Measurement And Study On The Critical Temperatures And Critical Pressures Of The Mixtures Related To Gasoline

Critical parameters are important thermodynamic properties. They are necessary tocalculate pVT and other thermodynamic properties. They are also necessary for thechemical industrial processes, such as supercritical extraction and supercriticalreactions. So it is of great importance to measure or calculate the critical propertiesaccurately for mixtures.In this study, high pressure phase equilibrium equipment K was built to determinethe critical temperatures and critical pressures of the mixtures with definedcomposition. The critical point was recognized as the point where the meniscusdisappeared and reappeared.In order to check the reliability of the apparatus, the critical temperatures (Tc) andcritical pressures (pc) of pure n-heptane, cyclohexane, methanol, ethanol,1-propanol,Methyl tert-butyl ether (MTBE) and binary mixture n-hexane+ethanol weremeasured. The experimental data are in good agreement with the literature data,which proves great reliability of the apparatus used in the work. The criticaltemperatures and critical pressures of ten binary mixtures (n-heptane+cyclohexane,n-heptane+methanol, n-heptane+ethanol, n-heptane+1-propanol, MTBE+n-heptane, MTBE+cyclohexane, MTBE+methanol, MTBE+ethanol, MTBE+1-propanol) and three ternary mixtures (MTBE+methanol+1-propanol, methanol+1-propanol+n-heptane, MTBE+n-heptane+ethanol) were measured. All criticallines for the mixtures studied are continuous which connect the critical points of thetwo pure components, indicating their phase diagrams all belong to Type I proposedby Scott and van Konynenburg.Three-parameter Redlich-Kister equation was used to fit the critical temperatureand critical pressure for the binary mixture, and the parameters were obtained. Thecalculated results show that Redlich-Kister equation can fit the critical properties well.Peng-Robinson equation of state (PR EOS) with the Wong-Sandler (WS) mixing rulewas used to calculate the critical properties of the binary and ternary mixtures and thebinary interaction parameter was obtained. The calculated results show that PREOS with the WS mixing rule can fit the critical properties well.In this study, an efficient algorithm and procedures suggested by Heidemann andKhalil was used to calculate critical points for the ternary mixtures. In this calculation,the PR EOS with WS rule was chosen, and the binary interaction parameters obtained by the experimental critical data of the binary mixtures were used. The results showthat the critical temperature and critical pressure for the ternary mixtures could becalculated well by this method from related binary mixture experiment data.