PURPOSE: When pyridine bases are obtained from acetaldehyde and ammonia and ammonia is recovered by distillation, sodium or potassium hydroxide is added to prevent the precipitation of crystals caused by carbonate groups.

CONSTITUTION: The reaction of acetaldehyde, or sometimes of a combination thereof with formaldehyde or acrolein, with ammonia is conducted to form pyridine bases and ammonia is recovered as an aqueous solution from the resultant uncondensed gas, then more than 0.05wt% of sodium hydroxide or potassium hydroxide is added to the solution and the ammonia is recovered by distillation. The sodium or potassium hydroxide is added in a form of solid or solution. In order to avoid the precipitation of carbonate salts, potassium or sodium hydroxide is preferably added to the crude reaction mixture by about 1/5 of the above amount as well.

EFFECT: No clogging takes place by precipitation of crystals.