GB577461A - Improvements in or relating to beta-aminopropionic acid and process of preparing same - Google Patents

Abstract

b -Aminopropionic acid is prepared by reacting acrylonitrile and aqueous ammonia in a closed vessel at a temperature ranging from about 150 DEG C. to 225 DEG C. and under the corresponding autogenic pressure. Desirably, the reaction period ranges from one to twenty-four hours and is preferably four hours. Pure crystals of the acid are obtained by diluting the concentrated reaction mixture with methanol. Preferably, a small quantity of a corrosion and oxidation inhibitor, such as a diphenylamine, is incorporated in the reaction mixture. The aminopropionic acid may be converted into acid salts, such as the hydrochloride or metal salts such as an alkali or alkaline earth metal salt and isolated as such, if desired. Numerous examples are given illustrating the above process of which the following are typical: (1) 66.5 parts of acrylonitrile, 540 parts of 28 per cent aqueous ammonia, 1375 parts of water and 1.5 parts of diphenylamine were heated at 150 DEG C. in a closed autoclave for 8 hours; the reaction mixture, after treatment with activated carbon, was concentrated to a syrup and added to methanol whereupon beta-aminopropionic acid (39 parts) crystallised out; (5) 132 parts of acrylonitrile, 600 parts of 28 per cent aqueous ammonia, 1080 parts of water, and 2 parts of diphenylamine were treated as above for 4 hours at 200 DEG C. and 60 parts of aminopropionic acid recovered; (11) and (12) the solutions remaining after recrystallisation of aminopropionic acid from a number of experiments carried out as described in (1) and (5) were evaporated to reclaim the methanol; the residue containing unreacted acrylonitrile was further treated with aqueous ammonia as above and additional quantities of aminopropionic acid obtained. Reference is made by way of disclaimer to Specification 558,682. The Specification as open to inspection under Sect. 91 comprises also the addition of dehydration catalysts and ammonium salts of weak acids, such as ammonium carbonate, to the reaction mixture. This subject-matter does not appear in the Specification as accepted.