PTA – Manufacturing process of PTA (Terephthalic acid)

Modern technologies produce purified terephthalic acid by the catalytic liquid phase oxidation of paraxylene in acetic acid, in the presence of air. The process uses manganese or cobalt acetate as a catalyst. The reaction is exothermic, producing water which is removed in a solvent recovery system. Acetic acid from this is returned to the reactor together with the oxidation catalyst. The resulting PTA is purified in a crystalliser where the unreacted xylene and water are flashed off.

It exists several process licensed by : BP (Amoco), Advansa (ICI), Dow (Inca), Mitsubishi, Eastman and Mitsui. The figure below presents the simplified process of Hitachi :