We present a review of recent advances in the statistical associating fluid theory (SAFT). In contrast to the “chemical theory”, in which nonideality is explained in terms of chemical reactions between the species, SAFT and similar approaches relate nonideality to the intermolecular forces involved. Such physical theories can be tested against molecular simulations, and improvements to the theory can be made where needed. We describe the original SAFT approach and more recent modifications to it. Emphasis is placed on pointing out that SAFT is a general method and not a unique equation of state. Applications to a wide variety of fluids and mixtures are reviewed, including aqueous mixtures and electrolytes, liquid−liquid immiscible systems, amphiphilic systems, liquid crystals, polymers, petroleum fluids, and high-pressure phase equilibria.

Molecular-Based Equations of State for Associating Fluids: A Review of SAFT and Related Approaches

FT-IR studies on excess thermodynamic properties of binary liquid mixtures o-chlorotoluene with 1-propanol, 1-butanol, 1-pentanol, 1-hexanol and 1-heptanol at different temperatures

Publisher Summary This chapter is focused on theoretical methods for predicting the thermodynamic behavior of associating liquids and their mixtures. The existing chemical engineering folklore for dealing with associating mixtures is largely based on the “chemical theory”, in which the associating complexes are treated as distinct new chemical species, so that the apparently anomalous physical behavior is ascribed to the change in chemical composition (higher molecular mass, fewer molecules, and so on). Chemical equilibria between the initial components and these complexes are written down, and the chemical equilibrium constants then appear in the equations for the thermodynamic properties. However, the approach is of limited predictive value since one must know in advance all the “reactions” involved and be able to measure or predict the equilibrium constants as a function of temperature. Recently more fundamental statistical mechanical approaches have become available and much of this chapter is concerned with these newer developments. These new theoretical equations relate the thermodynamic properties to physical intermolecular forces, so that associating liquids are treated on the same footing as simple liquids of more weakly interacting molecules.

12 Associating fluids and fluid mixtures

Excess volumes (V E), ultrasonic sound velocities (u), and viscosities (η) have been measured for the binary mixtures of acetophenone with o-chlorotoluene, m-chlorotoluene, p-chlorotoluene, o-nitrotoluene, and m-nitrotoluene at 303.15 K. Excess volumes are positive over the entire composition range in all the binary mixtures. Furthermore, from the experimental sound velocity data isentropic compressibility (KS) and deviation in isentropic compressibility (ΔKS) from ideal behavior was also computed at the same temperature, and these values are negative in all the binary mixtures. The viscosity data are analyzed on the basis of corresponding states approach. Deviation in viscosities are positive over the entire composition range. The measured data are explained on the basis of intermolecular interactions between unlike molecules.

Excess Volumes, Speeds of Sound, Isentropic Compressibilities, and Viscosities of Binary Mixtures of Acetophenone with Chlorotoluenes and Nitrotoluenes at 303.15 K

Studies on the importance of nature of substituent on the thermodynamic and transport properties of liquid mixtures at various temperatures

Excess volumes of binary mixtures of acetophenone with some substituted aromatic hydrocarbons

Excess volumes of binary mixtures of trichloroethylene with some aliphatic, alicyclic and aromatic hydrocarbons

Excess volumes for binary mixtures of tetrachloroethylene with hexane, heptane, cyclohexane, methylcyclohexane, toluene, bromobenzene, chlorobenzene and nitrobenzene have been determined dilatometrically at 303.15 K. The measured VE values are negative for the mixtures of tetrachloroethylene with hexane, heptane and nitrobenzene and are positive for the systems containing cyclohexane, methylcyclohexane and toluene. In case of tetrachloroethylene + bromobenzene and + chlorobenzene systems inversion of sign of VE is observed. The data are interpreted in terms of (1) loss of dipolar association, difference in size and shape of the molecules and (2) specific interactions between unlike molecules.

K. N. Surendranath

Papers

Excess volumes of binary mixtures of acetophenone with some substituted aromatic hydrocarbons

Excess volumes of binary mixtures of trichloroethylene with some aliphatic, alicyclic and aromatic hydrocarbons

Excess Volumes of Tetrachloroethylene with Some Aliphatic, Alicyclic and Substituted Aromatic Hydrocarbons