METHOD FOR AVOIDING CORROSION

摘要

The invention relates to a method for avoiding corrosion on the separation of methylamine from a product stream (10) with the components monomethylamine, dimethylamine, trimethylamine, ammonia and methanol, arising during the production of methylamine by the gas phase reaction of methanol and ammonia, whereby ammonia is separated off in a first column (1), by simple distillation and the bottom components of the product stream remaining in the kettle (12) are fed to a second column (2). Trimethylamine (14) is separated off in the second column (2), by means of extractive distillation with addition of water. The further components of the product stream remaining in the kettle (15) of the second column (2) are introduced into a third column (3), in which monomethylamine and dimethylamine are separated off through the head. The monomethylamine and dimethylamine are separated in a fourth column (4) by distillation. In order to avoid corrosion, alkaline hydroxide is added to the second or third column (3).