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Abstract

A process for producing terephthalic acid, which comprises dissolving crude terephthalic acid in an aqueous medium, contacting it with a platinum group metal catalyst for purification under a temperature condition of from 260.degree. to 320.degree. C., crystallizing terephthalic acid from the aqueous solution of terephthalic acid by cooling the aqueous solution stepwise in a plurality of crystallizers connected in series, in such a manner that in a first crystallization zone, the crystallization temperature is adjusted to a level within a range of from 240.degree. to 260.degree. C. and agitating is carried out by impeller with a power requirement of impeller within a range of from 0.4 to 10 kw/m.sup.3, and then, in a second crystallization zone, the crystallization temperature is adjusted to a level within a range of from 180.degree. to 230.degree. C., which is lower by from 20.degree. to 60.degree. C. than the crystallization temperature in the first crystallization zone, followed by solid-liquid separation, and drying the separated terephthalic acid crystals to obtain terephthalic acid particles wherein the proportion of particles having particle sizes exceeding 210 .mu.m is at most 10 wt %.

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