The reaction network and mechanism of the synthesis of methylenedianiline (MDA) from the condensation product of aniline and formaldehyde (aminal) on microporous acidic materials has been elucidated. The first step of the reaction, the decomposition of the aminal to N- benzylanilines, is limited by film diffusion, and the second and significantly slower step, the acid catalyzed rearrangement of these intermediates to MDA, is controlled by ...