METHOD FOR PREPARING DIAMINO-DICYCLOHEXYL METHANE

摘要

Disclosed is a method for preparing diamino-dicyclohexyl methane (H12MDA) by hydrogenation of diamino-diphenyl methane (MDA). In the process, 4,4′-MDA used as the starting material is firstly hydrogenated to prepare 4,4′-H12MDA. When the activity of the catalyst is reduced, the feed is switched from 4,4′-MDA to the mixture of 2,4′-MDA and 4,4′-MDA, and then when the conversion is stabilized, the feed is switched to 4,4′-MDA again. The deactivated catalyst is activated on line by switching the feed to the mixture of 2,4′-MDA and 4,4′-MDA. 4,4′-H12MDA having the trans-trans isomer content of 16˜24 wt % is produced, and the mixture of 2,4′-H12MDA and 4,4′-H12MDA is also produced, wherein the content of 2,4′-H12MDA in the mixture is 4˜15 wt %.

主权项

1. A method for preparing diamino-dicyclohexyl methane, wherein said method comprising the following steps:
1) 4,4′-diamino-diphenyl methane feed is hydrogenated in a reactor packed with catalyst to prepare 4,4′-diamino-dicyclohexyl methane at the conversion of 98-99.99%; 2) When the conversion in step 1) is 90-98%, the feed is switched from 4,4′-diamino-diphenyl methane to a mixture of 2,4′-diamino-diphenyl methane and 4,4′-diamino-diphenyl methane, and the hydrogenation reaction is continued to prepare 2,4′-diamino-dicyclohexyl methane and 4,4′-diamino-dicyclohexyl methane; 3) After the conversion of the mixture of 2,4′-diamino-diphenyl methane and 4,4′-diamino-diphenyl methane in step 2) is ≧90% and the reaction is lasted at said conversion for 20-40 h, the feed is switched from the mixture of 2,4′-diamino-diphenyl methane and 4,4′-diamino-diphenyl methane to 4,4′-diamino-diphenyl methane, and the hydrogenation reaction is continued to prepare 4,4′-diamino-dicyclohexyl methane.