Synthesis of 3,3′-dimethyl-4,4′-diaminodiphenylmethane catalyzed by zeolites replacing mineral acids

•A new route of synthesizing MDT catalyzed by zeolites replacing mineral acids•The catalytic activity varied with the order of Hβ > HY > HZSM-5•High MDT yield of 87.5% by Hβ under optimal reaction conditions•N, N′-di-o-tolyl-methanediamine found to be a key reaction intermediate

Synthesis of 3,3′-dimethyl-4,4′-diaminodiphenylmethane (MDT) from o-tolylamine and formaldehyde over zeolites was investigated. Among the three tested zeolites, Hβ showed higher catalytic activity than HY and HZSM-5 for MDT synthesis. In the case of Hβ as a catalyst, the effects of feed composition, reaction time and temperature on the yield and selectivity of product MDT were further examined to optimize process conditions. In an o-tolylamine:formaldehyde = 8:1 molar ratio, the two-step reaction running at 413 K for 0.5 h and then 433 K for 0.5 h gave the MDT yield of 87.5%.

Graphical abstractOverview of reaction sequence for MDT synthesis over Hβ zeolite.Figure optionsDownload full-size imageDownload as PowerPoint slide