Mutual Solubility and Lower Critical Solution Temperature for Water + Glycol Ether Systems

Abstract

Mutual solubility and the lower critical solution temperature (LCST) are reported for a number of water + ethylene glycol ether and water + propylene glycol ether systems near atmospheric pressure. For the systems studied, the LCST is in the range of −10 °C to 48 °C. Glycol ethers are unusual organic solvents in that they have both hydrophobic and hydrophilic functionality and can hydrogen bond with water. Because of this, their interactions with water are complex and difficult to predict. The presence of an LCST is characteristic of hydrogen-bonding mixtures, and the value of the LCST reflects the relative magnitude of hydrophobic/hydrophilic interactions in solution. A higher LCST value is indicative of a glycol ether with greater hydrophilic character. For water + ethylene glycol ether mixtures, the glycol ether becomes increasingly hydrophilic (LCST increases) as the number of oxyalkylene repeating units increases. The opposite effect is seen for water + propylene glycol ether mixtures. In this case, the glycol ether becomes more hydrophobic (LCST decreases) as the number of oxyalkylene repeating units increases. The results clearly demonstrate that water + glycol ether interactions are strong functions of both chemical structure and temperature.

Liquid–liquid equilibria for the ternary system (water+hexadecane+dipropylene glycol n-propyl ether)

“…As the number of propylene oxide group OCH(CH 3 )CH 2 (the number of j) increases, the LCST of the ternary system (water + dodecane + C 3 P j ) would decrease [17]. The effect of the propylene oxide group on the LCST of the ternary (water + dodecane + C 3 P j ) system is the same with that of the binary system (water + C 3 P j ) [18]. In this work, the fish-shaped phase diagram of the ternary system (water + hexadecane + C 3 P 2 ) was performed at constant water/hexadecane mass ratio (1/1), and the UCST was determined.…”

Benchmarks for the fifth industrial fluid properties simulation challenge

“…The mole fraction of the organic was then calculated for each phase and the ratio of the mole fractions gave K OW (x). The experimental setup was similar to that described by Christensen et al [8]; see also Ref. [9] for a general description of liquid-liquid equilibria measurements.…”

A Thermodynamical Approach for Evaluating Energy Consumption of the Forward Osmosis Process Using Various Draw Solutes

“…An organic solute with a low critical solution temperature (LCST) point is completely miscible with water below the phase transition temperature, making it possible to provide enough osmotic pressure to withdraw the water from feed solutions [30]. At an elevated temperature above the LCST point, the miscible organic-water solution would exhibit the liquid-liquid phase separation.…”