Compounds In Supercritical CO2 Research Articles

A new simple model for calculation of solubilities of derivatized anthraquinone compounds in supercritical carbon dioxide

A new modified Redlich–Kwong equations of state (βRK-EoS) is proposed to calculate the solubilities of eight dyeing compounds from anthraquinone family in supercritical CO2. In order to evaluate the results, the proposed model was also compared with the Peng–Robinson equation of state (PR-EoS) in combination with the van der Waals (vdW1) and Wong–Sandler (WS) mixing rules. The βRK–vdW0 model was found to deviate from the experimental results by 3.65%, whereas higher deviations were observed in PR–vdW1 and PR–WS models with providing AARDs of 11.44% and 6.8%, respectively. The modeling results show that the combination of βRK equation of state with vdW0 mixing rules, despite its simplicity, offers better results than other models and this combination can be used as a proper model to calculate the solubility of dye compounds in supercritical CO2.

A thermodynamic approach for correlating the solubility of drug compounds in supercritical CO2 based on Peng-Robinson and Soave-Redlich-Kwong equations of state coupled with van der Waals mixing rules

In the present study, the effect of equations of state and mixing rules in a thermodynamic approach has been investigated for the correlation of the solubility of four new solid pharmaceutical compounds, namely, benzamide, cetirizine, metaxalone and niflumic acid in supercritical CO2 at different temperatures and pressures. Two equations of state, the Peng?Robinson (PR) and Soave?Redlich?Kwong (SRK), coupled with mixing rules of one-parameter van der Waals (vdW1) and two-parameter van der Waals (vdW2) were used, where the binary interaction parameters for these sets of equations were evaluated. The approach correlations and the robustness of the numerical technique were validated with the experimental data previously reported for these compounds at different temperatures and pressures. The calculated average absolute relative deviations (AARD) were 7.51 and 5.31 % for PR/vdW1 and PR/ /vdW2 couples, and 11.05 and 10.24 % for SRK/vdW1 and SRK/vdW2 couples, respectively. It was also found that the PR equation of state results in modeling performance better than the SRK equation, and the vdW2 mixing rule better than the vdW1 one. These results obviously demonstrate that the combined approach used in this study is applicable for correlation of solid solubilities of some pharmaceutical compounds in supercritical CO2. Additionally, a semiempirical correlation is proposed for estimating the solubility of drug solids in supercritical CO2 as a function of pressure and temperature.

Solubility of functional compounds in supercritical CO2: Data evaluation and modelling

The solubility data of functional compounds in supercritical carbon dioxide were compiled and discussed. The investigation included essential oils, phenolic compounds, carotenoids, tocopherols, carboxylic acids, alkaloids and vitamins. The data were correlated with four mathematical models. The parameters of each model were adjusted for each compound using the experimental data from literature. From the evaluation of the compiled data, it was possible to observe that the essential oils are the most soluble compounds and the phenolic compounds are the least soluble compounds in supercritical CO2, in the range of temperatures and pressures that were evaluated. In relation to the models, it was observed that the prediction of the solubilities of the biocompounds in supercritical fluids was acceptable for all the models, with the Jiang et al. equation being the model that presented the best results to predict the solubility for all functional groups.

Efficient modeling of drug solubility in supercritical carbon dioxide

Development of new models and correlations to determine the drug solubility in supercritical fluids, i.e., supercritical CO2, helps us to avoid time-consuming computations with poor outcomes while improving the supercritical technology. In this communication, a supervised technique, namely, the least square support vector machine (LSSVM) was employed to estimate the solubility of 33 different drug compounds in supercritical CO2. The corresponding solubility was determined as a function of temperature, pressure, density of supercritical CO2, and two physical properties of drug, i.e. molecular weight and melting point. The results obtained from the employed LSSVM model were compared with eight correlations. The obtained average absolute relative deviation and the square of regression coefficient for the testing group of LSSVM model were found to be 5.61% and 0.9975, respectively. Therefore, the model developed in this work can be reliably applied to the studied drugs by only knowing their physical properties.

New models for correlating and predicting the solubility of some compounds in supercritical CO2

Two new semi-empirical models were proposed to calculate and predict the solubility data of some compounds in supercritical carbon dioxide (SCCO2). The new model I was constructed based on the models of Chrastil. Its ability of calculating solubility data was evaluated and compared with the models of Chrastil, Adachi-Lu and de Valle using solubility data of 40 compounds collected from literature published in recent years, and results showed that the new model I is better than other models. However, the new model I as well as other models mentioned above can only be fitted for each solute without the ability of prediction for the unknown solubility data. Meanwhile, the molecular connectivity indices (MCIs) have been widely used as the structure descriptors encoding a large amount of structure information on an entire molecule. Therefore, the new model II was developed by combining the modified MCIs with the new model I to calculate the solubility data of fatty acids, fatty alcohols, fatty acid esters and aromatic compounds in SCCO2. The relation between the solutes' solubility data and their molecular structures was developed by a one-off correlation of experimental data and then the inductive relation was used in the new model II to predict the solubility data of homogeneous solutes successfully.

Applications of SSAFT EOS for determination of the solubilities of solid compounds in supercritical CO 2 .

Using statistical thermodynamics such as Simplified SAFT equation of state (SSAFTEoS) for estimating phase equilibrium and fluid properties of different materials have been used widely. SSAFT EoS has been developed for associative and non-associative compounds. At high pressure inter molecular forces are very important, on the other hand, in spite of the fact that SSAFT EoS has strength theoretical foundation, it can predict the behavior of high pressure systems. In this research, four solid solubility of benzoic acid, naphthalene, pyrene and Phenanthrene in supercritical carbon dioxide have been studied, SSAFT EoS has been used for modeling. At the end the results have been compared with experimental data. The highest and the absolute average deviation error (AAPD), for carbon dioxide - Phenanthrene and benzoic acid - carbon dioxide systems have been reported 2.22 and 4.43 respectively. Keywords : SSAFT EoS; Supercritical carbon dioxide; Solid compounds; Solubility.

Applications of SSAFT EOS for determination of the solubilities of solid compounds in supercritical CO2.

Using statistical thermodynamics such as Simplified SAFT equation of state (SSAFTEoS) for estimating phase equilibrium and fluid properties of different materials have been used widely. SSAFT EoS has been developed for associative and non-associative compounds. At high pressure inter molecular forces are very important, on the other hand, in spite of the fact that SSAFT EoS has strength theoretical foundation, it can predict the behavior of high pressure systems. In this research, four solid solubility of benzoic acid, naphthalene, pyrene and Phenanthrene in supercritical carbon dioxide have been studied, SSAFT EoS has been used for modeling. At the end the results have been compared with experimental data. The highest and the absolute average deviation error (AAPD), for carbon dioxide - Phenanthrene and benzoic acid - carbon dioxide systems have been reported 2.22 and 4.43 respectively.Keywords: SSAFT EoS; Supercritical carbon dioxide; Solid compounds; Solubility.

Prediction of solubility of solid compounds in supercritical CO2 using a connectionist smart technique

In this communication, an Adaptive Neuro-Fuzzy Inference System (ANFIS) was developed for estimation of solubility of several solid species in supercritical CO2. A total of 795 data points were collected from the literature and used in the process of model development and evaluation. The Genetic Algorithm (GA) was implemented to optimize the radius of influence of initial Fuzzy Inference System (FIS). The tuning parameters of FIS structure were optimized by utilizing a new method based on conjugation of hybrid and Particle Swarm Optimization (PSO) method namely CHPSO method. The accuracy of the proposed model was evaluated using graphical and statistical analysis and by comparing the results with another model reported in the literature. Results show that the developed conjugate ANFIS model is robust and precise in prediction of experimental data and is superior to other literature model.

Modified Redlich-Kwong and Peng-Robinson Equations of State for Solubility Calculation of Solid Compounds in Supercritical Carbon dioxide

The modified Redlich-Kwong (βRK) and modified Peng-Robinson (βPR) Equations of State (EoSs) combined with the van der Waals mixing rule (vdW0) have been proposed to evaluate the solubilities of ten solid compounds in supercritical CO 2 . These ten solid compounds are including Methimazole, Ascorbic acid, Ascorbyl palmitate, Propyl gallate, Aspirin, Fluoranthene, Triclocarban, Hinokitiol, Phenol, and Climbazole. In order to recognize the accuracy of the proposed EoSs, the results of these models have been compared with the calculation results of SRK and PR equations of state in combination with the vdW1 and the Wong-Sandler (WS) mixing rules and other models reported in the literature. The results showed that the proposed models are well for solubility calculation of these ten solid compounds in supercritical CO 2 and the RK EoS in combination with the vdW0 mixing rule led to better correlation (AARD = 5.1%) compared with other ones.

Formation of molecular complexes of salicylic acid, acetylsalicylic acid, and methyl salicylate in a mixture of supercritical carbon dioxide with a polar cosolvent

The solvate structures formed by salicylic acid, acetylsalicylic acid, and methyl salicylate in supercritical (SC) carbon dioxide with a polar cosolvent (methanol, 0.03 mole fractions) at a density of 0.7 g/cm3 and a temperature of 318 K were studied by the molecular dynamics method. Salicylic and acetylsalicylic acids were found to form highly stable hydrogen-bonded complexes with methanol via the hydrogen atom of the carboxyl group. For methyl salicylate in which the carboxyl hydrogen is substituted by a methyl radical, the formation of stable hydrogen bonds with methanol was not revealed. The contribution of other functional groups of the solute to the interactions with the cosolvent was much smaller. An analysis of correlations between the obtained data and the literature data on the cosolvent effect on the solubility of the compounds in SC CO2 showed that the dissolving ability of SC CO2 with respect to a polar organic substance in the presence of a cosolvent increased only when stable hydrogen-bonded complexes are formed between this substance and the cosolvent.

Correlating and estimating the solubilities of solid organic compounds in supercritical CO2 based on the modified expanded liquid model and the group contribution method

The expanded liquid model was investigated and a modified solution model was proposed in this paper. The results showed that in the expanded liquid model the accuracy of the solubility parameters of supercritical CO2 (sc-CO2) can affect the change of the variables. If the solubility parameters of sc-CO2 are accurate, the variables in the expanded liquid model are nearly temperature-independent. If the inaccurate solubility parameters of sc-CO2 were used, the variables in the model would be slightly temperature-dependent. When using the solubility parameter of the solute as variable and calculating the solubility parameters of sc-CO2 with accurate method in the expanded liquid model, it is found that the solubility parameter of the solute is the linear function of the ratio of the solubility parameter and molar volume of sc-CO2 (δ1/v1). Based on this linear function, the expanded liquid model was modified. In the modified model, the slope and the intercept of the linear function were used as the fitting parameters. The modified model was compared with the other two-parameter expanded liquid models and the results showed the modified model can provide better correlation results with the average absolute relative deviation (AARD) being 13.31%. A group contribution method was developed to estimate the parameters in the modified model. Based on the modified model and the group contribution method, the solubilitis of most of the solutes in sc-CO2 can be estimated in the order of magnitude.

Dissolution of surfactants in supercritical CO2 with co-solvents

The dissolution of surfactant-like compounds in supercritical CO2 in presence of co-solvents was investigated. The solubility measurement was conducted using a visualized PVT cell combined with UV spectrophotometer method at different pressures and 313K. The viscosity of mixtures of CO2 and co-solvents with or without dissolved surfactants was also measured at similar conditions using a capillary tube rheometer. Nonionic surfactants (N-NP-10c, branched alkylphenol ethoxylates and APG-1214, alkyl polyglucoside) and anionic surfactants (N-NP-15c-H, sulfonated alkylphenol ethoxylates) were studied, which are good CO2 foaming agents. Experimental results showed that increasing pressure and addition of co-solvents could effectively improve solubility of surfactants in supercritical CO2. The addition of ethanol as a co-solvent could increase N-NP-10c's solubility in CO2 from 0.15g (100g)−1 to 1.76g (100g)−1 (over 11 times). APG-1214 with a mixture of ethanol and ethylene glycol as co-solvents exhibited an immediate dissolution capability in CO2, and its solubility could reach up to 1.99g (100g)−1. The solubility of N-NP-15c-H in comparison with APG-1214 was relatively low, only 0.57g (100g)−1 was obtained with the same co-solvents and at similar conditions. The addition of ethanol into CO2 could slightly increase its viscosity, while the effect of ethylene glycol and surfactants was much higher than that of ethanol, which indicates that the dissolution of surfactants in CO2 with co-solvents involves complicated interactions between molecules.

Modeling solubility in supercritical carbon dioxide using quantitative structure–property relationships

Prediction of solubility in supercritical CO2 (SC-CO2) as a function of system pressure and temperature aids selection of process condition for extraction processes. Previously, other groups have developed semi-empirical models to predict solubility of different compounds in SC-CO2. We built quantitative structure–property relationships (QSPRs) to predict the parameters of the solubility equation of Chrastil using a small set of descriptors obtained from their equilibrated 3D structure after molecular dynamic simulations in implicit CO2. Using 30 compounds for training and testing the model, leave-one-out strategy was used to select the descriptors, and leave-10%-out was used for crossvalidation. These models, that give very good correlations (R2>0.91 for test set), were tested against five new compounds for validation giving accurate predictions of the solubility as function of pressure and temperature, for three of them. In an alternative approach, accurate predictions of solubility as function of pressure and temperature were obtained for the five compounds if the experimental value of the solubility at a reference temperature was known and only the effect of pressure and temperature was obtained through the model.

Modeling of Askarel solubility in supercritical CO2 aiming solid residue treatment

Polychlorinated biphenyls (PCB) are chlorinated organic substances which are highly toxic and also considered persistent organic pollutants (POP). It should be emphasized the environmental importance for treating wastes with PCB. For instance, Stockholm convention on POP established the elimination of the use of PCB in equipments, e.g., electrical transformers and capacitors, by 2025. The decontamination of materials containing PCB may be performed by supercritical extraction technology using carbon dioxide (CO2) as solvent. The first objective of this work was the formulation of a computational tool to correlate solubility data of aromatic compounds in supercritical CO2, using Peng–Robinson equation of state. In a second step, a description of Askarel oil, like Araclor 1254, solubility in supercritical CO2 was provided for simulation purposes of the extraction process. PCB mixture has predominance of congeners: tetra, penta, hexa, heptachloro biphenyl, tri and tetrachlorobenzene. The calculation procedure was initially applied for a series of aromatic compounds (naphthalene, biphenyl, anthracene and phenanthrene) in order to validate the approach. Experimental solubility data collection has been elaborated from the literature, providing a systematic series of the studied aromatic compounds with CO2. The binary parameters for the classical van der Waals quadratic mixing rule (vdW2) were systematically estimated, together with a new set of Clausius–Clapeyron solute vapor pressure in order to describe the temperature dependence and achieve experimental solubility uncertainties. Finally, the estimated parameters were used to simulate solubility values of Askarel oil as function of the operational conditions of extraction by a simultaneous solution of the equilibrium equations for each compound. The thermodynamic modeling demonstrated to be feasible for process analysis and design.

Correlation of solid solubility of 1,4-bis(alkylamino)-9,10-anthraquinones in supercritical carbon dioxide using solution model approach

In this study, solid solubility data of six 1,4-bis(alkylamino)-9,10-anthraquinones (AQs) in supercritical carbon dioxide (CO2) are correlated using a two-parameter solution model developed from the regular solution model coupled with the Flory–Huggins equation. This two-parameter solution model yields satisfactory correlated results comparable to those from commonly used three-parameter semi-empirical equations. The average deviation in correlated solubilities using our two-parameter solution model is about 6%. With appropriate model simplification and generalization procedure, a predictive solution model is proposed in this study for solubility prediction using the chain length of alkyl group of alkylamino side chain. The proposed predictive solution model provides acceptable predicted results and yields average deviation in predicted solubilities of 17%. In addition, the proposed predictive solution model is also employed to predict the solubility data of AQs that are not originally included in the generalization procedure. The calculated results obtained in this study demonstrate that the solution model adopted in this study is applicable for correlation and prediction of solid solubilities of structure-related compounds in supercritical CO2.

Correlation and estimation of solubilities of fatty acids in supercritical carbon dioxide using solution model approach

In this study, solid solubility data of five fatty acids in supercritical carbon dioxide (CO2) at different temperatures and pressures are correlated using a two-parameter solution model developed from the regular solution model coupled with the Flory⿿Huggins equation. The developed solution model with fewer parameters yields correlated results comparable to those from commonly used semi-empirical equations. In addition, both parameters in the solution model can be further generalized with the chain length of fatty acids and a new predictive solution model is proposed for solubility prediction. The predictive solution model proposed in this study provides better predicted results and yields average deviation in predicted solubilities of 22.1%. To further apply this solution model to other compounds, solid solubility data of three triglycerides in supercritical CO2 at 313K are also correlated. After model simplification and generalization, a new predictive solution model for triglycerides is also proposed, which yields average deviation in predicted solubilities of 29.8%. These results demonstrate that the solution model used in this study is applicable for correlation and prediction of solid solubilities of structure-related compounds in supercritical CO2.

Correlating and predicting the solubilities of structurally similar organic solid compounds in supercritical CO2 using the compressed gas model and the reference solubilites

In this paper, the solubilities of some structurally similar organic solid compounds namely 9,10-anthraquinone derivatives, thioxanthone derivatives, pyrazolones and steroids were correlated and predicted using the compressed gas model combined with the Carnahan–Starling–van der Waals equation of state (CS–VDW EoS) and the Peng–Robinson equation of state (PR EoS), respectively. To avoid using the sublimation pressure of the solute and reduce the applied pressure range of the corresponding equation of state, a solubility datum was used as the reference solubility in the compressed gas model. By introducing the reference solubility, the simple van der Waals one-parameter (VDW1) mixing rules can be used for the supercritical solutions and the calculated solubilities are not sensitive to the binary parameter in the compressed gas model. So in solubility prediction, the binary parameter in the compressed gas model can be set constant for a series structurally similar organic compound. The prediction results showed that the compressed gas model combined with the CS–VDW EoS–VDW1 provide better prediction (average absolute relative deviations, AARD=18.41%) for the compounds with similar structure and without intermolecular hydrogen bond. For the compounds with larger structural differences, the compressed gas model combined with the PR EoS–VDW1 is recommended. However, for the compounds with intermolecular hydrogen bond, neither of the two EoS can provide satisfactory prediction results.

A New Glimpse into the CO2‐Philicity of Carbonyl Compounds

We report a theoretical study on non-conventional structures of 1:1 complexes between carbon dioxide and carbonyl compounds. These structures have never been reported before but are relevant for understanding the solubility of carbonyl compounds in supercritical CO(2). The work is based on the results of ab initio calculations at the MP2 and CCSD(T) levels using aug-cc-pVDZ and aug-cc-pVTZ basis sets. Investigated systems include aldehydes, ketones and esters, together with some fluorinated derivatives. The results are interpreted in terms of natural bond orbital analyses. Harmonic vibrational frequency calculations have also been done in order to compare them with available experimental data. We show for the first time that complexes where CO(2) behaves globally as a Lewis base are stable in the case of ketones and esters, but not in the case of aldehydes, and their stability is similar to that of traditional complexes in which CO(2) behaves as a Lewis acid. This finding considerably modifies the concept of CO(2)-philicity and may have important ramifications in the development of green reactions in supercritical CO(2).

Solubilities and partial molar volumes of N,N′-dibutyl-oxalamide, N,N′-dihexyl-oxalamide, N,N′-dioctyl-oxalamide in supercritical carbon dioxide

Three new potent CO2-philic compounds were synthesized and their structures were characterized by FT-IR, NMR, and elemental analysis. The solubility of the three compounds in supercritical CO2 was determined at T=(313 to 353)K from 9.1MPa to 15.0MPa. The experimental data were correlated with two density-based models proposed by Bartle and Chrastil, and the calculated results showed good agreement with the tested data. The calculated data by Bartle model differed from the measured values by (6.76 to 9.60)%, and the average value of absolute relative deviations (AARD) with Chrastil model were observed to be between (7.42 to 12.27)%. Furthermore, solubility data were also utilized to estimate the partial molar volume V¯2 for each compound in the supercritical phase using the theory developed by Kumar and Johnston.

Effect of gas pressure on the phase behaviour of organometallic compounds

The knowledge of the phase behaviour of organometallic compounds in supercritical CO 2 is the key factor for determining the feasibility of homogeneous catalysis in supercritical fluid reaction. In the present study, the solid–liquid–gas equilibrium line for the system CO 2/Cu(thd) 2, CO 2/Pt(COD)Me 2 and He/Pt(COD)Me 2 was determined from 0.1 MPa to 25 MPa. In addition, experimental solubility data of Cu(thd) 2 in CO 2 at 333 K and pressures ranging from 10 MPa to 17 MPa as well as of Pt(COD)Me 2 in CO2 at 313 K, 333 K and 353 K and pressures ranging from 12 MPa to 32 MPa are presented. The solubility data are correlated using the linear relationship between the logarithm of the solubility and the logarithm of the reduced density of pure CO 2 proposed by Kumar and Johnston as well as an extension of the theory of dilute solution proposed by Mendez-Santiago and Teja. Both approaches gave reasonable results in the correlation of the experimental solubility data.