PROCESS FOR PREPARING AROMATIC CARBOXYLIC ACID WITH EFFICIENT ENERGY RECOVERY

PROBLEM TO BE SOLVED: To provide a process for preparing aromatic carboxylic acids by exothermic liquid-phase oxidation reaction of an aromatic compound feedstock, wherein energy is efficiently recovered from the exothermic oxidation reaction. SOLUTION: The process for preparing comprises (a) a step for generating gaseous high-pressure overhead flow containing water, gaseous by-products, and gaseous low molecular monocarboxylic acid solvent by oxidizing an aromatic compound feedstock, in a liquid phase reaction mixture comprising water, a low molecular monocarboxylic acid solvent, a heavy metal oxidizing catalyst and a molecular oxygen source at 0-35 kg/cm2pressure and 150-240°C temperature, (b) a step for forming a second high-pressure overhead flow containing water and gaseous by-products, formed in oxidation reaction by supplying the gaseous overhead flow into a high-efficiency separator of separating water from the low molecular carboxylic acid to remove at least 95 wt% of the low molecular monocarboxylic acid from the gaseous high-pressure overhead flow, and (c) a step for directly or indirectly supplying the second high-pressure overhead flow of the step (b) to an expander for recovering energy from the second high-pressure over head flow. COPYRIGHT: (C)2006,JPO&NCIPI