GB581539A - Improved process for making monoaminoethyl sulphuric acid ester - Google Patents

Abstract

Mono-aminoethyl ester of sulphuric acid is prepared by reacting monoethanolamine and sulphuric acid in the presence of solid phase or crystalline monoamino ethyl sulphuric acid ester. Thus, a reaction mixture of monoethanolamine and sulphuric acid in substantially equimolar proportions and containing solid phase ester is heated under such conditions of temperature and water content that the ester is maintained in the solid phase; by correlating the heating and removal of water formed to maintain solid phase ester in the mixture improved yields are obtained as compared with known processes of esterification where no solid phase ester is present. Preferably, heating is carried out under reduced pressure, the temperature being above 100 DEG C., and preferably between 130 DEG to 250 DEG C., the pressure being progressively reduced to as low as 40 mm. mercury. It is desirable that a slight excess of acid should be present initially as this accelerates the reaction. Commercial grades of sulphuric acid of 77 to 95 per cent concentration are suitable. In carrying out the process the solid phase ester may be provided by reacting the amine and acid under such conditions of concentration and temperature as to bring about crystallisation or the reaction mixture may be seeded; preferably the solid phase ester is used in a comminuted form. The reaction mixture may be formed by simultaneous addition of the amine and acid to a suitable vessel maintained under reflex conditions at about 170 DEG C. or if desired the reactants may be mixed at room temperature and then heated to the selected temperature. In a modification the crude solid ester, obtained by old processes wherein equimolar portions of amine and acid are reacted together, which contains unreacted amine and acid is heated under controlled conditions of temperature and removal of water whereby solid phase ester is maintained present, resulting in increased purity without loss in weight. The following are typical of the examples: (1) a mixture of monoethanolamine and sulphuric acid in equimolar proportions are partially reacted at 100 DEG -140 DEG C. under a slowly increasing vacuum, and the mixture converted to a granular mass by rapid increase of vacuum with consequential removal of water; the solid mass is then further heated under vacuum yielding a high quality ester. (2) Equimolar portions of monoethanolamine and sulphuric acid are introduced into a reaction vessel heated under reflux from 170 DEG up to 210 DEG C. and after the addition is completed a vacuum is applied to remove water short of the point at which the mass would spontaneously crystallise; a portion of the product which is rapidly chilled has an ester content of 70 per cent, a portion maintained at 100 DEG -150 DEG C. for ten minutes contains 80-85 per cent pure ester, and a portion of the product of 70 per cent purity is heated in the solid phase from 150 DEG to 250 DEG C. yielding an ester of 96 to 97 per cent purity.