Selection and evaluation of alternative solvents for caprolactam extraction

Extraction of Caprolactam with an Alternative Benign Solvent in a Pulsed Disc and Doughnut Column

“…The physical properties of the quaternary systems water þ caprolactam (CPL) þ the mixed solvent were correlated by the equations as presented by van Delden et al [3,8] These correlations cover the entire range of concentrations and temperatures applied in this study, except for the interfacial tension. The latter is only valid for concentrations of caprolactam in the organic phase from 0 up to 5 mass%.…”

“…For experimental conditions with higher concentrations the relation was therefore extrapolated to determine the interfacial tension. The equilibrium distribution ratio, K D 0 , was based on equilibrium data [3] and fitted as a function of the feed-phase concentration by relevant first or second order polynomials. The mass fraction of caprolactam in both the organic and the aqueous phase and of heptanol in the organic phase was determined by gas chromatography, where the same analytical method was applied for both phases.…”

“…The mass fraction of caprolactam in both the organic and the aqueous phase and of heptanol in the organic phase was determined by gas chromatography, where the same analytical method was applied for both phases. [3,8] Hydraulic Experiments: Experimental Results and Data Correlation…”

“…In previous studies, the mixed solvent heptane-heptanol (40 mass %) was selected via an experimental screening procedure based on a relatively high distribution ratio of caprolactam, a low mutual solvent solubility, beneficial physical properties, and a low distribution ratio of impurities. [3,4] From the phase compositions it was calculated that when using the mixed solvent less theoretical stages are required in the forward extraction compared to benzene and toluene, NTS ¼ 5 relative to 9 and 11, respectively, whereas this trend was reverse in the back-extraction, NTS ¼ 10 compared to 5 and 4, respectively. The physical properties showed slightly higher viscosities, but lower densities and interfacial tensions for the mixed solvent.…”

Impurity Distribution Behavior in Caprolactam Extraction with Environmentally Benign Mixed Solvents

“…In a previous study a mixed solvent composed of an alkane, being heptane or methylcyclohexane, and an alcohol, 40 mass % heptanol, was selected from an experimental screening procedure. The solvent mixture heptane + heptanol (40 mass %) was finally selected as a replacement solvent based on its beneficial physical properties, since the phase compositions of both candidate solvent mixtures are similar and the results are satisfying relative to conventional solvents [3].…”