Reactive extraction of succinic acid using supercritical carbon dioxide

Reactive extraction using supercritical carbon dioxide (scCO₂) and tri-n-octylamine (TOA) was evaluated as a separation method of succinic acid from an aqueous solution. The reactive extraction of succinic acid was performed at varying initial acid concentrations in aqueous solution (0.07–0.45 mol?dm^?3), temperature (35–65°C) and pressure (8–16 MPa). The succinic acid separation was conducted in both batch mode and semi-continuous mode. The highest reactive extraction efficiency of approx. 62% was obtained for the process conducted in semi-continuous mode at 35°C and 16 MPa for the initial acid concentrations in aqueous phase of 0.39 mol?dm^?3.     

Solubilities of chlormezanone,metaxalone and methocarbamol in supercritical carbon dioxide

The solubilities of three active pharmaceutical ingredients (APIs) in supercritical carbon dioxide were measured in this study using a semi-flow apparatus. These APIs are chlormezanone (C₁₁H₁₂ClNO₃S), metaxalone (C₁₂H₁₅NO₃) and methocarbamol (C₁₁H₁₅NO₅) that are all used as skeletal muscle relaxants. The solubility data are reported for three isotherms at 308.2, 318.2 and 328.2 K, with the pressure range from 12 to 24 MPa. Most solubility data are within the range of 10⁻⁶ to 10⁻⁴ mole fraction for each API. The crossover phenomena were observed from the experimental results for all three systems. These solubility data satisfied the thermodynamic consistency tests. They were then correlated using three semi-empirical models. With the optimally fitted binary interaction parameters, satisfactory correlation agreement is presented for each binary mixture.     

Solubility of chlorpheniramine maleate in supercritical carbon dioxide

Solubility of chlorpheniramine maleate in supercritical carbon dioxide at different temperatures (308–338 K) and pressures (160–400 bar) is measured using static method coupled with gravimetric method. The measured solubility data demonstrated that the solubility of chlorpheniramine maleate was changed between 1.54 × 10⁻⁵ and 4.26 × 10⁻⁴ based on the mole fraction as the temperature and pressure are changed. The general trend of measured solubility data shows a direct effect of pressure and temperature on the solubility of chlorpheniramine maleate. Finally, the obtained solubilities correlated using four semi-empirical density-based correlations including Mendez Santiago–Teja (MST), Kumar and Johnston (KJ), Bartle et al., and Chrastil models. Although the results of modeling showed that the KJ model leads to the average absolute relative deviation percent (AARD %) of 8.1% which is the lowest AARD %, deviation of other utilized correlations are rather the same.     

Solubility of cyproheptadine in supercritical carbon dioxide; experimental and modeling approaches

Solubility of solute in supercritical fluids at different pressures and temperatures is one of the most important parameters necessary for design of any supercritical fluid-based processes. Among different supercritical fluids, carbon dioxide is one of the most widely used solvents due to its useful and green characteristics. In this work, with the assist of supercritical carbon dioxide as the solvent, solubility of cyproheptadine in different temperatures (308–338 K) and pressures (160–400 bar) are measured using static method. The obtained results demonstrated that solubility of cyproheptadine ranged between 3.35 × 10⁻⁵ and 3.09 × 10⁻³ based on mole fraction. A closer examination of measured solubility data show that not only solubility of cyproheptadine increases by increasing pressure but also experiences a cross over pressure about 200 bar. At last, the measured solubility data are correlated using four widely used density based correlations namely Mendez Santiago–Teja (MST), Kumar and Johnston (KJ), Bartle et al., and Chrastil models. The obtained results demonstrated that the best correlative capability was observed for KJ model leads to the average absolute relative deviation percent (AARD %) of 6.3%.     

Extraction of protocatechuic acid from Scutellaria barbata D. Don using supercritical carbon dioxide

The use of supercritical carbon dioxide (SC⿿CO₂), with water as a modifier, was evaluated in this study as a method to extract protocatechuic acid (PA) from Scutellaria barbata D. Don. The highest extraction yield of PA, 64.094 ± 2.756 μg/g of dry plant, was achieved at 75 °C and 27.5 MPa, with the addition of 15.6% (v/v) water as a modifier. The mean particle size was 0.355 mm, the CO₂ flow rate was 2.2 mL/min (STP) and the dynamic extraction time was 100 min. At pressures of 16.2⿿30.0 MPa and temperatures of 45⿿75 °C, the mole fraction solubilities of PA in SC⿿CO₂ ranged from 2.829 ÿ 10^⿿7 to 9.631 ÿ 10^⿿7. The solubility data for PA fit well in the Chrastil model. It is evident that the SC⿿CO₂ extraction uses less solvent, saves both energy and time and is an environmentally friendly extract technology that can be used in the food, cosmetic and pharmaceutical industries.     

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.     

Solubility of the silver nitrate in supercritical carbon dioxide with ethanol and ethylene glycol as double cosolvents: Experimental determination and correlation

Solubility of the silver nitrate in the supercritical carbon dioxide containing ethanol and ethylene glycol as double cosolvents was measured under certain pressure and temperature range(10–25 MPa, 323.15–333.15 K). The impact of the pressure and temperature on the solubility was also investigated. Based on the experiment data,a correlation model concerning solid's solubility in supercritical fluids was established by combining the solubility parameter with the thermodynamic equation when a binary interaction parameter and a mixed solvent solubility parameter were defined. Experiments show the solubility of AgNO_3 increases with the pressure at a certain temperature. However, the influence of temperature is related to a pressure defined as the turnover pressure(12.3 MPa). When the pressure is higher(or lower) than this turnover pressure, silver nitrate's solubility shows increasing(or decreasing) trend as the temperature rises. Satisfactory accuracy of our presented model was revealed by comparing experimental data with calculated results.     

Determination and calculation of solubility of bisphenol A in supercritical carbon dioxide

Supercritical fluid technology (SFT) as a new technique is very important for clean environment and removal of chemical pollutants. The lack of solubility data of solid solute in certain supercritical fluid is a great obstacle to the successful implementation of SFT. In this work, the solubility of bisphenol A in supercritical carbon dioxide was determined by the dynamic method at the temperatures ranging from 308 to 328 K and pressure range of 11.0–21.0 MPa. The effects of temperature and pressure on solubility were analyzed according to molecular motion theory. The solubility data were correlated using eight different semi-empirical models (Chrastil, Adachi–Lu, Kumar–Johnston, Tang, Sung–Shim, Bartle, Méndez Santiago–Teja and Yu). The comparison between different models was discussed. The thermodynamic properties (total enthalpy ΔH, enthalpy of sublimation Δ_subH and enthalpy of solvation Δ_solvH) of the solid solute were obtained.     

Continuous extraction of glycerol acetates from their mixture using supercritical carbon dioxide

Supercritical carbon dioxide was used for partially selective extraction of triacetin from a mixture of triacetin, diacetin, and monoacetin with a molar ratio of 1:2:1. The extraction was carried out in two stages. In the first stage, a central composite design was used to optimize the four variables of pressure, temperature, liquid CO₂ flow rate, and extraction time at three levels using a semi-continuous, supercritical carbon dioxide extraction setup. The composition of the extract under the predicted optimum conditions (i.e., 109 bar, 56 °C, 0.86 mL min⁻¹, and 61 min) was about 69% triacetin accompanied by only 30% diacetin and no detectable monoacetin. In the second stage, the effect of the two factors, pressure (100, 109, and 140 bar) and liquid CO₂ flow rates of 0.86 and 1.5 mL min⁻¹ measured at average laboratory temperature (27 °C) and pressure (0.89 bar), were studied using a continuous, supercritical carbon dioxide fractionation setup equipped with a glass-bead packed column kept under a thermal gradient of 56-70 °C. The experimental design was organized as a 3 × 2 general factorial design. Under the best conditions (i.e., 140 bar and 1.5 mL min⁻¹), the extraction yield of triacetin and diacetin were 41.8 and 3.0%, respectively, without any detectable monoacetin as verified by GC-FID.     

Solubility analysis of clozapine and lamotrigine in supercritical carbon dioxide using static system

The experimental techniques used to obtain the solubilities of clozapine and lamotrigine in supercritical carbon dioxide include a simple static technique. The solubility measurements were performed at temperatures between 318 and 348 K and pressures between 121.6 and 354.0 bar. These chemicals have solubilities with values ranging from 3.6 × 10⁻⁶ to 4.2 × 10⁻⁵ (clozapine) and 1 × 10⁻⁶ to 6 × 10⁻⁵ (lamotrigine) mole fraction. The solubility data were correlated using four semi-empirical density-based models (Chrastil, Bartle, K-J and M-T models). Correlation of the results shows good self-consistency of the data obtained with the Bartle model for clozapine with an overall average absolute relative deviation (AARD%) of 11.21. The calculated results with each four models show satisfactory agreement with the experimental data for lamotrigine with an overall AARD% 11.72, 8.99, 2.75, 3.86 for Chrastil, K-J, Bartle, M-T models, respectively. Using the correlation results, the heat of drug-CO₂ solvation and that of drug vaporization were approximated.     

超临界CO_2萃取浓缩大豆粗磷脂的研究

以浓缩大豆粗磷脂作为液态物料的模型材料进行了超临界CO2萃取研究。通过实验考察了萃取温度、压力、时间和溶剂流量等对萃取效果的影响,确定了对于该种物质萃取的最佳操作条件。通过与传统的水蒸汽蒸馏法和有机溶剂萃取法生产的产品进行对比(酸碱度、含水量、有机溶剂残余量、色泽、气味等方面),表明了超临界流体萃取技术用于热不稳定物质的萃取所具有的独特优势。     

Prediction of solute solubility in supercritical carbon dioxide: A novel semi-empirical model

Solubility data of solutes in supercritical fluids (SCF) are crucial for designing extraction processes, such as extraction using SCF or micronization of drug powders. A new empirical equation is proposed to correlate solute solubility in supercritical carbon dioxide (SC CO₂) with temperature, pressure and density of pure SC CO₂. The proposed equation is ln y₂ = J₀ + J₁P² + J₂T² + J₃ ln ρ where y₂ is the mole fraction solubility of the solute in the supercritical phase, J₀ − J₃ are the model constants calculated by least squares method, P (bar) is the applied pressure, T is temperature (K) and ρ is the density of pure SC CO₂. The accuracy of the proposed model and three other empirical equations employing P, T and ρ variables was evaluated using 16 published solubility data sets by calculating the average of absolute relative deviation (AARD). The mean AARD for the proposed model is 7.46 (±4.54) %, which is an acceptable error when compared with the experimental uncertainty. The AARD values for other equations were 11.70 (±23.10), 6.895 (± 3.81) and 6.39 (±6.41). The mean AARD of the new equation is significantly lower than that obtained from Chrastil et al. model and has the same accuracy as compared with Bartle et al. and Mèndez-Santiago–Teja model. The proposed model presents more accurate correlation for solubility data in SC CO₂. It can be employed to speed up the process of SCF applications in industry.     

二氧化碳超临界萃取乙基香兰素粗制品的研究

采用二氧化碳超临界萃取乙基香兰素粗品,研究萃取压力、萃取温度、萃取时间、流体流量等工艺条件对萃取效率和产品质量的影响.得出最佳工艺条件,采用萃取压力25～30 MPa,萃取温度55～60℃,流体流量5 L/h,萃取5～6 h,萃取效率可以达到95％,可以得到质量分数大于95％的乙基香兰素产品.     

Solubility of red palm oil in supercritical carbon dioxide: Measurement and modelling

The solubility of red palm oil(RPO) in supercritical carbon dioxide(scCO_2) was determined using a dynamic method at 8.5–25 MPa and, 313.15–333.15 K and at a fixed scCO_2 flow rate of 2.9 g·min~(-1) using a full factorial design. The solubility was determined under low pressures and temperatures as a preliminary study for RPO particle formation using scCO_2. The solubility of RPO was 0.5–11.3 mg·(g CO_2)~(-1) and was significantly affected by the pressure and temperature. RPO solubility increased with pressure and decreased with temperature. The Adachi–Lu model showed the best-fit for RPO solubility data with an average relative deviation of 14% with a high coefficient of determination, R~2 of 0.9667, whereas the Peng–Robinson equation of state thermodynamic model recorded deviations of 17%–30%.     

超临界CO2萃取丁香挥发油的实验研究

采用正交实验法对超临界CO2萃取丁香挥发油的条件进行了研究。考察了萃取温度、压力、CO2流量等因素在不同水平下对丁香挥发油提取率的影响。得到了超临界C02萃取丁香挥发油的最佳实验条件：萃取压力30MPa、温度40℃、CO2流量40kg／h和萃取时间80min,得率为20．62％。与水蒸气蒸馏法比较,超临界CO2萃取的收率高,萃取时间短。     

Solubility and partial molar volume of N,N-dimethylformamide diethyl acetal in supercritical carbon dioxide: Measurement and correlations

The solubilities of N,N-dimethylformamide diethyl acetal were measured at temperatures ranging from 313 to 353 K and pressures from 7.8 to 13.3 MPa in supercritical carbon dioxide. The measured solubility data were correlated using the Chrastil, Sung and Shim (SS), and Jouyban–Chan–Foster (JCF) semiempirical models. Consequently, the calculated results showed satisfactory agreement with experimental data and differed from the measured values by between 4.56 and 6.10%. The correlated results indicated that the JCF model provided the best fitness. Solubility data were also utilized to estimate the partial molar volume for the compound in the supercritical phase using the theory developed by Kumar and Johnston.     

Solubility of thymol in supercritical carbon dioxide and its impregnation on cotton gauze

Through this study, an attempt has been made to evaluate the solubility of thymol in supercritical carbon dioxide as well to investigate a prospect of its impregnation on cotton gauze on laboratory scale. Solubility of thymol in supercritical carbon dioxide was determined at temperatures of 35 °C, 40 °C and 50 °C, and pressures ranging from 7.8 to 25 MPa (CO₂ density range 335.89–849.60 kg/m³) using a static method. The solubility data were correlated using semi-empirical equations introduced by Chrastil, Adachi and Lu and del Valle and Aguilera. Taking into account obtained results, temperature of 35 °C and pressure of 15.5 MPa were selected as operating conditions for the impregnation process. Impregnation of cotton gauze with thymol was performed in a cell using carbon dioxide as a solvent. Kinetics of the process was determined and modeled. Masses of thymol on cotton gauzes after 2 h and 24 h of impregnation were 11% and 19.6%, respectively. FT-IR analysis confirmed the presence of thymol on the surface of the cotton fibers. The impregnated gauze provided strong antimicrobial activity against tested strains of Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis and Candida albicans.     

Equilibrium solubilities of a p-toluenesulfonamide and sulfanilamide mixture in supercritical carbon dioxide with and without ethanol

Supercritical separation processes for a multi-component mixture of solutes are of practical interest. In this study, the experimental equilibrium solubilities of two solute mixtures, p-toluenesulfonamide (p-TSA) and sulfanilamide (SNA), in supercritical carbon dioxide (SC CO₂) were measured at temperatures of 308, 318 and 328 K and pressures in the range of 11.0-21.0 MPa using a dynamic flow method. The effect of cosolvent on the multi-component system was investigated by the addition of a 3.5 mol% ethanol. In the ternary system (p-TSA + SNA + CO₂), the solubility of SNA increased as compared to its binary system (SNA + CO₂), while the solubility of p-TSA decreased. In the quaternary system (p-TSA + SNA + ethanol + CO₂), a significant solubility enhancement was observed for both p-TSA and SNA. The selectivity, which is thought to imply the intermolecular interactions between p-TSA and SNA, was also enhanced by the presence of ethanol so that the two solutes could be separated by a max. purity of 99.4%. The influence of the hydrogen bond interaction on solubility was discussed. The equations of Chrastil, Méndez-Santiago and Teja, and their modified forms were used to correlate the experimental data.     

Preparation, characterization, and supercritical carbon dioxide foaming of polystyrene/graphene oxide composites

Graphene oxide (GO) was prepared by oxidation of graphite using the Hummers method, and was modified by isocyanate to obtain dispersed GO sheets in dimethylformamide. Polystyrene (PS)/GO composites were prepared by solution blending, and their morphologies and properties were characterized. The addition of GO increased the glass transition temperature of the PS/GO composites. The storage modulus and thermal stability of the composites were also improved compared with PS. Foams of PS and PS/GO composites were prepared by supercritical carbon dioxide foaming. The composite foams exhibited slightly higher cell density and smaller cell size compared with the PS foam, indicating the GO sheets can act as heterogeneous nucleation agents.     

Correlation of solute solubility in supercritical carbon dioxide using a new empirical equation

A new empirical equation is proposed to correlate solute solubility in supercritical carbon dioxide (SCCO₂). The new empirical model has four parameters per each solute that can be obtained by correlation of the experimental solubility data. The input variables of the equation are pressure, temperature and density of pure SCCO₂. The new equation is applied for correlation of solubility of 24 compounds in SCCO₂ at wide range of temperatures and pressures. The overall percent of absolute average relative deviation (%AARD) of the new equation for correlation of the experimental data is 6.54%. Comparison of the results of the present model with a three-parameter and a four-parameter empirical model demonstrates good accuracy of the new empirical model.