Acrylonitrile

摘要

Acrylonitrile is obtained by the reaction of acetylene and hydrogen cyanide in an aqueous solution of a catalyst for the reaction by passing the acetylene and hydrogen cyanide through the catalyst solution and bringing both the catalyst solution and the output gases which have left the solution into contact with an aromatic solvent for acrylonitrile with which the catalyst solution is substantially immiscible and in which acetylene and hydrogen cyanide are substantially insoluble, whereby the acrylonitrile is separated from the catalyst solution and from the output gases immediately or shortly after it is formed. Unreacted acetylene and hydrogen cyanide and the catalyst solution may be separated from the aromatic solvent and recycled. The catalyst solution preferably comprises cuprous chloride and preferably also ammonium chloride. The aromatic solvent is preferably a hydrocarbon such as toluene, one or more of the xylenes or diphenyl, or an ether such as diphenyl ether. In the Figure, the apparatus comprises a reactor 2 packed with copper turnings 3 and filled with a catalyst solution 4 consisting of cuprous chloride, ammonium chloride and water and maintained at a pH of 1.0 by the addition of aqueous hydrochloric acid and a small amount of formic acid. The catalyst solution is kept at between 70 DEG and 100 DEG C. and a mixture of 1 volume of hydrogen cyanide to 1.3 volumes of acetylene is fed into the reactor through a pipe 1. The gas mixture resulting from the reaction and comprising acrylonitrile, unchanged acetylene, and hydrogen cyanide, passes upwardly through pipe 5 into an extractor 6 charged with toluene whilst at the same time part of the catalyst solution is carried over into the extractor 6 by the action of the bubbles of gas passing through it. The catalyst solution sinks to the bottom of the extractor and forms a definite interface 7 with the toluene and is returned by gravity flow through line 9 to the lower end of reactor 2. Undissolved gases pass to a condenser 10 where any undissolved acrylonitrile is condensed and returned to the extractor and uncondensed gases leave through pipe 10A and are recycled to the reactor along with any necessary make-up gas. The toluene continuously overflows from the extractor and is passed through cooler 12 to a still 13 in which the acrylonitrile which it contains is distilled off. Any water carried into the cooler 12 drops into the foot 21 and may be withdrawn through valve 22. The acrylonitrile vapour from still 13 is then condensed in condenser 15 and run off at 16. The stripped toluene is passed from the reboiler 14 which is provided on the still 13 to the cooler 18 where its temperature is reduced to about 10 DEG to 30 DEG C. after which it is forced by pump 19 to the condenser 10 where it scrubs the undissolved and uncondensed gases before returning to extractor 6.