Preparation of aromatic polycarboxylic acids.

摘要

1,177,430. Polycarboxylic aromatic acids. E.I. DU PONT DE NEMOURS & CO. 18 July, 1968, No. 34384/68. Heading C2C. Polycarboxylic acids are prepared by oxidizing a polyalkyl-substituted aromatic compound with molecular oxygen in the liquid phase at elevated temperature and pressure and in the presence of an oxidation catalyst containing bromine and metal, the oxidation being carried out: (a) at a lower elevated temperature in the presence of little or no added water to convert a major proportion of the starting aromatic compound to an oxidation product comprising only a minor proportion of the desired polycarboxylic acid, and then (b) at a higher temperature, in the presence of sufficient water to maintain the solids content below 70% by weight to convert the oxidation product to the desired polycarboxylic acid. The second stage of the oxidation is carried out at a temperature, preferably at least 25‹ C. above that of the first. The process may be used for the conversion of p-ethyl toluene and/or p-diisopropyl benzene to terephthalic acid; o-xylene or o-isobutyl toluene to o-phthalic acid; m-xylene to isophthalic acid; ditolylethanes to phthalic acids; mesitylene to trimesic acid; pseudocumene to trimellitic acid durene to pyromellitic acid; dimethylnaphthalenes to dicarboxynaphthalenes and dimethylbiphenyls to biphenyldicarboxylic acids.