GB1024117A - Distillation of diphenylolalkanes - Google Patents

Abstract

Bisphenol-A and other gem-diphenylolalkanes are purified by vacuum distillation in the form of a liquid stream flowing on a substantially horizontal surface, the length of the flowpath being at least 50 times the average of its width and depth. In an example, a mixture of phenol, acetone, and a small proportion of resin (recovered by extraction of the product) is saturated with hydrogen chloride and continuously fed to the first of three reactors arranged in series and maintained at a temperature of 50 DEG C. Phenol is added to the material leaving the last reactor, and the mixture is fed to the top of a column in which all the HCl and water, and some of the phenol, are driven off under vacuum. The mixture leaving the bottom of the column is fed through inlet 5 into vacuum chamber 2 where it flows in a zigzag path over the horizontal surface 3 which is <FORM:1024117/C2/1> <FORM:1024117/C2/2> heated so that vapours of phenol, isopropyl phenol, 2,2 - (2,41 - dihydroxy - diphenyl) propane, the 2,2-(2,21) isomer, and 2,2,4-trimethyl-4-p-hydroxyphenyl chroman are discharged from the chamber through pipe 7. The liquid withdrawn through outlet 6 is passed to a second vacuum chamber of the same type where bisphenol-A is distilled off from higher-boiling impurities. The bisphenol-A distillate is fed into a trough in which an internally-cooled cylinder is rotating. A layer of solid crude bisphenol-A builds up on the cylinder. The solid is removed by a blade, ground and then fed to a vessel where it is extracted with benzene. The extracted bisphenol-A is centrifuged and dried in vacuum. The benzene containing the extracted impurities is distilled at atmospheric pressure, leaving a resin which is recycled to the reactors.