Two-stage process for cost-effective deposition of homogeneous catalysts in MDA synthesis

摘要

The invention provides a process for preparing diphenylmethanediamine, comprising the steps of:
a) reacting aniline with formaldehyde in the presence of an acid,b) neutralizing the predominant part of the acid with ammonia and/or aqueous ammonia solution,c) separating the reaction mixture from step b) into an aqueous phase and an organic phase,d) neutralizing the other part of the acid, present in the organic phase, with aqueous alkali metal hydroxide solution,e) separating the reaction mixture from step d) into an aqueous phase and an organic phase,f) treating the aqueous phase obtained in step c) or optionally the combined aqueous phases from steps c) and e) with at least one oxide or hydroxide of an alkaline earth metal,g) removing the ammonia obtained in step f).

主权项

1. A process for preparing diphenylmethanediamine and more highly condensed polyphenylenepolymethylenepolyamines, comprising:
a) reacting aniline with formaldehyde in the presence of an acid, b) neutralizing a first part of the acid with ammonia or an aqueous ammonia solution, to obtain a first reaction mixture, c) separating the first reaction mixture into a first aqueous phase and a first organic phase, d) neutralizing a second part of the acid, present in the first organic phase, with an aqueous alkali metal hydroxide solution, to obtain a second reaction mixture, e) separating the second reaction mixture into a second aqueous phase and a second organic phase, f) treating the first aqueous phase or optionally a combination of the first and second aqueous phases with at least one oxide or hydroxide of an alkaline earth metal, to obtain a third reaction mixture, comprising ammonia, and g) removing the ammonia from the third reaction mixture.