Patent ID: 7566802

Claim:
A continuous process for preparing aromatic carboxylic acids comprising: a). oxidizing an aromatic feedstock composition to an aromatic carboxylic acid composition in an oxidation reaction zone comprising water, mono-carboxylic acid solvents, an oxidation catalyst composition and a source of molecular oxygen, under reaction conditions which produce an oxidation reaction offgas comprising water, gaseous by-products, and vaporized mono-carboxylic acid solvent; b). feeding said oxidation reaction offgas from step a) directly or indirectly to an expander for recovering mechanical power producing a gaseous expander outlet product; and c). feeding said expander outlet product from step b) directly or indirectly to a fractionation zone producing a liquid containing partially de-watered mono-carboxylic acid product and producing at least one overhead aqueous product wherein the fractionation zone comprises at least two (2) theoretical stages.