Patent GB-631672-A (GB)
Title: Improvements in and relating to the separation of organic nitrogen compounds
Filed: 1946-11-29
Abstract: Monomethylamine, or a phase enriched therewith, is separated from mixtures with dimethylamine and trimethylamine, by selectively absorbing at least one of the other amines in an organic liquid and removing monomethylamine as vapour, the organic liquid being selected from the following: alkyl substituted anilines; alicyclic amines; lower aralkyl ethers; quinoline; mono-nitroderivatives of benzene and of alkyl benzenes; hydrogenated naphthalenes; higher alkyl benzenes; terpenes and chlorinated aromatic hydrocarbons, the process of Specification 631,673 being disclaimed.  The organic liquid preferably has a boiling point at least 50 DEG  C. higher than the boiling point of the most soluble of the methylamines.  Preferably the mixture is fed into a column at an intermediate point, the extracting liquid being fed in above this point (preferably at the top) the vapour being taken off at the top.  Part of the more soluble amines may be returned as reflux at the bottom of the column either by employing a boiler or by separately stripping them from the solution taken from the bottom of the column and returning them. The process may be operated to obtain pure monomethylamine and a solution containing some monomethylamine and the other amines, or to obtain monomethylamine mixed with the other amines and a solution free therefrom.  The solution may be distilled to obtain the methylamines content, which may be returned to the amination unit or separated from each other by fractional distillation or selective absorption. Where the amine mixture contains ammonia, the latter may be first removed or be removed together with the monomethylamine as vapour and separated therefrom by treatment with a liquid in which ammonia is less soluble than monomethylamine, i.e. most organic solvents.  The preferred extracting liquids are: dimethylaniline, monoethylaniline, diethylaniline, dimethylcyclohexylamine, quinoline, tetrahydronaphthalene, decahydronaphthalene, cymene, pinene, o-dichlorbenzene, alphachlornaphthalene, and anisole. Temperatures from 8 DEG  to 40 DEG  C., preferably about 20 DEG  C. and pressures below atmospheric or up to 20 atmospheres, but preferably atmospheric are used.  The extracting liquid is preferably selected so that the ratio of the solubility of monomethylamine to the solubility of the next least soluble methylamine measured in gas volumes is not more than 0.71. Specification 630,884 also is referred to.ALSO:Monomethylamine, or a phase enriched therewith, is separated from mixtures with dimethylamine and trimethylamine, by selectively absorbing at least one of the other amines in an organic liquid and removing monomethylamine as vapour, the organic liquid being selected from the following: alkyl substituted anilines; alicyclic amines; lower aralkyl ethers; quinoline; mono-nitroderivatives of benzene and of alkyl benzenes; hydrogenated naphthalenes; higher alkyl benzenes; terpenes and chlorinated aromatic hydrocarbons, the process of Specification 631,673 being disclaimed.  The organic liquid preferably has a boiling point at least 50 DEG  C. higher than the boiling point of the most soluble of the methylamines.  Preferably the mixture is fed into a column at an intermediate point, the extracting liquid being fed in above this point (preferably at the top) the vapour being taken off at the top.  Part of the more soluble amines may be returned as reflux at the bottom of the column either by employing a boiler or by separately stripping them from the solution taken from the bottom of the column and returning them. The process may be operated to obtain pure monomethylamine and a solution containing some monomethylamine and the other amines, or to obtain monomethylamine mixed with the other amines and a solution free therefrom.  The solution may be distilled to obtain the methylamines content, which may be returned to the amination unit or separated from each other by fractional distillation or selective absorption. Where the amine mixture contains ammonia, the latter may be first removed or be removed together with the monomethylamine as vapour and separated therefrom by treatment with a liquid in which ammonia is less soluble than monomethylamine, i.e. most organic solvents.  The preferred extracting liquids are: dimethylaniline; monoethylaniline; diethylaniline; dimethylcyclohexylamine; quinoline; tetrahydronaphthalene; decahydronaphthalene; cymene, pinene; o-dichlorbenzene; alphachlornaphthalene, and anisole. Temperatures from 8 DEG  to 40 DEG  C., preferably about 20 DEG  C., and pressures below atmospheric or up to 20 atmospheres, but preferably atmospheric, are used.  The extracting liquid is preferably selected so that the ratio of the solubility of monomethylamine to the solubility of the next least soluble methylamine measured in gas volumes is not more than 0.71. Specification 630,884, [Group III], also is referred to.