Synthesis of 4,4′-Methylenedianiline Catalyzed by SO3H-Functionalized Ionic Liquids

Abstract

4,4′-Methylenedianiline (4,4′-MDA) is a key intermediate for the production of polyurethanes. A series of SO3H-functionalized ionic liquids (SFILs) were synthesized, and their catalytic performance was evaluated in the condensation reaction of aniline with formaldehyde for the synthesis of 4,4′-MDA. The result showed that SFILs had excellent catalytic activity, and their catalytic activity was consistent with their acid strength. [HSO3-bmim]CF3SO3 (SImTf) with the highest acid strength showed the best catalytic activity. Then, the influence of reaction conditions on the condensation reaction of aniline with formaldehyde to 4,4′-MDA was investigated using SImTf as the catalyst, and suitable reaction conditions were obtained as follows: molar ratio of aniline to formaldehyde = 5, mass ratio of SImTf to formaldehyde = 3.5, reaction temperature of 80 °C, and reaction time of 8 h. Under the above reaction conditions, the conversion of aniline was 36.3%, and the yield and selectivity of 4,4′-MDA were 79.4% and ...