METHOD OF PRODUCING HIGHLY PURE TEREPHTHALIC ACID Russian patent published in 2010 - IPC C07C51/47 C07C63/26 C07C51/42 C07C51/265 

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of producing highly pure terephthalic acid which involves the following steps: (a) an oxidation reaction, where p-xylene is oxidised in an acetic acid solution in the presence of a catalyst to form terephthalic acid, (b) obtaining crystals of crude terephthalic acid, where the suspension containing the precipitate of the obtained terephthalic acid is separated into a solid phase and a liquid to obtain crystals of crude terephthalic acid, (c) hydrogenation step, where crystals of crude terephthalic acid are dissolved in water to form an aqueous solution which is hydrogenated, (d) crystallisation of highly pure terephthalic acid, where terephthalic acid is crystallised from the hydrogenated aqueous solution to form a suspension of highly pure terephthalic acid, (e) obtaining crystals of highly pure terephthalic acid, where the suspension of highly pure terephthalic acid is separated into a solid phase and a liquid to obtain crystals of highly pure terephthalic acid and a primary mother solution, and (f) extraction of p-toluic acid from the primary mother solution and taking it to the oxidation reaction step, where the p-toluic acid extraction step includes the following steps: (I) adsorption step, where primary or secondary mother solution, obtained by cooling the primary mother solution in order to separate the solid phase and liquid, is fed in form of treated liquid into an adsorption column filled with an adsorption agent, where the p-toluic acid breakthrough time is greater than that of benzoic acid, for adsorption of p-toluic acid and benzoic acid from the treated liquid on the adsorption agent, (II) cutting supply of the treated liquid into the adsorption column for at a certain moment in time when concentration of benzoic acid in the effluent from the adsorption column reaches at least 10% of the concentration of benzoic acid in the treated liquid, (III) desorption step, where a desorption agent in form of acetic acid, methylacetate or their mixture is fed into the adsorption column for desorption of the adsorbed p-toluic acid and (IV) circulation step, where p-toluic acid contained in the desorption agent flows from the adsorption column and taken to the oxidation reaction step.

EFFECT: design of a method of obtaining highly pure terephthalic acid through selective extraction of p-toluic acid from waste water currently released, and use of the waste water as raw material for producing terephthalic acid.

19 cl, 6 dwg, 5 ex, 1 tbl