GB831052A - A process for concentrating aqueous acrylic acid - Google Patents

Abstract

A process for concentrating aqueous acrylic acid comprises dissolving aqueous acrylic acid in a ketone which is at least partially miscible with water but immiscible with a concentrated aqueous solution of nickel, copper or cobalt salts and capable of forming together with water an azeotropic mixture boiling below 140 DEG C. at atmospheric pressure, shaking the solution with a pulverulent anhydrous nickel, cobalt or copper salt, the relative quantities of aqueous acrylic acid, ketone and metal salt used being such as to form a concentrated aqueous solution of the metal salt and disposed as a layer on the metal salt solution-a solution of acrylic acid in water and ketone, the relative quantities of water and ketone being such that the water content of the azeotropic mixture of water and ketone at atmospheric pressure is not exceeded, and then, after separation of the upper layer from the lower layer, distilling off the azeotrope of ketone and water and finally anhydrous acrylic acid from the upper layer. The aqueous acrylic acid is suitably one having a concentration of 35 to 40% and specified ketones are methyl ethyl (propyl or isopropyl) ketone, diethyl ketone, ethylisopropyl ketone and di-isopropyl ketone. Suitable salts are copper sulphate, cobalt chloride and preferably nickel chloride and/or nickel bromide and one or more of the metal salts may be used. The shaking of the solution with the metal salt or salts should preferably be effected at about 40 DEG C. and the subsequent azeotropic distillation and the acrylic acid distillation is preferably carried out in the presence of a polymerization inhibitor, e.g. hydroquinone. Examples are given in which methyl ethyl ketone is used as solvent and nickel chloride and nickel bromide respectively as the metal salt. Specification 781,805 is referred to.