Study On Solubility Of CO₂ In Cycloalkanes And Cycloalkane Volume Expansion

Cycloalkanes are important components of petroleum.In previous studies,people most focus on the phase behavior of CO₂+normal alkanes,there is no research on the comparison of the solubility of CO₂ in cycloalkanes and methylcycloalkanes.This paper studied the solubility of CO₂ in cyclohexane?CH?,methyl cyclohexane?MCH?,cyclopentane?CH?,methyl cyclopentane?MCH?,ethylcyclohexane?ECH?,normal hexane?nC6?,normal pentane?nC5?at different pressures and temperatures.The volume expansion effect of alkanes was also studied.All experiments were carried on in a high pressure and high temperature PVT equipment.The effect of temperature,pressure,molecular structure on intermolecular force,solubility and volume expansion effect were systematically discussed.The extended Chrastil model,SRK equation of state,PR equation of state,PT equation of state and Van der Waals mixing rule were used to correlate the experimental data,the parameters in the equation were calculated as well.The main results are as followed:?1?The increasing of temperature can reduce the intermolecular force between alkanes,which is not benefit for the dissolution of CO₂ in alkanes.?2?The increasing of pressure strengthens the intermolecular force between CO₂ molecules,the solubility increases.?3?The addition of methyl or ethyl on cycloalkanes increases the polar of molecules,the dipole-dipole attraction becomes dominant in interaction between cycloalkane molecules.As a result,the solubility decreases.?4?For homologues,with the increasing of carbon atom number,the mole mass and molecular deformability increase as well.The dispersion force between cycloalkane molecules increases,which reduces the solubility.?5?Compared to normal alkanes with the same carbon atom number,the cycloalkane molecule has a larger area to contact.The interaction between molecules increases,and it's more difficult for CO₂ to dissolve.?6?The extended Chrastil model is the best in calculation accuracy,the PR equation of state is better than PT equation of state in general,the PT equation of state is better than SRK equation of state.However,in calculating the solubility of CO₂ in nC5 and nC6,the calculation accuracy of PR equation of state is not always better than SRK equation of state and PT equation of state.