Yoshio Koga

Influence of cosolvent on solubilities of fatty acids and higher alcohols in supercritical carbon dioxide

Abstract Influences of cosolvents on the solubilities of fatty acids (palmitic acid (C 15 H 31 COOH) and stearic acid (C 17 H 35 COOH)) and higher alcohols (cetyl alcohol (C 16 H 33 OH) and stearyl alcohol (C 18 H 37 OH)) in supercritical carbon dioxide were measured by using a flow-type apparatus. Experiments were carried out at 308.2 K under 9.9, 14.8 and 19.7 MPa. Ethanol and octane were used as cosolvents. The concentration of cosolvent was up to 10 mol %. The experimental results were correlated by the regular solution model coupled with the Flory-Huggins theory using the local composition of cosolvent around the solute molecule.

Monte Carlo simulation for chain molecules in supercritical ethane

Monte Carlo simulation was applied to calculate the static properties of chain molecules (C28H58, C30H62, and C32H66) in supercritical ethane at 308.15 K. Chain molecule and ethane were treated as a linear chain with many sites and single site molecules, respectively. The potential functions proposed by Jorgensen et al. were used for the interaction energy between pair sites and the rotational potential energy of valence bonds. The residual chemical potential was calculated by the isothermal–isobaric Kirkwood method in order to calculate the solubilities of chain molecules in supercritical ethane. An intermolecular interaction parameter between ethane and chain molecule was introduced to fit the calculated solubilities to the literature data. Furthermore, the mean‐square end‐to‐end separation, the mean‐square radius of gyration, the probability density distribution of rotational angles of the chain molecules, and the radial distribution function were reported as fundamental knowledge of the microstructure of the chain molecule in supercritical ethane.

Monte carlo simulation of solubilities of naphthalene in supercritical carbon dioxide

Abstract The test particle method proposed by Widom was applied to calculate the solubilities of naphthalene in supercritical carbon dioxide at 308.15 and 328.15 K. The Lennard-Jones (12-6) potential was used as the intermolecular potential. The solubilities of naphthalene in supercritical carbon dioxide have been calculated quantitatively by introducing two binary interaction parameters k 12 and l 12 between unlike molecules. The binary interaction parameter K 12 is used to calculate the energy parameter e 12 , while l 12 is used to calculate the size parameter σ 12 . The calculated results by the Monte Carlo simulation show in good agreement with the experimental data.

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.

Monte Carlo simulation for solubility and spatial structure of fatty acid and higher alcohol in supercritical carbon dioxide with octane

Abstract Monte Carlo simulation has been applied to calculate the static properties such as solubilities and spatial structures of the fatty acids palmitic acid (C 15 H 31 COOH) and stearic acid (C 17 H 35 COOH), and of the higher alcohol stearyl alcohol (C 18 H 37 OH) in supercritical carbon dioxide with octane at 308.2 K. Carbon dioxide and octane were treated as single-site molecules for simplification, while the chain molecules (fatty acids and higher alcohol) were approximated as many-site molecules. The residual chemical potentials of the chain molecules in supercritical carbon dioxide with octane were calculated by the isothermal-isobaric Kirkwood method. It was shown that the solubilities (solid-gas equilibria) of fatty acids and higher alcohol in supercritical carbon dioxide with octane as a cosolvent can be calculated quantitatively by introducing an inter-site interaction parameter between unlike pair sites. Further, the mean-square end-to-end separations and the radial distribution functions of carbon dioxide and octane for chain molecules are reported as fundamental knowledge of the microstructure of chain molecules in the supercritical fluid phase.

Monte Carlo simulation of n-paraffins and higher alcohols in supercritical carbon dioxide

Abstract Monte Carlo simulation has been applied to calculate the static properties of n-paraffins; octacosane (C 28 H 58 ) and triacontane (C 30 H 62 ) and higher alcohols; cetyl alcohol (C 16 H 33 OH), stearyl alcohol (C 18 H 37 OH) and arachidyl alcohol (C 20 H 41 OH) in supercritical carbon dioxide at 308.2 K. Carbon dioxide was treated as single site molecule for simplification, while chain molecules (n-paraffins and higher alcohols) were approximated as many sites molecules. The residual chemical potential was calculated by the isothermal-isobaric Kirkwood method. It was shown that the solubilities (solid-gas equilibria) of n-paraffins and higher alcohols in supercritical carbon dioxide can be calculated quantitatively by introducing only one intermolecular parameter between unlike sites. The calculated results of mean-square end-to-end separations of n-paraffins increases with the pressure both in supercritical carbon dioxide and in supercritical ethane. The mean-square end-to-end separations of n-paraffins in supercritical carbon dioxide are shorter than those in supercritical ethane. Furthermore, the first peaks of the radial distribution functions of carbon dioxide for n-paraffins are lower than those of ethane for n-paraffins. These facts mean that supercritical carbon dioxide acts to n-paraffins as a poor solvent compared with supercritical ethane. The radial distribution functions of carbon dioxide for higher alcohols imply that carbon dioxide tends to cluster around hydroxyl group.