Improvements in and relating to the separation of di-isopropylamine from water and iso-propanol by azeotropic distillation

摘要

Di-isopropylamine is isolated from mixtures containing it together with isopropanol and water, by submitting the mixture to fractional distillation in the presence of a hydrocarbon or hydrocarbonfraction, which is free from olefinic or acetylenic unsaturation and boils within the range 68 DEG -75 DEG C, whereby a hydrocarbon-isopropanol-water ternary azeotrope and a hydrocarbon-isopropanol binary azeotrope are distilled over in that order, leaving purified di-isopropylamine, together with any excess hydrocarbon, in the still. The process may be applied in the separation of di-isopropylamine from the products of the amination of isopropanol. The hydrocarbon may be methyl cyclopentane or n-hexane. A suitable hydrocarbonfraction may be obtained by isolating a 68 DEG -75 DEG C cut from the products of the destructive hydrogenation of creosote oil, and treating it with sulphuric acid. In an example, one litre of a mixture comprising di-isopropylamine (85.7 per cent), water (6.3 per cent), isopropanol (5.5 per cent) and mono-isopropylamine (2.5 per cent) was distilled with 250 ml. of methyl cyclopentane in a fractionating still equivalent to 70 theoretical plates. The fraction distilled over between 37 DEG and 58.7 DEG C comprised 83 per cent mono-isopropylamine. The ternary azeotrope distilled over between 58.7 DEG and 58.9 DEG C. This was condensed and the condensate was passed to a decanter maintained at 45 DEG C, whereupon it separated into two liquid layers. The upper layer was returned to the still; and the lower layer, which contained 92 per cent water, was discarded. The binary azeotrope, which contains 21 per cent isopropanol, distilled over between 58.9 DEG and 64 DEG C (reflux ratio 40:1). There were then obtained two small fractions containing 98 per cent methyl cyclopentane and 80 per cent di-isopropylamine was distilled over between 84 DEG and 84.4 DEG C. The methyl cyclopentane may be recovered from the binary azeotrope either by washing it with water, or by submitting it to fractional distillation in the presence of water. In the latter case, the condensed distillate is passed to a decanter at a temperature not exceeding room temperature.