GB1165278A - Separation of Dimethylacetamide from Mixtures by Distillation - Google Patents

Abstract

1,165,278. Dimethylacetamide, separation from acatic acid by distillation. E. I. DU PONT DE NEMOURS & CO. 14 Dec., 1967 [15 Dec., 1966], No. 56841/67. Heading BIB. [Also in Division C2] N,N-Dimethylacetamide (DMAC) is separated from a mixture containing it together with acetic acid by submitting the mixture to consecutive fractional distillation operations at different pressures. If. for example, the DMAC concentration in the initial mixture exceeds that in the DMAC/HAc azeotrope, the mixture is preferably submitted to distillation in a column maintained at reduced pressure (e.g. 50 to 300 mm. Hg) to distil off DMAC until the composition of the residual mixture, approaches the azeotropic composition. The residual mixture is then distilled at atmospheric pressure to recover acetic acid as distillate. The cycle of low-pressure and highpressure operations may then be repeated. In continuous operations, it is convenient to employ two distillation columns operated at different pressures. The bottoms fraction from each column is introduced into the middle of the other column; and additional starting mixture is fed to either column determined by its composition.