Method of the regeneration of solutions of thiocyanate, organic, for example, having been used as solvents in the preparation of polyacrylonitrile

摘要

PICT:0895756/III/1 The sulphate ion content of an inorganic thiocyanate solution supersaturated in an inorganic sulphate is reduced by passing the solution through a slurried bed of a sulphate salt. The sulphate salt in the bed may be the same salt as the inorganic sulphate in the solution, while the sulphate in solution may have the same cation as the thiocyanate, e.g. sodium. The thiocyanate solution may be at an elevated temperature, e.g. 41 DEG C., and after passing through the bed may be passed through a zone of minimum turbulence, so as to settle entrained solid sulphate, and filtered or centrifuged to free it of solid. The thiocyanate solution may have been concentrated, to produce a supersaturated solution, before treatment and may be diluted afterwards. An apparatus for the continuous removal of sodium sulphate from a sodium thiocyanate solution containing it at supersaturation level has a port 8 for the introduction of sulphate salt into tank 1 while the supersaturated solution is continuously introduced through inlet 9. Rotating shaft 5 mixes by distributer disc 10 and flat scraper 11 prevents blocking of inlet 9 by sulphate. Baffles 12 above the mixing bed reduce the flow of liquid after it has passed through the bed while treated solution passes through slots 13 disposed in a ring around the vessel and enclosed by an annular overflow channel 14, from which the solution drains continuously via outlet pipe 15. Specifications 796,294, 824,361 and 864,096 are referred to.ALSO:Spent thiocyanate solution from acrylonitrile polymerization supersaturated in an inorganic sulphate is treated to reduce the sulphate ion content by passing the solution through a slurried bed of a sulphate salt. The sulphate in solution may have the same cation as the thiocyanate, and the sulphate in the main bed may be the same salt as the inorganic sulphate in supersaturated solution. Sodium sulphate is specified while the thiocyanate solution may be at an elevated temperature. Specifications 796,294, 824,361 and 864,096 are referred to.