Liquid−Liquid Equilibria and Physical Properties of the Quaternary Systems Water + Caprolactam + Ammonium Sulfate + Benzene and Toluene

Abstract

Modeling of extraction operations for caprolactam requires an accurate description of the phase compositions and the physical properties of all liquid phases. Therefore experimental liquid-liquid equilibrium data were measured for the systems water (1) + caprolactam (2) + ammonium sulfate (3) + organic solvent (4) at 293 K, 313 K, and 333 K, where the organic solvent was either benzene or toluene. Furthermore, the physical properties, density and viscosity of the separate phases and the interfacial tension of the two-phase systems, were determined. The equilibrium phase composition data were correlated using the nonrandom two-liquid model. Density data were fitted via the concentration influence of the solutes and the thermal expansion coefficient. Viscosity data were correlated using the DoleJones equation for describing the influence of the solute concentration and the Guzman-Andrade equation for describing the influence of temperature. Interfacial tension data were described using the Szyzkowski and the Jasper equation for describing the influence of solute concentration and temperature. Excellent agreement was found between the measured data and developed correlations.

Selection and evaluation of alternative solvents for caprolactam extraction

“…The following procedure was followed to obtain experimental data [23]. The used apparatus consisted of a stirred glass vessel surrounded by a thermostated jacket.…”

“…The activity coefficients used in the model are based on the data available in the Dortmund Data Bank. Using the resulting model, phase compositions were calculated for the systems water + caprolactam + benzene, toluene, 1-heptanol or cyclohexane at 293 K. The calculated and experimentally determined equilibrium caprolactam concentrations [7,23] are presented in Fig. 2.…”

“…Viscosities were described with the (extended) Dole-Jones and the Guzman-Andrade equation. The interfacial tension was correlated via the Szyzkowski isotherm and the Jasper equation [23]. Finally, the best candidate solvent was determined.…”

Entrainment Reduction in a Static-Mixer Settler Setup by Electric Field Enhanced Coalescence

“…This was determined by circulating the two phases at a low flowrate (no droplet entrainment) until equilibrium was established. This was validated with separate equilibrium data from literature for the caprolactam system (19). Once this was determined, the droplet entrainment was measured by subtracting the solubility from the total water content.…”

Caprolactam recovery by a column packed with polysulfone microcapsules containing 1-octanol

“…Solvent extraction is an effective way to recover caprolactam massively [2]. Benzene, the most widely used extractant in industry, its extraction capacity is small when caprolactam content in aqueous phase is low [3]. Therefore, high theoretical plate number is required to ensure the recovery ratio of caprolactam.…”