Effect of Separating Agent in Extractive Distillation

The possibility of the formation of practically nonvolatile molecular complexes between the components of mixture and the separating agent of various compositions has been shown using the benzene–heptane–N-methylpyrrolidone system as an example. When modeling the vapor–liquid phase equilibrium, as a rule, the real structure of the solution is not taken into account, assuming the monomolecular structure of the substances contained in the solution. This significantly affects the real values ​​of coefficients of relative volatility, leading to the appearance of concentration inversion. The values ​​of fractions of substances in a monomolecular form are experimentally determined.