Liquid–liquid equilibrium (LLE) data of the solubility curves and tie-line compositions have been determined for mixtures of (water + 2,3-butanediol + butyl acetate) at (298.15, 308.15, and 318.15) K and atmospheric pressure. Distribution coefficients and separation factors have been evaluated for the immiscibility region. The Othmer−Tobias correlation provides the coefficients of the log–log plot that is not a sensitive criterion. The LLE data of the ternary systems have been predicted by UNIFAC methods.
The
thermodynamic data in distillation, i.e., isobaric vapor–liquid
equilibrium data, have been measured for the three binary systems
of 1,2-ethanediol + 1,2-propanediol, 1,2-ethanediol + 2,3-butanediol,
and 1,2-propanediol + 2,3-butanediol at 101.3 kPa. The accuracy of
the experimental data was confirmed by both Herington test and Van
Ness test. The thermodynamic properties of the vapor phase have been
calculated with the Hayden–O’Connell equation in consideration
of nonideality. The liquid activity coefficients have been satisfactorily
correlated with the Wilson, NRTL, and UNIQUAC models, while the estimated
results from the UNIFAC model are not satisfactory. The corresponding
binary interaction parameters of the three models Wilson, NRTL, and
UNIQUAC were calculated and used to obtain the residual curves of
the ternary system 1,2-ethanediol + 1,2-propanediol + 2,3-butanediol.
Based on all of the preceding results, a two-column distillation process
has been designed to obtain the required products.
Enhanced extraction of 2,3-butanediol by adding salt into solvent n-butanol has been studied in this paper. Ternary phase diagrams for 2,3-butanediol + water + salt have been determined. The influences of phase ratio, type of salts and salt content on distribution coefficient and selectivity have also been investigated systematically. With phase ratio of 0.75 (w/w) and salt content of K 2 HPO 4 of 25% (w/w), the distribution coefficient, separation factors and recovery yield in a single extraction process by n-butanol can reach 5.2%, 34% and 80%, respectively. Salt addition can greatly enlarge the two phase region and enhance extraction simultaneously in this system.
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