Cubic equation of state for pure compound vapor pressures from the triple point to the critical point

A new procedure is proposed for obtaining the temperature dependence of the attractive energy parameter of equations of state (EOS's). The procedure can be applied to two-parameter cubic and noncubic EOS's, and it is used for the Peng-Robinson (PR) EOS. The modified form of the PR-EOS, the ZVPR-EOS, can accurately reproduce the vapor pressure for a wide variety of pure compounds from the triple point to the critical point. The experimental information required for each pure compound is the acentric factor, the normal boiling point temperature, and the temperature and pressure coordinates at the critical and triple points. Tables of parameters and complete vapor-pressure relative-error information are provided for more than 100 compounds of industrial interest. Additionally, for the PR-EOS, Soave's noniterative calculation procedures have been extended to the low-temperature range.