IMPROVED METHOD FOR COMBINED PRODUCTION OF ACRYLONITRILE AND HYDROGEN CYANIDE Russian patent published in 2013 - IPC C07C253/34 C07C255/08 C01C3/02 

FIELD: chemistry.

SUBSTANCE: invention relates to a method for combined production of acrylonitrile and hydrogen cyanide by treating a combined stream obtained by combining an acrylonitrile product stream and a stream containing hydrogen cyanide, where said streams are obtained concurrently in separate reactor systems. The method comprises steps (a) to (e). Step (a) involves obtaining acrylonitrile and providing an acrylonitrile product stream. Step (b) involves obtaining hydrogen cyanide and providing a stream containing hydrogen cyanide. Step (c) involves combining the stream containing hydrogen cyanide and the acrylonitrile product stream in an absorption column with water to obtain a combined product stream having the ratio of the acrylonitrile product stream to the stream containing hydrogen cyanide of about 9 to 1 or less. Step (d) involves treatment of the combined product stream successively in a recovery column, a decantation tank having an aqueous layer and an organic layer, and a column for separating head fractions, where pH is controlled by adding an acid to pH 7.0 or lower in the absorption column and the recovery column and to pH below 4.5 in the decantation tank and the column for separating head fractions. Step (e) involves separating the stream of crude HCN from the stream of crude acrylonitrile in the column for separating head fractions, treating the stream of crude HCN in a column for distilling HCN and treating the stream of crude acrylonitrile in a drying column. The pH in the column for distilling HCN is kept below 4.5, and temperature in the decantation tank is below 50°C.

EFFECT: method increases output of hydrogen cyanide and prevents polymerisation thereof.

8 cl, 1 dwg, 2 ex