Cleavage of acetone cyanohydrin - after neutralising acid stabiliser with ammonia or cyanide salt

摘要

Cleavage of acetone cyanohydrin (I) contg. an acid stabiliser comprises first (partially) neutralising the acid with metal or ammonium cyanide or NH3, then sepg. the metal or NH4 salts formed. The treated (I) is then heated at 60-160 (70-110) degrees C and opt. the HCN and acetone in the cleavage prods. sepd. by distillation. Pref. neutralisation is with 70-95% of the stoichiometric amt. of NH3 or NaCN and the pptd. salt is removed by filtration, esp. with addn. of a filter aid. Pref. a fraction, 0.1-5 wt.% on (I) charged, is withdrawn as sump prod. and opt. HCN, acetone and (I) removed as overhead (for recycle) by thin-film distn., from the heavy ends. (I) is an easily-handled and transported form of HCN. Cleavage is now achieved without use of steam and without formation of resins, salts or interfering volatile by-prods.