Method of self-similar functions for estimating the critical properties of homologous series

Abstract

The coefficients of equations for estimating the critical temperatures, pressures, and densities of homologous series with the general formula R1(CH2)nR2 have been calculated using the current experimental database. The equations are based on the hypothesis of functional self-similarity and the scaling behaviour of the critical constants of long-chain molecules (Nikitin et al. Fluid Phase Equilib., 2005, 235, 1). The equations allow predicting the critical constants of any member of any homologous series of this type if these quantities are known for one substance which belongs to this series. The method works well for compounds with a rather large number of CH2 groups in a molecule (n≥4). The results of calculating the critical temperatures, pressures, and densities of 16 homologous series by the proposed method have been compared with the critical properties estimated by the Constantinou/Gani, Marrero/Gani, and Hukkerikar et al. techniques.