Method for preparing diamino-dicyclohexyl methane

A method for preparing diamino-dicyclohexyl methane (H12MDA) by catalytic hydrogenation of diamino-diphenyl methane (MDA). In the process, 4,4'-MDA is firstly used as starting material to prepare 4,4'-H12MDA by catalytic hydrogenation. When the activity of the catalyst decrease, the deactivated catalyst is activated online by switching the feed as the mixture of 2,4'-MDA and 4,4'-MDA.