Process for production of terephthalic acid

Abstract

The invention provides a method for producing terephthalic acid, characterized by including subjecting a p-phenylene compound to liquid-phase oxidation reaction by use of a molecular-oxygen-containing gas in the presence of a catalyst at least containing a heavy metal compound and a bromine compound, and hydrous acetic acid having a water content of 1 to 15 mass %, to thereby yield a slurry; regulating the temperature of the slurry to 35 to 140° C., to thereby cause terephthalic acid to precipitate; removing the terephthalic acid through solid-liquid separation, to thereby recover a mother liquor; and recovering the catalyst from the mother liquor through a series of the following steps (1) to (4) for reusing at least a portion of the catalyst in the liquid-phase oxidation reaction: (1) an adsorption step including regulating the ratio “amount by mole of bromide ions in the mother liquor/total amount by mole of heavy metal ions in the mother liquor” to 0.6 to 3, and then exposing the mother liquor to a pyridine-ring-containing chelate resin which has been heated to 35 to 140° C., so that the resin adsorbs catalyst-derived heavy metal ions and bromide ions, and also adsorbs a carboxylic acid mixture which has been by-produced through the liquid-phase oxidation reaction, (2) an elution step (A) of exposing hydrous acetic acid having a water content of 1 to 15 mass % to the pyridine-ring-containing chelate resin which has undergone the adsorption step, thereby yielding an eluate containing the by-produced carboxylic acid mixture, (3) an elution step (B) of exposing water or hydrous acetic acid having a water content of 20 mass % or more to the pyridine-ring-containing chelate resin which has undergone the elution step (A), thereby yielding an eluate containing catalyst-derived heavy metal ions and bromide ions, and (4) a displacement step of exposing hydrous acetic acid having a water content of 1 to 15 mass % to the pyridine-ring-containing chelate resin which has undergone the elution step (B), serving as a displacement liquid, thereby regenerating the resin.

1 . A method for producing terephthalic acid comprising:
 subjecting a p-phenylene compound to a liquid-phase oxidation reaction by the use of a molecular-oxygen-containing gas in the presence of a catalyst at least containing a heavy metal compound and a bromine compound, and hydrous acetic acid having a water content of 1 to 15 mass %, to thereby yield a slurry;   regulating the temperature of the slurry to 35 to 140° C., to thereby cause terephthalic acid to precipitate;   removing the terephthalic acid through solid-liquid separation, to thereby recover a mother liquor; and   recovering the catalyst from the mother liquor through a series of operations (1) to (4) for reusing at least a portion of the catalyst in the liquid-phase oxidation reaction:   (1) an adsorption operation including regulating the amount by mole of bromide ions in the mother liquor/total amount by mole of heavy metal ions in the mother liquor ratio to 0.6 to 3, and then exposing the mother liquor to a pyridine-ring-containing chelate resin which has been heated to 35 to 140° C., so that the resin adsorbs catalyst-derived heavy metal ions and bromide ions, and also adsorbs a by-produced carboxylic acid mixture which has been by-produced through the liquid-phase oxidation reaction,   (2) an elution operation (A) of exposing hydrous acetic acid having a water content of 1 to 15 mass % to the pyridine-ring-containing chelate resin which has undergone the adsorption operation, thereby yielding an eluate containing the by-produced carboxylic acid mixture,   (3) an elution operation (B) of exposing water or hydrous acetic acid having a water content of 20 mass % or more to the pyridine-ring-containing chelate resin which has undergone the elution operation (A), thereby yielding an eluate containing catalyst-derived heavy metal ions and bromide ions, and   (4) a displacement operation of exposing hydrous acetic acid having a water content of 1 to 15 mass % to the pyridine-ring-containing chelate resin which has undergone the elution operation (B), serving as a displacement liquid, thereby regenerating the resin.   
   
   
       2 . The method for producing terephthalic acid as described in  claim 1 , wherein hydrous acetic acid is recovered from the mother liquor which has undergone the adsorption operation, from the eluate obtained through the elution operation (A), and from the displacement liquid employed in the displacement operation, and the recovered hydrous acetic acid is reused in the liquid-phase oxidation reaction as at least a portion of hydrous acetic acid having a water content of 1 to 15 mass %. 
   
   
       3 . The method for producing terephthalic acid as described in  claim 1 , wherein hydrous acetic acid is recovered from the mother liquor which has undergone the adsorption operation, from the eluate obtained through the elution operation (A), and from the displacement liquid employed in the displacement operation, and the recovered hydrous acetic acid is reused in the elution operation (A) as at least a portion of hydrous acetic acid having a water content of 1 to 15 mass %. 
   
   
       4 . The method for producing terephthalic acid as described in  claim 1 , wherein hydrous acetic acid is recovered from the mother liquor which has undergone the adsorption operation, from the eluate obtained through the elution operation (A), and from the displacement liquid employed in the displacement operation, and the recovered hydrous acetic acid is reused in the displacement operation as a displacement liquid. 
   
   
       5 . The method for producing terephthalic acid as described in  claim 1 , wherein the eluate obtained through the elution operation (B) is returned to the liquid-phase oxidation reaction, and reused as at least a portion of the catalyst. 
   
   
       6 . The method for producing terephthalic acid as described in  claim 1 , wherein a regenerated pyridine-ring-containing chelate resin which has been obtained through the displacement operation is reused in the adsorption operation as the pyridine-ring-containing chelate resin. 
   
   
       7 . The method for producing terephthalic acid as described in  claim 1 , wherein the hydrous acetic acid having a water content of 1 to 15 mass % and employed in the elution operation (A) contains bromide ions in an amount of 1 to 1,000 mass ppm. 
   
   
       8 . The method for producing terephthalic acid as described in  claim 1 , wherein the hydrous acetic acid having a water content of 1 to 15 mass % and employed in the displacement operation as a displacement liquid contains bromide ions in an amount of 1 to 1,000 mass ppm. 
   
   
       9 . The method for producing terephthalic acid as described in  claim 1 , wherein, in the adsorption operation, the amount by mole of bromide ions in the mother liquor/total amount by mole of heavy metal ions in the mother liquor ratio is regulated to 1.6 to 2.5. 
   
   
       10 . The method for producing terephthalic acid as described in  claim 1 , wherein when Q represents the total amount (g) of hydrous acetic acid having a water content of 1 to 15 mass % supplied in the elution operation (A), and V represents the volume (mL) of a pyridine-ring-containing chelate resin layer, the ratio Q/V is 0.5 to 10.