Compounds In Supercritical Carbon Dioxide Research Articles

Theoretical Studies of Energetics and Diffusion of Aromatic Compounds in Supercritical Carbon Dioxide

Atomic and molecular interactions of aromatic compounds in carbon dioxide are studied with ab initio and molecular dynamics techniques. Ab initio calculations are used to determine the nature of the CO2−CO2, CO2−benzene, and benzene−benzene interactions. We select an explicit all-atom force field without partial atomic charges to describe the intermolecular and intramolecular pair interactions of CO2 with benzene and toluene. Molecular dynamics simulations are used to calculate diffusion coefficients for benzene and toluene at infinite dilution in CO2 along isotherms at 313.15, 323.15, and 333.15 K, in the density range from 1.35ρc to 2.10ρc (ρc = critical CO2 density). Diffusion coefficients are also calculated with a model based on perturbation theory of simple liquids. The calculated diffusion coefficients agree fairly well with the experimental results of Suarez et al. (Chem. Eng. Sci. 1993, 48, 2419).

Prediction of Supercritical Carbon Dioxide Solubility of Organic Compounds from Molecular Structure

A diverse data set of 58 compounds taken from the literature was used to create models for the prediction of the solubility of organic compounds in supercritical carbon dioxide. Descriptors encoding information about the topological, geometric, and electronic properties of each compound in the data set were calculated from the molecular structures. A multiple linear regression model containing seven descriptors was generated. Several new descriptors, which were not present in the original pool, were calculated. One of the new descriptors was used to create the final seven descriptor linear model, which had a better root mean square (rms) error than the original model. The seven descriptors that appeared in the final model were used to make a neural network model which had a significantly better rms error than the linear model.

Monte Carlo Simulation of Solubilities of Aromatic Compounds in Supercritical Carbon Dioxide by a Group Contribution Site Model

The Monte Carlo method was applied to calculate the solubilities of phenol, xylenol isomers, naphthol isomers, and dimethylnaphthalene isomers in supercritical carbon dioxide. These systems are binary mixtures under gas−solid equilibrium conditions. Carbon dioxide was treated as a single-site molecule, and aromatic compounds were treated as multisite molecules. For the aromatic compounds, a benzene ring, a methyl group, and a hydroxyl group were adopted as sites (groups). The Lennard-Jones (12−6) potential was used as the site−site potential, and the Lorentz−Berthelot mixing rules were adopted for unlike pair sites. A modified test particle method was adopted to calculate the residual chemical potentials of aromatic compounds in supercritical carbon dioxide based on the canonical (NVT) ensemble. The calculated solubilities were in good agreement with the experimental data by using common potential parameters determined. The solubilities of isomers can be quantitatively distinguished by the group contribution site model without any binary interaction parameters. Moreover, the microscopic structures of supercritical carbon dioxide around aromatic isomers were studied. The structures of supercritical carbon dioxide around aromatic isomers were found to be different because of the screen effect of substituents.

Monte Carlo calculation of solubilities of aromatic compounds in supercritical carbon dioxide

Monte Carlo method has been applied to calculate the solubilities (gas-solid equilibria) of naphthalene, dimethylnaphthalene isomers, and xylenol isomers in supercritical carbon dioxide. Carbon dioxide was treated as single-site molecule and naphthalene, dimethylnaphthalenes, and xylenols were treated as two-site (two benzene-ring groups), four-site (two benzene-ring and two methyl group), four-site (one benzene-ring, one hydroxyl, and two methyl groups) molecules, respectively. The Lennard-Jones (12-6) potential was used as the site-site potential and the Lorentz-Berthelot mixing rules were adopted for unlike site pairs. A modified test particle method was used to calculate the residual chemical potentials of aromatic compounds in supercritical carbon dioxide based on the NVT canonical ensemble. The calculated results of solubilities show good agreement with the experimental values. The solubilities of isomers can be distinguished by the site model. The residual chemical potentials of xylenol isomers calculated by the site model are affected by the position of methyl group. This fact suggests the screen action of methyl group against hydroxyl group. The site model is very useful to explain the screen action.

Solid solubilities of methoxyphenylacetic acid isomer compounds in supercritical carbon dioxide

The solid solubilities of the isomers o-, m-, and p-methoxyphenylacetic acid were measured in supercritical carbon dioxide at 308.2 K over a pressure range of 11--34 MPa. The results were correlated by the Peng-Robinson equation of state and the augmented van der Waals-density-dependent local composition equation. The data showed that solubility increased in the order of o-, p-, and m-methoxyphenylacetic acid, and the latter equation of state gave a much better correlation than the Peng-Robinson equation.

Calculations of solubilities of aromatic compounds in supercritical carbon dioxide. [Erratum to document cited in CA117(6):56879v

ADVERTISEMENT RETURN TO ISSUEPREVArticleCalculations of solubilities of aromatic compounds in supercritical carbon dioxide. [Erratum to document cited in CA117(6):56879v]Yu Jane Sheng, Ping Chin Chen, Yan Ping Chen, and David Shan Hill WongCite this: Ind. Eng. Chem. Res. 1992, 31, 6, 1581Publication Date (Print):June 1, 1992Publication History Published online1 May 2002Published inissue 1 June 1992https://doi.org/10.1021/ie00006a025RIGHTS & PERMISSIONSArticle Views24Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (61 KB) Get e-Alerts Get e-Alerts

Calculations of solubilities of aromatic compounds in supercritical carbon dioxide

Solubilities of five aromatic compounds in supercritical carbon dioxide are calculated by using the Patel-Teja equation of state. Unlike the traditional van de Waals mixing rules, the energy parameter of the equation of state is evaluated by equating the excess free energy calculated by the equation of state to that from a UNIFAC group contribution liquid model. New UNIFAC group interaction parameters of carbon dioxide and various hydrocarbons groups are obtained through regression of experimental vapor-liquid equilibrium data. A new mixing rule for the excluded volume parameter of the equation of state is proposed, and a generalized correlation of that parameter is presented

Determination of binary diffusion coefficients of organic compounds in supercritical carbon dioxide by supercritical fluid chromatography

Binary diffusion coefficients, D 12, in supercritical carbon dioxide were determined in a supercritical fluid chromatographic apparatus by the peak-broadening method. Organic compounds belonging to three different classes, namely ketones, fatty acids and liquid crystals and additionally squalene were investigated as a function of pressure between 9.5 and 18 MPa at about 314 K. The resulting D 12 values are of the order of 10 −8 m 2 s −2 and 1n D 12 decreases approximately linearly with increasng density of the carbon dioxide.

Effect of added water on voltammetry in near-critical carbon dioxide

The use of microvoltammetric electrodes in near-critical carbon dioxide has been investigated. The working electrode is a platinum disk of 5 ..mu..m radius and the test compound employed is ferrocene. Voltammetry is not possible without the addition of water to the electrochemical cell. At temperatures and pressures above the critical point for pure CO/sub 2/, a well-defined voltammetric wave for ferrocene is obtained in the presence of 0.64 M water. Added water also enables the dissolution of tetrahexylammonium hexafluorophosphate in this medium. The diffusion coefficient obtained from voltammograms of ferrocene recorded in these fluids is similar to that reported for other compounds in supercritical carbon dioxide. However, in the presence of a high concentration (0.05 M) of the added salt, the value of the diffusion coefficient is lowered. These results demonstrate that the addition of water to near-critical carbon dioxide results in a fluid which has much greater solvating power than the pure supercritical fluid.

Capacity ratios and diffusion coefficients of low-volatile organic compounds in supercritical carbon dioxide from supercritical fluid chromatography (SFC)

Capacity ratios k have been determined for phenyl myristate, phenyl palmitate and phenyl stearate from supercritical fluid chromatography (SFC) at 35 to 56°C and 85 to 190 bar using supercritical CO 2 as mobile phase and Perisorb A and Perisorb RP8 as stationary phases. For the esters used a rise in pressure from 90 to 190 bar produces a drop of k by about two orders of magnitude giving evidence of the rapidly increasing solvent power of supercritical CO 2 with increasing density. At a constant CO 2 density, k decreases with increasing temperature. The separation of the esters was found to be the better the lower the pressure was. An apparatus for the chromatographic determination of binary diffusion coefficients in supercritical gases is described. D 12 values for some organic compounds in carbon dioxide at 40°C and in the pressure range from 80 to 160 bar are presented. With an improved electronic flow regulator an overall precision of the D 12 values of ±3% is obtained.