KR970042471A - Method for producing terephthalic acid (3) - Google Patents

Abstract

The present invention relates to a method for preparing terephthalic acid, and more particularly, to waste polyethylene terephthalate (Polythylene terephthalate) by using an alkaline weight loss liquid discharged from a polyester fiber weight reduction process to make a slurry of sodium terephthalate salt, and water Dissolved in and adsorbed to remove impurities, and then neutralized with acid to prepare terephthalic acid of high purity. It relates to a method of recovery.

Description

Method for producing terephthalic acid (3)

Since this is an open matter, no full text was included.

Claims (16)

A method for producing terephthalic acid by hydrolyzing and crystallizing polyethylene terephthalate, comprising the steps of: a) forming a terephthalate sodium salt by hydrolyzing the waste polyethylene terephthalate with an alkaline weight loss solution and a wetting agent; B) solid-liquid separation of the aqueous solution obtained by dissolving the terephthalate sodium salt in water, and the solid is fed back to the above hydrolysis process, and the liquid is transferred to the next adsorption process; C) a step of sucking the aqueous terephthalate sodium salt solution and neutralizing with acid to obtain terephthalic acid; D) a crystallization step of enlarging terephthalic acid; E) a method of producing terephthalic acid, characterized in that the enlarged terephthalic acid is cooled under reduced pressure, filtered and dried. The method of claim 1, wherein a) polyethylene terephthalate in the hydrolysis process, waste polyester fiber, waste polyethylene terephthalate bottle, waste polyethylene terephthalate container, waste polyethylene terephthalate chip generated during the polymerization of polyethylene terephthalate, or A method for producing terephthalic acid, characterized by using waste polyester yarns produced during polyester fiber production. The method for producing terephthalic acid according to claim 1 or 2, wherein the waste polyethylene terephthalate is added in an amount of 1 to 25% by weight in the total hydrolysis reactants. The method for producing terephthalic acid according to claim 1, wherein the a) waste liquid discharged from the weight loss processing step of the polyester fiber is used as the alkali loss solution in the hydrolysis step. The method for producing terephthalic acid according to claim 4, wherein the alkaline weight loss solution is added so that 5-30% by weight of sodium hydroxide is contained in the total hydrolyzate. The method for producing terephthalic acid according to claim 5, wherein the alkaline weight loss liquid contains 1 to 20% of sodium hydroxide. The method for producing terephthalic acid according to claim 5, wherein sodium hydroxide is added together when the alkaline weighting waste solution is added. The method for producing terephthalic acid according to claim 1, wherein the wetting agent is added in an amount of 1 to 30% by weight in the total hydrolysis reactants. The method for preparing terephthalic acid according to claim 1, wherein the a) hydrolysis process is performed at a reaction temperature of 30 to 200 ° C and a reaction pressure of 1 to 20 kg / cm 2. The method for producing terephthalic acid according to claim 1, wherein water is used in a dissolution step in an amount of 0.5 to 3.0 times by weight based on the terephthalate sodium salt solution. 2. The terephthalic acid according to claim 1, wherein the crystallization process is performed in a crystallization tank in which 1 to 5 crystallization tanks are connected in series and installed so that the temperature of each stage crystallization tank is reduced by 30 to 50 ° C. Manufacturing method. The method for producing terephthalic acid according to claim 11, wherein the crystallization tank is maintained at a temperature of 120 to 300 ° C. and a pressure of 2 to 86 kg / cm 2. The method for producing terephthalic acid according to claim 1, wherein the cooling step is performed at a temperature of 60 to 90 ° C. and a pressure of 0.1 to 1.0 kg / cm 2. The method for producing terephthalic acid according to claim 1 or 13, wherein in the e) cooling step, the alcohol and water discharged are fed back to the a) hydrolysis step. According to claim 1, wherein the filtrate discharged from the filtration process is put into an electro-dialyzer using a bipora membrane (separated into acid and sodium hydroxide), the acid (acid) is C) A method of producing terephthalic acid, characterized in that it is fed back to the neutralization process, and sodium hydroxide is fed back to the hydrolysis process described above. In the apparatus for producing terephthalic acid using pe polyethylene terephthalate as a raw material, a hydrolysis device (1) in which the pe polyethylene terephthalate is hydrolyzed by an alkali reduction waste solution, a dissolving device (2) for dissolving terephthalate sodium salt, and centrifugation Separator (3), adsorption tower (4), neutralizing device (5) for neutralizing sodium terephthalate with acid to produce terephthalic acid, crystallizing device (6), cooling device (7), enlarged A filtering device (8) for filtering terephthalic acid and a drying device (9) for drying the filtered terephthalic acid are continuously provided.