Patent ID: 9045409
Filing Date: 2015-06-02
Classification: C07C

Abstract:
1. A process for producing a purified terephthalic acid (PTA) comprises the following steps: a. Dissolve parxylene (PX) in acetic acid and water; add 50-3000 ppm of cobalt acetate, manganese acetate and hydrobromic acid wherein the ratio of cobalt acetate: manganese acetate: hydrobromic acid is 1:1-2.5:1-3 by mass; b. Add above mixture into a first oxidation reactor, add oxygen-containing gas from the bottom of the oxidation reactor while maintain the temperature between 90 and 180° C., and the pressure between 0.1 and 1.8 MPaG, and adjust the concentration of acetic acid down to 90% with water; c. Move the mixture resulted from step b to a tower to remove the non-oxidized PX and partial acetic acid, then add water to adjust the concentration of acetic acid down to 20%; d. Pump the mixture resulted from step c to the top of a second oxidation reactor, and add oxygen-containing gas at the bottom above the equilibrium zone of the oxidation reactor while maintain the temperature between 260 and 350° C., and the pressure between 7.0 and 8.5 MPaG, and adjust the concentration of acetic acid about 20% with water and acetic acid; e. Move the mixture resulted from step d to the bottom of the second oxidation reactor, equilibrium zone, maintain the temperature between 260 and 350° C. and the concentration of acetic acid at 20%; f. Crystallize the terephthalic acid (TA) from the mixture resulted from step e by flash vaporization in a crystallizer, wherein the first oxidation reactor is an oxidation reactor consisting of an inner chamber and an outer chamber and the second oxidation reactot is a tower-type of oxidation reactor.