En trainers

If a naphtha fraction has been used in the dilution and as the en-trainer, it is left in as a diluent for reducing the viscosity in pumping the oil to the refinery. Alternatively, some or all is removed as a slip stream from the reflux going to the top of the azeotropic column. If toluene or other aromatic solvent is used, it would be so removed or removed in a separate distillation for recycle. 

Chialvo, A. J. Solute solute and solute solvent correlations in dilute near-critical ternary mixtures—Mixed-solute and en-trainer effects. J. Phys. Chem. 1993, 97, 2740-2744. 

Phenol, a common priority pollutant, was extracted from two environmental matrices, soil and water, using near critical and supercritical carbon dioxide. The primary objective of this study was to determine the distribution of the contaminant between the soil or water and the supercritical phase, and the effect of soil moisture and co-solvents on the distribution coefficients. Static equilibrium extractions were performed on dry and wetted soil contaminated with 1 wt.% phenol and on water containing 6.8 wt.% phenol. Supercritical carbon dioxide (with and without en-trainers) was chosen as the solvent for the study. An appropriate entrainer for dry soil extractions (methanol) ffiffered from that found for aqueous extractions (benzene). However, soil moisture was found to have a significant impact on the effectiveness of en-trainers for soil extractions of phenol. Entrainers appropriate for extracting wetted soil were found to be the same as those advantageous for aqueous extractions. Benzene was also extracted from dry and wetted soil to investigate the extractability of a hydrophobic compound. 

Chialvo, A. A. 1993b. Solute-solute and solute-solvent correlations in dilute near-critical ternary mixtures Mixed-solute and en trainer effects. Journal of Physical Chemistry. 97, 2740. Chialvo, A. A., S. Chialvo, J. M. Simonson, and Y. V. Kalyuzhnyi. 2008. Solvation phenomena in dilute multicomponent solutions. I. Formal results and molecular outlook. Journal of Chemical Physics. 128, 214512. 

Figure 4.23. Reversible intermediate section trajectories for extractive distillation of four-component mixtures (a) mixture 1,2 is overhead product, and component 4 is en-trainer (b) component 1 is overhead product, and mixture 3,4 is entrainer. Short segments with arrows, liquid-vapor tie-lines in arbitrary cross-sections.

Figure 8.27. Phase equilibria map and sequences for distillation of a binary azeotropic mixture (1,2) with an intermediate boiling en-trainer (3) (a) indirect split 2,3 1 in the first column, (b) direct split 2 1,3 in the first column, and (c) preferred split 2,3 13 in the first column.

Reversible distillation region of section (Regrev.n Re ev,s Re ev,e) unification of several regions of components order for which one and the same component appears to be (1) the most heavy-volatile for rectifying section, (2) the most light-volatile for stripping section, and (3) middle-volatile between top and en-trainer components for extractive section. 

JM Walsh, GD Ikonomou, MD Donohue. Supercritical phase behavior the en-trainer effect. Fluid Phase Equil 33 295, 1987. 

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