Prediction of vapor-liquid equilibrium in highly asymmetric paraffinic systems with new modified EOS-GE model

A new modified EOS-GE model is developed for the highly asymmetric paraffinic systems, where the volume translated Peng-Robinson EOS is adopted coupled with the LCVM mixing rule. In the new modified EOS-GE model, the original UNIFAC is replaced by a newly established UNIFAC where the nonlinear calculation of the segment fractions of molecules in γC (the combinatorial activity coefficient) is introduced to modify the traditional assumption that “all groups are isotropic in solution”. A total of 956 vapor-liquid experimental bubble points in highly asymmetric paraffinic systems including binary systems, ternary systems, quaternary systems and multiple systems are used to test the new developed EOS-GE model. Results show that the original UNIFAC and the improved UNIFAC both perform well if the molefractions of light components (CH4 or C2H6) are low; however, with the increase of the light components, the improved UNIFAC is remarkably superior to the original UNIFAC.