Supercritical fluids

The morphology and structure of ultradispersed polytetrafluoroethylene (UPTFE, FORUM trademark) samples after treatment with supercritical carbon dioxide (sc-CO 2) were studied by physicochemical methods. It was shown that, in sc-CO 2 , low-molecular-weight fractions are dissolved and removed from pristine UPTFE. The structures of separated fractions were studied. With an increase in the dissolving power of sc-CO 2 (by increasing pressure and varying temperature), the fractionation process gradually involves oligomers with higher molecular weights.

The aim of this work was to evaluate the potential of supercritical carbon dioxide to extract fatty acid methyl esters (FAME) from the microalgae Nannochloropsis oculata at low temperatures (37 and
55 oC) and pressures (5.9 and 7.6 megapascals (MPa)). A qualitative gas chromatography (GC) analysis showed that the individual FAME extracted varied depending on the co-solvent (methanol or hexane) used with supercritical CO2. Using hexane, FAME compounds produced were similar to those extracted with soxhlet extraction alone while longer chain FAME were produced when methanol was the co-solvent. The effects of pressure and temperature variations were shown to be of statistical significance. The chromatograms produced in this work demonstrate that altering one of these parameters (co-solvent, temperature, pressure) can produce different compounds owing to the tunability of the technique.

The mandarin (Citrus reticulata) peel oil consists of more than 98 wt.% terpenes and a small fraction of oxygenated components responsible for its distinct smell. The terpene fraction is composed mostly of limonene and the oxygenated aroma fractions are composed mainly of linalool and decanal. The removal of terpenes must be performed in order to increase the storage time of citrus oils. In this work, the deterpenation of two different cold-pressed mandarin peel oils employing countercurrent extraction and ad-/desorption with supercritical CO 2 and a combination of these processes were investigated. Countercurrent experiments were carried out at pressures ranging from 8.5 to 10.0 MPa and at 50 and 60 • C. At 10.0 MPa and 60 • C, a maximum selectivity of 12.8 between terpenes and aromas could be obtained at a folding ratio of 5.0, showing that the fractionation by means of countercurrent gas extraction could be employed. To investigate the complete removal of terpenes, ad-/desorption experiments were also performed and both the raffinate samples obtained through the countercurrent fractionation and the crude cold-pressed peel oils were used as feed material. The components evaluated were desorbed from silica-gel and the best fractionation results were obtained at 40 • C, 25 wt.% oil loading in two sequential pressure steps. Initially, terpenes were completely desorbed at 8.0 MPa. The second desorption step was carried out at 20.0 MPa and a selective fractionation of important aroma components was observed. Additionally, scale-up experiments were performed.

Isolation of carrot fruit (Daucus carrota L., cultivar ''Chanteney") essential oil by supercritical carbon dioxide was investigated from the pretreatment of herbaceous matrix and extraction conditions to the chemical composition of obtained extract and its antimicrobial activity. The qualitative and quantitative analyses of the supercritical extract, as well as of the essential oil obtained by hydrodistillation, were done by GC/FID and GC/MS methods. Antimicrobial properties of both samples were investigated against ten species of microorganisms. Experimental results showed that the particle size had no influence on the extraction process. The highest yield was obtained at 40°C and 10 MPa. The main component of the supercritical extract, as well as of the essential oil was carotol. The supercritical extract was characterized by the presence of heavier molecular weight compounds, while some lighter compounds, e.g. pinenes, were not detected. The supercritical extract and the essential oil were the most effective against Gram-positive bacteria.

The extraction of essential oil from vegetable matrices with supercritical fluids is a promising technology which is still searching for an economical method to recycle the dense carbon dioxide (CO 2 ). The use of the reverse osmosis membrane separation process can be an alternative to avoid the intense depressurization step which is necessary for the recovering of the extracts. The membranes exhibit satisfactory permeability for supercritical CO 2 filtration, with very good resistance under the severe experimental operating conditions. In this work, four commercial reverse osmosis and nanofiltration membranes were applied to perform the separation of limonene and supercritical carbon dioxide. The tests were conducted under a pressure of 12 MPa, a transmembrane pressure of 0.5 MPa and a temperature of 40 • C. Pure CO 2 flux, limonene + CO 2 flux and the limonene retention factor were measured. The highest limonene retention factor was above 0.94.

Due to the potential of ionic liquids for industrial application in CO 2 capture and gas separation processes, solubility of near or supercritical CO 2 in ionic liquids has been object of extensive research during the last few years. This work studies the solubility of CO 2 in phosphonium-based ionic liquids that, unlike imidazolium-based ILs, have received little attention in spite of their interesting characteristics. This work addresses the study of the gas-liquid equilibrium of two ionic liquids, trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide and trihexyltetradecylphosphonium chloride, in a wide range of temperatures, pressures, showing that phosphonium ionic liquids can dissolve even larger amounts of CO 2 (on a molar fraction basis) than the corresponding imidazolium-based ILs. In particular trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide seems to be the IL with the largest CO 2 sorption capacity reported up to present, revealing the potential of phosphonium-based ILs for CO 2 capture.

The objective of this work was to assess the influence of compressed CO 2 on the specific activity of peroxidase (POD) from radish (Raphanus sativus L.). The protein concentrate, in phosphate buffer, was obtained through the precipitation of proteins with (NH 4 ) 2 SO 4 . The peroxidase activity was determined using guaiacol as substrate. A semi-factorial experimental design was adopted to evaluate the effects of temperature (30-50 • C), exposure time (1-6 h), carbon dioxide density (ρ R = 0.6-1.8, resulting in pressures from 70.5 to 254.4 bar), and depressurization rate (10-200 kg/m 3 /min) on the peroxidase activity. Samples of lyophilized proteic concentrate were also submitted to high pressure and the effect of water content on the enzymatic activity in compressed CO 2 was studied. The water content in lyophilized samples was determined by thermogravimetric analysis. The results showed that the treatment of the enzymatic concentrate with CO 2 at high pressure could be a promising route to increase the POD activity.

The electrospinning of polymers has become a potentially important process for the production of tissue engineering scaffolds. CO2 impregnation of these scaffolds may provide a method for tailoring the chemistry of these relatively high surface area scaffolds without altering their biomimetic architecture. In pursuing this we found that electrospun polycaprolactone (PCL) fibers melt when exposed to supercritical CO2 even at

Supercritical dyeing has risen good expectation in the last few years due to the attractive perspective of complete elimination of water from dyeing processes. A lot of research activities have been developed in the last decade both to deepen the knowledge of the interaction mechanisms between CO2, dye and polymers and to solve the technological problems of the process set-up.

There is an increasing public awareness of the health, environment and safety
hazards associated with the use of organic solvents in food processing and the possible
solvent contamination of the final products. The high cost of organic solvents and the
increasingly stringent environmental regulations together with the new requirements of the medical and food industries for ultra-pure and high added value products have pointed out the need for the development of new and clean technologies for the processing of food products. Supercritical fluid extraction using carbon dioxide as a solvent has provided an excellent alternative to the use of chemical solvents. Over the past three decades, supercritical CO2 has been used for the extraction and isolation of valuable compounds from natural products

Different extraction processes were employed to extract the polyphenolic compounds from pitanga (Eugenia uniflora L.) leaves: a one-step process using water, ethanol or supercritical CO 2 as solvents, and a two-step process using supercritical CO 2 followed by either water or ethanol. The total polyphenolic compounds, total flavonoids and antioxidant activity were determined in all the extracts obtained. The process performance was evaluated with respect to three variables: global extraction yield, concentration and yield of both polyphenols and flavonoids in the extracts. For the one-step extraction, the results showed that the extraction yield increased with solvent polarity. For the two-step process, the results suggested that water was more efficient in extracting the phenolic compounds from E. uniflora when the matrix was previously extracted with scCO 2 . With respect to the antioxidant activity, the ethanolic extracts obtained from both processes, using either the DPPH radical scavenging method or the ␤-carotene bleaching method, presented high antioxidant activities.

 SFEE encapsulated copaiba oleoresin and reduced ethyl acetate to below 5000 ppm.  The mean droplets size in the dispersed systems is not modified in SFEE.  The dried particles by spray-drying and freeze-drying showed monomodal size distribution.  The micrographs obtained by CLSM confirm the encapsulation the copaiba oleoresin in the modified starch.

The vapour–liquid equilibria of α-pinene, limonene and fenchone, and solubility behaviour of camphor were measured in supercritical carbon dioxide (SC-CO2) as a function of pressure and temperature using the static method. Experiments were carried out in the ...

Supercritical carbon dioxide extraction of Alnus glutinosa (L.) Gaertn. was performed (P = 300/450 bar, T = 40/60 • C, EtOH addition = 0/5/10%) in order to determine preferable process conditions. Phytochemical composition of extracts were analyzed by means of TLC, GC-MS, LC-MS, RP-HPLC. Total of 11 pentacyclic triterpenes and ␤-sitosterol were identified. The results indicated that SFE is an advantageous method over Soxhlet extraction in terms of yield and recovery of target compounds. Overall extraction curves revealed that pressure had little influence on extraction yield, while temperature and amount of co-solvent increased it. The optimum SFE condition was 300 bar/60 • C/10% EtOH, where the amount of extracts was 3.81% compared to n-hexane (2.56%). Highest amount of betulin, betulinic acid and lupeol was 3.57, 2.95 and 14.33 g/100 g extract, respectively, depending on the applied SFE condition. Ethanolic Soxhlet extraction ensures the highest yield (40.90%), but provides the extracts diluted with undesirable substances hence the concentration of triterpenes in the extract was very low.

The aim of this study was to use a benign technique for the sterilization of ultra-high molecular weight polyethylene (UHMWPE), which is broadly used in artificial joints. The feasibility of using supercritical (SC) CO 2 modified with additives such as ethanol, water and hydrogen peroxide was assessed for the sterilization of UHMWPE. The operating conditions and the amount of modifiers were changed to achieve a complete inactivation of bacteria such as spores and fungi. Complete inactivation of all microorganisms including spores was achieved within 2 h at 37 • C and 170 bar CO 2 , when at least 25 L hydrogen peroxide was mixed with equal volume of other modifiers. The physio-chemical properties of the polymer were tested for untreated, as well as treated samples. Mechanical strength and elongation of the polymer were measured using an Instron and the oxidation of the polymer was measured using FTIR. Both the physical and chemical properties of the polymer were unchanged after the SC CO 2 sterilization technique.

It is currently impossible to control irrigation at the level of a single plant. Even with drip irrigation, in which emitters could conceivably be placed on a plant-by-plant basis, there is no way to control the amount of water emitted according to the needs of the individual plants. If such a capability were practically available on farms, the result would be a step change in precision agriculture, such that the water input for every plant in a farm (or field) could be optimized. Therefore, we are exploring the possibility of developing a microfluidic system that could be controlled, capillary by capillary, to deliver the needed amount of water to individual plants in a large field. The principal aim is to show proof of concept by building and testing a prototype to produce data suggestive of the potential for multiple individually controllable microfluidic ports along a pressurized tube of water. Hence, in this study we perform experiments using a thermally actuated microvalve for...

Isolation of carrot fruit (Daucus carrota L., cultivar ''Chanteney") essential oil by supercritical carbon dioxide was investigated from the pretreatment of herbaceous matrix and extraction conditions to the chemical composition of obtained extract and its antimicrobial activity. The qualitative and quantitative analyses of the supercritical extract, as well as of the essential oil obtained by hydrodistillation, were done by GC/FID and GC/MS methods. Antimicrobial properties of both samples were investigated against ten species of microorganisms. Experimental results showed that the particle size had no influence on the extraction process. The highest yield was obtained at 40°C and 10 MPa. The main component of the supercritical extract, as well as of the essential oil was carotol. The supercritical extract was characterized by the presence of heavier molecular weight compounds, while some lighter compounds, e.g. pinenes, were not detected. The supercritical extract and the essential oil were the most effective against Gram-positive bacteria.

The supercritical fluid enhanced atomization (SEA) process was used to produce cocrystals of six different active pharmaceutical ingredients (APIs): indomethacin, theophylline, caffeine, sulfamethazine, aspirin and carbamazepine. Micrometric cocrystals using the FDA-approved sweetener saccharin (SAC) as a cocrystal former were produced from ethanol solutions using supercritical CO 2 as the atomization enhancing fluid. The corresponding cocrystalline phases were characterized by differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD). Particle morphologies and size distributions were analyzed by scanning electron microscopy (SEM) and by aerosizer.

The extraction of antioxidant additives, such as, Irganox 1076 and Irgafos 168, from low-density polyethylene (LDPE) and Irganox 1010 and Irgafos 168 from high-density polyethylene (HDPE) was carried out by supercritical fluid extraction (SFE) working in constant pressure, conventional reflux, and automatic Soxhlet system (Soxtec). Recoveries and repeatability of the evaluated methods, using LDPE and HDPE reference materials, showed some differences between them, but more significant differences were found with features such as sample-processing and time required, which are both crucial for the exploitation of these techniques for quantification in routine industrial quality analysis for additives. SFE was found to be the most advantageous technique in terms of simplicity, cost-effectiveness and speed in comparison to conventional reflux and Soxtec procedures.

Supercritical CO2 extraction has been proved to be a potential tool in the recovery of aroma compounds from different natural sources and in the removal of ethanol from aqueous solutions. In this work, both ideas are combined to develop a two-step process toward the production of a low-alcohol beverage from wine, but maintaining the aroma and the antioxidant activity similar to that of the original wine.First, the recovery of aroma from wine was attained in a countercurrent packed column (white and red wines were investigated) using very low CO2/wine ratios. Then, the aroma-free wine recovered from the bottom of the extraction column was dealcoholized by applying different extraction conditions.The results obtained from these studies permit the design of a two-step countercurrent CO2 extraction process at 9.5 MPa and 313 K, in which the different CO2/wine ratios employed in each step lead to the recovery of aroma or the removal of ethanol. The two-step process was applied to rose wine and the low-alcohol beverage obtained proved to have similar antioxidant activity and similar aroma profile to that of the original wine.► We produce a low-alcohol beverage from wine based on a supercritical process. ► The countercurrent-SFE process is a two-step process. ► First, recovery of aroma using very low CO2/wine ratios. ► Second, dealcoholization of the aroma-free wine. ► Beverage obtained have similar antioxidant activities and aroma to that original wine.

This paper focuses on supercritical CO 2 extraction of grape seed oil which has been analyzed both experimentally and theoretically. Extractions on crushed seeds at pressures varying in the range 280-550 bar and at a fixed temperature of 313 K were performed. From the initial linear portion of the experimental curves oil solubility data in the supercritical solvent have been obtained. By modeling the complete curves, the transport parameters regulating the oil mass transfer inside the seed particles have been calculated: the internal transport coefficient and the effective diffusivity.

This study aims to analyze the effects of supercritical carbon dioxide (SCCO 2 ) on the carbonation of Portland cement pastes, with and without mineral addition. The process is based on the advantages of the low viscosity and surface tension of SCCO 2 that allow the complete wetting of complex substrates with intricate geometries, including internal surfaces of agglomerates such of these found in cement pastes. The supercritical treatment alters the bulk chemical and structural properties of cement pastes by accelerating natural carbonation reactions, while at the same time it reduces both free and bound water. The observed overall effects of supercritical carbonation on Portland cement pastes were the neutralization of pore water alkalinity, the formation of calcium carbonate and the reduction in the Ca/Si ratio of the calcium silicate hydrate (CSH) gel. Moreover, the massive precipitation of calcium carbonate inside microcracks after supercritical treatment caused the refinement of the microstructure, thus, reducing water permeability to a large extent. Supercritical carbonation method can be completed in few hours, rendering it technically interesting. This work also contributes to the idea of increasing the durability of concrete by means of a preventive hydrophobic supercritical treatment against water ingress. A generic SCCO 2 method for concrete silanization is proposed here.

Oil deodorizer distillate (DOD), a byproduct from the soybean oil refining process, is rich in valuable compounds, such as natural tocopherols (vitamin E) and sterols. With the aim of concentrating tocopherols from methyl esterified DOD with supercritical CO 2 , a semi-continuous countercurrent process was developed using a fractionation column with a height of 2.4 m, an inner diameter of 20 mm, and a total volume of 750 mL. Operation parameters, pressure, the ratio of solvent to feed, and temperature of the column were investigated. The experimental results indicated that supercritical CO 2 effectively extracts fatty acid methyl esters at 16 MPa with a column temperature gradient of 313-348 K. By increasing pressure, natural tocopherols (>50%) can be obtained with high recovery (>80%). It is concluded that supercritical CO 2 fractionation is technically feasible for concentrating natural tocopherols from methyl esterified DOD.

Brazilian redspotted shrimp (Farfantepenaeus paulensis) waste is an important source of carotenoids such as astaxanthin and lipids with a high −3 fatty acids content, mainly docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). In order to establish an efficient and environmental friendly recovery process, the lipids and astaxanthin were extracted from the freeze-dried redspotted shrimp waste (including head, tail and shell) using supercritical carbon dioxide. The effects of the extraction conditions of pressure (200-400 bar) and temperature (40-60 • C) on the global yield (X 0 ), astaxanthin extraction yield and astaxanthin concentration in the extract were evaluated. It was found that the pressure and temperature showed a very low significant effect on the lipid extraction yield using supercritical CO 2 . In comparison with lipid extraction by solvents, maximum efficiency of supercritical fluid extraction achieved 64% of hexane extraction yield. On the other hand, temperature and pressure had significant effects on astaxanthin extraction yield. Thegreatest amount of extract was obtained at 43 • C and 370 bar, with 39% of recovery.

Supercritical fluid extraction of lipids from spent coffee grounds was studied in this work. Extraction experiments were carried out with supercritical carbon dioxide at different pressure and temperature conditions to study the influence of those process parameters on the extraction rate and oil composition. Supercritical carbon dioxide extracted up to 85% of the total amount of oil of spent coffee grounds after 3 h of extraction (corresponding to a maximum yield of 15.4 g oil /100 g dry spent coffee). The fatty acid composition of the extracted oil showed the presence of fatty acids of C14, C16, C18, and C20 carbon chains. Palmitic (C16:0) and linoleic (C18:2) acids were the major fatty acids and comprise about 35% each of the total fatty acid content of the oil. A soxhlet extraction with n-hexane was done for comparison resulting in a maximum yield of oil of 18.3 g oil /100 g dry spent coffee. Finally, a diffusional model that takes into account the properties of the substrate, the solute partition between the solid and the supercritical phase, and the mass transfer coefficient and axial dispersion in the fluid phase was applied to this system and a good agreement with experimental results was obtained.

Supercritical CO 2 and sub-critical propane extraction conditions on quality attributes of cardamom oil were studied. The yield and solvent extractability were examined as a function of extraction conditions such as temperature, pressure and solvent/solid ratio. Of the quality components of the recovered oil, pigments (chlorophylls and carotenoids), volatile constituents, fatty acids and tocopherols, were determined by high-performance liquid chromatography (HPLC) and gas chromatography-mass spectroscopy (GC-MS). Cardamom was found easy-to-extract by fluid CO 2 even at sub-critical conditions with very cost-effective ratio of solvent/solid. However, the maximum level of natural pigments and antioxidants achieved was found in extracts recovered by supercritical fluid CO 2 and sub-critical propane. Addition of ethanol to CO 2 up to 25% did not improve the extractability of fatty acids, but had negative effect on aroma profile and positively affected the natural pigment of the extract. Propane was found to be more capable than CO 2 to recover seed oil at sub-critical conditions with lower ratio of solvent/solid and better quality attributes. Supercritical fluid extraction conditions affected to some extent fatty acid composition and content of volatiles in the recovered extracts.

Separation process using supercritical CO 2 to concentrate ethanol from aqueous solution appears to be a promising technology. Knowledge of vapor-liquid equilibria (VLE) for systems consisting of CO 2 , ethanol and water is necessary for designing such separation technique. In this work, The Peng-Robinson equation of state (PR EoS) combined with classical and modified quadratic mixing rules were evaluated in predicting VLE of CO 2 +ethanol, CO 2 +water, ethanol+water and that of CO 2 +ethanol+water system using temperature dependence and independence of binary interaction parameters. For binary systems, evaluation was performed by comparing the calculated values with the literature data at the temperature range of 293.15 – 523.15 K and pressure range of 0.01–17.44 MPa. Using temperature independent parameters, PR EoS – Quadratic and PR EoS-Classical gave average absolute deviations (AAD) in pressure ≤ 3,70% and ≤ 5,46% respectively. PR EoS-Quadratic gave better prediction results than PR EoS-Classical. For ternary CO 2 +Ethanol+Water systems, evaluation was performed at the temperature range of 313.20 –343.20 K and the pressure range of 9.05 –11.3 MPa. The best prediction result of ternary system was obtained by optimized interaction parameter of CO 2 +Water from ternary VLE data and the other parameters from binary VLE data.

The past twenty years has seen an expansion of the “critical fluid” technology platform with respect to using or combining multiple types of unit operations and compressed fluids in both their sub- and supercritical states. Although supercritical fluid extraction (SFE) utilizing supercritical carbon dioxide (SC-CO2) has seen considerable industrial use, the high capitalization cost of building and running such production plants promotes expanding their use and functionality with respect to multi-unit operations and multiple fluids. An evaluation of the current status of implementing such an approach is provided, and a perspective of future needs suggested based on the senior author’s 40 years of experience in critical fluid processing of agriculturally-derived materials and natural products. The use of hot compressed water is no longer limited to just supercritical water processing, but can be advantageously exploited over a wide range of temperatures and appropriate pressures to include extraction and reaction of targeted substrates, including bioactive natural products, biomass conversion for renewable fuels, and synthesis of chemicals. As noted previously, combining SFE with fractionation methods using critical fluids, and/or reaction chemistry in critical fluid media can produce a variety of extracts or products [J.W. King, Sub- and supercritical fluid processing of agrimaterials: extraction, fractionation and reaction modes, in: E. Kiran, P.G. Debenedetti, C.J. Peters (Eds.), Supercritical Fluids: Fundamentals and Applications, Kluwer Publishers, Dordrecht, The Netherlands, 2000, pp. 451–488.] however the modification of processing equipment such as expellers, extruders, and particle production devices extend the use of the critical fluid technology platform. Sequential unit processing using multiple fluids also has been reported although demonstrated to a limited degree—however combining both compressed CO2 and water in a unit process can also impart some unique processing possibilities. The concept of multiple unit and fluid processing supports an environmentally benign or “green” production platform and is consistent with processing sustainable materials. Integration of critical fluids into existing processing concepts such as biomass conversion, biorefineries, and synthesis based on methyl ester intermediates are discussed.The past twenty years has seen an expansion of the “critical fluid” technology platform with respect to using or combining multiple types of unit operations and compressed fluids in both their sub- and supercritical states. Although supercritical fluid extraction (SFE) utilizing supercritical carbon dioxide (SC-CO2) has seen considerable industrial use, the high capitalization cost of building and running such production plants promotes expanding their use and functionality with respect to multi-unit operations and multiple fluids. An evaluation of the current status of implementing such an approach is provided, including systems based on pressurized liquid fluids, and a perspective of future needs in this area are discussed.

In this work, we use an efficient and reliable "dynamic-synthetic" method for the measurement of critical properties of a variety of pure compounds, binary mixtures, and one ternary mixture. The critical phenomenon is observed via the critical opalescence in a view cell, which withstands conditions up to 543 K and 20 MPa. Excellent agreements were obtained between the measured pure compounds' properties and those listed in recent databases. Among the pure compounds measured, several refrigerants less well described in open literature (C 3 F 6 , C 3 F 6 O, R365mfc) have been compared with conventional predictive models. The critical profiles of associating, azeotropic systems ethanol + n-alkanes (C 4 -C 8 ) are presented, as well as the critical surfaces for the ternary system n-pentane + ethanol + n-hexane. We present forms of the Cibulka and Singh's equation suitable for correlating ternary critical properties. (D. Richon). region, unless following in a rigorous manner the renormalizationgroup theory [3], or some form of the rectilinear scaling law [4]. It is for these reasons that experimental measurements of critical data remain of high value. Accurate critical data, readily achievable with the ideas proposed in this work, are being used to improve the performance of non-cubic equation of states, such as those of the SAFT-type equations , which lack constraints in the critical region.

In this paper a method to calculate the viscosity of supercritical CO2 is introduced. A rolling body viscometer equipped with a gas booster was used. Based on new experimental and available data, a new correlation is developed. The proposed correlation is valid in temperature range from 310 K to 900 K. Moreover, the model predictions are acceptable in pressures between 7.5 and 101.4 MPa. The model superiority over other conventional methods has been demonstrated. (M. Rahimi).

Solvents like propane and carbon dioxide have been studied in previous works at supercritical and subcritical conditions and also as highpressure liquid solvents for the extraction of lipids and oils. Propane is completely miscible with vegetable oils at room temperature but has liquid-liquid phase equilibrium with typical vegetable oils at temperatures between the lower critical end point (LCEP) and the upper critical end point (UCEP)-around 340 K and 370 K. In this temperature range, the propane solvent power for triglycerides is drastically reduced unless higher pressures are used to recover the single phase region.

Lemongrass (Cymbopogon citratus) essential oil was extracted with dense carbon dioxide at 23 -50°C and 85 -120 bar. The composition of samples collected during the first and the last hours of the extraction experiments was analyzed by gas chromatography-mass spectrometry, and coextraction of cuticular waxes was observed. Liquid carbon dioxide extracts had a larger quantity of coextracted waxes than the supercritical extracts. The process condition of 120 bar and 40°C was considered ideal for the extraction of lemongrass essential oil, as a good-quality product was obtained together with a good extraction rate and yield.

We present some selected results indicating the feasibility of preparing therapeutic finished ophthalmic articles, namely commercially available soft contact lenses, using a supercritical solvent impregnation (SSI) technique. Several commercial soft contact lenses were tested and, among these, four lenses were selected for more complete studies: Nelfilcon A (FocusDailies ® , CIBA Vision), Omafilcon A (Proclear ® Compatibles, CooperVision), Methafilcon A (Frequency ® 55, CooperVision) and Hilafilcon B (SofLens ® 59 Comfort, Bausch & Lomb). Supercritical carbon dioxide (scCO 2 ) was the chosen supercritical fluid and two ophthalmic drugs were tested: flurbiprofen (a NSAID, hydrophobic) and timolol maleate (an anti-glaucoma drug, hydrophilic). The effects of operational pressure, of impregnation duration and of the addition of a cosolvent (ethanol) were studied on the overall drug loading yields. Depending on the experiment, we employed pressures from 9 up to 16 MPa and impregnation times from 30 up to 180 min. Temperature was kept constant and equal to 313 K. The employed depressurization rates were kept low and between 0.1 and 0.2 MPa/min.

The solubility of many salts in water decreases dramatically with temperature in the vicinity of the critical point of pure water. Examples of these salts are sulfates of sodium, potassium, lithium and sodium carbonate. These salts are usually produced during supercritical water oxidation (SCWO) and contribute to fouling. The solubility of Na 2 CO 3 and Na 2 SO 4 has been determined in pure form and in the presence of each other, for the temperature range relevant to SCWO. The experimental procedure was to pass the salt solution through a tube at constant temperature. After a brief initiation period during which no salt sticks to the tube, the salt above the solubility limit deposited on the tube surface. The solution leaving the section was thus at the solubility limit. A rapid decrease in the salt solubility was observed just above the pseudo-critical temperature. For supercritical conditions, the solubility of each salt in the form of a mixture was quite close to the solubility of pure salt. At the highest fluid density considered (∼480 kg/m 3 ) the presence of Na 2 CO 3 reduces the solubility of Na 2 SO 4 , as might be expected from the "common-ion effect".

Solanesol is a long-chain terpenoid alcohol mainly existing in tobacco leaves. It is a useful starting material for the synthesis of high-value biochemicals. It can be extracted with supercritical CO 2 , but nicotine is co-extracted, which may be hazardous. In this work, operating conditions to obtain a solanesol-rich extract from tobacco leaves with high solanesol/nicotine ratios were optimized. The ranges of extraction temperatures and pressures were 25-60 • C and 8-25 MPa, respectively. GC coupled with MS detection was used to characterize the extracts, and free solanesol was identified and quantified as its trimethylsilyl derivative. Solanesol/nicotine ratios varied from 18 to 4. Average yields of solanesol were 0.188 mg/mg of extract.

Olive husk oil was extracted from olive husk under pressures of 12.0 to 18.0 MPa and temperatures of 308 to 330 K with supercritical carbon dioxide. Olive husk was supplied by an olive oil factory. The effects of pressure, temperature, extractor capacity and superficial velocity on the extraction rate of olive husk oil were studied. Extraction curves were evaluated by an empirical model, a 'hot sphere' model and by the extended Lack's plug-flow model and the relative merits of the models are demonstrated. The results are compared with those obtained in the literature. Good agreement between the extended Lack's plug-flow model and our experimental measurements was obtained. The empirical model (in which only one adjustable parameter varied with extraction conditions) also fitted the data well.

This work evaluated the technical feasibility of supercritical CO 2 extraction of caffeine from coffee husks, an abundant residue of the coffee industry. Different pre-treatments (initial humidity and milling) and operational conditions (pressure, temperature, time and flow rate) were studied in a CO 2 continuous flow laboratory-scale unit. While prior wetting of the coffee husks was needed, milling was not required to extract the caffeine. The use of higher flow rates and/or operational times resulted in higher extraction rates. The process was favoured with increased operational pressure and temperature due to higher solubility. The maximum extraction yield obtained of this alkaloid was 84% when working at 373 K and 300 bar, using 197 kg CO 2 /kg husks. After water washing, the caffeine was at least 94% pure. Comparing world production data, the initial caffeine content and global extraction yield data of other natural sources, this process could be very advantageous for its technological application.

The supercritical removal of ethanol from alcoholic beverages (brandy, wine, and cider) was studied using the GC-EoS model to represent the phase equilibria behavior of the CO 2 + beverage mixture. Each alcoholic drink was represented as the ethanol + water mixture with the corresponding ethanol concentration (35 wt% for brandy, 9-12 wt% for different wines and 6 wt% for cider). The thermodynamic modeling was based on an accurate representation of the CO 2 + ethanol and CO 2 + water binary mixtures, and the CO 2 + ethanol + water ternary mixture.