Compounds In Supercritical Carbon Dioxide Research Articles

Applications of cubic equations of state for determination of the solubilities of industrial solid compounds in supercritical carbon dioxide: A comparative study

Representation/predictions of the solubilities of industrial solid compounds in supercritical carbon dioxide have been a challenge since the last two decades. In this communication, the Soave–Redlich–Kwong (SRK), the Peng–Robinson (PR), the Patel–Teja–Valderrama (PTV), the Esmaeilzadeh–Roshanfekr (ER) and the modified Esmaeilzadeh–Roshanfekr (m-ER) equations of state (EoS) accompanied with several mixing rules including the Wong–Sandler (WS), the covolume-dependent (CVD) and the van der Waals one (vdW1) and two (vdW2) fluid mixing rules are applied to calculate/estimate the solubilities of 23 mostly used solid compounds in supercritical carbon dioxide. In addition, the Van-Laar excess Gibbs energy (Gex) activity model is also used in phase equilibrium calculations. The probable global optimal values of the proposed thermodynamic model parameters are evaluated by the differential evolution (DE) optimization strategy. The results indicate that the combination of the m-ER EoS with the WS mixing rule leads to more accurate predictions (AARD=7%) in comparison with other ones. Finally, application of Chrastil semi-empirical correlation for estimation of the solubilities of several compounds in supercritical carbon dioxide is investigated at wide ranges of temperatures.

Highly active and reusable palladium nanoparticle catalyst stabilized by polydimethylsiloxane for hydrogenation of aromatic compounds in supercritical carbon dioxide

This study describes a hydrogenation method for degrading polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) in supercritical carbon dioxide catalyzed by palladium nanoparticles stabilized in polydimethylsiloxane (Pd/PDMS). The process of synthesizing metal nanoparticles embedded in PDMS polymers involves the preparation of a homogenous mixture of metal salt, silicone elastomer, and a curing agent, followed by hydrogen reduction. PCBs and PAHs can be effectively hydrogenated to saturated hydrocarbons with greater than 99% efficiency in an hour under 200atm of CO2 containing 10atm of H2 at 313K using Pd/PDMS catalysts. The proposed Pd/PDMS catalysts can be reused without losing their activity and are significantly more active than commercial catalysts and a previously reported Pd nanoparticle catalyst stabilized in high-density polyethylene.

Solubility of pharmaceutical compounds in supercritical carbon dioxide

The solubility of pharmaceutical solid compounds in supercritical carbon dioxide is of great importance in a wide range of applications that include: development of drug delivery systems, powder processing, and precipitation/crystallization processes.This manuscript aims to estimate the solubility behavior of pharmaceutical compounds in supercritical fluids using an activity coefficient model based on linear solvation energy relationships. The parameters of this model were further generalized as a function of the properties of the pharmaceutical compounds. The selected compounds include antioxidants, antibiotics, steroids and anti-inflammatory and their solubility data were collected from literature.This model is able to estimate the solubility of the pharmaceutical compounds in supercritical carbon dioxide within acceptable accuracy for more than 60% of the proposed systems.

Infinite dilution partition coefficients of benzene derivative compounds in supercritical carbon dioxide + ionic liquid systems: 1-butyl-3-methylimidazolium chloride [bmim][Cl], 1-butyl-3-methylimidazolium acetate [bmim][Ac] and 1-butyl-3-methylimidazolium octylsulfate [bmim][OcSO4

Infinite dilution partition coefficients of benzene and benzene derivative compounds (chlorobenzene, bromobenzene, toluene, ethylbenzene, benzaldehyde, benzyl alcohol and phenol) between supercritical carbon dioxide and ionic liquids (1-butyl-3-methylimidazolium chloride [bmim][Cl], 1-butyl-3-methylimidazolium acetate [bmim][Ac] and 1-butyl-3-methylimidazolium octylsulfate [bmim][OcSO4]) were measured with a packed-column chromatographic technique. The Sanchez–Lacombe equation of state was used to correlate the data and could describe the qualitative changes of the infinite dilution partition coefficients over a wide range of temperatures (313–352K) and pressures (5–15MPa). A linear solvation energy relationship (LSER) model, LSER-δ, was developed for compressible phases that uses solute, solvent and ionic liquid solubility parameters. Partition coefficients were generally in the order of solute volatility with the exception of hydrogen bonding solutes. LSER solute volume (McGowan's volume, V) and solute dipolarity/polarizability (S) greatly affected the partition coefficient values. It was found that the McGowan's volume can be considered as a function of the CO2 solubility parameter, which may be helpful in extending LSER theory to supercritical fluid systems. Both models could describe the partition coefficient well and were useful in understanding some of the interactions of the solute with the supercritical CO2 and ionic liquid phases.

An improved density-based model for the solubility of some compounds in supercritical carbon dioxide

The ability to correlate the solubility of solutes in supercritical fluids (SCF) is of great importance for the design and evaluation of any supercritical process. The empirical equations are quite successful in correlating the solubility of compounds in the SCF. In this work, a new density-based semi-empirical model was proposed to correlate some compounds in supercritical carbon dioxide. Solubility data from 54 different compounds were collected from literature published in the last ten years and the different empirical models (Chrastil, Adachi-Lu, del Valle-Aguilera, Kumar-Johnston, Méndez Santiago-Teja, Gordillo, Jouyban, Sparks, Garlapati-Madras, and Ch-Madras) were evaluated. The results showed that, the proposed model produced the least global average absolute relative deviation (5.91%) compared to all other empirical models considered in this study.

A comparison between neural network method and semi empirical equations to predict the solubility of different compounds in supercritical carbon dioxide

Accuracy of seven semi empirical equations for the estimation of solubility of 30 different compounds in supercritical carbon dioxide has been compared with a new neural network method. To base this comparison on a fair basis, a unique set of experimental data was used for both optimization of semi empirical equations’ parameters and training, validation and testing of neural network. Results showed that neural network method with an average relative deviation of about 5.3% was more accurate than the best semi empirical equation with an average relative deviation of about 15.96% for same compounds. It was also found that the average relative deviation of semi empirical equations varies sharply among different compounds, while this quantity is less dependent on material type for neural network method.

Artificial Neural Network Modeling of Solubilities of 21 Commonly Used Industrial Solid Compounds in Supercritical Carbon Dioxide

In this communication, a feed-forward artificial neural network algorithm has been applied to calculate/predict the solubilities of 21 of the commonly used industrial solid compounds in supercritic...

Thermodynamic modeling of solubilities of various solid compounds in supercritical carbon dioxide: Effects of equations of state and mixing rules

No one can ever deny the significance of calculations of solubilities of industrial solid compounds in supercritical CO2 in separation processes. In this work, the Peng–Robinson (PR) and the Esmaeilzadeh–Roshanfekr (ER) equations of state (EoS) along with several mixing rules including the Wong–Sandler (WS), the covolume dependent (CVD) and the van der Waals one (VDW1) and two (VDW2) fluid mixing rules are applied to evaluate the solubilities of 52 mostly used solid compounds in supercritical carbon dioxide. Besides, the Van-Laar excess Gibbs energy (Gex) model is applied in phase behavior calculations by the WS mixing rule. The optimal values of the proposed thermodynamic model parameters are evaluated using the DE (differential evolution) optimization strategy. The absolute average deviations of the model results from 1776 experimental data points and the optimal values of the adjustable parameters of the model are reported to investigate the capabilities of combinations of each equation of state with different mixing rules in calculations of the solubilities. The results indicate that the combination of the ER EoS with the WS mixing rule leads to more accurate results (AAD=9.0%) compared with other ones.

A comparison between semiempirical equations to predict the solubility of pharmaceutical compounds in supercritical carbon dioxide

Abstract The aim of this work is to determine, depending on the operation conditions, which semiempirical equation provides the best fit to solubility data of pharmaceutical compounds in supercritical CO 2 . Solubility data from 27 different pharmaceutical solutes were collected from literature and the different density-based models (Chrastil, Adachi-Lu, del Valle-Aguilera, Sparks, Kumar-Johnston, Bartle, Mendez Santiago-Teja) together with the Yu's model and Gordillo's model were employed. The results showed that, in general, Sparks’ equation provides the best fit to the solubility data for this kind of solids in supercritical CO 2 . However, at certain specific conditions, the best correlation is obtained using Gordillo's equation. By means of a brief comparison with Peng-Robinson equation of state, semiempirical equations present a more accuracy prediction compared to cubic equations of state, and present no drawbacks such as properties estimation and computational difficulties.

Production of linear alkane via hydrogenative ring opening of a furfural-derived compound in supercritical carbon dioxide

A simple method has been described to accomplish the formation of linear alkane with >99% selectivity in supercritical carbon dioxide under very mild conditions using Pd/Al-MCM-41 catalyst. The linear alakne was formed through the hydrogenation and dehydration/hydrogenation of 4-5-(5-(hydroxymethyl)furan-2-yl)but-3-en-2-one, which is an aldol condensation product of 5-hydroxymethyl furfural and acetone.

Application of Dithiol Compounds in Supercritical Carbon Dioxide to Improve the Adhesive Properties of Copper-Plated p-Aramid Fibers

Supercritical carbon dioxide (scCO2) has been used to impregnate the organometallic complexes in a synthetic polymer prior to electroless copper plating. However, this method has not been applied to highly crystalline and highly oriented polymers, such as p-aramid fibers. In this study, triazine dithiols were used to create a network that consisted of Kevlar® fibers, the organometallic complex palladium (II) hexafluoroacetylacetonate [Pd(hfa)2], and a metal layer. This network improved the adhesion of a copper layer that was added by electroless plating. Three triazine thiols were used, two of which were soluble in scCO2 and one of which was soluble in water. Pretreatment of the Kevlar® fibers comprised two steps : 1) impregnation with a thiol compound, using sc-CO2 or the thiol-water solution ; and 2) impregnation with an organometallic metal complex using sc-CO2. Electroless plating was performed to coat the treated Kevlar® fibers with a layer of copper. By changing the experimental conditions (i.e., pressure, temperature, thiol concentration, and order of impregnation), we found that the triazine thiol improved the electrical resistivity and adhesion of the copper layer.

Diffusion coefficients of diesel fuel and surrogate compounds in supercritical carbon dioxide

Facilitating a new concept of clean diesel combustion using supercritical fluids requires a better understanding of thermophysical properties of the diesel fuel/diluent system. Mass diffusivity is one such property that is important to understand diesel fuel/diluent mixing and spray and combustion of supercritical fuel mixtures. In this work, diffusion coefficients of diesel fuel and surrogate compounds in supercritical carbon dioxide were experimentally determined by the Taylor dispersion method at temperatures from 313.15 to 373.15 K and pressures up to 30 MPa. Difficulties were encountered to measure diffusion coefficients using the Taylor dispersion method near the critical region of CO 2 which resulted in curve-fitting errors greater than 5%. Predictive correlations including Wilke–Chang, Scheibel, and He–Yu were examined. Diffusivity data were also fitted by D 12/ T − η and D 12 / T − ρ correlations. Results showed that the He–Yu correlation has the best prediction performance while the D 12/ T − η correlation best fits the data with AAD% < 8%.

Robust modelling of solubility in supercritical carbon dioxide using Bayesian methods

Two sparse Bayesian methods were used to derive predictive models of solubility of organic dyes and polycyclic aromatic compounds in supercritical carbon dioxide (scCO(2)), over a wide range of temperatures (285.9-423.2K) and pressures (60-1400 bar): a multiple linear regression employing an expectation maximization algorithm and a sparse prior (MLREM) method and a non-linear Bayesian Regularized Artificial Neural Network with a Laplacian Prior (BRANNLP). A randomly selected test set was used to estimate the predictive ability of the models. The MLREM method resulted in a model of similar predictivity to the less sparse MLR method, while the non-linear BRANNLP method created models of substantially better predictivity than either the MLREM or MLR based models. The BRANNLP method simultaneously generated context-relevant subsets of descriptors and a robust, non-linear quantitative structure-property relationship (QSPR) model for the compound solubility in scCO(2). The differences between linear and non-linear descriptor selection methods are discussed.

Study of impregnation of poly(l-lactide-ran-ε-caprolactone) copolymers with useful compounds in supercritical carbon dioxide

Outstanding controlled release materials were developed using statistically random copolymers of l-lactide (l-LA) with e-caprolactone (CL) using Sn(oct)2 as a catalyst at 150 °C for 24 h without solvent. Preparation of novel controlled release materials was carried out using useful organic compounds with low boiling points and synthetic random copolymers composed of l-LA and CL as base materials under supercritical carbon dioxide (scCO2). Low-boiling-point compounds such as d-limonene, hinokitiol, and trans-2-hexenal were used. In impregnation experiments using scCO2, the amounts of low-boiling-point compounds increased with an increase in l-LA content. When enzymatic degradation of poly(l-LA-ran-CL) was performed using lipase PS, copolymers with higher CL contents degraded more rapidly than did copolymers with higher l-LA content. In contrast, enzymatic degradation of copolymers occurred to a higher degree with increased l-LA content in enzymatic degradation by proteinase K. In a controlled release experiment with poly(l-LA-ran-CL) (=73/27), after 400 h of degradation by proteinase K, the remaining weight of the copolymer pellet was 6% and the amount of d-limonene remaining in the pellet was 15%.

Solid - Gas Equilibrium in Systems Containing Aromatic Compounds and Supercritical Carbon Dioxide

A cubic equation of state, GEOS, with quadratic mixing rules and two adjustable parameters was used to calculate the solid � gas equilibrium in aromatic compounds + supercritical carbon dioxide systems. The results are in good agreement with the experimental data for temperatures between 308 K and 343 K and pressures up to 360 bar. The adjustable parameters kij and lij used in the mixing rules vary linearly with the temperature or remain constant for the investigated systems. Based on this observation, the binary interaction parameters and hence, the solubilities of the studied solid aromatic compounds in supercritical carbon dioxide can be predicted.

Solubilities of Amide Compounds in Supercritical Carbon Dioxide

2,2′-Oxybis(N,N-diethylacetamide), 2,2′-oxybis(N,N-dibutylacetamide), and 2,2′-oxybis(N,N-dihexylacetamide) were synthesized, and their structures were confirmed by IR, NMR, and elemental analysis. The solubilities of compounds were measured at temperatures ranging from (313 to 333) K and pressures from (8.7 to 16.4) MPa in supercritical carbon dioxide. The measured solubilities were correlated using a semiempirical model. The calculated results showed satisfactory agreement with the experimental data and differed from the measured values by between (4.54 and 30.84) %.

Palladium Supported on an Acidic Resin: A Unique Bifunctional Catalyst for the Continuous Catalytic Hydrogenation of Organic Compounds in Supercritical Carbon Dioxide

Abstract1% Palladium‐doped acidic resin (Amberlyst® 15; styrene‐divinylbenzene matrix with sulfonic acid groups) is shown to be a highly active catalyst for the continuous catalytic hydrogenation of CC bonds in supercritical carbon dioxide (scCO2) without affecting CO bonds. This 1% Pd/Amberlyst‐15 catalyst promotes the industrially important selective formation of 2‐ethylhexanal from crotonaldehyde in a “one‐pot” pathway involving hydrogenation and aldol condensation with a number of merits. The selectivity behavior of 1% Pd/Amberlyst‐15 is strikingly different compared to that of 1% Pd/C and 1% Pd/Al2O3 due to its prominent bifunctional nature based on sulfonic acid groups adjacent to metallic Pd sites. Hybrid “[Pdn–H]+” sites are suggested to act as both metal and acid sites promoting the bifunctional catalysis.

Correlation for the solubilities of pharmaceutical compounds in supercritical carbon dioxide

The solid solubilities of pharmaceutical compounds in supercritical carbon dioxide were correlated using the regular solution model with the Flory–Huggins equation. The pharmaceutical compounds include steroids, antioxidants, antibiotics, analgesics and specific functional drugs. The molar volumes of these solid solutes in supercritical carbon dioxide were taken as the empirical parameters in this study. They were optimally fitted for each pharmaceutical compound using the experimental solid solubility data from literature. The logarithms of the molar volumes of these solutes were then correlated as a linear function of the logarithms of the densities for supercritical carbon dioxide. With one or two parameters in this linear equation, satisfactory solid solubilities were calculated that were comparable to those from the commonly used semi-empirical equations with more adjustable parameters. The parameters of this model were further generalized as a function of the properties of the pharmaceutical compounds. It was observed that the prediction of solubilities of pharmaceutical compounds in supercritical carbon dioxide was within acceptable accuracy for more than 50% of the systems investigated in this study.

Catalytic hydrogenation of polyaromatic hydrocarbon (PAH) compounds in supercritical carbon dioxide over supported palladium

A series of supported palladium catalysts were evaluated for their ability to mediate the complete hydrogenation of polycyclic aromatic hydrocarbon (PAH) compounds. Benzo[a]pyrene (B[a]P) or phenanthrene (Phe) in hexane was merged with a hydrogen-carbon dioxide [5% (w/w) H(2)/CO(2)] stream and transferred to a flow through mini-reactor (capacity ca. 1 g) that was maintained at 90 degrees C under a back-pressure of 20.68 MPa. Effluent from the reactor trapped in hexane was monitored/quantified by gas chromatography-mass spectrometry. Catalyst formulations supported on iron powder, high density polyethylene (HDPE) or gamma-alumina were prepared and compared in terms of hydrogenation activity as measured by the quantity of substrate per unit time that could be perhydrogenated to toxicologically innocuous products. Both of the Pd preparations supported on gamma-alumina were more efficient than a commercial Pd(0) (5% w/w) on gamma-Al(2)O(3) formulation or preparations supported on HDPE or the iron powder. Bimetallic mixtures with Pd increased the hydrogenation activity when co-deposited with Cu or Ni but not with Ag or Co. However, increases in hydrogenation activity by increasing the loading of Pd (or bimetallic mixture) on this surface were limited. Despite using supercritical carbon dioxide (scCO(2)) to swell the surfaces of the polymer, the deposition of nanoparticles within the polyethylene formulation was appreciably less active than either the oxidic or the Fe(0) formulations.

Determination of vapor pressure and solubility correlation of phenolic compounds in supercritical CO 2

New vapor pressure data for phenolic compounds (caffeic acid, ferulic acid, and p- and o-coumaric acids) were experimentally obtained and compared to values predicted by a group contribution method. A gas–liquid chromatography method was used to experimentally determine the vapor pressure since this method is reliable, reproducible and rapid. These vapor pressure data were then used to predict second cross virial coefficients of phenolic compounds in supercritical carbon dioxide (SC CO 2) using a method based on the residual chemical potential in terms of the virial coefficients and fluctuation theory. The solubility results obtained by this method were compared to those from two other correlations based on the regular solution theory and Chrastil equation. Good agreement was obtained with the correlations when compared to the experimental literature data on the solubility of phenolic compounds in SC CO 2.