Process for the manufacture and isolation of acrylic acid úe-butyl ester

摘要

Ammonium bisulphate is obtained as a by-product in a process for the preparation of acrylic acid n-butyl ester in which acrylonitrile is hydrolyzed in the presence of sulphuric acid and the product esterified with butanol. The impure compound contaminated with acrylic acid, hydracrylic acid and stabilizer residues is obtained as a molten mass from the base of the esterification column 10, heated in a rotary kiln 57, dissolved in water 58 and stirred with active carbon. The solution is filtered 64, and evaporated 68 to yield a white product. ALSO: Acrylic acid n-butyl ester is prepared by the esterification with butanol of sulphate of acrylamide prepared by the hydrolysis of acrylonitrile with sulphuric acid. The sulphate is contacted countercurrently with n-butanol and water, in an esterification stage wherein a molten salt mass of ammonium bisulphate is obtained as the sump product, and the top product comprising ester, residual n-butanol, acrylic acid and water is separated in three distillation stages, (1) in which the aqueous acrylic acid is the sump product and which is recycled to the esterification and the ether, butanol and water is the top product which is separated into (a) an aqueous phase, recycled to the esterification and (b) an organic phase which is distilled (2) in a dehydration distillation stage in which an aqueous phase is discharged at the head, and a mixture of ester and alcohol withdrawn from the sump and passed to (3) a distillation stage in which n-butanol is the top product which is recycled, and ester the final product which is condensed and collected. The esterification and distillation stages are heated under reflux and may be at atmospheric pressure, and stabilizers such as phenothiazine and methylene blue may be introduced. Pure ammonium bisulphate is obtained as a by-product from the sump of the esterification stage. Examples describe the preparation of esters from acrylonitrile hydrolysed at 90 DEG C. to 100 DEG C. with 85% sulphuric acid in a system comprising (Fig.), a hydrolysing vessel (2), a heated esterification column (10), to which water is added (14), and from which salt mixture is discharged (56). The impure ester mixture is passed by dephlegmator (17) to distillation column (20), condensed (26) and separated (27), distilled (30) and passed to the centre of a heated distillation column (44), and the ester vapour drawn off and condensed (52) and collected (53), while n-butanol is discharged at the top, condensed and recycled, and resinous products removed and collected (55). The by-product ammonium bisulphate from the esterification column 10, is heated, treated with animal charcoal, and separated as a purified product.