Patent GB-631675-A (GB)
Title: Improvements in and relating to the separation of organic nitrogen compounds
Filed: 1946-12-04
Abstract: <PICT:0631675/III/1> Dimethylamine is separated from mixtures with other methylamines, such as those obtained by the catalytic vapour phase amination of methanol, by continuous extractive distillation of the mixtures with aniline, taking off one or both of the other methylamines as vapour and the dimethylamine as solution.  Where the mixture contains ammonia it may be removed before the extraction or during it.  The resultant vapour mixture of mono- and tri-methylamine may be separated into its components by extractive distillation with aniline at 25 DEG  to 60 DEG  C., compared with the range 8 DEG  to 60 DEG  C., preferably 10 DEG  to 40 DEG  C., for the initial dimethylamine extraction.  As shown in the drawing accompanying the Provisional Specification, a mixture of gaseous amines is fed at an intermediate point to a column A packed with Raschig rings. The vapour leaving the top is bubbled through aniline in a pre-saturator B, cooled so that the exit temperature of the resulting amines solution is about 20 DEG  C.  The solution is fed via pipe a and distributer b into the top of the column A and the saturated solution of dimethylamines in aniline at about 35 DEG  C. is pumped from the bottom to a stripping still D from which dimethylamine vapour is taken off, while vaporized aniline is condensed in cooler G, and the aniline from the bottom of the still is returned to the pre-saturator.  The dimethylamine vapour from the stripping still D is in part returned to the column as reflux, the remainder, e.g. about 7.5 per cent, being taken to storage.  Specifications 630,884 and 631,672 are referred to.ALSO:<PICT:0631675/IV (b)/1> Dimethylamine is separated from mixtures with other methylamines, such as those obtained by the catalytic vapour phase amination of methanol, by continuous extractive distillation of the mixtures with aniline, taking off one or both of the other methylamines as vapour and the dimethylamine as solution.  Where the mixture contains ammonia it may be removed before the extraction or during it.  The resultant vapour mixture of mono- and tri-methylamine may be separated into its components by extractive distillation with aniline at 25 DEG  to 60 DEG  C., compared with the range 8 DEG  to 60 DEG C., preferably 10 DEG  to 40 DEG  C., for the initial dimethylamine extraction.  As shown in the drawing accompanying the Provisional Specification, a mixture of gaseous amines is fed at an intermediate point to a column A packed with Raschig rings.  The vapour leaving the top is bubbled through aniline in a presaturator B, cooled so that the exit temperature of the resulting amines solution is about 20 DEG  C.  The solution is fed via pipe a and distributer b into the top of the column A and the saturated solution of dimethylamines in aniline at about 35 DEG  C. is pumped from the bottom to a stripping still D from which dimethylamine vapour is taken off, while vaporized aniline is condensed in cooler G, and the aniline from the bottom of the still is returned to the presaturator.  The dimethylamine vapour from the stripping still D is in part returned to the column as reflux, the remainder, e.g. about 7.5 per cent, being taken to storage.  Specifications 630,884, [Group III], and 631,672 are referred to.