Isobaric Vapor - Liquid Equilibria of Gasoline Additives Systems At 101.3 kPa


In this study, isobaric vapor-liquid equilibrium of gasoline additives for threeternary systems: “MTBE + Ethanol + 2-Methyl-2-propanol”, “Ethanol + 2-Methyl-2-propanol + Octane”, and “MTBE + Ethanol + Octane” at 101.3kPa arestudied. Furthermore three binary systems: “ethanol + 2-Methyl-2-propanol”,“MTBE + Ethanol”, and “MTBE + Octane” at 101.3 kPa have been studied.The binary system “MTBE + Ethanol” forms minimum boiling azeotrope.The azeotrope data are x1(AZ) =0.955 mole fraction and T(AZ) =327.94 K. Theother ternary systems and the other binary systems do not form azeotrope.All the literature data used passed successfully the test for thermodynamicconsistency using McDermott-Ellis test method.In this study the calculation of VLE K–values is done by using threemethods, the first method uses modified Soave Redlich and Kwong (SRK),modified Peng and Robinson (PR) equations of state for two phases. The secondmethod uses SRK-EOS for vapor phase with (NRTL, UNIQUAC and UNIFACactivity coefficient models) for liquid phase and using PR-EOS for vapor phasewith (NRTL, UNIQUAC and UNIFAC activity coefficient models) for liquidphase. The third method uses the Wong- Sandler mixing rules and the PRSV- EOSbased on GE of (NRTL and UNIQUAC activity coefficient models).The non ideality of both vapor and liquid phases for the literature data forthe ternary and binary systems have been accounted for predicting VLE K–valuesusing the maximum likelihood principle for parameter estimation which provides amathematical and computational guarantee of global optimality in parametersestimation.The Wong- Sandler mixing rules and the PRSV- EOS based on excess Gibbs freeenergy GE of NRTL activity coefficient model give more accurate results forcorrelation and prediction of the K-values than other methods for the ternary andbinary systems which contain asymmetric and polar compounds.