Prediction of the surface tension of petroleum cuts using a modified UNIFAC group contribution method

The surface tensions of petroleum cuts were predicted using the modified UNIFAC group contribution method. Each petroleum cut was considered to be composed of three pseudocomponents: paraffinic, naphthenic and aromatic. The surface tension of the cut was predicted by calculating the bulk and surface activity coefficients, concentrations and surface tensions of the pseudo-components. The pseudocomponent surface tension was calculated from the critical properties using a corresponding state method. Crude oil cuts having boiling points ranging between 32 and 451°C were tested. Comparison of experimental and predicted surface tensions revealed quite good agreement, with a percentage absolute deviation of 4.1%.