A modified temperature dependence for the Peng-Robinson equation of state

Numerous modifications have been suggested for the temperature dependence of the Peng-Robinson equation of state (PR-EOS) through the a! function in the attraction term in the equation. In most cases, these modifications were motivated by the need to improve vapor pressure predictions for heavy hydrocarbons. While improvements have been realized, even the most successful a modifications suffer from (a) limited experimental p upsilonT and equilibrium measurements for heavy hydrocarbons on which to base the modification, and (b) reliance on the use of switching functions below and above the critical temperature. In this work, we proposed a new cr function for the PR-EOS. This new function is based on pure-component vapor pressures for different molecular species, including heavy hydrocarbons. The new PR-EOS a! function leads to improved vapor pressure predictions (about 1% absolute average percentage deviations) for the systems considered (28 pure fluids, encompassing over 1100 measurements). In addition, we updated the original PR-EOS a: function to improve its predictions for the heavy hydrocarbons. (C) 2001 Elsevier Science B.V. All rights reserved.