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%.     

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.     

Experimental measurement and correlation for solubility of piroxicam (a non-steroidal anti-inflammatory drugs (NSAIDs)) in supercritical carbon dioxide

Since the knowledge of pharmaceutical solubilities in the supercritical carbon dioxide is one of the first essential necessities for designing the supercritical carbon dioxide-based processes, solubility of piroxicam a non-steroidal anti-inflammatory drug was experimentally measured. In this regard, a static method coupled with gravimetric method was used to measure the solubility of piroxicam in the supercritical carbon dioxide in temperature and pressure range of 308.15–338.15 K and 16–40 MPa, respectively. The obtained solubility data were in the range of 1.17 × 10⁻⁵ and 5.12 × 10⁻⁴ based on the mole fraction (mole piroxicam/(mole piroxicam + mole CO₂)) then modeled using four different density based correlations namely Bartle et al., Mendez-Santiago-Teja, Chrastil and Kumar and Johnston models. The results of error analysis revealed that the used correlations were potential to correlate the solubility of piroxicam with minimum and maximum average absolute relative deviation percents (AARD%) of 14.4% and 15.2%, respectively.     

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.     

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.     

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%.     

Polymerization of acrylonitrile in supercritical carbon dioxide

A series of fluorinated diblock copolymers, consisting of styrene (St)-acrylonitrile (AN) copolymer [poly(St-co-AN)] and poly-2-[(perfluorononenyl)oxy]ethyl methacrylate, with various compositions as well as with different molecular weights were synthesized by atom transfer radical polymerization and characterized. Dispersion polymerization of acrylonitrile in supercritical carbon dioxide (scCO₂) at 30 MPa and at 65 °C with this kind of amphiphilic block copolymer as a stabilizer and 2,2′-azobisisobutyronitrile as an initiator was investigated. The experimental results indicated that, in the presence of a small amount of poly(St-co-AN) (5 wt% to AN), spherical particles of polyacrylonitrile (PAN) were prepared with small diameter and narrow polydispersity (d_n = 153 nm, d_w/d_n = 1.12), resulting from the high stabilizing efficiency of this fluorinated block copolymer. Furthermore, the polymerization of AN in scCO₂ under different initial pressures especially under low pressure (<14 MPa) was studied. When the polymerization was carried out around the critical pressure of CO₂ (7.7-7.8 MPa), the PANs with high molecular weight (M_ν ≈ 130,000-194,000) were synthesized at high monomer conversion (>90%) no matter whether the stabilizer was added, compared to those synthesized by dispersion polymerization at 30 MPa. It was also found that the crystallinity of PAN synthesized at 7.7-7.8 MPa was somewhat higher than that synthesized at 30 MPa, while its crystallite size did not change.     

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.     

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.     

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.     

Solubility prediction of disperse dyes in supercritical carbon dioxide and ethanol as co-solvent using neural network

Nowadays artificial neural networks(ANNs) with strong ability have been applied widely for prediction of nonlinear phenomenon. In this work an optimized ANN with 7 inputs that consist of temperature, pressure, critical temperature, critical pressure, density, molecular weight and acentric factor has been used for solubility prediction of three disperse dyes in supercritical carbon dioxide(SC-CO2) and ethanol as co-solvent. It was shown how a multi-layer perceptron network can be trained to represent the solubility of disperse dyes in SC-CO2. Numeric Sensitivity Analysis and Garson equation were utilized to find out the degree of effectiveness of different input variables on the efficiency of the proposed model. Results showed that our proposed ANN model has correlation coefficient, Nash–Sutcliffe model efficiency coefficient and discrepancy ratio about 0.998, 0.992, and 1.053 respectively.     

Acetylation of plant cellulose fiber in supercritical carbon dioxide

Natural cellulosic ramie fiber was acetylated using supercritical carbon dioxide (sc-CO₂) as a reaction medium. The structure and properties of the acetylated fibers were investigated using infrared spectroscopy, scanning electron microscopy, X-ray diffraction (including synchrotron microbeam X-ray diffraction), nano-Raman scattering, and a tensile test. The acetylation reaction proceeded without using an organic solvent, and it reached to the core part of the fiber within a short period while maintaining the fiber morphology. The crystallites of cellulose triacetate II and cellulose coexist in the fiber. The acetylated fiber with an average degree of substitution of 1.9 showed high modulus (34.5 GPa) and high strength (763 MPa), which are the highest values for cellulose diacetate so far reported to date.     

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.     

Development of activity coefficient model based on COSMO method for prediction of solubilities of solid solutes in supercritical carbon dioxide

A COSMO base activity coefficient model was newly developed to predict the solubilities of solid solutes in supercritical carbon dioxide. This activity coefficient model describes that the system is composed of the surface segments on the solvent molecule and vacancy unlike the conventional model based on COSMO method. The density change of supercritical fluid can be represented by the change of the surface area of the vacancy. This prediction model is referred to “COSMO-vac (vacancy)” model. The solubilities of 16 pharmaceuticals in supercritical carbon dioxide were predicted by COSMO-vac model. The averaged deviations between the logarithmic experimental and predicted results are smaller than unity. Furthermore, the predicted results for the solutes composed of only C, H and O atoms are better than those for the solutes including the other atoms. The percentage of the predicted results within the order of the experimental data at the pressure over 15 MPa is higher than that at the pressures below 15 MPa.     

Ternary solubility of mono- and di-tert-butyl ethers of glycerol in supercritical carbon dioxide

Using a continuous flow apparatus, the ternary solubility of mono- and di-tert-butyl ethers of glycerol (MTBG and DTBG, respectively) in supercritical carbon dioxide was measured at the temperatures of 313.15, 333.15, and 348.15 K; a pressure range of 80-200 bar; and an expanded gas flow rate of 180 ± 10 mL min⁻¹ at average laboratory temperature of 300.15 K and pressure of 0.89 bar. The ternary solubility of the ethers at the constant temperatures of 333.15 and 348.15 K increased with increasing pressure up to the crossover point (i.e., 152 bar for MTBG and 170 bar for DTBG). MTBG exhibited a higher solubility than DTBG in scCO₂. The experimental data for the ternary solubility of MTBG and DTBG were correlated using the Bartle equation.     

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.     

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.