| 摘要 |
Ammonia is recovered as a by-product in the preparation of carboxylic acid esters by heating nitriles in the presence of water and alcohol to between 90 DEG and 300 DEG C. in a salt melt of an acid sulphate and/or acid phosphate of an alkali metal and/or of ammonium, and optionally a neutral sulphate and/or phosphate of an alkali metal (see Division C2). The ammonia may be desorbed from the salt melt at between 350 DEG and 450 DEG C. and re-used for the preparation of nitriles either directly or by way of hydrogen cyanide.ALSO:Carboxylic acid esters are prepared by heating a nitrile in the presence of water and an alcohol to from 90 DEG to 300 DEG C. in a salt melt comprising an acid sulphate and/or acid phosphate of an alkali metal and/or of ammonium, and optionally a neutral sulphate and/or phosphate of an alkali metal. The carboxylic acid ester is separated, optionally with the unreacted nitrile and/or alcohol, and the ammonia is then removed from the salt melt by further heating to between 300 DEG and 500 DEG C. The melt may be re-used after removal of the ammonia and the process may be a continuous cycle. Melts of sodium and potassium bisulphates in a molar ratio of between 3:1 and 3:5, and of ammonium and potassium bisulphates are preferred. Gas-liquid countercurrent columns are suitable for gaseous reactants, and water may be introduced. Examples describe the treatment of adipic acid dinitrile to form adipic acid diethyl and monoethyl esters; cyanoacetic acid to form malonic acid di-n-butyl and diethyl esters; acetonitrile to form n-butyl acetate; acrylonitrile to form n-butyl acrylate; and glycolic acid nitrile to form glycolic acid n-butyl ester and n-butoxy-acetic acid n-butyl ester and the separation of ammonia. |
