GB728955A - Manufacture of acrylamides - Google Patents

Abstract

A process for the manufacture of acrylamide and a -alkyl-substituted derivatives thereof comprises subjecting in the vapour phase derivatives of propionamides of the general formula <FORM:0728955/IV (b)/1> in which R represents a hydrogen atom or an alkyl group and X is a group as defined below, to thermal decomposition in the presence of the vapour of a volatilizable strong mineral acid or the anhydride thereof. In the above formula X represents a hydroxy group, ether groups such as the methoxy-, ethoxy-, propoxy-, isopropoxy-, butoxy-, phenoxy-, and benzyloxy-group; ester groups such as the acetoxy-, propionoxy-, and benzoyloxy-group, or amino and substituted amino groups such as -NR1R2 where R1 and R2 each represent a hydrogen atom or a methyl-, ethylpropyl-, or benzyl-radical and R1 and R2 can be alike or different, and R1 and R2 can together with the nitrogen atom be one group such as a piperidino group. Preferred temperatures are 200 DEG to 600 DEG C., preferably 475 DEG to 525 DEG C. The catalysts mentioned are sulphuric acid, sulphur trioxide and hydrogen halides. They may be generated in situ, e.g. from alkyl esters of sulphuric acid such as mono- or di-ethyl sulphate or di-isopropyl sulphate. 0.1 to 1.5 Molar per cent on the propionamide may be used. The propionamide may be introduced as such or in a solvent, e.g. water or aliphatic alcohols. The reaction may be effected in a heated tube, preferably with pre-heating of the reactants. Any acrylonitrile produced as by-product may be isolated. In examples (1) b -methoxy propionamide and diisopropyl sulphate are dissolved in methyl alcohol, the solution is vaporized and passed through a glass tube filled with porcelain rings heated at 475 DEG to 490 DEG C., the contact time being about one minute, and the reaction product is condensed and distilled to give acrylamide and a small amount of acrylonitrile; (2) the process of (1) is repeated using an empty reaction tube; (3) concentrated sulphuric acid is used as the catalyst, with b -methoxy-propionamide, and the reaction time is about 48 seconds at 486 DEG C.