration, polymer flow rate, and die diameter. Cellular PLA, with densities as low as 30 kg/m³, was obtained under the most favorable conditions. It was shown that the crystallinity development in PLA enhances its cellular structure formation and enables the fabrication of quality cellular materials at lower CO₂ concentration. The presence of PLA crystallites within expanded cell walls leads to a peculiar 2D‐cavitation phenomena observed only in the cell walls of semicrystalline foams. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Continuous catalyst-free production of fatty acid ethyl esters from soybean oil in microtube reactor using supercritical carbon dioxide as co-solvent

This work reports the transesterification of soybean oil in supercritical ethanol in a continuous catalyst-free process in microtube reactor using carbon dioxide as co-solvent. For this purpose it was employed two microtube reactors with different internal diameter, 0.775 and 0.571 mm. The experiments were performed in the temperature range of 523-598 K, pressure of 10 MPa and 20 MPa, oil to ethanol molar ratio of 1:20 and 1:40, and co-solvent to substrates mass ratio from 0.05:1 to 0.2:1. Results demonstrated that temperature, pressure and co-solvent to substrate mass ratio had a positive effect on fatty acid ethyl esters (FAEE) production, with appreciable yields achieved at 598 K, 20 MPa, oil to ethanol molar ratio of 1:20, using a CO₂ to substrate mass ratio of 0.2:1. The micro-reactor with the smallest inner diameter led to slightly higher FAEE yields at the specified reactions conditions compared to the micro-reactor with greater internal diameter. A semi-empirical kinetic model was proposed in attempt to represent the experimental data with satisfactory fitting results found.     

Cosolvent-modified supercritical carbon dioxide extraction of phenolic compounds from bamboo leaves (Sasa palmata)

This study highlights the possibility of supercritical carbon dioxide for extracting phenolic compounds from bamboo leaves that have shown antioxidant and anticancer activities. The CO₂ extraction solvent was modified by adding ethanol–water mixture cosolvent of different concentrations to allow extraction of both polar and non-polar compounds. Conventional Soxhlet extraction was also done to investigate the advantages of supercritical extraction over the conventional extraction method. For addition of 5% (mol) of a 25:75 (mol:mol) ethanol–water mixture solvent to CO₂, the highest amount of polyphenols (7.31 ± 0.06 mg/g bamboo leaves in catechin equivalents) and radical scavenging activity (3.65 ± 0.05 mg/g bamboo leaves in BHA equivalents) at 20 MPa and 95 °C, could be obtained among the mixture cosolvents studied. For Soxhlet extraction with a 25:75 (mol:mol) ethanol–water mixture, 1.48 times the amount of phenolic compounds (10.85 ± 0.52 mg/g bamboo leaves in catechin equivalents), could be isolated compared with the supercritical extraction method, however, the radical scavenging activity (3.30 ± 0.05 mg/g bamboo leaves in BHA equivalents) was 0.90 times lower than the extract obtained from the supercritical extraction method. The seven major antioxidative compounds identified from the SC-CO₂ extraction method were: (1) dl-alanine, (2) gluconic acid, (3) phosphoric acid, (4) ß-siosterol, (5) β-amyrene, (6) α-amyrin acetate and (7) friedelin.     

Process integration of supercritical carbon dioxide extraction and acid treatment for astaxanthin extraction from a vegetative microalga

Astaxanthin (AXA) is a carotenoid with strong antioxidant activity that has been reported to have beneficial effects on human health. Unlike the case of Haematococcus pluvialis cysts, the study of other AXA-producing vegetative microalgae as alternative AXA sources has been minimal, because of inefficient AXA extraction yield and difficulty in separating chlorophyll and AXA. In this study, a novel method was developed to extract AXA from a vegetative green microalga (Monoraphidium sp. GK12) and to separate chlorophyll and AXA using a supercritical-CO₂ extraction (SCE) and acid treatment. AXA in the microalgal biomass was extracted completely by SCE, while simple ethanol soaking could not extract AXA well. The addition of ethanol as a co-solvent improved AXA extraction yield. The method employed low CO₂ pressure and reaction temperature as well as a short reaction time, making it energy-efficient. Chlorophyll in AXA-containing extract was easily removed by acid addition (H₂SO₄ or HCl) and centrifugation. Since those acids can be neutralized by alkaline, which produces nontoxic salt, and AXA in the extract can be condensed by reducing pressure, the developed method is expected to stimulate commercialization of a vegetative microalga as an alternative AXA source for food applications.     

超临界CO_2提取绿萝花中总黄酮的工艺研究

采用超临界CO_2提取绿萝花中总黄酮,考察了提取温度、提取压力、提取时间、夹带剂种类、浓度及流速对提取效果的影响。结果表明,最佳工艺条件为:提取温度50℃,提取压力30 MPa,提取时间2 h,夹带剂浓度80%的乙醇,流速0.4 m L/min。在此条件下,黄酮的提取率和纯度分别为0.868%,8.298%,该方法绿色环保、快速高效。     

超临界CO_2提取绿萝花中总黄酮的工艺研究

采用超临界CO_2提取绿萝花中总黄酮,考察了提取温度、提取压力、提取时间、夹带剂种类、浓度及流速对提取效果的影响。结果表明,最佳工艺条件为:提取温度50℃,提取压力30 MPa,提取时间2 h,夹带剂浓度80%的乙醇,流速0.4 m L/min。在此条件下,黄酮的提取率和纯度分别为0.868%,8.298%,该方法绿色环保、快速高效。     

Characterization of purified phospholipids from krill (Euphausia superba) residues deoiled by supercritical carbon dioxide

Purification of phospholipids (PL) from the Antarctic krill (Euphausia superba) using a two-step extraction process has been investigated. Using supercritical carbon dioxide (SC-CO₂) extraction with optimal extractions conditions of 45 °C, 25MPa, and CO₂ flow rate of 22 g/min, most of the neutral lipids were extracted. PC, PE and PI were then extracted in a second step conducted with modified existing method using ethanol, hexane and acetone as solvents. The major PL of krill residues was quantified by high performance liquid chromatography (HPLC-ELSD). The fatty acid compositions of total PL, PC, PE and PI were analyzed by gas chromatography (GC). A significant amount of polyunsaturated fatty acids (PUFA) was present in both total and PLs fractions. The purified PLs were characterized by their acid value, peroxide value, and the oxidative stability. The purity of PL ranged between 93 and 97% and was evaluated by spectrophotometry.     

Preparation of poly(L-lactic acid) submicron particles in aerosol solvent extraction system using supercritical carbon dioxide

The aerosol solvent extraction system process (ASES), which is one of the supercritical anti solvent processes (SAS), was used to produce poly(L-lactic acid) (PLLA) into the submicron particles. Dichloromethane (DCM, CH₂Cl₂) and carbon dioxide were selected as a solvent and as an antisolvent for PLLA, respectively. The objective of this study was to investigate the effect of the various process parameters such as temperature, pressure, and solution concentration on PLLA particles. With increasing temperature and pressure, particle size was increased. Also, higher PLLA concentration led to larger particle size and broader particle size distribution. A scanning electron microscope (SEM) was used to observe the morphology and size of PLLA particles recrystallized by ASES process. The mean particle size and its distribution of processed particles were measured by using a laser diffraction particle size analyzer (PSA).     

Extraction and identification of proanthocyanidins from grape seed (Vitis Vinifera) using supercritical carbon dioxide

In this study, supercritical carbon dioxide extraction of proantocyanidins (PRCs) was performed and the effect of different pressure, temperature and ethanol percentage was investigated. High performance liquid chromatography was used for the analysis of the compounds and it was found that the most effective parameter on the extraction was the amount of the ethanol percentage. Each compound was extracted from grape seeds at their maximum level when different parameters were used which was probably because of their different polarities. Gallic acid (GA), epigallocatechin (EGC) and epigallocatechingallate (EGCG) were extracted at their maximum level when the 300 bar 50 °C and 20% of ethanol was used. The maximum amount of catechin (CT) and epicatechin (ECT) were obtained when 300 bar 30 °C and 20% of ethanol was used for extraction, and 250 bar, 30 °C and 15% of ethanol was needed to extract highest amount of epicatechingallate (ECG).     

Improving the exfoliation of layered silicate in a poly(ethylene terephthalate) matrix using supercritical carbon dioxide

A technique for improving the exfoliation of organically modified layered silicate (OMLS) in a poly(ethylene terephthalate) (PET) matrix using super critical carbon dioxide (scCO₂) is compared to traditional direct melt blending. The process relies on the rapid expansion of a scCO₂/OMLS mixture directly into the second stage of a single screw extruder where the clay and scCO₂ mixture is subsequently melt blended with the PET matrix. The simple, environmentally benign process results in a more highly delaminated system than traditional direct melt compounding. X‐ray diffraction analysis is used to reveal improved clay morphologies and the resulting mechanical properties are examined. Rheology is used as a tool to draw conclusions about the effect that scCO₂ has on reducing PET matrix degradation during processing. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Synthesis of 2-methyl-1,4-naphthoquinone (vitamin K3) using nanostructured gold catalysts in acetic acid and in supercritical carbon dioxide

The synthesis of 2-methyl-1,4-naphthquinone (vitamin K3) by the oxidation of 2-methylnaphthalene and 2-methyl-1-naphthol using nanostructured gold catalysts supported on super-cross-linked polystyrene ((5% Au)/SCP) has been investigated. The temperature effect on the oxidation process is reported. An attempt has been made to replace acetic acid, a common solvent, with supercritical carbon dioxide, an environmentally friendly substance. With supercritical CO₂, the selectivity of the process toward 2-methyl-1-naphthol oxidation into the target product remains at a high level (close to 100%) and the substrate conversion is 10–15% higher. In the oxidation of 2-methylnaphthalene, use of supercritical CO₂ leads to a dramatic decrease in substrate conversion and target-product selectivity. This is due to the fact that peracetic acid, which is the main oxidizer in this process, does not form under these conditions. The nanostructured gold catalysts are usable in the selective oxidation of 2-methyl-1-naphthol and 2-methylnaphthalene into 2-methyl-1,4-naphthquinone (99 and 58 %, respectively).     

Gas chromatographic analysis of malonaldehyde and 4-hydroxy-2-(E)-nonenal produced from arachidonic acid and linoleic acid in a lipid peroxidation model system

Malonaldehyde (MA) and 4-hydroxynonenal (4-HN) formed upon oxidation with Fe²⁺/H₂O₂ from arachidonic acid and linoleic acid, and their ethyl esters were analyzed by gas chromatography (GC). The MA and 4-HN produced were reacted withN-methylhydrazine (NMH) to give 1-methylpyrazole and 5(1′-hydroxyhexyl)-1-methyl-2-pyrazoline, respectively. The derivatives were analyzed by GC on a fused silica capillary column using a nitrogen-phosphorus detector. With arachidonic acid, more MA and 4-HN were formed from the ester (88 nmol/mg and 23 nmol/mg, respectively) than from the free acid (25 nmol/mg and 9 nmol/mg, respectively). In contrast, with linoleic acid, more MA and 4-HN were produced from the free acid (53 nmol/mg and 13 nmol/mg, respectively) than from the ester (39 nm/mg and 8 nmol/mg, respectively).     

Fatty acid composition,cytotoxicity and anti-inflammatory evaluation of melon (Cucumis melo L. Inodorus) seed oil extracted by supercritical carbon dioxide

ABSTRACT

Melon seed oil has been extracted by Soxhlet (hexane) and by supercritical CO₂ operating to various pressures and temperatures. Linoleic acid (67.06–68.22%) was the most abundant followed by oleic acid (21.63–22.45%), palmitic acid (5.57–6.23%) and stearic acid (2.98–3.67%). The highest inhibition of inflammation was 18.8% at 50 µg/mL for hexane and SC-CO₂ extracts obtained under 55 MPa and 70°C. The largest inhibition of IGROV and OVAR tumor cell lines were 29.9% and 21.6%, respectively, at 50 µg/mL for the ethanol extract. These results of biological activities indicate that melon seed oils can be dedicated to nutrition.     

Direct synthesis of poly(l-lactic acid) in supercritical carbon dioxide with dicyclohexyldimethylcarbodiimide and 4-dimethylaminopyridine

The direct synthesis of poly(l-lactic acid) (PLLA) from an l-lactic acid oligomer has been performed in supercritical carbon dioxide (scCO₂) using an esterification promoting agent, dicyclohexyldimethylcarbodiimide (DCC), and 4-dimethylaminopyridine (DMAP) as a catalyst. PLLA within M_n of 13,500 g/mol was synthesised in 90% yield at 3500 psi and 80 °C after 24 h. The molecular weight distribution of the products was narrower than PLLA prepared with melt-solid phase polymerisation under conventional conditions. Both DCC and DMAP showed high solubility in scCO₂ (DCC: 7.6 wt% (1.63×10⁻² mol/mol CO₂) at 80 °C, 3385 psi, DMAP: 4.5 wt% (1.62×10⁻²mol/mol CO₂) at 80 °C, 3386 psi) and supercritical fluid extraction was found to be effective at removing excess DMAP and DCC after the polymerisation was complete. We show that DCC and DMAP are effective esterification promoting reagents with further applications for condensation polymerisations in scCO₂.     

Characterization of oil including astaxanthin extracted from krill (Euphausia superba) using supercritical carbon dioxide and organic solvent as comparative method

Krill oil including astaxanthin was extracted using supercritical CO₂ and hexane. The effects of different parameters such as pressure (15 to 25MPa), temperature (35 to 45 °C), and extraction time, were investigated. The flow rate of CO₂ (22 gmin⁻¹) was constant for the entire extraction period of 2.5 h. The maximum oil yield was found at higher extraction temperature and pressure. The oil obtained by SC-CO₂ extraction contained a high percentage of polyunsaturated fatty acids, especially EPA and DHA. The acidity and peroxide value of krill oil obtained by SC-CO₂ extraction were lower than that of the oil obtained by hexane. The SC-CO₂ extracted oil showed more stability than the oil obtained by hexane extraction. The amount of astaxanthin in krill oil was determined by HPLC and compared at different extraction conditions. The maximum yield of astaxanthin was found in krill oil extracted at 25 MPa and 45 °C.     

Modification of the surface of poly(ethylene terephthalate) fabrics by application of a water-repellent coating in supercritical carbon dioxide medium

It was shown that in treating PET fibre materials with a solution of ultradisperse, low-molecular-weight polytetrafluoroethylene in supercritical carbon dioxide, an ultrathin layer of fluoropolymer that gives the fabric a high degree of water repellency is formed on the surface. Translated from Khimicheskie Volokna, No. 1, pp. 26-30, January-February, 2009.     

Electrodeposition of lead dioxide on carbon substrates from a high internal phase emulsion (HIPE)

PbO₂ coatings on carbon electrode substrates were produced by anodic electrodeposition from a stationary high internal phase emulsion (HIPE) with the bath components added in the water phase. The deposits have a distinct structure consisting of 10–50 m high pyramidal aggregates, pitted with smaller pores. This is attributed to the growth of the deposits through the aqueous network of the HIPE emulsion that is, through the tortuous paths formed by its interconnected water cavities. The coatings thus produced are characterised by enhanced electrochemical activity towards the PbO₂/PbSO₄ transformation.