GROUP CONTRIBUTION THEORY OF THERMODYNAMIC PROPERTIES
Abstract
The group contribution model developed by Nitta et al. has been extended to mixtures of ring-containing molecules and to strongly hydrogen bonded aqueous solutions. A shape correction parameter is introduced for rings in molecules, and applied to aromatic compounds and their mixtures. The interactions of water molecules are represented in two types: the hydrogen bonds and the cavities. Group properties are determined by fitting data on pure water and aqueous solutions. Significant structure theory is extended to chain molecules by considering group contributions. The partition function of translational degree of freedom is obtained from significant structure theory developed by Eyring. Additional degrees of freedom at high densities due to rotational and vibrational motions of a molecule are treated as equivalent external degrees of freedom. The ideal gas limit is satisfied as density approached zero. Group properties and their interactions are determined for four homologous series: normal alkanes, isoparaffins, cyclohexanes and aromatics, and three polymers: polyisobutylene, polydimethylsiloxane and polystyrene. Perturbation theory of the fluid state is extended to structurally complex molecules. The rotational and vibrational modes of motion of a molecule are treated as equivalent rotational motions. The partition function of rotational mode is derived from the Boublik-Nezbeda equation of state of hard dumbbell molecules. The resulting Chain-of-Rotators equation of state requires three parameters for each pure substance, and values of the parameters are determined for more than 60 pure substances. VLE properties of mixture are then calculated using van der Waals' one fluid mixing rule. One additional binary interaction parameter is needed. Correlations of the binary interaction parameters were developed for some binary mixtures of light gas with hydrocarbon. Finally, the molecular equation parameters are estimated using a group contribution method. Extensive comparisons are made of the predictions of the method with data.
Degree
Ph.D.
Subject Area
Chemical engineering
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