Process for preparing aromatic polycarboxylic acid by liquid phase oxidation in the presence of a solvent, a catalyst and a promoter

Abstract

The invention relates to a process for preparing an aromatic polycarboxylic acid by liquid phase oxidation of a di- or tri-substituted benzene or naphtalene compound, the process comprising a step of contacting the aromatic compound with an oxidant in the presence of a craboxylic acid solvent, a metal catalyst and a promoter in a reaction zone, wherein the promoter is an ionic liquid comprising an organic cation and a bromide or iodide anion. Advantages of this process include high conversion without severe corrosion problems otherwise associated with halogen-containing compounds as promoter. The procss does not necessitate the use of special corrosion-resistant material or liners in the process equipment, thus offering savings on investment and maintenance costs and increasing plant reliability. The process of the invention is especially suited for production of terephthalic acid from p-xylene.