| 摘要 |
<PICT:0904931/IV (b)/1> <PICT:0904931/IV (b)/2> Acrylic acid methyl ester is prepared by the esterification with methanol, of the sulphate of acrylamide prepared by the hydrolysis of acrylonitrile with 85% sulphuric acid in a molar ratio of acid to acrylonitrile of 1.1:1. The sulphate is contacted countercurrently with methanol and water in a molar ratio of 1:4:0.5-1, at 120-170 DEG C., in an esterification stage wherein an aqueous salt mass of the ammonium bisulphate is obtained as the sump product, and the top product comprises ester, and residual methanol. The methyl ester is separated by extractive distillation with water, and subsequently distilled from the water to yield pure ester. The esterification, extraction and distillation stages are operated under reflux and may be at atmospheric pressure, and stabilizers such as phenothiazine and methylene blue are present. In an example (Fig. 1) acrylonitrile is hydrolysed with 85% sulphuric acid, in vessel (2) and the product passed to esterification column (10), into which is passed methanol (72) and water (14). The head product, a binary azeotrope of ester and methanol is extractively distilled with water in column (20). The product is condensed (26), separated (27) and dehydrated in column (30) to yield pure vaporous ester which is condensed (86) and collected (87). Methyl alcohol is stripped (74) from the water and recycled and the ammonium bisulphate worked up as described in the parent Specification. The apparatus and that of the parent Specification may be combined and a suitable modification may be made by the use of valves (88 and 89). |
