Process for production of isophthalic acid

Abstract

The invention provides a method for producing isophthalic acid, characterized by including subjecting a m-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 isophthalic acid to precipitate; removing the isophthalic acid through to 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 0.3 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 isophthalic acid, comprising:
 subjecting a m-phenylene compound and a molecular-oxygen-containing gas to liquid-phase oxidation reaction in the presence of a catalyst comprising 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 precipitate isophthalic acid;   removing the isophthalic acid through solid-liquid separation, to thereby recover a mother liquor; and   recovering the catalyst from the mother liquor by following (1) to (4) for reusing at least a portion of the catalyst in the liquid-phase oxidation reaction:
 (1) regulating the ratio of an amount by mole of bromide ions in the mother liquor over total amount by mole of heavy metal ions in the mother liquor to 0.3 to 3, and then exposing the mother liquor to a pyridine-ring-containing chelate resin which is heated to 35 to 140° C., wherein the resin adsorbs catalyst-derived heavy metal ions and bromide ions, and also adsorbs a by-produced carboxylic acid mixture which is produced by the liquid-phase oxidation reaction, 
 (2) (A) yielding an eluate comprising the by-produced carboxylic acid mixture by exposing hydrous acetic acid having a water content of 1 to 15 mass % to the pyridine-ring-containing chelate resin which is processed by (1), 
 (3) (B) yielding an eluate comprising catalyst-derived heavy metal ions and bromide ions by exposing water or hydrous acetic acid having a water content of 20 mass % or more to the pyridine-ring-containing chelate resin which is processed by (A), and 
 (4) exposing hydrous acetic acid having a water content of 1 to 15 mass % to the pyridine-ring-containing chelate resin which is processed by (B), serving as a displacement liquid, thereby regenerating the resin. 
   
     
     
         2 . The method for producing isophthalic acid according to  claim 1 , wherein hydrous acetic acid is recovered from the mother liquor which is processed by (1), from the eluate obtained by (A), and from the displacement liquid in (4), 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 isophthalic acid according to in  claim 1 , wherein hydrous acetic acid is recovered from the mother liquor which is processed by (1), from the eluate obtained by (A), and from the displacement liquid employed in (4), and the recovered hydrous acetic acid is reused in (A) as at least a portion of hydrous acetic acid having a water content of 1 to 15 mass %. 
     
     
         4 . The method for producing isophthalic acid according to  claim 1 , wherein hydrous acetic acid is recovered from the mother liquor which is processed by (1), from the eluate obtained by (A), and from the displacement liquid in (4), and the recovered hydrous acetic acid is reused in (4) as a displacement liquid. 
     
     
         5 . The method for producing isophthalic acid according to  claim 1 , wherein the eluate obtained by (B) is returned to the liquid-phase oxidation reaction, and reused as at least a portion of the catalyst. 
     
     
         6 . The method for producing isophthalic acid according to  claim 1 , wherein a regenerated pyridine-ring-containing chelate resin which is obtained by (4) is reused in (1) as the pyridine-ring-containing chelate resin. 
     
     
         7 . The method for producing isophthalic acid according to  claim 1 , wherein the hydrous acetic acid having a water content of 1 to 15 mass % and employed in (A) comprises bromide ions in an amount of 1 to 1,000 mass ppm. 
     
     
         8 . The method for producing isophthalic acid according to  claim 1 , wherein the hydrous acetic acid having a water content of 1 to 15 mass % and employed in (4) as a displacement liquid comprises bromide ions in an amount of 1 to 1,000 mass ppm. 
     
     
         9 . The method for producing isophthalic acid according to  claim 1 , wherein, in (1), the ratio of an amount by mole of bromide ions in the mother liquor over total amount by mole of heavy metal ions in the mother liquor is regulated to 1.4 to 2.5. 
     
     
         10 . The method for producing isophthalic acid according to  claim 1 , wherein Q represents the total amount (g) of hydrous acetic acid having a water content of 1 to 15 mass % supplied in (A), V represents the volume (mL) of a pyridine-ring-containing chelate resin layer, and the ratio Q/V is 0.5 to 10.