Catalytic Amination of Bisphenol F to Methylenedianiline via Tandem Hydrogenation-Amination-Dehydrogenation

This is the authors' abstract. We don't add key points for this paper.

Methylenedianiline (MDA) is a crucial intermediate for the production of methylenediphenyl diisocyanate (MDI), a key building block in polyurethane manufacturing. The traditional aniline synthesis, starting from petrochemical feedstocks, involves a hazardous and environmentally demanding multistep process (nitration, reduction). Consecutive condensation with formaldehyde and rearrangement to MDA are characterized by a challenging overall regioselectivity, resulting in an atom- and step-inefficient process. Herein, we report a sustainable amination process for the synthesis of MDA starting from bisphenols as an alternative and sustainable raw material. Pd/C was identified as a suitable catalyst, giving good yields (64%) with limited input of NH 3 and H 2 . A low partial pressure of H 2 facilitates the hydrogenation–amination–dehydrogenation pathway. The acid–base properties of the catalyst support strongly affect the reaction outcomes, which can be rationalized by the adsorption of the reactants and (intermediate) products. Through the addition of a potassium base (K 2 CO 3, KOH) yields of up to 89% MDA and 97% diamines were obtained while limiting undesired side reactions like overhydrogenation of phenol to cyclohexanol and defunctionalization. Further insight into the reaction network was gained through dehydrogenation experiments; reaction parameters were related to NH 3 temperature-programmed desorption (NH 3 -TPD) and CO-chemisorption catalyst characterization data.