VLE in (C6H14 + C16H34) Mixture. Prediction with Elbro Free Volume Method

The main purpose of thisworkwas a search for the dependence of VLE prediction quality on the kind of chosen n-alkanemodel system. The activities and total vapour pressure for (n-C6H14 + n-C16H34) mixture at 293.15 K, 313.15 K and 333.15 K were successfully predicted with Elbro free volume method using three sets of UNIQUAC Aij interaction parameters: (1) Aij obtained with the semi-empirical quantum mechanical method AM1 (Austin Model 1) for (n-C6H14 + n-C16H34) system, (2) Aij adjusted to (n-C6H14 + n-C16H34) VLE experimental data, (3) Aij obtained with the CFF (Consistent Force Field) method for the chosen (n-alkane + n-alkane) model system. The predicted curves were compared with experimental data. It has been found that when sizes of the solvent molecule and a chosen segment in the second long chain molecule are comparable to the model system size then the UNIQUAC interaction parameters obtained with molecular mechanics quantitatively describe the real intermolecular forces in n-hexane + n-hexadecane system.