Kinetics Of Supercritical Fluid Extraction Research Articles

Chromatography-like propagation of water along raw material bed in supercritical fluid extraction

A chromatography-like propagation of water through the material bed was observed while performing supercritical fluid extraction of aroma plants having high moisture content. While parts of raw material bed placed at the inlet of the extraction vessel get dried after appropriate extraction time, the parts closer to the outlet not only stay wet but, in fact, gain more moisture than initial raw material. Presumably, water and other extractables with limited solubility in supercritical CO2, get re-adsorbed onto the plant material surface along the extraction column and then desorbed further on. If the effect is of general nature, it might be important for modeling kinetics of supercritical fluid extraction of non-volatile compounds.

Kinetic Study on Nannochloropsis Oculata's Lipid Extraction Using Supercritical CO2 and n-Hexane for Biodiesel Production.

Biodiesel as a renewable fuel has attracted increasing attention in recent years. Microalgae biomass is becoming an attractive raw material for producing biodiesel using supercritical CO2 (SC-CO2) as a safe and environmentally friendly technique with high efficiency for lipid extraction. In this study, the lipid of Nannochloropsis oculata was extracted under different conditions of SC-CO2 to assess the kinetics of supercritical fluid extraction. The effective parameters on lipid extraction, including temperature, pressure, and the existence of n-hexane as a co-solvent, were investigated. The results show that an increase in temperature at low or high pressures causes the kinetic constant of lipid extraction to decrease or increase, respectively. Also, an increase in pressure causes the kinetic constant of lipid extraction to increase at low or high temperatures. The most yield and the most kinetic constant value during extraction with pure CO2 are about 0.262 [g extracted lipid/g microalgal biomass] and 0.062 min–1, respectively, at the highest pressure and temperature (i.e., 550 bar and 75 °C). Using SC-CO2 laced with n-hexane increases both the final yield and the rate of lipid extraction. Also, it improves the quality of the biodiesel fuel through the extraction of unsaturated fatty acids with a concentration of almost two times more than saturated fatty acids. Additionally, results reveal that the effect of adding n-hexane to CO2 in lipid extraction would be more efficient by increasing the temperature and lowering the pressure.

A Simplified Method to Estimate Sc-CO2 Extraction of Bioactive Compounds from Different Matrices: Chili Pepper vs. Tomato By-Products

In the last few decades, the search for bioactive compounds or “target molecules” from natural sources or their by-products has become the most important application of the supercritical fluid extraction (SFE) process. In this context, the present research had two main objectives: (i) to verify the effectiveness of a two-step SFE process (namely, a preliminary Sc-CO2 extraction of carotenoids followed by the recovery of polyphenols by ethanol coupled with Sc-CO2) in order to obtain bioactive extracts from two widespread different matrices (chili pepper and tomato by-products), and (ii) to test the validity of the mathematical model proposed to describe the kinetics of SFE of carotenoids from different matrices, the knowledge of which is required also for the definition of the role played in the extraction process by the characteristics of the sample matrix. On the basis of the results obtained, it was possible to introduce a simplified kinetic model that was able to describe the time evolution of the extraction of bioactive compounds (mainly carotenoids and phenols) from different substrates. In particular, while both chili pepper and tomato were confirmed to be good sources of bioactive antioxidant compounds, the extraction process from chili pepper was faster than from tomato under identical operating conditions.

Modeling of the Kinetics of Supercritical Fluid Extraction of Lipids from Microalgae with Emphasis on Extract Desorption.

Microalgae contain valuable biologically active lipophilic substances such as omega-3 fatty acids and carotenoids. In contrast to the recovery of vegetable oils from seeds, where the extraction with supercritical CO2 is used as a mild and selective method, economically viable application of this method on similarly soluble oils from microalgae requires, in most cases, much higher pressure. This paper presents and verifies hypothesis that this difference is caused by high adsorption capacity of microalgae. Under the pressures usually applied in supercritical fluid extraction from plants, microalgae bind a large fraction of the extracted oil, while under extremely high CO2 pressures their adsorption capacity diminishes and the extraction rate depends on oil solubility in supercritical CO2. A mathematical model for the extraction from microalgae was derived and applied to literature data on the extraction kinetics in order to determine model parameters.

Supercritical Fluid Extraction of Vegetable Oils: Different Approaches to Modeling the Mass Transfer Kinetics

Supercritical fluid extraction (SFE) of vegetable oils is an alternative method to organic solvent (namely hexane) and mechanical extraction. To exploit the SFE technology at industrial scale, the process has to be optimized. An effective way to perform optimization is to resort to models that are capable to describe and simulate the SFE process. Plenty of models are available in the literature concerning the SFE of vegetable oils. Modeling the process in a semi-continuous extraction column (the bed of matrix to be extracted is stationary, the supercritical fluid moves continuously through it) requires an equipment model, the column model, and a particle model accounting for mass transfer mechanisms. Column models are quite established. Thus, to achieve a satisfactory description of the process, having a very effective particle model seems the key-point. In this work the SFE kinetics of seed oil (namely: grape seed oil) was modeled using different particle models: the broken and intact cells (BIC) and the shrinking core (SC) models, and the results were compared with literature values obtained utilizing the combined BIC-SC model. The three models not only allowed to fit satisfactorily the experimental data, but also resemble the real physical structure of the vegetable matrix and the actual elementary steps (mass transfer phenomena) which are expected to occur at the micro- scale level. As a whole, the present analysis provides an insight of interest for the audience concerned with modeling the SFE process.

Influence of the bed geometry on the kinetics of rosemary compounds extraction with supercritical CO2

Bed geometry plays an important role in supercritical fluid extraction kinetics. Thus, the objective of this study was to compare the overall extraction curves (OEC's) of rosemary compounds obtained in two beds of 1L each with different geometries (in terms of height to bed (HB) diameter (DB) ratios, HB/DB). A scale-up study was carried out maintaining the solvent mass to feed mass (S/F) ratio equal for both beds. Other process variables, such as bed porosity, apparent and true densities of the raw material, particle average size, temperature, pressure and time of extraction, were also maintained constant. The kinetic parameters were obtained by fitting the OEC to a spline model. The results revealed differences of mass transfer rates, mass ratios of solute in the fluid phase and yields of extract in the constant extraction rate period. The evaluation of the OEC's and kinetic parameters indicated that the bed with lower HB/DB ratio (HB/DB=2.7) was more favorable for obtaining rosemary extract. The kinetics of extraction of oxygenated monoterpenes (i.e., 1,8-cineole and camphor) and phenolic diterpenes (i.e., carnosic acid) were also different for both bed geometries. These behaviors suggest that the bed geometry presents a pronounced influence in the mass transport properties in supercritical media. Thus, in spite of the scale-up criterion be successful for several botanic matrices such as clove buds, sugarcane residue and grape seeds residue, the criterion applied in this study (maintaining a constant S/F ratio for a given time of extraction) was not suitable for this raw material.

Modeling of supercritical fluid extraction of flavonoids from Calycopteris floribunda leaves

AbstractThe aim of this study was to obtain flavonoids extracts from Calycopteris floribunda leaves using supercritical fluid extraction (SFE) with CO2 and a co-solvent. Pachypodol, a potential anticancer drug lead compound separated from the extracts, was examined. Classical organic solvent extraction (CE) with ethanol was performed to evaluate the high pressure method. HPLC analysis was introduced to interpret the differences between SFE and CE extracts in terms of antioxidant activity and the concentration of pachypodol. SFE kinetics and mathematical modeling of the overall extraction curves (OEC) were investigated. Evaluation of the models against experimental data showed that the Sovová model performs the best. The supercritical fluid extraction process was optimized using a central composite design (CCD), where temperature and pressure were adjusted. The optimal conditions of SFE were: pressure of 30 MPa and temperature of 35°C.

Supercritical fluid extracts from tamarillo (Solanum betaceum Sendtn) epicarp and its application as protectors against lipid oxidation of cooked beef meat

The possibility of using the tamarillo (Solanum betaceum (Cav.) Sendtn (syn. Cyphomandra betacea)) epicarp as source of compounds with antioxidant activity in cooked beef meat (CBM) was explored. Extracts from tamarillo by supercritical fluid extraction (SFE) and Soxhlet extraction (SE) were obtained. The SFE was performed using pure CO2 at different temperatures and pressures (40 and 50°C; 10, 20 and 30MPa) and CO2 added with ethanol (CO2/EtOH) as co-solvent (2, 5 and 8%, w/w). The SFE kinetics and mathematical modeling of the overall extraction curves (OEC) were also investigated. EtOH and hexane were used in the SE. The antioxidant activity (AA) of extracts was evaluated in CBM as well as the protection against lipid oxidation was determined by measuring lipid hydroperoxides (LHP) and thiobarbituric acid reactive species (TBARS). The extract obtained by SFE with CO2/EtOH (50°C/30MPa and 2% of EtOH) showed the highest AA. In SFE, the co-solvent addition improved considerably the AA and the extraction yield. The extracts obtained by SFE with CO2/EtOH showed a better AA compared with the synthetic antioxidant TBHQ. The highest yield values were achieved by SE with ethanol (7.7±0.4%) and by SFE with 5% EtOH (1.9±0.1%). The results indicate that extracts of tamarillo epicarp are a potential source of antioxidant compounds.

Supercritical fluid extraction of Agaricus brasiliensis: Antioxidant and antimicrobial activities

The objective of this study was to obtain extracts from the mushroom Agaricus brasiliensis using supercritical fluid extraction (SFE) with pure CO2 and with CO2 plus 2.5%, 5.0% and 10.0% (w/w) of ethanol as co-solvent. In order to evaluate the high-pressure method in terms of process yield, extract composition and biological activity, low-pressure methods, such as maceration with ethanol (Mac), Soxhlet (Sox) with different organic solvents, and hydrodistillation (HD), were also applied to obtain extracts. The SFE conditions were temperatures of 313.15K, 323.15K and 333.15K and pressures from 10 to 30MPa. The SFE kinetics was investigated through the overall extraction curve (OEC). The extracts obtained by Sox with water and ethanol showed the best results for the global extraction yield. The best conditions in the studied range to obtain high yields using pure CO2 resulted to be 30.0MPa and 323.15K. The antioxidant potential of the extracts was evaluated by the DPPH method and by the Folin–Ciocalteau method. Maceration extract presented low yield, but good results of antioxidant activity by DPPH assays and total phenolic. The antimicrobial activity of the extracts was also studied. The main identified compounds in the extracts were linoleic and palmitic acids.

Supercritical fluid extraction from spent coffee grounds and coffee husks: Antioxidant activity and effect of operational variables on extract composition

The present study describes the chemical composition and the antioxidant activity of spent coffee grounds and coffee husks extracts, obtained by supercritical fluid extraction (SFE) with CO2 and with CO2 and co-solvent. In order to evaluate the high pressure method in terms of process yield, extract composition and antioxidant activity, low pressure methods, such as ultrasound (UE) and soxhlet (SOX) with different organic solvents, were also applied to obtain the extracts. The conditions for the SFE were: temperatures of 313.15K, 323.15K and 333.15K and pressures from 100bar to 300bar. The SFE kinetics and the mathematical modeling of the overall extraction curves (OEC) were also investigated. The extracts obtained by LPE (low pressure extraction) with ethanol showed the best results for the global extraction yield (X0) when compared to SFE results. The best extraction yield was 15±2% for spent coffee grounds with ethanol and 3.1±04% for coffee husks. The antioxidant potential was evaluated by DPPH method, ABTS method and Folin–Ciocalteau method. The best antioxidant activity was showed by coffee husk extracts obtained by LPE. The quantification and the identification of the extracts were accomplished using HPLC analysis. The main compounds identified were caffeine and chlorogenic acid for the supercritical extracts from coffee husks.

Steps of supercritical fluid extraction of natural products and their characteristic times

Kinetics of supercritical fluid extraction (SFE) from plants is variable due to different micro-structure of plants and their parts, different properties of extracted substances and solvents, and different flow patterns in the extractor. Variety of published mathematical models for SFE of natural products corresponds to this diversification. This study presents simplified equations of extraction curves in terms of characteristic times of four single extraction steps: internal diffusion, external mass transfer, hypothetic equilibrium extraction without mass transfer resistance, and displacement of the solution from the extractor. Preliminary evaluation of experimental extraction curves using these equations facilitates the choice of proper detailed model for SFE and enables estimation of changes in the extraction kinetics with the changes in operation conditions and extraction geometry.

Bioactive extracts of orange ( Citrus sinensis L. Osbeck) pomace obtained by SFE and low pressure techniques: Mathematical modeling and extract composition

The objective of this study was to obtain orange ( Citrus sinensis L. Osbeck) pomace extract using supercritical fluid extraction (SFE) with CO 2 and with CO 2 and co-solvent. In order to evaluate the high pressure method in terms of process yield, extract composition and biological activity, low pressure methods were also applied to obtain orange extracts, such as ultrasound (UE) and soxhlet (SOX), with different organic solvents, and hydrodistillation (HD). The SFE conditions were temperatures of 313.15 K and 323.15 K and pressures from 100 to 300 bar. The SFE kinetics and mathematical modeling of the overall extraction curves (OEC) were also investigated. The antioxidant potential of the extracts was evaluated by the DPPH method, by the Folin–Ciocalteau method and by the β-carotene/linoleic acid bleaching method. The antimicrobial activity of the extracts was also studied. The main compounds identified were l-limonene, palmitic and oleic acids, n-butyl benzenesulfonamide and β-sitosterol.

Supercritical fluid extraction of fig leaf gourd seeds oil: Fatty acids composition and extraction kinetics

Fig leaf gourd ( Cucurbita ficifolia, Bouché) seeds oil was extracted in a Soxhlet apparatus (oil content of 43.5%) and by supercritical fluid extraction (SFE) in the temperature and pressure ranges of 308–318 K and 18–20 MPa, respectively. Both oil batches showed similar fatty acids compositions. Main fatty acids were ω6-linoleic acid (about 60%), palmitic acid (about 15%) and oleic acid (about 14%). The induction time was used to determine the oxidative stability, 4.2 and 8.3 h being obtained for SFE extracted oil and n-hexane extracted oil, respectively. Regarding the kinetics of supercritical fluid extraction, the Sovová’s model was selected and successfully applied to the description of the oil extraction curves. The fitted parameters, the overall mass transfer coefficient for the fluid phase, K f , and the overall mass transfer coefficient for the solid phase, K s , vary in the ranges 2.34–4.57 × 10 −2 s −1 and 1.73–4.34 × 10 −4 s −1, respectively. The free oil content for milled seeds, f k , was calculated as 61%. These parameters are consistent with those published for several other oils.

Extraction of Clove and Vetiver Oils with Supercritical Carbon Dioxide: Modeling and Simulation

The kinetics of supercritical fluid extraction (SFE) of clove and vetiver oils using carbon dioxide as solvent was studied, in order to establish an efficient method to predict extraction curves on large scale. The mass transfer model of Sovová was used to adjust the experimental SFE data, which were obtained at 100 bar and 35 °C for clove and 200 bar and 40 °C for vetiver, using extraction columns of different geometry and solvent flow rates. Some other process parameters, such as bed density and porosity, solvent to feed ratio and solvent velocity were kept constant from one experiment to another, in order to verify if the mass transfer coefficients adjusted by the model varied. The results show that the model of Sovová was able to predict an overall extraction curve for clove from data obtained with twenty times less raw material, since the mass transfer coefficients remained the same and the predicted curves were similar to the observed ones. For vetiver, the simulation was not as effective, probably due to the effects of transport properties on the process.

Kinetics of extraction of coal-tar pitch components with supercritical carbon dioxide

AbstractThe extraction of a coal-tar pitch with supercritical carbon dioxide was performed under optimal pressure, flow rate, and three different constant temperatures. The extraction kinetics was examined for each temperature and it was surprisingly found that the extraction rate of most components was governed by the first-order kinetics. It was assumed that this deviation from typical models of supercritical fluid extraction kinetics was caused by high pitch concentrations and low solubilities of the components.

Multicomponent Model To Describe Extraction of Ginger Oleoresin with Supercritical Carbon Dioxide

The kinetics of supercritical fluid extraction from vegetable raw materials in fixed beds was studied. The operational conditions used in the extraction of ginger oleoresin were pressures of 150, 200, and 250 bar, temperatures of 20, 30, and 40 °C, and a solvent flow rate of (5.6 ± 0.3) × 10-5 kg/s of CO2. A mathematical model obtained from the differential mass balance in the extraction bed was presented. This model considers the extract as a mixture of various groups of compounds, classified according to their chemical characteristics. The interfacial mass flux of each group of compounds was assumed to be described by one of the solutions of the logistic equation. The model was able to describe quite well the experimental results for ginger oleoresin extraction, considering the extract either as a single pseudocompound or as the sum of three groups of compounds. The overall extraction curves were fitted by both the proposed model and Sovová's model; the sum of square deviations was lower for the proposed model.

Kinetics of Supercritical Fluid Extraction

Kinetics of Supercritical Fluid Extraction

Supercritical CO 2 extraction of essential oil from orange peel; effect of the height of the bed

The influence of the height of the particle bed on the kinetics of supercritical fluid extraction (SFE) of essential oil from orange peel is analyzed in this article. Peel of dehydrated oranges of the satsuma and naveline cultivars was used. A series of experiments were designed wherein, for the same conditions, particle height varied widely. These experiments were also carried out on different scales with extraction volumes of 0.5 and 5 l. The results of the experiments were interpreted using Sovová's extended flow model as has been done in previous studies. The bibliography indicates that a number of phenomena may distort the process. One of these phenomena is the formation of masses of particles, due to their oil content, which increases resistance to mass transfer inside the particle. However, this phenomenon was barely noticeable in our experiments. Also, some reordering of the particles may take place due to the differing densities of the two phases and a certain drag effect exercised on the particles by the fluid. This situation can cause a lack of homogeneity in the fluid, further reducing the effectiveness of the process. In the experiments with the satsuma cultivar, where the bed-height range was broader, a base of diatomaceous earth was added in the extractor in order to reduce the lack of homogeneity in the fluid flow. Very similar behavior was found in all the experiments and we can, therefore, conclude that where there is homogeneous flow the height of the bed has very little effect, at least on the same scale of operation.

Effect of Entrained Helium on the Kinetics of Supercritical Fluid Extraction with Carbon Dioxide

Effect of Entrained Helium on the Kinetics of Supercritical Fluid Extraction with Carbon Dioxide

Rate and Extent of Supercritical Fluid Extraction of Cyclic Trimer from Poly (Ethylene Terephthalate) at Elevated Temperatures

Supercritical fluid extraction (SFE) and liquid solvent extraction procedures are compared for the determination of the cyclic trimer content of poly (ethylene terephthalate) film. SFE with carbon dioxide at 400 atm and temperatures up to 215°C is much more rapid, gives better repeatability, and yields extracts that are not contaminated with extracting solvent. The kinetics of SFE fit a model that presumes extraction is diffusion-limited. The variation of diffusion coefficients with temperature for cyclic trimer in PET shows Arrhenuis-type behavior.