Supercritical extraction

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.

BACKGROUND: Microorganisms have often been considered for the production of oils and fats as an alternative to agricultural and animal resources. Extraction experiments were performed using a strain of the yeast Yarrowia lipolytica (Y. lipolytica), a high-lipid-content yeast. Three different methods were tested: Soxhlet extraction, accelerated solvent extraction (ASE) and supercritical carbon dioxide (SCCO 2 ) extraction using ethanol as a co-solvent. Also, high pressure solubility measurements in the systems 'CO 2 + yeast oil' and 'CO 2 + ethanol + yeast oil' were carried out.

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.

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.

This study evaluated the temperature and pressure effects in the extraction of the sunflower seed (Heliantus annuus L.) oil using as solvents carbon dioxide and propane. The experiments were performed at the temperature range of 30-60 • C and pressure range of 8-25 MPa. A factorial experimental design 2 2 with triplicate at the central point was effectuated in order to evaluate the influence of this two variable in the mass of oil extracted ratio by mass of solvent consumed. Analysis of oxidative stability and chemical composition of the oil were performed as well. The best extraction for sunflower seed oil was obtained with propane as solvent, because of the high extraction yield in comparison with carbon dioxide. The quantity of fatty acids detected in the samples of oil extracted with carbon dioxide and propane were similar and presented a high time of oxidative induction than the sample extracted with hexane. However, the oil extract obtained with propane showed a high concentration of vitamin E (␣-tocopherol). To describe the extraction kinetic was used the Sovová mathematical model, which showed a high precision in all the conditions investigated.

An interdisciplinary team of students from Michigan Technological University completed a series of tests using Supercritical Carbon Dioxide (SC-C02) to extract water and volatile compounds from samples of corroded archaeological iron artifacts. Test samples were then cracked and examined using backscatter SEM. Qualitative visual inspection showed that pores and microfissures were clear and opened after SC-C02 extraction. Another SC-CO2 treatment then impregnated the test objects with an environmentally-benign polymer (Acryloid/Paraloid TM B-72) to consolidate fragile structures and seal objects against future water absorption. Following treatment, these samples were also cracked and examined with SEM. Chemical traces of the polymer demonstrated the complete diffusion of the B72 into the pores and microfissures of the sample. These tests were paralleled by the design and execution of traditional conservation plans for twenty ferrous metal artifacts. The project team developed essential comparative perspectives on existing techniques, while being engaged in considerations of professional ethics, practicality, and economic value. This study showed that the emerging application of Supercritical Fluid (SCF) Extraction can be used to rapidly stabilize batches of corroded ferrous metal artifacts, including cast and wrought iron and steel, as well as composite artifacts. This will allow labs to avoid or safely delay traditional electrochemical techniques that can require months of expert treatment. This technique works as a batch operation, allowing groups of small artifacts to be quickly stabilized and consolidated, potentially even in field settings. The process may also be tailored to treat objects from sites with soil contamination or materials from heritage collections, where potentially hazardous chemicals are also extracted during dewatering. While critically important questions remain to be addressed before the technique can be made systematically operational, particularly those surrounding chloride salts, the technique has tremendous potential to improve best practices in metals conservation. Our proof-of-concept experiments allowed us to improve our procedures for the next phase of development. Students and faculty disseminated their findings at four separate archaeological and conservation conferences where results could be disseminated to different professional communities. Team members also prepared blog posts about their experiments targeted to public audiences. The project established a sustained collaborative relationship between the Departments of Social Sciences, Materials Science and Engineering, and Chemical Engineering at Michigan Technological University. Project scientists also developed professional connections with practicing conservators for future collaborations.

EXTRACTION xtraction is a process whereby a mixture of several substances in the liquid phase is at least partially separated upon addition of a liquid solvent in which E the original substances have different solubilities. When some of the original substances are solids, the process is called leaching. In a sense, the role of solvent in extraction is analogous to the role of enthalpy in distillation. The solvent-rich phase is called the extract, and the solvent-poor phase is called the raffinate. A high degree of separation may be achieved with several extraction stages in series, particularly in countercurrent flow. crystallization, or adsorption sometimes are equally possible. Differences in solubility, and hence of separability by extraction, are associated with differences in chemical structure, whereas differences in vapor pressure are the basis of separation by distillation. Extraction often is effective at near-ambient temperatures, a valuable feature in the separation of thermally unstable natural mixtures or pharmaceutical substances such as penicillin. The simplest separation by extraction involves two substances and a solvent. Equilibria in such cases are represented conveniently on triangular diagrams, either equilateral or right-angled, as for example on Figures 14.1 and 14.2. Equivalent representations on rectangular coordinates also are shown. Equilibria between any number of substances are representable in terms of activity coefficient correlations such as the UNlQUAC or NRTL. In theory, these correlations involve only parameters that are derivable from measurements on binary mixtures, but in practice the resulting accuracy may be poor and some multicomponent equilibrium measurements also should be used to find the parameters. Finding the parameters of these equations is a complex enough operation to require the use of a computer. An extensive compilation of equilibrium diagrams and UNlQUAC and NRTL parameters is that of Sorensen and Ark (1979-1980). Extensive bibliographies have been compiled by Wisniak and Tamir (1 980-198 1). The highest degree of separation with a minimum of Processes of separation by extraction, distillation, On a ternary equilibrium diagram like that of Figure 14.1, the limits of mutual solubilities are marked by the binodal curve and the compositions of phases in equilibrium by tielines. The region within the dome is two-phase and that outside is one-phase. The most common systems are those with one pair (Type I, Fig. 14.1) and two pairs (Type 11, Fig. 14.4) of partially miscible substances. For instance, of the approximately lo00 sets of data collected and analyzed by Sorensen and Arlt (1979), 75% are Type I and 20% are Type 11. The remaining small percentage of systems exhibit a considerable variety of behaviors, a few of which appear in Figure 14.4. As some of these examples show, the effect of temperature on phase behavior of liquids often is very pronounced. Both equilateral and right triangular diagrams have the property that the compositions of mixtures of all proportions of two mixtures appear on the straight line connecting the original solvent is attained with a series of countercurrent stages. Such an assembly of mixing and separating equipment is represented in Figure 14.3(a). and more schematically in Figure 14.3(b). In the laboratory, the performance of a continuous countercurrent extractor can be simulated with a series of batch operations in separatov funnels, as in Figure 14.3(c). As the number of operations increases horizontally, the terminal concentrations E, and R3 approach asymptotically those obtained in continuous equipment. Various kinds of more sophisticated continuous equipment also are widely used in laboratories; some are described by Lo et a/. (1983, pp, 497-506). Laboratory work is of particular importance for complex mixtures whose equilibrium relations are not known and for which stage requirements cannot be calculated. In mixer-separators the contact times can be made long enough for any desired approach to equilibrium, but 80-90% efficiencies are economically justifiable. If five stages are required to duplicate the performance of four equilibrium stages, the stage efficiency is 80%. Since mixer-separator assemblies take much floor space, they usually are employed in batteries of at most four or five units. A large variety of more compact equipment is being used. The simplest in concept are various kinds of tower arrangements. The relations between their dimensions, the operating conditions, and the equivalent number of stages are the key information. Calculations of the relations between the input and output amounts and compositions and the number of extraction stages are based on material balances and equilibrium relations. Knowledge of efficiencies and capacities of the equipment then is applied to find its actual size and configuration. Since extraction processes usually are performed under adiabatic and isothermal conditions, in this respect the design problem is simpler than for thermal separations where enthalpy balances also are involved. On the other hand, the design is complicated by the fact that extraction is feasible only of nonideal liquid mixtures. Consequently, the activity coefficient behaviors of two liquid phases must be taken into account or direct equilibrium data must be available. mixtures. Moreover, the relative amounts of the original mixtures corresponding to an overall composition may be found from ratios of Line segments. Thus, on the figure of Example 14.2, the amounts of extract and raffinate corresponding to an overall composition M are in the ratio E , / R N = M R N / E , M. Experimental data on only 26 quaternary systems were found by Sorensen and Arlt (1979), and none of more complex systems, although a few scattered measurements do appear in the literature. Graphical representation of quaternary systems is possible but awkward, so that their behavior usually is analyzed with equations. To a limited degree of accuracy, the phase behavior of complex mixtures can be predicted from measurements on binary mixtures, and considerably better when some ternary measurements also are available. The data are correlated as activity coefficients by means of the UNIQUAC or NRTL equations. The basic principle of application is that at equilibrium the activity of each component is the same in both phases. In terms of activity coefficients this 459

This work reports the extraction of ginger (Zingiber officinale Roscoe) roots using sub and supercritical CO 2 and compressed propane as solvents. Antioxidant activity effect and phenolic content were evaluated on the extracts obtained. The extractions were performed in a laboratory scale unit at pressures of 8.0 MPa, 16.5 MPa and 25.0 MPa using CO 2 and 3.0 MPa, 6.5 MPa and 10.0 MPa using propane, and at 293.15 K, 313.15 K and 333.15 K for both solvents. The operating conditions tested achieved a maximum yield of 3.21 wt% for the CO 2 extraction and 2.75 wt% for the extraction using propane as solvent. When CO 2 was used as solvent, the pressure and temperature presented significant effect on the extraction yield. When propane was used, the most important variable was the pressure that presented a positive effect on the extraction yield. The chemical profiles were determined by gas chromatography and were similar for the two solvents, in which the main compounds were ␣-zingiberene, ␤-sesquiphellandrene, ␣-farnesene, geranial, ␤-bisabolene and ␤-eudesmol. The antioxidant activity assays were performed on the extracts obtained using the phosphomolybdenum reducing method. The extracts obtained using supercritical CO 2 and compressed propane presented antioxidant effects. The highest antioxidant activity (931.67 ± 2.51 mg of ␣-tocopherol/g of extract) was found for extracts obtained using supercritical CO 2 as solvent at 313.15 K and 16.5 MPa.

Objective: The purpose of the study is to optimize supercritical fluid extraction (SFE) conditions for the flavonoids from the seeds of Buchanania lanzan Spreng. followed by quantitative determination of the antioxidant ability of the supercritical fluid (SCF) extract. Methods: The conditions optimized for supercritical fluid extraction (SFE) were temperature, pressure, carbon dioxide (CO2 Results: The optimum supercritical fluid extraction conditions were temperature 35 °C, pressure 19.61 MPa, carbon dioxide flow rate 3 ml/min and co-solvent 5.66 %. The extraction yield obtained was 20.50±0.47 %. The polyphenolic content was 52.14±0.7 mg Gallic acid equivalents (GAE)/g extract. EC) flow rate and co-solvent percentage. High-performance liquid chromatography (HPLC) method was used to determine the flavonoid content at each condition for optimization. Chromatographic conditions were mobile phase–Methanol: Acetonitrile: Orthophosphoric acid: Acetic acid: Water (200:100:10:10:200 v/v), flow rate–1 ml/min, column–Kromasil C18, 250 x 4.6 mm and detection was done in PDA range. Quantitative estimation of polyphenols was done spectrophotometrically. In vitro antioxidant ability of the extract was checked using free radical scavenging activity by 1, 1–Diphenyl–2–picrylhydrazyl (DPPH) assay and ferric reducing power (FRAP) assay. 50 Conclusion: Supercritical fluid extraction (SFE) technique could be used as an alternative technique for obtaining the maximum yield of flavonoids from the seeds of Buchanania lanzan. The results showed that the supercritical fluid (SCF) extracts exhibited good antioxidant activity which could be due to the presence of polyphenols and flavonoids value for free radical scavenging activity was 124.58±1.6 µg/ml, and ferric reducing capacity was 456.06±5.61 µg/ml.

Experiments involving the supercritical extraction of bitumen using various solvent mixtures were carried out in a 2-l batch autoclave to determine the effect of modifier type and concentration on deasphalted oil (DAO) yield and quality. Athabasca bitumen was used as the feedstock and n-pentane was used as the primary solvent for extraction. Acetone, toluene, methanol and ethyl acetate were each added to n-pentane as modifiers in different concentrations to form the solvent mixtures. Extraction temperatures and pressures were maintained at around 200°C and 1100 psi to achieve supercritical conditions for solvents, and the solvent-to-feed volume ratio was kept around 6.5. Higher DAO yields were obtained with increasing modifier concentrations in n-pentane. DAO yields ranged from 79 to 92 wt.% of the bitumen, with n-pentane/toluene mixtures providing the highest yields and n-pentane/methanol mixtures producing the lowest. Increases in DAO yield were accompanied by higher nickel, vanadium, nitrogen, sulfur and microcarbon residue content in DAO. Moreover, it was found that n-pentane/methanol and n-pentane/acetone solvent mixtures had lower selectivities for metals impurities than the other modifiers, while n-pentane/toluene had the highest selectivities.

"En este trabajo se presentó la extracción de aceite esencial y pectina a partir dela cascara de naranja (Citrus sinensis) como un proceso integral. Se realizó el proceso de extracción utilizando un simulador comercial adaptandose al proceso real. Se realizaron pruebas experimentales con un kilogramo de cáscara de naranja procesado a las mismas condiciones de la simulación con el fin de comparar los rendimientos obtenidos, logrando una concordancia aceptable. Posteriormente se escaló el proceso a una tonelada. Como resultado no solo se demuestran las ventajas del proceso integral, sino también la posibilidad de su implementación a nivel industrial. Se concluye ademas que las técnicas de simulación son una herramienta poderosa que permite minimizar tiempo,costos y experimentación en el diseño de procesos como los de extracción de aceite esencial y pectina"

In this study, the supercritical carbon dioxide extraction of essential oils from plants which contain secretory ducts as essential oil reservoirs was investigated and modelled. Supercritical carbon dioxide extraction of essential oils from Asteraceae family species, marigold and chamomile, indicated that particle size had no significant influence on the extraction rate in two outermost cases: fine milled plant material and plant material cut to particle length of 5 mm. This confirmed previously reported phenomenon that in some cases particle size had no influence on the rate of supercritical extraction process. In order to explain this behavior, the mathematical model which took into consideration the phenomena occurring on the secretory duct scale, was developed and applied to simulate experimental data of marigold and chamomile supercritical carbon dioxide extraction. Proposed model was also applied to the literature experimental data of fennel fruit supercritical fluid extraction where the same phenomenon had been observed. To obtain information regarding secretory structure, scanning electron microscopy investigation of the plant material was performed. Very good agreement of the model results and experimental data in the case of different plant species, extraction conditions and particle sizes, confirmed the basic hypothesis of the model.

Stevia rebaudiana Bertoni contains glycosides, which are insoluble in carbon dioxide and soluble in mixtures of carbon dioxide and a polar solvent. The purpose of this work was to study the supercritical fluid extraction of these glycosides from stevia leaves using a two-step process: (i) CO 2 extraction at 200 bar and 30°C, and (ii) CO 2 þ water extraction. The chemical compositions of the extracts were analyzed by GC-FID, GC-MS, TLC and HPLC. The overall extraction curves for the system stevia þ CO 2 had the typical shape and were successfully described by the Sovov a aÕs model. Approximately 72% of the CO 2 -soluble compounds were recovered and the major compound was austroinulin. The system stevia þ CO 2 þ water behaved as expected at 10 and 16°C and 120 and 250 bar but its behavior was unusual at 30°C and 250 bar. The process removed approximately 50% of the original stevioside and about 72% of the rebaudioside A.

Saponins are surfactants that reduce the surface tension of aqueous solutions, besides having pharmacological actions. In order to extract and fractionate saponins from Pfaffia glomerata roots and Hebanthe eriantha roots using supercritical technology, fractionated extracts were obtained from a sequential process in fixed bed using supercritical CO 2 (scCO 2 ), ethanol, and water as solvents. All extractions were carried out in four sequential steps, at 50 • C and 300 bar. In the first step, pure scCO 2 was used as solvent, while (a) scCO 2 /etanol (70:30, w/w); (b) ethanol, and (c) ethanol/water (70:30, v/v) were used as solvents in the three subsequent steps. The extracts were analyzed by thin layer chromatography (TLC) and surface tension. The extraction yields of the four steps were 0.16, 0.55, 1.00, and 6.90% for P. glomerata roots, and 0.17, 0.58, 0.89, and 28% for H. eriantha roots, showing a predominance of high polarity compounds in these species. TLC analysis showed that the extraction process was selective according to the polarity of the solvent, and provided extracts containing different saponins, except for scCO 2 extraction. The extracts from the extraction using ethanol + scCO 2 (Step 2) showed the greatest ability to reduce the surface tension of water from 72 mN m −1 (pure water) to 25 mN m −1 , suggesting that this step was the best for extraction of less polar saponins in the extracts. The critical micelle concentration (CMC) values were approximately 2 and 8 g L −1 for P. glomerata and H. Eriantha, respectively. These results confirmed the efficacy of the extraction process under study. (F.A. Cabral).

An interdisciplinary team of students from Michigan Technological University completed a series of tests using Supercritical Carbon Dioxide (SC-C02) to extract water and volatile compounds from samples of corroded archaeological iron artifacts. Test samples were then cracked and examined using backscatter SEM. Qualitative visual inspection showed that pores and microfissures were clear and opened after SC-C02 extraction. Another SC-CO2 treatment then impregnated the test objects with an environmentally-benign polymer (Acryloid/ParaloidTM B-72) to consolidate fragile structures and seal objects against future water absorption. Following treatment, these samples were also cracked and examined with SEM. Chemical traces of the polymer demonstrated the complete diffusion of the B72 into the pores and microfissures of the sample. These tests were paralleled by the design and execution of traditional conservation plans for twenty ferrous metal artifacts. The project team developed essential comparative perspectives on existing techniques, while being engaged in considerations of professional ethics, practicality, and economic value.
This study showed that the emerging application of Supercritical Fluid (SCF) Extraction can be used to rapidly stabilize batches of corroded ferrous metal artifacts, including cast and wrought iron and steel, as well as composite artifacts. This will allow labs to avoid or safely delay traditional electrochemical techniques that can require months of expert treatment. This technique works as a batch operation, allowing groups of small artifacts to be quickly stabilized and consolidated, potentially even in field settings. The process may also be tailored to treat objects from sites with soil contamination or materials from heritage collections, where potentially hazardous chemicals are also extracted during dewatering. While critically important questions remain to be addressed before the technique can be made systematically operational, particularly those surrounding chloride salts, the technique has tremendous potential to improve best practices in metals conservation. Our proof-of-concept experiments allowed us to improve our procedures for the next phase of development.
Students and faculty disseminated their findings at four separate archaeological and conservation conferences where results could be disseminated to different professional communities. Team members also prepared blog posts about their experiments targeted to public audiences. The project established a sustained collaborative relationship between the Departments of Social Sciences, Materials Science and Engineering, and Chemical Engineering at Michigan Technological University. Project scientists also developed professional connections with practicing conservators for future collaborations.

Haematoccocus pluvialis is the main natural source of astaxanthin. Extraction with SuperCritical (SC) carbon dioxide (CO 2 ) is an interesting choice for astaxanthin recovery because the medium-to-high yield, high selectivity for high-value compounds, and avoidance of thermal damage to labile bioactive compounds. In the case of heavy and/polar compounds such as astaxanthin, yield can be increased using GRAS polar cosolvents or modifiers such as ethanol. For this reason SC CO 2 extraction was carried out at 313-343 K and 30-55 MPa using pure or ethanol-modified (4 or 8% v/v) CO 2 . Response surface analysis showed a positive effect of pressure and mild negative effect of temperature in the astaxanthin recovery. Besides, added ethanol improves astaxanthin recovery but up to a maximal using 4.5% (v/v). The model of Sovova fitted well experimental data for astaxanthin extraction using pure and ethanol-modified CO 2 under selected experimental conditions. Best-fitting model parameters suggest that improvement in astaxanthin recovery when adding ethanol is due to its large positive effect on mass transfer within unbroken H. pluvialis cysts rather than in the solubility in SC CO 2 or solute partition between SC CO 2 and pretreated cysts.

A B S T R A C T Nowadays jojoba (Simmondsia chinensis) wax production with an industrial or energetic objective can be focused on a bio-refinery processing perspective where the fatty alcohols are the main products and fatty acid methyl esters (FAMEs) the by-products. To date, jojoba wax methanolysis has been performed using catalytic processes where long reaction times and downstream separation and purification steps are required. However, jojoba wax transesterification using a non-catalytic process such as the supercritical methanolysis has not been reported yet. The yield of jojoba fatty alcohols and FAMEs was determined in the temperature and reaction time ranges of 250–350 °C (12–42 MPa) and 15–90 min, respectively, at a methanol-to-wax molar ratio of 15:1. The maximum experimental yield of fatty alcohols and FAMEs (95.3 and 95.4 mol%, respectively) was reached at 350 °C after 90 min of reaction. Therefore, no thermal decomposition of jojoba alcohols and FAMEs was observed under the most severe experimental reaction conditions studied, which can be explained by the highly monounsaturated nature of the products obtained and the protective antioxidant effect of β-sitosterol present in jojoba wax. The rate constants obtained for this process were: 1 × 10 −5 , 3×10 −5 , 1.1 × 10 −4 , 4.1 × 10 −4 and 6.5 × 10 −4 s −1 , at 250, 275, 300, 325 and 350 °C, respectively, with an activation energy of 115.5 kJ/mol. In addition, response surface methodology was used to determine the optimal reaction conditions that maximize the yield of fatty alcohols and FAMEs: 338.9 °C and 90 min to obtain yields of 96.8 mol% and 97.0 mol%, respectively. Thus, it can be concluded that jojoba wax methanolysis under non-catalytic supercritical conditions is an alternative way to obtain high-added value compounds and biodiesel.

In this study, supercritical fluid extraction has been successfully applied to a sequential fractionation of fatty acids and polyphenols from wine wastes (2 different vitis vinifera grapes). To this aim, in a 1st step just fatty acids were extracted and in a 2nd one the polyphenols. The variables that affected to the extraction efficiency were separately
optimized in both steps following an experimental design approach. The effect of extraction temperature flow, pressure, and time were thoroughly evaluated for the extraction of fatty acids, whereas the addition of methanol was also considered in the case of the polyphenols extraction. A quantitative extraction with high efficiency was achieved at a very short time and low temperatures. Concerning quantification, fatty acids were determined by means of gas chromatography coupled to mass spectrometry after a derivatization step, whereas the polyphenols were analyzed by means of high performance liquid chromatography coupled to tandem mass spectrometry and the Folin–Ciocalteu method.

Supercritical fluid extraction is an interesting alternative for the fractionation of essential oils, in order to obtain concentrates or compounds of interest. This technique requires information about the distribution of the components of the mixture between the phases present at different conditions of pressure, temperature and composition. In this work equilibrium information of three bioactive essential oils (Salvia officinalis, Mentha piperita and Tagetes minuta oil) with near-critical and supercritical carbon dioxide is measured using a dynamic apparatus in the range of 313-323 K and 60-120 bar. The distribution of monoterpenes, oxygenated terpenes and sesquiterpenes in the extract phase is determined by gas chromatography in order to explore the best operating conditions for the separation of the fractions or compounds with higher biocidal activity. Predictive calculations are performed using the group contribution equation of state (GC-EOS) and compared with the experimental data.

Macrocyclic ligands were designed according to the principle of ion recognition, synthesized and tested in their capability to extract AuIII. Different from other complexants which require ligand exchange prior to complexation, the reported ligands bind the complexes AuCl3 and AuCl4−. With a sufficiently sized macrocyclic cavity, hydrophobic calix[6]arenes derivatized at the “lower rim’ were employed for that purpose. Their ligating functionalities contain pyridino, amide or thioamide groups in order to achieve electron donor-acceptor and electrostatic host-guest interactions. We report the synthesis route and results on extraction, selectivity, kinetics and back-extraction and compare with commercial extractants. Quantitative extraction from hydrochloric acid solutions was achieved as well as over 99% recovery in back-extraction in one step each. Data on the selectivity over base metals, which are representative for the matrix in gold ores are provided. The ligands are powerful extractants for AuIII and show fast complexation kinetics. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)

Grape seeds are a waste by-product obtained after wine or juice making and present a good source of functional compounds, such as polyphenols. Extraction is a very important step for later use of phenolic components. The effect of different temperatures and solidliquid ratios on the solid-liquid extraction yield of total polyphenols and the effect of four classes of particle size on the extraction kinetics of total polyphenols with 50% of aqueous ethanol were studied. Temperature, solid-liquid ratio and milling degree had positive influence on extraction rate and extent of extraction. The 1.47-6.68% of total polyphenols per dry matter of grape seeds was extracted during 200 min. Extraction kinetics was estimated using non-experimental two-parameter equation-modified Peleg's model. Results showed a good prediction of Peleg's model for extraction kinetics in all experiments (q > 0.994), which gave the possibility for estimation of initial rate and extent of solid-liquid extraction.

Supercritical carbon dioxide extraction investigated as a green technology for the extraction of antioxi-dant compounds from Crocus sativus petals. A Box-Behnken design (BBD) was employed to optimize the extraction temperature (40-80 • C), extraction time (20-60 min), and extraction pressure (90-180 bar). Optimization process using response surface methodology carried out and 3D response surfaces were plotted from the mathematical model. The optimum conditions of extraction were estimated to be temperature of 62 • C, time of 47 min and pressure of 164 bar. Extraction using these optimized conditions achieved the best total phenolic content (1423 mg/100 g), total flavonoid content (180 mg/100 g), total anthocyanin content (103.4 mg/100 g), 2, 2-diphenyl-1-picrylhydrazyl free radical-scavenging activity (74.5%) and ferric reducing/antioxidant power value (3.9 mM). The experimental values agreed with those predicted, thus representing fitness of the model employed and the success of BBD in optimizing the extraction conditions. Principal components analysis (PCA) provided a better understanding of interactions between characteristics of extracted antioxidants.

syzygium alternifolium is a member of Myrtacea family, is used for curing various ailments according to relevant traditional approaches on the plant drugs therapy. The present study was carried out to evaluate the antimicrobial properties of the methanolic, petroleum ether, ethylacetate, chloroform, benzene extracts of syzygium alternifolium leaves on certain pathogens. The methanolic, benzene, and petroleum ether showed significant results whereas the chloroform extract did not show any antimicrobial activity on any pathogen, also all these extracts were in significant on aspergillus niger. It was observed that as the disc dosage level increases the inhibitory effect also increased. These findings justify the use of the plants for the study of antibacterial activity. Their toxicity level and antimicrobial activity with different extraction solvents should further be studied to use them as potential sources and templates for the synthesis of drugs to control infectious diseases.

The Saar basin contains bituminous coals (high volatile A and B), Five coals of Westphalian and Stephanian age with distinctly varying maceral compositions were analysed by Soxhlet extraction and supercritical extraction with different solvents and microscopically. From the data obtained it is concluded that the oldest coals have a potential for oil generation, whereas the younger coals do not. This conclusion is explained by varying liptinite contents and varying adsorption capacities of different vitrinite macerals for bitumen.

An interdisciplinary team of students from Michigan Technological University completed a series of tests using Supercritical Carbon Dioxide (SC-C02) to extract water and volatile compounds from samples of corroded archaeological iron artifacts. Test samples were then cracked and examined using backscatter SEM. Qualitative visual inspection showed that pores and microfissures were clear and opened after SC-C02 extraction. Another SC-CO2 treatment then impregnated the test objects with an environmentally-benign polymer (Acryloid/Paraloid TM B-72) to consolidate fragile structures and seal objects against future water absorption. Following treatment, these samples were also cracked and examined with SEM. Chemical traces of the polymer demonstrated the complete diffusion of the B72 into the pores and microfissures of the sample. These tests were paralleled by the design and execution of traditional conservation plans for twenty ferrous metal artifacts. The project team developed essential comparative perspectives on existing techniques, while being engaged in considerations of professional ethics, practicality, and economic value. This study showed that the emerging application of Supercritical Fluid (SCF) Extraction can be used to rapidly stabilize batches of corroded ferrous metal artifacts, including cast and wrought iron and steel, as well as composite artifacts. This will allow labs to avoid or safely delay traditional electrochemical techniques that can require months of expert treatment. This technique works as a batch operation, allowing groups of small artifacts to be quickly stabilized and consolidated, potentially even in field settings. The process may also be tailored to treat objects from sites with soil contamination or materials from heritage collections, where potentially hazardous chemicals are also extracted during dewatering. While critically important questions remain to be addressed before the technique can be made systematically operational, particularly those surrounding chloride salts, the technique has tremendous potential to improve best practices in metals conservation. Our proof-of-concept experiments allowed us to improve our procedures for the next phase of development. Students and faculty disseminated their findings at four separate archaeological and conservation conferences where results could be disseminated to different professional communities. Team members also prepared blog posts about their experiments targeted to public audiences. The project established a sustained collaborative relationship between the Departments of Social Sciences, Materials Science and Engineering, and Chemical Engineering at Michigan Technological University. Project scientists also developed professional connections with practicing conservators for future collaborations.

he Instituto Colombiano del Petróleo (ICP), has implemented a methodology for separating vacuum residue fractions using the technique of supercritical fluid extraction at the pilot scale. The present study evaluates the efficiency of extraction of fractions of a typical vacuum residue in the Barrancabermeja refinery. The extraction test was carried out with n-hexane under supercritical conditions of temperature and pressure of the 265ºC in the range from 450 to 1250 psi, respectively. Finally, each of the fractions were analyzed for their density, viscosity, sulfur content, Conradson Carbon Residue (CCR) content, SARA compositional analysis, and metals.

Supercritical fluid extraction (SFE) with CO 2 of the volatile oil from fennel (Foeniculum vulgare ssp. piperitum (Ucria) Coutinho) was carried out at temperatures of 40 and 50°C and pressures of 90 and 100 bar in a flow apparatus using a two-stage fractional separation technique. The best conditions for extraction (pressure P = 90 bar, and temperature, T = 40°C) and separation (P = 80 bar, T = −10°C for the first separator and P = 20 bar, T = −10°C for the second) were used to assess the effect of different mean particle size and flow rate of CO 2 . The yield of the extraction and composition of the volatile oil were compared with those obtained by hydrodistillation. The study showed that the particle size of the fruits does not practically affect either the yield or the composition of the oil, with the exception of the presence of a small amount of waxes in the volatile oil extracted by SFE from the fruits presenting the highest particle size. Further, increasing of the flow rate of CO 2 does not seem to influence the composition, although it increases the rate of extraction, thus leading to a decrease of the extraction time. The fennel oil was analysed by gas chromatography (GC) and chromatography-mass spectrometry (GC-MS). The main compounds identified in the oils were fenchone (17%), estragol (21%) and (E)-anethole (43%).

A theoretical method based on combining the virial expansion and fluctuation theory for calculating the chemical potential of a solute in a supercritical fluid is presented. The method is compared to literature results from Monte Carlo simulations based the Widom method for evaluating the chemical potential. For one-center and two-center Lennard Jones (2CLJ) potential models, the average difference from simulated results for the chemical potential is about 5% at densities up to twice the critical density. The method requires virial coefficients up to C(T) (the third) to achieve this level of accuracy. Correlations based on corresponding states principles for the prediction of B(T) [AIChE J. 20 (1974) 263; AIChE J. 21 (1975) 827; AIChE J. 24 (1978) 1978] and C(T) [AIChE J. 29 (1983) 107] are used to estimate these virial coefficients. A comparison with experimentally determined values for naphthalene in carbon dioxide shows the estimates to be accurate at typical supercritical extraction conditions. These correlations are then used to determine virial coefficients and chemical potentials for naphthalene, benzoic acid and phenanthrene in carbon dioxide at several different state conditions for which solubility data exist. The theoretical results are compared to chemical potentials obtained from experimental solubility data. The method is found to be accurate, tractable and systematically improvable through the inclusion of higher order terms in the virial expansion.

The correlation of experimental data of solubility of solids in supercritical solvents using equations of state Ž . Ž EOS is a well known and relatively simple approach. Normally, cubic EOS with quadratic mixing rules or . modifications of them may be satisfactorily used for fitting purposes and much research is being done in order to improve the predictive capabilities of present models. Usually, models are assessed in terms of goodness of fit of solubility data; however, in spite of the pressure and temperature conditions of supercritical extraction processes, the critical behavior predicted by models used for correlating data is rarely analyzed. In this work, the analysis of critical lines in the presence of solid-fluid equilibria is proposed as an additional test of models because it gives the correct topology of predicted phase diagrams. It is shown that multiphase equilibria is normally predicted in ranges of interest for supercritical extraction. Multiphase equilibria is not obvious when a stability analysis is ignored, inducing possible modeling pitfalls. In addition, multiphase behavior affects the prediction of stable solid-fluid equilibria. Examples and phase diagrams are discussed in detail using a modified van der Waals EOS and quadratic mixing rules. q

The partition coefficients of N, N-dimethylacetamide (N,N-DMA) between the water and the supercritical and near-critical carbon dioxide (CO 2 ) phases were measured in the temperature range of 298.15-328.15 K and the pressure range of 8.3-24.1 MPa. The measurements were carried out in a 56 ml vessel by contacting the carbon dioxide and the aqueous phases. The partition coefficients of N,N-DMA increased from 0.05 to 0.150 with increasing pressure at a constant temperature and increased with temperature at a constant density. The bubble point pressures of N,N-DMA-CO 2 mixtures were measured at 298.15 K, 308.15 K and 318.15 K and were found to increase with increasing mole fraction of CO 2 . The partition coefficients were modeled using the Peng-Robinson Equation of State (PREOS) combined with modified van der Waals mixing rule. The binary interaction parameters for the CO 2 -H 2 O pair were taken from the literature and were regressed for CO 2 -N,N-DMA and H 2 O-N,N-DMA pairs by fitting partition coefficients data. The binary interaction parameter for CO 2 -N,N-DMA pair was found to depend linearly on temperature. The bubble point pressures of N,N-DMA and CO 2 were also measured and could be predicted fairly well using the regressed binary interaction parameters.

1 Laboratoire de Botanique et de Biologie végétale, Université de Tunis, Tunisia; E-mail: hanen_marzouki7@yahoo.fr 2 Dipartimento di Scienze Chimiche, Università degli Studi di Cagliari, Cittadella Universitaria di Monserrato, SS 554, Km 4.500, 09042 Cagliari, Italy; E-...

In general, dewatering of plant tissues (such as vegetables) and food materials is achieved by heating. In order to prevent the degradation of biologically active components in plant materials, the dewatering process should be carried out at low temperature. Therefore, in the present study, we attempted to develop a simple protocol for dewatering cryo-preserved plant tissues using liquefied dimethyl ether (DME). Prior to dewatering from frozen plant materials, we have examined the efficiency of liquefied DME for cryogenic removal of water from ice cubes. Here, lemon peel residue (consisting of flavedo and albedo) was chosen as the model plant material for dewatering and concomitant extractions of water-soluble components such as ascorbate and citric acid and hydrophobic components, chiefly, essential oils (EOs). By focusing on the exploitation of unused resources after food processing, the juice extraction residues from lemon fruits (lemon peels) were used as the starting materials. The yield of vitamin C (VC) extracted from the peel tissues derived from a single lemon fruit exceeded the amount of VC found in the manually press-extracted juice from a single lemon fruit. The major components in DME-extracted crude lemon EOs were determined and quantified with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detector (GC-FID) to be limonene (40.4%, w/w), β-pinene (10.4%, w/w), and γ-terpinene (6.9 %, w/w).

This review provides an updated overview of the most important applications of supercritical fluids in the extraction of bioactive compounds from plant matrices. The main factors influencing the extraction yields, solubility, and manufacturing costs are described. Aspects concerning the operational processing in the extraction and fractionation are also discussed. The data compiled herein are focused on the extraction of essential oils, phenolic compounds, carotenoids, tocopherols, and tocotrienols.

Predictions of critical parameters and the Pitzer factor for three different group contribution methods are compared and used in correlative predictions of virial coefficients. These virial coefficients are then used to determine the chemical potential of a solute in supercritical carbon dioxide as a function only of the solute structure. Experimental chemical potentials are determined from measured solubility data and compared to calculated chemical potentials by using both experimental vapour pressures and vapour pressures estimated from the solute structure by group contribution methods. The group contribution method of Marrero and Gani is shown to best reproduce experimental solubility data with an average absolute relative deviation of 10.4% (" exact " experimental input data only yields an accuracy of 10.7% for the molecules studied here). The obtained accuracy for several common organic pollutants (naphthalene, benzoic acid, anthracene, phenanthrene, naphthol-2 and pyrene) suggests that the method is applicable for predictions on previously unmeasured systems as long as the molecule has fewer than 20 non-hydrogenic atoms and is relatively rigid.

New model for supercritical fluid extraction (SFE) of natural products is presented. Like other models based on the concept of broken and intact cells, it is particularly suited to fit experimental data as it almost independently simulates two extraction periods, the first one governed by phase equilibrium and the second one governed by internal diffusion in particles. Its new feature is a detailed description of the first extraction period where different types of phase equilibrium and solvent flow patterns are taken into account. A simplified approximate form of the model is used to analyse its properties and to estimate its parameters. The number of model parameters is, in dependence on the complexity of the extraction process, 1-3 for phase equilibrium, 2-3 for mass transfer and 1 for flow pattern. The model is versatile, but, as a consequence, more data are necessary than a single extraction curve to determine its parameters in the first period. The evaluation of model parameters from extraction curves is shown on data sets from literature.

This current study focuses on the modelling and optimization of supercritical fluid extraction of Quercus infectoria galls oil. In this case, response surface methodology (RSM) and artificial neural network (ANN) were applied for the modelling and prediction of extraction yield of galls oil. A 17-run Box-Behnken Design (BBD) was employed to statistically optimize the process parameters of SC-CO2 extraction of Quercus infectoria galls at a condition as follows: pressure (5000, 6000, 7000 Psi), temperature (40, 50, 60°C) and extraction time (30, 45, 60 min). The maximum yield of the extracted oil is1.12 % and the optimum conditions are at an extraction pressure of 5574 Psi; extraction temperature of 75°C and extraction time of 54 min. Under the optimal conditions, the experimental results agree with the predicted values obtained through analysis of variance (ANOVA). This indicates a successful response surface methodology and highly satisfactory goodness of fit of the model used. The analysis of experimental design for process optimization results demonstrates that temperature and extraction time are the main parameters that influence the oil extraction of Quercus infectoria.

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 (CO2). 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

Kinetics and selectivity of supercritical carbon dioxide (SC CO 2) extraction of Helichrysum italicum flowers were analyzed at pressures in the range of 10-20 MPa and temperatures of 40 • C and 60 • C (density of SC CO 2 from 290 to 841 kg/m 3) and also at 10 MPa and 40 • C using flowers with different moisture contents (10.5% and 28.4%). Increased moisture content of H. italicum flowers resulted in enchased solubility of solute enabling decrease of SC CO 2 consumption necessary for achieving desired extraction yield. The most abundant compounds in the supercritical extracts are sesquiterpenes and waxes while monoterpenes and sesquiterpenes are the main constituents of essential oil obtained by hydrodistillation. The optimal set of working parameters with respect to extraction yield, SC CO 2 consumption and chemical composition of extract were defined related to moisture content of raw material and SC CO 2 density.

Separating and purifying biological materials via supercritical fluid extraction and retrograde condensation (SFE/RC) have become viable alternatives to liquid  extraction and distillation. Although SFE has actually been in use since the late 1800s - - its first application being to dissolve solid compounds in gases--renewed interest in the process stems from supercritical fluids' impressive solvent powers. In combination with retrograde condensation (RC) - which has long been used in the petroleum and natural gas industries for recovering heavy hydrocarbons from oil - the two processes  are now sophisticated enough to be applied to biological separations on an industrial scale.