PVT Properties Of One-component Fluid And Phase Equilibria And Critical Curves Of Binary System At High Pressure

A set of variable-volume autoclave with a quartz window has been made. Using this high pressure autoclave the molar volume isotherms of trans-decahydronaphthalene (C10H8) between 293K and 446K and at pressures from 10 MPa to 200MPa have been determined. A modified Tait equation of state is used to fit each experimental molar volume isotherm. The thermal expansivity (cubic expansion coefficient)αand isothermal compressibilityκwere determined by fitting the slopes of the isobaric curves and isotherms, respectively, The coefficients in equations have been fitted with average deviation of 0.029% and does not exceed 2.62%.The vapor-liquid equilibrium data (including compositions, densities and molar volumes of vapor phases and liquid phases) have been measured at different temperatures and pressures of the three binary systems (SC CO2 + methanol, SC CO2 + ethanol and SC CO2 + ethyl propanate). The experimental data show the solubilities of SC CO2 in three solvents increase drastically with increasing pressures at the given temperature, but the contents of three solvents in gas phases increase faintly the solubilities of SC CO2 in esters is higher than that in alcohols. The critical values pc, Tc, xc and Vc of the three binary systems were estimated.The critical curves are also calculated with an equation of state for binary fluid systems of partners, which differ significantly in molecular size and polarity. The equation consists of a hard body repulsion term and an additive perturbation term, which takes care of the attractive molecular interation. For the repulsion, a Carnahan-Starling-One-Fluid (CSOF) expression or suitable extensions are used. The attractive term used square well potentials. The calculated results are given in figures. The necessary three parameters for(CO2+CH3OH, CO2+C2H5OH, CH4+CH3OH , N2+ CH3OH, CO2+ EP, H2O+n-alkane (C1~C6))systems are listed.