Preparation of crystalline hydroxylammonium sulfate having a low ammonium sulfate content

摘要

Crystalline hydroxylammonium sulfate is prepared by a process which comprises the following steps: (a) Bringing an aqueous solution which contains from 0.02 to 0.3 part by weight of ammonium sulfate and from 0.02 to 0.2 part by weight of sulfuric acid per part by weight of hydroxylammonium sulfate into contact with a basic ion exchanger and obtaining a solution which has a pH of from 3.0 to 4.0, (b) separating off the basic ion exchanger from the aqueous hydroxylammonium sulfate solution, (c) evaporating down the resulting aqueous hydroxylammonium sulfate solution under reduced pressure at <100 DEG C. and obtaining a concentrated hydroxylammonium sulfate solution, (d) crystallizing out not more than 70% by weight of the hydroxylammonium sulfate present in the aqueous solution to give crystalline hydroxylammonium sulfate and a mother liquor, and (e) isolating and crystalline hydroxylammonium sulfate from the mother liquor.