Salt effect in distillation: A literature review II

Abstract

A salt dissolved in a mixed solvent is capable, through preferential association or other structure‐related effects in the liquid phase, of altering the composition of the equilibrium vapor phase. Hence salt effect on vapor‐liquid equilibrium relationships provides a potential technique of extractive distillation for difficult separations. The literature pertaining to salt effect in vapor‐liquid equilibrium and in extractive distillation over the period 1966‐present is reviewed, and also the remainder of work up to 1966 not covered in the Part I review.

Reducing the Energy Demand of Cellulosic Ethanol through Salt Extractive Distillation Enabled by Electrodialysis

“…These energy saving techniques have been shown to significantly reduce the distillation energy demand for the water-ethanol system (40-51); for instance, distillation energy demand reduction on the order of 42% has been reported for doubleeffect distillation with split feed compared to conventional distillation with a single column for distilling 93 wt% ethanol from a feed containing 7 wt% ethanol (43). Conversely, the VLE of the water-ethanol system can be improved towards ethanol separation by dissolving a salt in the liquid phase to raise the equilibrium vapor ethanol content (52)(53)(54)(55). Since salt remains as a nonvolatile component, the VLE of the water-ethanol-salt system can be studied and depicted as a pseudo binary system considering the equilibrium liquid composition on a salt free basis as is commonly done in literature (54,(56)(57)(58)(59)(60).…”

Liquid–liquid equilibria of the systems isobutyl acetate+isobutyl alcohol+water and isobutyl acetate+isobutyl alcohol+glycerol at different temperatures

“…This can be overcome by several techniques including azeotropic and extractive distillation [1][2][3], reactive distillation [4,5], liquid-liquid extraction (LLE) [6], adsorption [7], membrane pervaporation [8], salt addition [9] and pressure-swing distillation (PSD) [10].…”

Thermodynamics of solvent-driven water extraction from hypersaline brines using dimethyl ether

“…The introduction of a salt can drastically alter the phase equilibria of a solvent mixture, particularly when its constituent ions interact preferentially with one solvent species relative to another [99]. Salts comprising small ions, such as NaCl, can interact strongly with highly polar solvents, such as water, enhancing solvent structure and lowering the chemical potential of more polar solvent species [100][101][102][103][104][105][106][107]. At equilibrium, a salt-driven reduction in the chemical potential of the more polar solvent species relative to the less polar species often leads to the enrichment of the more polar solvent in the salt-containing phase and its depletion from the fluid phase that does not contain salt [99].…”