Phase equilibria of 3-methylstyrene, 4-methylstyrene, alpha-methylstyrene and a methylstyrene mixture in supercritical CO 2

Phase equilibria of 3-methylstyrene, 4-methylstyrene, alpha-methylstyrene and a methylstyrene mixture (mainly 3-methylstyrene (60% mol) and 4-methylstyrene (40% mol)) in supercritical CO2 were measured using high-pressure variable-volume view cells based on the static synthetic method. The systems were investigated between 308 and 353 K, with mass fractions of solute ranging continuously from 0.0275 to 0.65 and pressures up to 15 MPa. The experimental data shows a linear relationship between the phase transition pressure and the system temperature at constant composition. When the solubilities are compared, the methylstyrene isomers show little yet significant differences between them with the methylstyrene mixture being the most soluble. As the temperature increases, a decrease in the difference between the phase transition pressures of the methylstyrene structural isomers were observed. Lastly, the experimental data were correlated with the Peng-Robinson cubic equation of state using one temperature-independent binary interaction parameter and satisfactory results were obtained in both low and high solute concentration regions.