A process for producing pyromellitic acid which comprises oxidizing 2,4,5-trimethylbenzaldehyde
and/or its oxidized derivative in the presence of a catalyst containing iron, manganese
and bromine, or additionally containing zirconium or cerium continuously or semi-continuously
using aqueous acetic acid solvent and 0.05-2% by weight of bromide ion. The catalyst
used in the present invention has high activity, and the catalyst solution has
low corrosive because the reaction is performed at low bromide concentration by
using a solvent of aqueous acetic acid. So pyromellitic acid is produced industrially
advantageously in high yield continuously or semi-continuously which has been a
major difficulty up to now.
