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Thermodynamics of solvent selectivity in extractive distillation of hydrocarbons
Author(s) -
Prausnitz J. M.,
Anderson Ralph
Publication year - 1961
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690070123
Subject(s) - selectivity , chemistry , solvent , distillation , thermodynamics , polar , work (physics) , intermolecular force , solvent effects , solvophobic , cosmo rs , chemical polarity , polarity (international relations) , organic chemistry , molecule , catalysis , biochemistry , physics , ionic liquid , astronomy , cell
The selectivity of a polar solvent is expressed in terms of an approximate theory of solutions. The theoretical results are insufficiently precise for the accurate prediction of activity coefficients, but the analysis shows that in the absence of chemical effects selectivity depends primarily on the difference in molar volumes of the hydrocarbons to be separated and on the polar energy density of the solvent. The effectiveness of a solvent is related to its polarity (which should be large) and to its molecular size (which should be small). In cases where chemical effects are important or where the molar volumes of the hydrocarbons to be separated are only slightly different, selectivity also depends on the relative ability of the hydrocarbons in acting as electron donors and on the ability of the solvent to act as an electron acceptor in forming acid‐base complexes. The theoretical conclusions, which are based on modern thermodynamics and on the theory of intermolecular forces, are in agreement with experimental observations. The results obtained in this work provide theoretical criteria for the selection of an optimum solvent for a given separation and give semiquantitative explanations of solution phenomena related to extractive distillation.