A GENERALIZED EXPRESSION FOR THE RATIO OF THE CRITICAL-TEMPERATURE TOTHE CRITICAL PRESSURE WITH THE VAN-DER-WAALS SURFACE-AREA

Using an extensive database of experimental critical properties for he avy compounds, which have been compiled mostly from recent literature sources, it is shown that the ratio T-c:P-c (critical temperature over critical pressure) can be expressed in terms of the van der Waals sur face area (Q(w)), which is readily available for any compound from the group contributions of Bondi (given also in UNIFAC tables). The propo sed correlation is based on the hole theory of Kurata and Isida for n- paraffin liquids, which is mathematically equivalent to Flory's theory of polymer solutions. The method is suitable for medium to high molec ular weight compounds with unknown critical constants. For example, if only one of the two critical constants is available, then the propose d generalized equation offers a useful rapid procedure for the estimat ion oi the other critical property for use in corresponding states, an d other relevant applications where knowledge of the critical properti es is required. Furthermore, the T-c:P-c method can be used in many ca ses for identifying the most suitable among the existing group contrib ution methods for estimating the critical properties of heavy and comp lex compounds for which experimental values are, very often, not avail able. Published by Elsevier Science Ltd.