Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
1998-06-29
2001-10-30
Geist, Gary (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S485000, C562S487000, C422S245100, C422S251000, C422S135000
Reexamination Certificate
active
06310239
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to a process for manufacturing terephthalic acid and more particularly, to a process for manufacturing and recovering the highly purified terephthalic acid, in accordance with the practice of this invention comprising the following procedures: alkali weight-reduction waste water discharged from weight-reduction process in a polyester textile dyeing complex is dissolved in water, adsorbed to remove impurities, and through acid-neutralization, terephthalic acid of this invention may be obtained.
“Alkali weight-reduction waste water” is a remaining reactant discharged in a weight reduction-processing stage which is designed to give the polyester textile a silky property, as well as to improve the dyeing capability by treating the polyester textile with alkali metal/earth metal hydroxide, and thereby causing a part of the textile to become depolymerization. Said alkali waste water contains a large amount of alkali metal/earth metal hydroxide, terephthalic acid alkali metal/earth metal salt and ethylene glycol. In the past, a considerable amount of alkali weight-reduction waste water, generated from the large industrial complex crowded with dyeing plants, has been discharged by a conventional waste water treatment. Besides that, the sludges neutralized with such strong acid as hydrochloric acid or sulfuric acid have been used for landfills or sea-abandonments, while the remaining reactants have been discharged by a conventional waste water treatment. Therefore, the alkali weight-reduction waste water generated from the polyester weight-reduction process has caused severe environmental problems and such treatment conventionally requires a large amount of investment for anti-pollution facilities. Recently, various methods have been proposed for the recovery of terephthalic acid from the polyester weight-reduction waste water, since said recovery may be useful not only in reusing the resources, but also in abating the enviromental problems.
The conventional processes of manufacturing and recovering terephthalic acid are as follows, using polyester weight-reduction waste water:
In Japanese Patent Unexamined Publication No. 50-104,276, terephthalic acid alkali salt was neutralized with sulfuric acid to give terephthalic acid.
In Japanese Patent Unexamined Publication No. 60-19,784, ultra-filtration was introduced to remove impurities and then, terephthalic acid was obtained through neutralization with sulfuric acid.
In Japanese Patent Unexamined Publication No. 60-163,843, alkali waste water was centrifuged and neutralized with sulfuric acid to give terephthalic acid.
In Japanese Patent Unexamined Publication No. 60-216,884, alkali waste water was passed through ion-exchange membrane to give terephthalic acid.
In Japanese Patent Unexamined Publication No. 60-233,033, alkali waste water was neutralized at 120° C. and 1.7 atm to give terephthalic acid.
In Japanese Patent Unexamined Publication No. 61-43,139, alkali waste water with low concentration was adjusted to pH 5 to 6 and pH 4 two times to deposit terephthalic acid and then, centrifuged to recover terephthalic acid.
In Japanese Patent Unexamined Publication No. 61-43,140, hydrochloric acid was added to alkali waste water until the pH of the solution became 5.4 and treated with activated charcoal. Then, the solution was again added with hydrochloric acid until the pH of the solution became 2, and terephthalic acid was obtained.
In German Patent No. 2,508,819, alkali waste water was treated with sulfuric acid at 60 to 94° C. to give terephthalic acid.
In U.S. Pat No. 5,210,292, alkali waste water was adjusted to pH 6 to 9, cooled to remove sodium sulfate and then, this material was again adjusted with sulfuric acid to pH 2 to 4 to give terephthalic acid.
These reported methods as aforementioned have also several problems as follows; a) a majority of their reactions was conducted under the severe conditions, b) excess water designed to enhance the purity of terephthalic acid, produced a considerable amount of waste water, which is economically unfeasible, c) terephthalic acid was not easily separated, through the method of modulating pH, from sodium salt generated from the neutralization reaction of alkali waste water, and d) said reported methods, which failed to illustrate some methods of removing impurities and purity-monitoring methods. Especially, these reported methods failed to remove sodium salt, by-product of acid neutralization, and it may be responsible for producing another environmental pollutants. In addition, in a process of filtering terephthalic acid as a final recovery step, the particle size of terephthalic acid should be sufficiently enlarged because small particles of terephthalic acid cause insufficient separation into solids and liquids which is responsible for reduction of recovery rate, and also make it difficult to perform the drying process.
Thus, the terephthalic acid obtained by the reported methods was not sufficient for reuse owing to reduction in recovery rate and purity and further, the purity of terephthalic acid in said reported methods was analyzed by general method instead of the method to analyze the quality of terephthalic acid. In this context, said reported methods are technically and economically unfavorable for commercialization.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawing is a schematic diagram showing the process of manufacturing terephthalic acid in accordance with this invention.
SUMMARY OF THE INVENTION
Therefore, the object of present invention is to provide a novel process for manufacturing terephthalic acid in accordance with the practice of this invention, specifically designed to obtain the following advantages: a) terephthalic acid of high purity can be obtained from alkali weight-reduction waste water, and b) sodium salt formed as a by-product in the process is separated and recovered as acid and alkali, thus reducing the production costs and abating the environmental problems.
DETAILED DESCRIPTION OF THIS INVENTION
The present invention may be described in more detail as shown below.
The present invention is characterized by a process for manufacturing terephthalic acid from alkali weight-reduction waste water comprising the following steps:
(a) a process in which an aqueous solution of alkali weight-reduction waste water dissolved in water is adsorbed;
(b) a process in which an aqueous solution is neutralized with acid to give terephthalic acid;
(c) a crystallization process to enlarge the particle of terephthalic acid;
(d) a process in which the enlarged particle of terephthalic acid is cooled under reduced pressure, filtered and dried.
The present invention also relates to several kinds of successively installed tanks for manufacturing terephthalic acid, which is characterized by the following systems: dissolving system where alkali weigh-reduction waste water is dissolved in water; centrifuge; adsorption tower; neutralization system where terephthalic acid alkali metal/earth metal salt is neutralized with acid to prepare terephthalic acid; crystallization system where the particle of terephthalic acid is enlarged; cooling system; filtering system where the enlarged particle of terephthalic acid is filtered; drying system where filtered terephthalic acid is dried.
The present invention is described in more detail as set forth hereunder.
This invention relates to a process for manufacturing and recovering terephthalic acid from a considerable amount of alkai weight-reduction waste water after the alkali weight-reduction process for polyester textile. In accordance with the practice of this invention, the highly purified terephthalic acid can be obtained in an easier manner. In addition, since the solvents and raw materials discharged in the reaction may be fed back, one can expect the reduction of production costs as well as to abate the environmental problems.
The process of manufacturing terephthalic acid according to this invention is referred in more detail to the drawings as follows:
Alkali weight
Bae Dongmok
Roh Hang-Duk
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Geist Gary
Oh Taylor V.
Sunkyong Industries Co., Ltd.
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