Manufacture of monovinylacetylene

摘要

A gaseous mixture of acetylene and monovinylacetylene is separated by countercurrent contact with a solution of acetylene in an organic solvent therefor to obtain (a) acetylene gas and (b) a solution of monovinylacetylene in the solvent. The solvent is preferably water-miscible and may be dimethylformamide, acetone, acetonitrile, butyrolactone, dioxane, diethylacetamide and butyrolactam (pyrrolidone). The process is used in the production of monovinylacetylene from acetylene by contact with a cuprous chloride catalyst. An acetylene-containing gas stream from an arc or pyrolysis process is contacted with a small amount of dimethylformamide to remove diacetylene and acetylene remaining in the gas is then dissolved by countercurrent contact with more dimethyl-formamide. The solution is introduced into an absorption column A (Fig. 1) into the bottom of which is introduced a mixture of acetylene and monovinylacetylene from reactor B. Acetylene from the top of absorber A passes to reactor B for conversion to monovinylacetylene. The solution from the bottom of absorber A containing monovinylacetylene and some acetylene is partially stripped in stripper C and the gas obtained containing some monovinylacetylene is recycled to absorber A. The solution from stripper C is treated in still D to recover monovinylacetylene and dimethylformamide. Divinylacetylene formed together with the monovinylacetylene may be removed from the gas stream leaving reactor B by contact with a small amount of solvent before passing to absorber A. Alternatively, the divinylacetylene is removed from the bottoms from the still D either by operating the still under conditions such that no polymerization occurs and the divinylacetylene is stripped from the solvent or the still is operated to polymerize the divinylacetylene and polymer is kept at a low level in the circulating solvent by treating a bleed stream with water, filtering off the polymer and distillating the solvent. The polymerization of acetylene is effected in solution with a cuprous chloride catalyst solubilized preferably with a hydrochloride of a primary or secondary amine in a liquid carboxylic acid amide, preferably dimethylformamide and, as a separate phase, a hydrocarbon or chlorinated hydrocarbon or an ether of ethylene glycol or diethylene glycol.