The problem of providing a metal complex having excellent gas adsorption performance, gas storage performance, and gas separation performance is solved by a metal complex comprising a dicarboxylic acid compound (I) including 20 to 99 mole % of a dicarboxylic acid compound (I-1) selected from terephthalic acid derivatives having an electron-donating group in the 2nd position such as 2-methoxyterephthalic acid, 2-methylterephthalic acid, and terephthalic acid, and 80 to 1 mole % of a dicarboxylic acid compound (I-2) selected from terephthalic acid derivatives having an electron-withdrawing group in the 2nd position such as 2-nitroterephthalic acid, 2-fluoroterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, and 2-iodoterephthalic acid; at least one kind of metal ion selected from metal ions belonging to Group 2 and Groups 7 to 12 of the periodic table; and an organic ligand capable of bidentate binding to the metal ion.

The problem of providing a metal complex having excellent gas adsorption performance, gas storage performance, and gas separation performance is solved by a metal complex comprising a dicarboxylic acid compound (I) including 20 to 99 mole % of a dicarboxylic acid compound (I-1) selected from terephthalic acid derivatives having an electron-donating group in the 2nd position such as 2-methoxyterephthalic acid, 2-methylterephthalic acid, and terephthalic acid, and 80 to 1 mole % of a dicarboxylic acid compound (I-2) selected from terephthalic acid derivatives having an electron-withdrawing group in the 2nd position such as 2-nitroterephthalic acid, 2-fluoroterephthalic acid, 2-chloroterephthalic acid, 2-bromoterephthalic acid, and 2-iodoterephthalic acid; at least one kind of metal ion selected from metal ions belonging to Group 2 and Groups 7 to 12 of the periodic table; and an organic ligand capable of bidentate binding to the metal ion.

The metal complex comprises a multivalent carboxylic acid compound, at least one metal ion selected from ions of metals belonging to Groups 2 to 13 of the periodic table, an organic ligand capable of multidentate binding to the metal ion, and a C.sub.1 or C.sub.2 monocarboxylic acid compound. The metal complex has excellent gas adsorption, storage, and separation performance as well as excellent durability. The metal complex is stably present under high temperature and high humidity, and can maintain high adsorption performance.

The metal complex comprises a multivalent carboxylic acid compound, at least one metal ion selected from ions of metals belonging to Groups 2 to 13 of the periodic table, an organic ligand capable of multidentate binding to the metal ion, and a C.sub.1 or C.sub.2 monocarboxylic acid compound. The metal complex has excellent gas adsorption, storage, and separation performance as well as excellent durability. The metal complex is stably present under high temperature and high humidity, and can maintain high adsorption performance.

Process to recover NaOH, polyester monomers, dyes and byproducts from an alkaline depolymerization liquor resulting from a depolymerization reaction of polyester in a blend textile. The process comprises concentrating the liquor solution in a mixture comprising water, solid NaOH, dyes and other liquid products, extracting ethylene glycol from the mixture, dissolving solid NaOH, recovering solid dyes and recovering terephthalic acid.

Process to recover NaOH, polyester monomers, dyes and byproducts from an alkaline depolymerization liquor resulting from a depolymerization reaction of polyester in a blend textile. The process comprises concentrating the liquor solution in a mixture comprising water, solid NaOH, dyes and other liquid products, extracting ethylene glycol from the mixture, dissolving solid NaOH, recovering solid dyes and recovering terephthalic acid.

The present disclosure provides a method for producing high-purity regenerated terephthalic acid using polyester depolymerization and high-purity regenerated terephthalic acid produced thereby. An object to be achieved by the present disclosure is to provide a method for producing terephthalic acid capable of obtaining high-purity terephthalic acid from waste polyester, reducing the amount of solvent used for hydrolysis, solvent recovery energy, and manufacturing cost, and increasing the stability of the solvent.

The present invention relates to a method for production of terephthalic acid using high polymerization degree polyethylene terephthalate, which includes: (i) introducing high polymerization degree polyethylene terephthalate having an intrinsic viscosity of 0.75 dl/g or more into a continuous reactor, and then heating and pressurizing the same to prepare a fluidal polyethylene terephthalate; (ii) introducing a mixed slurry prepared by mixing an alkaline material containing an alkali-metal, a weak acid salt of the alkali-metal and ethylene glycol together into an internal position of the continuous reactor, through which the fluidal polyethylene terephthalate passes, and implementing neat reaction of the fluidal polyethylene terephthalate with the mixed slurry in the continuous reactor to prepare alkali-metal terephthalate; and (iii) dissolving the prepared alkali-metal terephthalate in water, removing foreign substances through filtration and centrifugation, adding acid to the alkali-metal terephthalate dissolved in water and reacting the same, thereby producing terephthalic acid.

The present invention relates to a method for production of terephthalic acid using high polymerization degree polyethylene terephthalate, which includes: (i) introducing high polymerization degree polyethylene terephthalate having an intrinsic viscosity of 0.75 dl/g or more into a continuous reactor, and then heating and pressurizing the same to prepare a fluidal polyethylene terephthalate; (ii) introducing a mixed slurry prepared by mixing an alkaline material containing an alkali-metal, a weak acid salt of the alkali-metal and ethylene glycol together into an internal position of the continuous reactor, through which the fluidal polyethylene terephthalate passes, and implementing neat reaction of the fluidal polyethylene terephthalate with the mixed slurry in the continuous reactor to prepare alkali-metal terephthalate; and (iii) dissolving the prepared alkali-metal terephthalate in water, removing foreign substances through filtration and centrifugation, adding acid to the alkali-metal terephthalate dissolved in water and reacting the same, thereby producing terephthalic acid.