Improvements in the refining of acrylonitrile

摘要

Acrylonitrile contaminated with divinylacetylene is purified by vaporizing substantially anhydrous contaminated acrylonitrile under distillation conditions while countercurrently contacting the vapours with water so as to repress distillation of the major portion of the acrylonitrile while permitting distillation of the divinylacetylene, the residue comprising an aqueous solution of acrylonitrile substantially free from divinylacetylene, and recovering acrylonitrile from the residue. Preferably the distillate is condensed and mixed with additional water to form two layers, one being an aqueous solution of acrylonitrile contaminated with a minor amount of divinylacetylene and the other predominantly divinylacetylene. The acrylonitrile is subsequently removed from the aqueous residue by distillation. In a preferred embodiment (Example 1) 80 grams of acrylonitrile contaminated with 1.5% of divinyl acetylene, and 2000 grams of water is fed into the middle of the extraction still column 11. The distillate comprising 14.7 grams of water and acrylonitrile with 1.28 grams of divinylacetylene is led to a condenser 20 and additional water added. After passing to a decanter 23 and allowing to settle, the lower layer containing acrylonitrile and water with a trace of divinylacetylene is returned to the extraction still. The product from the kettle 15 passes to a stripping still 16 and gives rise to 60 grams of acrylonitrile containing less than 0.1 part per million of divinylacetylene.