Prediction of physical properties for non-polar compounds, petroleum and coal liquid fractions

Abstract

Several correlations for the prediction of critical properties (Tc, Pc) and acentric factor (ω) for pure compounds and undefined petroleum and coal liquid fractions are tested directly, using a large critical properties' databank for such systems; and indirectly, using the obtained Tc, Pc and ω values to predict vapor pressures (P 8 and saturated liquid volumes (V 1 with the translated Peng-Robinson (t-PR) and van der Waals (t-vdW) Equations of State. Best overall results are obtained with a revised Riazi-Daubert method that uses the normal boiling point (Tb) and the specific gravity at 15°C (SG 15). For heavy fractions, where low vapor pressure data, but not the normal boiling point (Tb) and densities at higher than 5°C temperature are available, a modification also of the Riazi-Daubert method is proposed that employs the saturation temperature 10mmHg (T 10 and SG at 25°C (SG 25, thus avoiding the uncertainty involved in obtaining Tb and SG 15 by extrapolation. The obtained results are very satisfactory, with typical average absolute errors in P 8 and V 1 5–10% and 5–15% respectively.