GB1078818A - Process for hydrolysing nitriles and for the recovery of nitrile-nitrogen - Google Patents

Abstract

Nitriles are hydrolysed to the corresponding carboxylic acids and the ammonia also formed during the hydrolysis is recovered by subjecting the nitrile, together with water or a substance yielding water under the reaction conditions, to hydrolysis, e.g. at temperatures up to 250 DEG C., in the presence of a molten salt melt comprising alkali metal and/or ammonium hydrogen sulphates or phosphates or mixtures thereof, separating the carboxylic acid formed, and heating the melt charged with ammonia to a higher temperature, e.g. 300 DEG to 450 DEG C., to recover the ammonia. The salt melt may additionally contain neutral alkali metal suphates or phosphates and part of the salts in the melt may be present in solid form. The removal of the ammonia may be assisted by passing an inert gas, e.g. N2, H2, air or steam through the melt. The process may be carried out in a continuous manner by recycling the melt (freed from ammonia) to the hydrolysis stage after cooling. Examples are given for the hydrolysis of acetonitrile, acrylonitrile, and adipic and terephthalic acid dinitriles.ALSO:Nitriles are hydrolysed to the corresponding carboxylic acids by subjecting them, together with water or a compound yielding water under the reaction conditions, to hydrolysis conditions in the presence of a molten salt melt comprising alkali metal and/or ammonium hydrogen sulphates or phosphates or mixtures thereof, separating the carboxylic acid formed and heating the melt charged with ammonia by-product to a higher temperature to recover the ammonia. The melt which preferably comprises NH4HSO4, NaHSO4 or KHSO4 or potassium hydrogen phosphate (m.p. 253 DEG C.) or a mixture of NaHSO4 and KHSO4 may also additionally contain neutral alkali metal sulphates or phosphates and it is not essential for the melt to constitute a homogeneous liquid phase since part of the salts may be present in solid form. The hydrolysis temperature should generally not exceed 250 DEG C. and the removal of the ammonia is generally effected at between 300 DEG and 450 DEG C. and may be assisted by passing an inert gas, e.g. N2, H2, air, or steam, through the melt. The removal of the carboxylic formed can also be promoted by stripping with a carrier gas, e.g. steam, air, or N2. Examples are given for the hydrolysis of acetonitrile, acrylonitrile, adipic acid dinitrile and terephthalic acid dinitrile and the process may advantageously be carried out in a continuous manner by recycling the melt (freed from ammonia) to the hydrolysis stage after cooling.