Process for producing purified terephthalic acid
AssigneeXiangjin Zhou
InventorXiangjin Zhou
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Abstract
A new process for the production of purified terephthalic acid (PTA) is disclosed to keep terephthalic acid (TA) in dissolved state during the process of oxidation reaction, to obtain intermediate product crude terephthalic acid (CTA) not containing the two impurities of 4-carboxyl benzaldehyde (4-CBA) and p-methyl benzoic acid (PT acid), so that it can eliminate the “purified” production process, and reduce the consumptions of raw materials, acetic acid, fuel and power, and water, thereby saving production costs.
Claims13
A process for producing a purified terephthalic acid (PTA) comprises the following steps:
- a. Dissolve parxylene (PX) in 94% acetic acid and 6% 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 first section of an oxidation reactor, maintain the temperature between 90 and 180° C., and adjust the concentration of acetic acid down to 90% with water;
- c. Move the mixture resulted from step b to second section of the oxidation reactor, increase the temperature between 180 and 210° C., and adjust the concentration of acetic acid down to 80% with water;
- d. Move the mixture resulted from step c to third section of the oxidation reactor, increase the temperature between 210 and 260° C., and adjust the concentration of acetic acid down to 20% with water;
- e. Move the mixture resulted from step d to forth section of the oxidation reactor, increase the temperature between 260 and 350° C., add oxygen-containing gas while maintain the—concentration of acetic acid at 20%;
- f. Move the mixture resulted from step e to fifth section, equilibrium zone, of the oxidation reactor maintain the temperature between 260 and 350° C. and the concentration of acetic acid about 20%;
- g. Crystallize the terephthalic acid (TA) from the mixture of step f by flash vaporization in a crystallizer;
A process for producing a purified terephthalic acid (PTA) comprises the following steps:
- a. Dissolve parxylene (PX) in 94% acetic acid and 6% 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;
Dependencies are inferred from the claim text.