New pure component parameters are presented for the MOSCED limiting activity coefficient model for 133 solvents with an absolute average deviation of 10.6% to experimental literature data. The MOSCED model has been applied to solid-liquid equilibria correlation and compared with the experimental data available in the literature. The correlation of solubility of 26 solids in organic solvents has an average absolute deviation of 25%. This compares favorably to the prediction of the modified UNIFAC model.

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.

This article describes how a fiber-optic turbidity probe may be used as an inferential sensor to aid in the control of commercial-scale batch crystallizations. The discussion focuses on several unseeded crystallization examples involving cooling or cooling plus addition of antisolvent. In a typical control scheme, the fiber-optic probe is used to detect an initial nucleation event, to control a subsequent digestion step for fines dissolution with the potential for modification of nuclei size, number, and purity, and then to monitor a growth period. During the digestion step, temperature is increased and adjusted to achieve a desired reduction in the fiber-optic signal in order to control the extent of digestion. Within Dow, this approach has proven to be robust and cost-effective for numerous commercial-scale batch crystallizations including those with highly fouling or corrosive environments.

Infinite-dilution relative volatilities (R i,water ∞ ) were measured at 50 °C and 80 °C using a Rayleigh distillation apparatus for dilute solutions of propylene glycol n-butyl ether (PnB), propylene glycol n-propyl ether (PnP), and dipropylene glycol n-butyl ether (DPnB) dissolved in water and brine (3 wt % NaCl). The data were analyzed to determine infinite-dilution activity coefficients (γ i,aqueous ∞ ), Henry's Law constants, partial molar enthalpies of mixing, and Setschenow constants. Partition ratios (K values) for extraction of PnP also were measured using 14 hydrophobic organic extraction solvents, including alcohols, ketones, ethers, chlorinated hydrocarbons, aromatics, and aliphatics. An interpretation of molecular interactions in solution is given based on the analysis of activity coefficients, as a function of temperature and salt concentration. General rules are proposed for the class of hydrogen-bonding organic compounds characterized by the presence of a lower critical solution temperature (LCST) in the organic + water phase diagram. The value of R i,water is likely to increase as the temperature increases for stripping volatile LCST-type hydrogen-bonding organics from dilute aqueous solution, provided the pure-component vapor pressure relative to water (p i SAT /p water SAT ) also increases or stays approximately the same. For extraction of LCST-type compounds from aqueous solution, K is likely to increase as the temperature increases, provided that the mutual solubility between phases is low.

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