The prediction of high temperature vapor—liquid equilbiria from lower temperature heat of mixing data

Abstract

A method for predicting high temperature vapor—liquid equilibria using only lower temperature heat of mixing data and pure component vapor pressure data is presented. Ten binary hydrocarbon liquid mixtures were studied. The method consists of evaluating the parameters of the LEMF equation at different temperatures from isothermal heat of mixing data of the binary pair at the respective temperatures. The parameters obtained are extrapolated as a linear function of temperature to the temperature at which the VLE data are to be calculated. The parameters are used to compute actively coefficients which in turn are used together with pure component vapor pressures to calculate VLE data. Results were also obtained when heats of mixing data for a given system were available at only two temperatures. For the systems studied, this method predicted the composition of the vapor phase with an average standard deviation of 4–5% for those systems where heat of mixing data is available at three or more temperatures and of 10–12% for those systems where only two sets of heat of mixing data are available.