A salting-out strategy for the efficient separation of an azeotropic mixture of allyl alcohol and water

Abstract

Allyl alcohol and water can form the lowest boiling point azeotrope, but it is very hard to acquire high-purity allyl alcohol by normal distillation methods. Herein, a separation and purification protocol is developed for perfectly separating an azeotropic mixture of allyl alcohol and water using the salting-out method, in which three potassium phosphate salts, K5P3O10, K3PO4, and K4P2O7, are systematically investigated as salting-out agents, and finally a product consisting of > 99% allyl alcohol is obtained. A thermodynamic study demonstrates that this process involves endothermy and increment entropy. There is a good correlation between the solubility of allyl alcohol and the molar concentration of salt (mol per 1 kg water), and the solubility of the allyl alcohol in the organic phase or the water phase can be forecast using the mass percentage of salts. This work provides a new methodology for the efficient separation of an azeotropic mixture of allyl alcohol and water.