Experimental investigation and modeling of the solubility of carvedilol in supercritical carbon dioxide

This study was aimed to measure the solubility of carvedilol in the temperature and pressure ranges of 308⿿338 K and 160 bar to 400 bar, respectively. In this direction, a homemade high pressure visual equilibrium cell was used to measure the solubility of carvedilol using a static method coupled with gravimetric technique. The results revealed that the carvedilol solubility was ranged between 1.12 ÿ 10^⿿5 and 5.01 ÿ 10^⿿3 based on the mole fraction (mole of carvedilol/mole of carvedilol + mole of CO₂) in this study as the temperature and pressure was changed. Finally, the results were correlated using four density-based semi-empirical correlations including Chrastil, Mendez⿿Santiago⿿Teja (MST), Bartle et al., and Kumar and Johnston (K-J) models. Results revealed that although the K-J model leads to the lowest average absolute relative deviation percent (AARD %) of 6.27%, but it could not be considered as the most accurate correlation since all the used four correlations introduces AARD % of about 6⿿10% which may be in the same range as the experimental error.     

Synthesis,characterization and structure effects of polyethylene glycol bis(2-isopropoxyethyl) dimethyl diphosphates on lanthanides extraction with supercritical carbon dioxide

Three new CO₂-philic open-chain organophosphorous chelating ligands, i.e. ethylene glycol bis(2-isopropoxyethyl) dimethyl diphosphate (EG2IPE), triethylene glycol bis(2-isopropoxyethyl) dimethyl diphosphate (EG3IPE), and tetraethylene glycol bis(2-isopropoxyethyl) dimethyl diphosphate (EG4IPE), were synthesized and characterized. Solubilities of these ligands in scCO₂ were determined at different combinations of temperature (313.15⿿333.15 K) and pressure (9⿿20 MPa), which generally showed considerable solubility in each case. These experimental data are in agreement with computed data via a semi-empirical model, in which the average absolute relative deviations lie in the range of 4.09⿿4.95%. The effect of these ligands on supercritical fluid extraction of selected rare earth metals (La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Gd³⁺, Er³⁺, and Yb³⁺) was investigated at 313.15 K and 20 MPa. The extraction efficiency of this system was found to increase in the order EG4IPE < EG3IPE < EG2IPE with a range from 55% to 79%. The rationale behind different selectivities toward these metals was also discussed in comparison to other traditional organophosphorous agents. A detailed experimental analysis of the complexation patterns by means of a combination of IR, ¹H NMR and ESI-MS has revealed that the interaction of ether oxygen group in EG4IPE with metals and the corresponding extraction mechanism.     

Extraction of jojoba seed oil using supercritical CO2+ethanol mixture in green and high-tech separation process

In this study, the extraction of jojoba seed oil obtained from jojoba seed using both supercritical CO₂ and supercritical CO₂+ethanol mixtures was investigated. The recovery of jojoba seed oil was performed in a green and high-tech separation process. The extraction operating was carried out at operating pressures of 25, 35 and 45 MPa, operating temperatures of 343 and 363 K, supercritical fluid flow rates of 3.33 × 10⁻⁸, 6.67 × 10⁻⁸ and 13.33 × 10⁻⁸ m³ s⁻¹, entrainer concentrations of 2, 4 and 8 vol.%, and average particle diameters of 4.1 × 10⁻⁴, 6.1 × 10⁻⁴, 8.6 × 10⁻⁴ and 1.2 × 10⁻³ m. It was found that a green chemical modifier such as ethanol could enhance the solubilities, initial extraction rate and extraction yield of jojoba seed oil from the seed matrix as compared to supercritical CO₂. In addition, it was found that the solubility, the initial extraction rate and the extraction yield depended on operating pressure and operating temperature, entrainer concentration, average particle size and supercritical solvent flow rate. The solubility of jojoba seed oil and initial extraction rate increased with temperature at the operating pressures of 35 and 45 MPa and decreased with increasing temperature at the operating pressure of 25 MPa. Furthermore, supercritical fluid extraction involved short extraction time and minimal usage of small amounts entrainer to the CO₂. About 80% of the total jojoba seed oil was extracted during the constant rate period at the pressure of 35 and 45 MPa.     

Extraction of low-molar-mass phenolics and lipophilic compounds from Pinus pinaster wood with compressed CO2

Near-supercritical and supercritical CO₂ was used to extract low-molar-mass phenolics and lipophilic compounds from Pinus pinaster wood. Extraction of samples containing sapwood and knotwood was carried out at 10⿿25 MPa and 30⿿50 °C to assess the influence of the operational conditions on the yields of total extracts and phenolics, as well as on the radical scavenging capacity of extracts. The use of ethanol as a co-solvent increased both the extraction yields and the concentration of phenolics in extracts. Operating under selected conditions (25 MPa, 50 °C, 10% ethanol), the extraction yield accounted for 4.1 wt% of the oven-dry wood. The extracts contained up to 7.6 g of phenolic compounds (measured as gallic acid equivalents) per 100 g extract, and showed one third of the radical scavenging capacity of Trolox. Native resin acids accounted for about 24 g per 100 g extracts, whereas flavonoids, lignans, stilbenes and juvabiones were found at lower proportions.     

Supercritical fluid extraction for quality control in beer industry

The knowledge of lipid composition in beer ingredients (malt and corn grits) and wort enables the quality control for final product. Since supercritical fluid extraction (SFE) is an efficient technique for preparing samples for analysis without the use of solvents, in this research Supercritical CO₂ (SC–CO₂) extraction was compared with the traditional Soxhlet one for a gravimetric determination of total lipids on malt and corn grits. The obtained extracts were then analyzed by HPLC-ELSD after TLC separation of triacylglycerols (TAGs) for lipids fingerprint. The extraction of total fats achieved by a 60-min run with pure CO₂ at 65 MPa and 100 °C was 43% higher than that produced by Soxhlet performed for 9 h for malt. The extraction was intermediate for SFE at 60 and 80 °C. The recovery of the TAG obtained with SC–CO₂ at 100 °C was statistically comparable with results from Soxhlet extraction.     

A shrinking core model and empirical kinetic approaches in supercritical CO2 extraction of safflower seed oil

Utilization of supercritical CO₂ in safflower seed extraction was performed using a semi-batch extractor. Different extraction parameters, such as 40–60 MPa pressure, 323–347 K temperature, 20–76 min time, and 1–3 mL/min CO₂ flow rate were applied. A two-stage experimental design application was performed in order to maximize the oil yield. First of all, a 3² factorial design was applied to estimate the effect of the main factors and their interactions. The second part of the experimental design was improved and accelerated using the steepest ascent method. Optimum extraction parameters were determined to be 50 MPa pressure, 347 K temperature and 76 min time at a constant CO₂ flow rate (3 mL/min) according to the 2² design. Under these conditions, the oil yield obtained was 39.42%, comparable with Soxhlet extraction (40%) for 8 h. Shrinking core and empirical kinetic models were applied in order to generalize the extraction process. The predicted data was compatible with the experimental data.     

Extraction of bioactive enriched fractions from Eruca sativa leaves by supercritical CO2 technology using different co-solvents

Supercritical fluid extraction from freeze-dried Eruca sativa leaves is assessed with the aim of studying the feasibility to obtain bioactive enriched fractions containing different classes of valuable compounds. Total extraction yields and compositions using pure CO₂ and CO₂ + selected co-solvents are compared. Overall extraction curves, fitted by the model of broken and intact cells developed by Sovová, are reported and the influence of the main parameters that affect the extraction process is analysed. The extract with the highest content in glucosinolates and phenols was collected at 30 MPa and 75 °C using 8% (w/w) of water with respect to the CO₂ flow rate, whereas the fraction richest in lipids was obtained using 8% (w/w) of ethanol as co-solvent at 45 °C and 30 MPa. A process including a first step with supercritical CO₂ extraction using water as co-solvent followed by a second step, where a fraction rich in lipids is extracted using ethanol as co-solvent, is proposed. SCCO₂ results are compared with Soxhlet and other methods that combine organic solvents with ultrasounds.     

Response surface optimization of Smyrnium cordifolium Boiss (SCB) oil extraction via supercritical carbon dioxide

In this study, the essential oil of aerial parts of a species of a plant called Smyrnium cordifolium Boiss (SCB) was extracted by supercritical CO₂. The essence was analyzed by the method of GC/MS. Design of experiments was carried out with response surface methodology by Minitab 16 software to optimize four operating variables of supercritical carbon dioxide (SC-CO₂) extraction (pressure, temperature, CO₂ flow rate and extraction dynamic time). This is the first report announcing optimization of the operation of supercritical extraction of SCB in laboratorial conditions. Optimizing process was done to achieve maximum yield extraction. Independent variables were dynamic time (t_d), pressure (P), temperature (T) and flow rate of SC-CO₂ (Q) in the range of 30–150 min, 10–30 MPa, 40–60 °C and 0.5–1.7 ml/min, respectively. The experimental optimal recovery of essential oil (0.8431, w/w%) was obtained at 13.43 MPa, 40 °C, 150 min (dynamic) and 1.7 ml/min (CO₂ flow rate).     

Decaffeinated black tea: Process optimization and phenolic profiles

The low-quality black tea was extracted at 27 different conditions using a lab-scale supercritical fluid extraction system according to four factor, three level Box–Behnken design [pressure (150–450 bar), temperature (40–80 °C), modifier flow rate (0.5–1.0 ml/min), and ethanol concentration in aqueous solution (75–100%)] at constant CO₂ flow rate (2 l/min). Response surface methodology was used in order to optimize the extraction conditions for obtaining minimum caffeine and maximum phenolic profiles of the decaffeinated black tea. The R² values for caffeine and phenolics were 99.5 and 96.6%, respectively. The lowest caffeine and the highest phenolics were obtained at following conditions [pressure (300 bar), temperature (53 °C), modifier flow rate (0.70 ml/min), and ethanol concentration (87.5%)] for 1 h. Using these conditions, the average loss of caffeine and phenolics in the decaffeinated tea were 99.8 and 3.3%, respectively. The present work suggests that optimum extraction conditions found can be applied for a pilot or large-scale production of decaffeinated black tea.     

Supercritical CO2 oilseed extraction in multi-vessel plants. 1. Minimization of operational cost

This work uses a fully predictive mass transfer model to simulate the supercritical CO₂ extraction of vegetable oils from prepressed oilseeds in the 1-m³ vessel of an industrial multi-vessel plant operating at 40 °C and 30 MPa with the purpose of minimizing the operational cost. The work analyses the effect of particle diameter (0.5, 1, 2, 3, and 4 mm), superficial CO₂ velocity (2.76, 5.52, or 11.0 mm/s), and number of extraction vessels (2, 3, or 4) on optimal extraction time and minimal operational cost. Keeping other variables constants, cost diminishes as particle diameter decreases. Although the optimal superficial CO₂ velocity increases as particle diameter decreases, in the case of small (≤1 mm) particles, substrate fluidization may place an upper limit to the superficial velocity. Within the studied region, best superficial CO₂ velocities are 11.0 mm/s for particles smaller than 1–2 mm, 2.76 mm/s for particles larger than 3–4 mm, and 5.52 mm/s for particles in between. Keeping other variables constant, the cost of extraction of medium-to-large (≥2 mm) particles decreases as the number of extraction vessels increases, at the expense of an increase in extraction time. However, because of a sharp transition wave that develops when extracting small (≤1 mm) particles that separates fully extracted (downstream) from virtually unextracted (upstream) substrate within extraction vessels, two-vessel plants are best for small particles. The lowest operational cost observed in this work was USD 4.08 kg⁻¹ oil for the extraction of 2-mm particles using 3.30 m³/h of CO₂ (U = 2.76 mm/s) in a four-vessel plant.     

Supercritical CO2 oilseed extraction in multi-vessel plants. 2. Effect of number and geometry of extractors on production cost

The objective of this work was to study production costs for the supercritical CO₂ extraction of a pre-pressed oilseed (packed bed with 2-mm particles) in a 2-m³ industrial multi-vessel plant operating at 40 °C and 30 MPa, using a fully predictive mass transfer model to simulate the process. We modified the inner diameter (47.3 ≤ D ≤ 65.6 cm) and number (n = 2, 3, or 4) of extraction vessels, and the mass flow rate of CO₂ (Q = 3000 or 6000 kg/h), thus changing the aspect ratio of the extraction vessels (3 ≤ L/D ≤ 8), and superficial velocity (2.71 ≤ U ≤ 10.8 mm/s) and specific mass flow rate (6 ≤ q ≤ 24 kg/h per kg substrate) of CO₂. Production cost decreased when increasing the mass flow rate of CO₂ or the number of extraction vessels (or when increasing q). Production cost did not depend on the geometry of extraction vessel for a constant specific mass flow rate of CO₂, but it decreased with a decreasing of the L/D ratio of the vessel for a constant superficial velocity of CO₂. For any given plant, the contribution of fixed cost items (capital, labor) to the production cost increased with extraction time, unlike that of variable cost items (substrate, CO₂, energy), which decreased. Thus, there was an optimal extraction time that minimized production cost for each plant. This work proposes an expression for capital cost of an industrial multi-vessel plant as a function of the mass flow rate of CO₂ (which defines the cost of the solvent cycle of the plant), and the volume of the extraction vessels (which together with number of extraction vessels define the cost of extraction section of the plant), with a scaling factor of 0.48 for both items. Under optimal conditions, capital cost represented 30–40% of the production cost, but uncertainties in capital cost estimates (about ±50% using the proposed expression) may largely affect these estimates. The lowest production cost estimated in this work was USD 7.8/kg oil for the extraction of prepressed oilseed in a four-vessel plant using 6000 kg/h of CO₂. The mass flow rate of CO₂ and number of extraction vessels also affected annual productivity that was about 360 ton oil for the same plant operating 7200 h per year. Oil yields were above 90% for both three- and four-vessel plants.     

Supercritical carbon dioxide extraction of Capsicum peppers: Global yield and capsaicinoid content

The objective of this study was to select a variety of pepper with high concentration of capsaicin and subject it to supercritical fluid extraction (SFE), in order to determine the best conditions of temperature (40, 50 and 60 °C) and pressure (15, 25 and 35 MPa) in terms of global yield (X₀) and capsaicinoids content of the extracts. The influence of drying process (freeze and oven drying) on X₀, capsaicin (C) and dihydrocapsaicin (DHC) contents and total phenolics was also analyzed. Capsicum frutescens showed the highest levels of capsaicinoids (1516 μg/g fresh fruit). For the responses C and DHC, the extraction conditions of 15 MPa and 40 °C provided the highest concentrations (C ⿿ 42 mg/g extract and DHC ⿿ 18.5 mg/g extract). The freeze drying process resulted in extracts with the highest concentration of capsaicinoids (61 mg/g extract), but in contrast, the phenolics were less susceptible to different drying processes, with a mean concentration of 35 mg GAE/g extract. The kinetics experiments indicated that the extraction rate of oleoresin was slightly slower than that of capsaicinoids at the operation conditions (40 °C and 15 MPa).     

Obtaining phenolic compounds from jatoba (Hymenaea courbaril L.) bark by supercritical fluid extraction

The extraction of polyphenol compounds from jatoba (Hymenaea courbaril L. var stilbocarpa) bark using supercritical fluid extraction (SFE) with CO₂ and cosolvents has been investigated. Among the solvent systems studied, SFE using CO₂ and water (9:1, v/v), at 323 K and 35 MPa, presented the best results, with extract yield of 24%, and with high antioxidant activity (IC₅₀ of 0.2 mg/cm³). This solvent system was used to determine global yield isotherms, which were built at 323 and 333 K, and 15, 25, and 35 MPa, using a second lot of jatoba. The highest yield was 11.5% at 15 MPa and 323 K, with maximum total phenolic compounds (TPC) of 335.00 mg TAE/g extract (d.b.) and total tannins content of 1.8 g/100 g raw material. A kinetic experiment was performed using optimized conditions, yielding 18% extract, and the kinetic parameters were used to scale-up the process from laboratory to pilot scale. Chemical analyses showed high content of phenolic compounds in the extracts of jatoba bark mostly due to the presence of procyanidins.     

Supercritical CO2 extraction of lutein esters from marigold (Tagetes erecta L.) enhanced by ultrasound

As a novel technique, supercritical CO₂ (SC-CO₂) extraction enhanced by ultrasound was applied to the extraction of lutein esters from marigold and the extraction curves were described by Sovová model. The mass transfer coefficient in the solid phase (k_s) increased from 3.1 × 10⁻⁹ to 4.3 × 10⁻⁹ m/s due to ultrasound. The effect of extraction parameters including particle size of matrix, temperature, pressure, flow rate of CO₂, and ultrasonic conditions consisting of power, frequency and irradiation time/interval on the yield of lutein esters were investigated with single factor experiments. The results showed that the yield of lutein esters increased significantly with the presence of ultrasound (p < 0.05). The maximal yield of lutein esters (690 mg/100 g) was obtained for a particle size fraction of 0.245–0.350 mm, extraction pressure of 32.5 MPa, temperature of 55 °C and CO₂ flow rate of 10 kg/h with ultrasonic power of 400 W, ultrasonic frequency of 25 kHz and ultrasonic irradiation time/interval of 6/9 s.     

Extraction of curcuminoids from deflavored turmeric (Curcuma longa L.) using pressurized liquids: Process integration and economic evaluation

Pressurized liquid extraction (PLE) of curcuminoids from deflavored turmeric rhizomes was optimized. The rhizomes were initially deflavored by extraction with supercritical CO₂. Immediately after SFE, PLE process was performed using ethanol as the solvent and a static extraction time of 20 min, and the independent variables were the temperature (333–353 K) and pressure (10–35 MPa). The results indicate that the optimum extraction temperature and pressure were 333 K and 10 MPa, respectively. PLE required three and six times less extraction time than low-pressure solvent extraction and Soxhlet extraction, respectively, to produce similar extraction yields. The cost of manufacturing (COM) decreased from US$ 94.92 kg⁻¹ to US$ 88.26 kg⁻¹ when the capacity of the two-extractor system increased from 0.05 m³ to 0.5 m³ and from US$ 94.92 kg⁻¹ to US$ 17.86 kg⁻¹ when the cost of the raw materials decreased from US$ 7.91 kg⁻¹ to US$ 0.85 kg⁻¹ for a two 0.05 m³ extractor system.     

Supercritical fluid extraction and convergence chromatographic determination of parthenolide in Tanacetum parthenium L.: Experimental design,modeling and optimization

Feverfew (Tanacetum parthenium L., Asteraceae) is a perennial medicinal plant which has been used to alleviate the symptoms of migraines, headaches and rheumatoid arthritis. The herb contains various potentially active constituents such as sesquiterpene-γ-lactones, flavonoids and volatile oil. The main sesquiterpene-lactone in feverfew is parthenolide which is considered to be responsible for the therapeutical effects. Supercritical CO₂ extraction was carried out at different pressures (10–30 MPa), temperatures (40–80 °C) and co-solvent contents (0–10% ethanol) in order to study the extraction yield and the parthenolide recovery of the extracts. Leaves collected before and during flowering and flower heads were investigated. A factorial experiment using a full 3³ design was followed during the experiments and response surface methodology was implemented to analyze the influence of the variables and optimize the extraction. The critical values of parthenolide content were found to be 7% EtOH, 22 MPa and 64 °C in case of all three samples. It was determined, that the optimal conditions of the extraction, where the maximum parthenolide content and extract yield can be reached, do not coincide. The highest yield of parthenolide was obtained in the flower heads (0.604 wt.%).     

Optimization of essential oil supercritical extraction from Algerian Myrtus communis L. leaves using response surface methodology

The present work deals with the application of the supercritical fluid extraction process to extract essential oils from the leaves of an Algerian myrtle plant (Myrtus communis L.). Using the surface response methodology, an optimization of the extraction recovery was carried out, varying the pressure in the range of [10–30 MPa], the temperature within [308–323 K], a solvent flow rate fixed at 0.42 kg h⁻¹ and a mean particle diameter equal to 0.5 mm or less than 0.315 mm. The maximum value of essential oil recovery relative to the initial mass of leaf powder was 4.89 wt%, and was obtained when the SC–CO₂ extraction was carried out under 313 K, 30 MPa and with a particle diameter less than 0.315 mm. A second-order polynomial expression was used to express the oil recovery. The calculated mass of recovered oil using the response surface methodology was very close to the experimental value, confirming the reliability of this technique.     

Extraction of sunflower oil with supercritical CO2: Experiments and modeling

Extraction of sunflower oil from sunflower seeds (Heliantus annuus L.) using supercritical CO₂ was studied. The shrinking core model was applied to the modeling of the packed-bed extraction process. The experimental data were obtained for extraction conducted at the pressures of 20, 30, 40, 50 and 60 MPa; the temperatures of 313, 333 and 353 K, the CO₂ flow rates of 1–4, and 6 cm³ CO₂ min⁻¹; the mean particle diameters of 0.23, 0.55, 1.09, 2.18 mm. The supercritical CO₂ extraction process was modeled by a quasi steady state model as a function of extraction time, pressure, temperature, CO₂ flow rate, and particle diameter. The supercritical CO₂ extraction process. The intraparticle diffusion coefficient (effective diffusivity) D_e was used as adjustable parameter. The model using the best fit of D_e was correlated the data satisfactorily.     

Experimental design on supercritical extraction of essential oil from valerian roots and study of optimal conditions

Supercritical CO₂ extraction from valerian (Valeriana officinalis L.) roots was studied. The objective of this study was to optimize the independent process parameters (temperature, pressure, dynamic time and modifier volume) in order to attain the highest yield of the essential oil and valerenic acids as the desired compounds. The process optimization was based on a simplex centroid design (mixture design), coupled with the statistical and graphical analysis of the results. Due to the features of mixture method and to the proper ratios of four independent variables, the optimal points were in the range of temperature (37 °C), pressure (24.3–25.0 MPa), dynamic time (19–24 min) and modifier volume (100–200 μl).     

Exploiting microalgae as a source of essential fatty acids by supercritical fluid extraction of lipids: Comparison between Scenedesmus obliquus,Chlorella protothecoides and Nannochloropsis salina

Supercritical CO₂ extraction from microalgae is applied with the aim of obtaining an oil rich in α-linolenic (ALA) essential fatty acid and with a low ω6:ω3 ratio. The maximum extraction yield is obtained at 60 °C and 30 MPa with 0.4 kg/h of CO₂ and 5% of co-solvent (ethanol). When the effect of pressure, temperature and density on the supercritical extraction yield and solubility are studied, the thermodynamic cross-over is found at a pressure close to 30 MPa, while the extraction cross-over occurs at around 25 MPa. The experimental solubility data are correlated by literature empirical models. Mathematical models developed by Sovová are applied to describe the experimental extraction curves. Soxhlet extraction of lipids is also carried out, obtaining a similar fatty acids profile but proving to be less selective than SCCO₂ method. Among the three species of microalgae examined, results show that Scenedesmus obliquus oil is richer in ω-3 fatty acids and ALA than Chlorella protothecoides and Nannochloropsis salina lipids. The effect of the extraction parameters on ALA content and the fatty acid profile is also analysed, concluding that the ω-3 percentage is favoured by lower temperatures, lower pressures and shorter extraction times.