Process for the production of aromatic carboxylic acids

A continuous process for producing an aromatic polycarboxylic acid product from an exothermic reaction, comprising:

• combining in a pressurized oxidation reactor alkyl aromatic hydrocarbon, oxidation catalyst, aqueous solvent of C.sub.2 -C.sub.6 aliphatic, monocarboxlyic acid and oxygen-containing gas to produce a reaction mixture having a vapor phase and a product-containing liquid phase;
• removing heat and water generated by exothermic reaction from the vapor phase by withdrawing a portion of the vapors from the reactor and passing the withdrawn vapors directly into a bottom portion of a water removal column;
• generating from the water removal column a bottoms liquid containing partially de-watered solvent and overhead aqueous vapors having minimal solvent content therein;
• recycling to the reactor a portion of the bottoms liquid in the form of a spray above the phase separation of the gas/liquid contents of the reactor, whereby the water content of the vapors from the reactor is enriched;
• and
• condensing the overhead aqueous vapors from the water removal column and refluxing a portion of the condensate into a fractionating zone of the water removal column and disposing of the other portion of the condensate,
• whereby the water removal column is operated utilizing the heat generated by the exothermic reaction to produce the condensate having minimal solvent content.

Method for the continuous production of terephthalic acid in a pressurized oxidation reactor by liquid-phase, exothermic oxidation of p-xylene with oxygen-containing gas in the presence of oxidation catalyst and aqueous acetic acid which comprises the steps of:

• (1) continuously feeding to a reactor p-xylene, aqueous, acetic acid having oxidation catalyst dissolved therein and air;
• (2) continuously removing from the lower portion of the reactor product-containing liquid comprising terephthalic acid and aqueous acetic acid having the oxidation catalyst dissolved therein;
• (3) continuously removing from the upper portion of the reactor and feeding directly into a lower portion of a water removal column reactor off-gas comprising oxygen-depleted gas and vaporized aqueous, acetic acid;
• (4) continuously removing from the lower portion of the water removal column a bottoms liquid containing partially de-watered acetic acid;
• (5) returning to the reactor 10 to 100% of the of the bottoms liquid obtained in step (4) in the form of a spray above the phase separation of the gas/liquid contents of the reactor;
• (6) continuously removing from the water removal column overhead aqueous vapors having minimal acetic acid therein;
• (7) condensing the overhead aqueous vapors into a distillate product;
• and
• (8) returning to the fractionating zone of the water removal column at least a portion of the distillate product obtained in step (7).