Continuous purifn of crude terephthalic acid

摘要

Process, using is not >50% 2-4C alkanol/aqueous soln. as solvent, comprises introducing 6-40 parts terephthalic acid dissolved in 100 pts solvent into a first crystallisation receiver to adiabatically evaporate 10 - 60% of the solvent so that part of the terephthalic acid precipitates whilst the mixture becomes a suspension. The suspension is transferred to a second or opt. more precipitation receivers in series to remove 10-60% of the solvent in each. The concn. in each receiver is regulated to not more than 60%, pref. by adding refluxed condensed solvent evaporated from the receivers. The temp. of the first receiver is pref. 260-310 degrees C.