GB1398501A - Purification of 2-pyrrolidone - Google Patents

Abstract

1398501 Purification of 2-pyrrolidone S F POSZTASZERI 30 Jan 1973 [7 Feb 1972] 4611/73 Heading C2C [Also in Division B1] Substantially pure, substantially anhydrous 2-pyrrolidone is obtained from commercial liquid 2-pyrrolidone, by: (a) dissolving in the commercial 2-pyrrolidone from 0À1 to 0À8% by weight, based on the weight of the 2-pyrrolidone, of an analytical grade substantially anhydrous alkali metal or alkaline earth metal hydroxide (e.g. KOH); (b) slowly applying the solution to a surface heated to a temperature of from 90‹ to 120‹ C. under a pressure of not more than 5 mm. mercury in a molecular still (a falling film vacuum distillation device) to selectively flash-vaporize the 2-pyrrolidone while the non-volatile impurities of the solution remain on the heated surface together with the metal hydroxide; and (c) condensing and collecting the vaporized 2-pyrrolidone as substantially pure, colourless and odourless liquid 2-pyrrolidone. The commercial 2-pyrrolidone is preferably pre-purified by cooling to below its crystallization temperature but not less than 20‹ C., draining off the liquid impurities from the crystalline 2-pyrrolidone and warming the latter to not more than 28‹ C. to liquefy the same. Preferably the rate of addition of the solution to the heated surface is sufficiently fast to cause a small amount of 2-pyrrolidone to remain on the heated surface to function as a solvent for the impurities and for the metal hydroxide.