| 摘要 |
Hydrogen cyanide is removed from a dilute aqueous solution of acrylonitrile containing also an aliphatic aldehyde and hydrogen cyanide by distilling the solution in a first still to take off overhead a fraction containing acrylonitrile, hydrogen cyanide, aldehyde and water and feeding this fraction without condensation to a second still which is operated continuously under such conditions that the hydrogen cyanide is removed in an overhead fraction and acrylonitrile is recovered as the base product. The process is preferably used for the separation of hydrogen cyanide from acrylonitrile obtained by the reaction of acrolein with ammonia and molecular oxygen at elevated temperature in the presence of a catalyst, e.g. molybdic oxide. Preferably a vapour divider is provided at the head of the first still to enable a proportion of the overhead fraction to be condensed and returned to the still as reflux. The second still is advantageously operated under reduced pressure. It is desirable to operate the distillations in the presence of a conventional polymerisation inhibitor.ALSO:Acrylonitrile is produced by passing a mixture of acrolein, ammonia and air in vapour phase over a molybdic oxide catalyst. The gas leaving the reactor containing acrylonitrile, acrolein and hydrogen cyanide is scrubbed first with dilute sulphuric acid to remove ammonia and then with water. The acrylonitrile is separated from the resulting mixture by a process of distillation (see Group III). |
