A method of obtaining purified terephthalic and isophthalic acid from a mixture of xylenes

 

The invention relates to an improved process for the preparation of terephthalic and isophthalic acids. In particular, the invention relates to a method of purification of crude terephthalic acid (TPA) from a liquid dispersion containing terephthalic and isophthalic acid obtained by oxidation of a mixture of xylenes. The invention also relates to a method of purification of crude terephthalic acid and isophthalic acid from a liquid dispersion containing terephthalic, isophthalic acid and other impurities resulting from the oxidation of a mixture of xylenes. Terephthalic and isophthalic acid can be used to produce fibers, films, plastic bottles and structures polyester resins, often reinforced by other materials, such as fiberglass. The method allows separating terephthalic acid from its isomers, such as isophthalic acid, as well as to obtain purified terephthalic and isophthalic acid in a single process. 3 C. and 20 C.p. f-crystals, 3 tab., 3 Il.

This application is a partial continuation of concurrently pending application U.S. serial 09/074 251, filed may 7, 1998, entitled "Method and apparatus for producing purified terephthalic acid", kotaniemi "Method and apparatus for producing purified terephthalic acid, now U.S. patent 5 767 311, and is a partial continuation of application U.S. serial 08/962 030, filed October 31, 1997, entitled "Method and apparatus for producing purified terephthalic acid, which is a partial continuation of application U.S. serial 08/760 890, filed December 6, 1996, entitled "Method and apparatus for producing purified terephthalic acid, which in turn is a partial continuation of concurrently pending application U.S. serial 08/477 898, filed June 7, 1995. entitled "Method and apparatus for producing purified terephthalic acid", now U.S. patent 5 767 311; in this case, all four applications submitted to the same assignee as this application, and incorporated herein in its entirety by reference for various purposes.

INTRODUCTION This invention relates to the production of terephthalic and isophthalic acids, and more particularly to a method of purification of crude terephthalic acid, and the method of purification of crude terephthalic and isophthalic acid from a mixture of xylenes.

BACKGROUND of the INVENTION Known methods for producing terephthalic acid (TPA) require relatively high purity p-xylene (99,7+%) to improve product quality and reduce the value the second method of purification of crude terephthalic acid, obtained at the stage of oxidation of these methods. Despite the fact that the method is highly selective hydrogenation to remove basic impurities, 4-carboxybenzene (4-CBA), by converting it into n-Truelove acid, this method can only be applied when there is a very small amount of 4-carboxyanhydride (preferably less than 3,000 parts per million ) of Known methods for producing terephthalic acid also does not include the separation of terephthalic acid from its isomers, such as isophthalic acid (IPA) and phthalic acid (PA).

The prior art method for the production of pure terephthalic acid by recrystallization (patents GB 818211 and GB 848189), a disadvantage of known methods is the lack of separation from isophthalic terephthalic acid and impurities.

To eliminate the disadvantage mentioned methods have been developed for purification of crude terephthalic acid and the crude terephthalic and isophthalic acid.

BRIEF description of the INVENTION IN contrast to the above-described known methods of obtaining terephthalic acid, the invention provides a method and apparatus for producing purified terephthalic acid and optionally isophthalic acid from a mixture of xylenes. What is traveling and isophthalic acid, as well as small amounts of isomers of 4-carboxyanhydride (4-CBA), 3-carboxyanhydride (3-CBA) and Truelove acid to produce purified terephthalic acid and optionally purified isophthalic acid as the result of a single process. These products can be used to produce fibers, films, plastic bottles and structures polyester resins, often reinforced by other materials, such as fiberglass.

In accordance with this invention provides a method and apparatus for producing purified terephthalic acid and optionally purified isophthalic acid from a mixture of xylenes in the unified process. In accordance with one variant of the method according to this invention includes obtaining raw mixed acids (including terephthalic and isophthalic acid) in the oxidation of a mixture of xylenes containing mainly p-xylene and a small amount of m-xylene and other isomers. Stage oxidation leads to the production not only of terephthalic and isophthalic acids, but also as a result of incomplete oxidation to obtain 4-carboxybenzene, 3-carboxymethylthio, p-Truelove acid, m-Truelove acid, and other traces of colomberie, containing unreacted starting materials, solvents, if used, products of side reactions, in particular the above-mentioned products, and other materials whose presence is undesirable in purified terephthalic and isophthalic acids.

The stream exiting the reactor, is fed into the series of crystallizers, which increases the amount of solids in the evaporation of the reaction solvent, preferably acetic acid, by reducing the pressure. The sludge from the last crystallizer filtered and washed. Then the filtered crystals are dried to remove the solvent to a level of less than 0.25% get raw, mixed acid crystals. The mother liquor from the filter is fed to the plant for dehydration of the solvent to extract the solvent (acetic acid) from the water to recycle it in an oxidizing apparatus.

In further accordance with this invention the crude mixed acid of a dryer section of the oxidation is again dissolved in a selective crystallization solvent, and then terephthalic acid (TPA) vykristallizovyvalas of selective crystallization solvent in one or preferably two acid from the solvent (with or without cosolvent) in accordance with this invention. The resulting ultimately pressed residue of terephthalic acid washed and impregnated with water, removing the color and the final traces of selective crystallization solvent from the finished terephthalic acid.

To retrieve isophthalic acid (IPA) from the mother liquor of the mold (after removal of solids terephthalic acid filter) add antibacterial, causing essentially complete precipitation of the terephthalic acid from the mother liquor. Free from terephthalic acid mother liquor is concentrated and viparita from it selective crystallization solvent and antibacterial, and cooled, causing the crystallization of crude isophthalic acid. Crude isophthalic acid is then purified by recrystallization in another selective crystallization solvent.

This invention also provides processes for the recovery and recycling of solvents in accordance with the present invention at each stage of crystallization and washing, and the final impregnation. Action is also taken for careful control over the allocation of any unwanted materials into the environment.

One important aspect of this invention is the eve acid from a crude mixture, containing terephthalic acid, up to 20% of isophthalic acid, a small amount of 3-carboxymethylthio, 4-carboxybenzene, m-Truelove acid, p-Truelove acid, etc., as a result of stages of crystallization and separation. These solvents can be summarized as follows.

Selective crystallization solvent applied in the practice of this invention for the purification of terephthalic acid include solvents in which (a) impurities (including isophthalic acid), subject to separation from terephthalic acid, relatively more soluble in the solvent than terephthalic acid essentially at any temperature that is included in the specified range of temperatures at which the process solvent containing terephthalic acid, and (b) terephthalic acid is more soluble at higher temperatures and less soluble at lower or cold temperature. In this description, the term "selective crystallization solvent" means any solvent suitable for the selective crystallization of terephthalic acid, as described above.

Antibacterial added to the stock solution (from the crystallization of flow thereisacow) terephthalic acid from the mother liquor and yet hold the main part of the isophthalic acid in the mother solution. Essentially free from terephthalic acid mother liquor is concentrated by evaporation or distillation), crystallizing them crude isophthalic acid, which is then separated by filtration and re-dissolved during the second selective crystallization, obtaining purified isophthalic acid.

In accordance with this invention the main preferred selective crystallization solvent for the purification of terephthalic acid is N-organic (NMP) for several reasons, described below, and due to its excellent properties. It contains no water, heat-resistant, non-toxic (safe for the environment), corrosion resistant and manufactured for industrial purposes. Terephthalic acid can be dissolved in N-organic at elevated temperature and precipitated or crystallized from N-methylpyrrolidone at low temperature. The main impurities such as 4-carboxybenzoyl, 3-carboxybenzoyl, p-tolarova acid, m-tolarova acid, and isophthalic acid, have relatively higher solubility in N-organic than terephthalic acid at any temperature. Therefore, when the temperature drops only to terephthalic the eve acid.

Although N-organic is the most preferred selective crystallization solvent, it is understood that in accordance with this invention can be selected other preferred selective crystallization solvent different from a polar organic solvents, including, but not limited to, N,N-dimethylacetamide, N, N-dimethylformamide, N-formylpiperidine, N-alkyl-2-pyrrolidone (such as N-ethylpyrrolidin), N-mercaptoethyl-2-pyrrolidone (such as N-mercaptoethyl-2-pyrrolidone), N-alkyl-2-cooperalion (such as N-methyl-2-cooperalion), N-oxoalkyl-2-pyrrolidone (such as N-oxyethyl-2-pyrrolidone), morpholines (such as morpholine and N-formylmorpholine), carbitol, C1-C12alcohols, ethers, amines, amides, and esters, and mixtures thereof.

The main preferred antibacterial is methanol, although antibacterial for essentially complete precipitation of the terephthalic acid from the mother liquor can also be selected from various polar organic solvents, including, but not limited to, methyl ethyl ketone, acetone, C1-C12alcohols, carbitol, esters, ethers, C1- the ionic solvent for the purification of terephthalic acid is methanol, although the solvent may also be selected from the group including, but not limited to, methyl ethyl ketone, acetone, C1-C12alcohols, carbitol, esters, ethers, C1-C12carboxylic acid, water, and mixtures thereof.

To remove residual solvent (for example, N-methylpyrrolidone) contained in the crystals end of terephthalic acid, washed crystals of the acid is preferably served in a high temperature reaction chamber, where the water used for the partial or complete dissolution of these crystals. Residual solvent (methanol) contained in crystals of finite isophthalic acid may be removed by drying to a level of less than 0.25%.

In accordance with one variant of the method according to this invention the purification of crude terephthalic acid (TPA) from a liquid dispersion containing terephthalic and isophthalic acid obtained by oxidation of a mixture of xylenes, includes the following stages: (a) dissolving crude terephthalic acid in a selective crystallization solvent at a temperature of from about 50 to 250oTo obtain a solution; (b) crystallization of the purified acid from the specified terephthalic acid from the solution; (d) re-dissolving the specified separated purified terephthalic acid in a selective crystallization solvent to obtain a second solution; (e) crystallizing purified terephthalic acid from the second stage from the specified second solution by reducing the temperature and pressure sufficient to instantaneous evaporation of the solvent from the specified terephthalic acid specified in the second solution, not specified cooling the solution below the 50oWith; (f) the Department indicated purified terephthalic acid from the second stage from the specified second solution; (g) washing the specified separated, purified terephthalic acid from the second stage of water; (h) impregnation specified washed, separated, purified terephthalic acid from the second stage of water at a temperature of from about 150 to 300oWith; (i) filtering and drying the specified water-soaked purified terephthalic acid from the second stage; (j) adding antibacterial to the specified filtered solution in (C), to precipitate essentially all of terephthalic acid; (k) the Department specified precipitated terephthalic acid from the specified solution of stage (j) and the connection specified precipitated terephthalic sour is filtered from the specified solution, free from terephthalic acid, at stage (k), for crystallization of terephthalic acid at a temperature of approximately from 5 to 100o(M) the Department specified crystallized crude isophthalic acid from this solution in stage (1), (n) re-dissolving the crude terephthalic acid in a selective crystallization solvent at a temperature of from about 50 to 250oWith to obtain a second solution; (o) crystallizing purified terephthalic acid from the specified second solution of stage (n) by reducing the temperature and pressure sufficient to instantaneous evaporation of the solvent from the specified isophthalic acid specified in the second solution, not specified cooling the solution below about 50oWith, and (b) separating and drying the indicated purified isophthalic acid from the second stage from the specified second solution.

Under this option, the dispersion contains up to 20% isophthalic acid (IPA), a small amount of 4-carboxaldehyde (4-CBA), 3-carboxyaldehyde (3-CBA) and impurities selected from unreacted starting materials, solvents, products of side reactions and/or other undesirable materials. Selective crystallization age is cetamide N,N-dimethylformamide, N-formylpiperidine, N-alkyl-2-pyrrolidone (such as N-ethylpyrrolidin), N-mercaptoethyl-2-pyrrolidone (such as N-mercaptoethyl-2-pyrrolidone), N-alkyl-2-cooperalion (such as N-methyl-2-cooperalion), N-oxoalkyl-2-pyrrolidone (such as N-oxyethyl-2-pyrrolidone), morpholino (such as morpholine and N-formylmorpholine), carbitol, C2-C12alcohols, ethers, amines, amides, esters, and mixtures thereof. Selective crystallization solvent for the purification of terephthalic acid in accordance with this variant is N-organic or N,N-dimethylacetamide, or N-organic. Antibacterial to precipitate terephthalic acid from the solution of terephthalic and isophthalic acids are selected from the group consisting of methanol, water, methyl ethyl ketone, acetone, C1-C12alcohols, carbitols, esters, ethers, C1-C12carboxylic acids, and mixtures thereof. Selective crystallization solvent for re-crystallization of terephthalic acid selected from the group consisting of methanol, water, methyl ethyl ketone, acetone, C1-C12alcohols, carbitols, simple and complex esters, C1-C12carboxylic acids, and mixtures thereof. Antiredeposition in respect of from 0.5 to 3, to cause precipitation of the terephthalic acid.

In accordance with another aspect of the invention relates to a method of purification of crude terephthalic acid (TPA) from a liquid dispersion containing terephthalic and isophthalic acid obtained by oxidation of a mixture of xylenes, comprising: (a) dissolving crude terephthalic acid in a selective crystallization solvent at a temperature of from about 50oWith up to 250oTo obtain a solution; (b) crystallization of the purified acid from this solution by reducing the temperature and/or pressure; (C) the Department specified crystallizing purified terephthalic acid from the solution; (d) re-dissolving the specified separated, purified terephthalic acid in a selective crystallization solvent to obtain a second solution; (e) crystallizing purified terephthalic acid from the second stage from the specified second solution by reducing the temperature and pressure sufficient to flash evaporation of solvent from the specified terephthalic acid specified in the second solution, not specified cooling the solution below the 50o;
(f) the Department indicated purified terephthalic acid with vtaraota with the second stage of water;,
(h) impregnation specified washed, separated, purified terephthalic acid from the second stage of water at a temperature of from about 150 to 300o;
(i) filtering and drying the specified soaked with water, purified terephthalic acid from the second stage;
(j) the concentration specified in the filtered solution from step (C) by evaporation and cooling of the concentrated solution for crystallization of terephthalic acid and a small part of isophthalic acid;
(k) the Department specified precipitated terephthalic acid and a small part of the terephthalic acid from the solution from step (j) and the recycling of specified solid mixture for processing in stage (a);
(l) the concentration specified in the filtered solution from step (k) by the second evaporation and cooling of the concentrated solution for further crystallization of terephthalic acid and a small part of isophthalic acid;
(m) the Department specified crystallized terephthalic acid and a small part of isophthalic acid from the specified solution (l) and recycling solid mixture for processing to the step (a);
(n) supply specified filtered solution from step (m) in the device up to 20% of isophthalic acid, small amounts of 4-carboxaldehyde, 3-carboxyaldehyde and impurities contained in the unreacted raw materials, solvents, products of side reactions and/or other undesirable materials.

Selective crystallization solvent for cleaning terephthalic acid selected from the group consisting of N-methylpyrrolidone (NMP), N,N-dimethylacetamide, N, N-dimethylformamide, N-formylpiperidine, N-alkyl-2-pyrrolidone (such as N-ethylpyrrolidin), N-mercaptoethyl-2-pyrrolidone (such as N-mercaptoethyl-2-pyrrolidone), N-alkyl-2-cooperalion (such as N-methyl-2-cooperalion), N-oxoalkyl-2-pyrrolidone (such as N-oxyethyl-2-pyrrolidone), morpholino (such as morpholine and N-formylmorpholine), carbitol, C1-C12alcohols, ethers, amines, amides, esters, and mixtures thereof. Selective crystallization solvent for the purification of terephthalic acid is N-organic or N,N-dimethylacetamide.

The following examples illustrate the effectiveness of the selective crystallization solvent in the separation of terephthalic and isophthalic acids, which is the principle and characteristic of this invention.

Example 1
This example describes experimental the selective crystallization solvent at three different temperatures and atmospheric pressure. Experiments conducted in a laboratory flask, immersed in a bath with a constant temperature to be maintained at the specified level. The temperature of the liquid phase in the flask was measured by a thermometer. For accurate temperature measurement use a reflux condenser, to restore the loss of solvent due to evaporation. In the course of the experiment to constantly stir the solution in the flask is added a small, gradually increase the amount of solids prior to the termination of their dissolution; in the presence of solids at this temperature the solution is saturated. Solubility determines, based on the weight of the solvent and the total mass of the added solids. table 1 summarizes the solubility of terephthalic and isophthalic acids in the N-organic, 15, 40, 70, and 160oC.

Data on solubility, are presented in table 1 show that terephthalic acid can be purified from a mixture of terephthalic acid, isophthalic acid and 4-carboxybenzene (3-carboxymethylthio) by crystallization, as isophthalic acid, and both carboxymethylthio tend to remain in the mother solution, due to its higher solubility. The crystals of terephthalic key is you compared to other components, contained in the mother solution.

Example 2
A solid mixture containing about 95 wt.% terephthalic acid and 5 wt.% isophthalic acid is added to N-organic in accordance with the solubility of terephthalic acid in N-organic at 160oC. the mixture is Then transferred to a cooling crystallizer equipped with a specially designed mixer that minimize damage to the crystals, heating jacket, and a steam condenser. The mold is slowly heated to 160oWith and maintain at this temperature for one hour to ensure dissolution of all solids. Then the mold is cooled to 45oC for 90 min to induce the growth of crystals of terephthalic acid. The contents of the mold are transferred into the filter cover and quickly filtered, maintaining the temperature from 40 to 45oC. For washing sludge use an appropriate amount of warm solvent (having a temperature of from 50 to 70oC). In some cases, after rinsing with warm solvent the residue is washed with hot water having a temperature of 95oC. the Washed precipitate is dried and subjected to analysis by gas chromatography, in order to define the phthalic acid terephthalic acid decreases dramatically (23-39 time) depending on the washing conditions. When the precipitate of terephthalic acid after crystallization washed with solvent at 70oC, followed by washing with water at 95o(Party 2), the content of isophthalic acid in fact reduced to 39 times after single-stage crystallization. After carrying out the same procedure, the content of isophthalic acid in a mixture of terephthalic acid can be reduced with 5 wt. % to 33 parts per million by weight. in the two-stage crystallization.

Example 3
This example provides experimental data on the solubility of terephthalic acid and isophthalic acid in methanol, after selective crystallization at different temperatures and atmospheric pressure. Experimental device and procedure are the same as described above in example 1, except that the vapor pressure exceeds atmospheric pressure. Solubility determines, based on the weight of the solvent and the total mass of the added solids. Table 3 summarizes the solubility of terephthalic and isophthalic acids in methanol at different temperatures.

From table 3 it follows that the solubility of terephthalic acid in methanol at approximately 8-20 times higher than the solubility of terephthalic acid when the temperature is E. high temperatures, such as 160-200oWith under pressure.

Example 4
On the basis of the example 3, it was found that the solubility of terephthalic acid in methanol is essentially higher than the solubility of terephthalic acid at room temperature (25 to 50oC). Accordingly, experiments were carried out to determine whether the precipitation of the terephthalic acid from the solution of terephthalic acid, isophthalic acid and small amounts of 4-carboxybenzene to be caused by adding to the solution the required amount of methanol. This solution can be the mother liquor from the crystallizer terephthalic acid after removal of the crystals of the acid through the filter. The mother solution may have the following composition: 100 g of N-methylpyrrolidone, 20 g of terephthalic acid, 10 g of isophthalic acid, and a small amount of 4-carboxyanhydride (and 3-carboxymethylthio).

This example shows that the addition of methanol to the stock solution may cause essentially complete precipitation of the terephthalic acid, but only a slight deposition of isophthalic acid. To a mixture of 100 g of N-methylpyrrolidone, 4 g of terephthalic acid and 1.5 g of isophthalic acid, with a room temperature we use and deposition of solids from the mixture. The crystals are filtered, washed and dried for analysis. It was determined that the extracted 47.5% of terephthalic acid in the mother solution, the crystals contain approximately a 99.0 wt.% terephthalic acid and 1.0 wt.% isophthalic acid.

In order to increase the recovery of terephthalic acid, the mother liquor is concentrated by removing part of the N-methylpyrrolidone, after which the mixture contains 100 g of N-methylpyrrolidone, 20 g of terephthalic acid and 10 g of isophthalic acid. To cause crystallization of terephthalic acid from the mixture at room temperature, there was added approximately 260 g of methanol. After adding methanol, the mixture is stirred for 90 min before filtering the crystals of terephthalic acid from the slurry. It was found that up to 97.5% of terephthalic acid extracted from the mother liquor and the crystals of terephthalic acid contain 97,3 wt.% terephthalic acid and 2.7 wt.% isophthalic acid. The data show that 100% extracted terephthalic acid can be achieved by removal of larger amounts of N-methylpyrrolidone from the mother liquor (higher concentration) or by adding more methanol to the stock solution, or both, along the N-methylpyrrolidone (0,01%). Since the content of 4-carboxybenzene in the mother solution is very low and its solubility in N-organic is very high at approximately room temperature (listed in table 1), add methanol should not cause the precipitation of 4-carboxybenzene from the mother liquor.

After removing 100% of terephthalic acid from the mother liquor and recirculatory by adding methanol mother liquor free from terephthalic acid, may be subjected to further processing to extract isophthalic acid. The details of the process scheme shown in Fig.1 and described in the next section.

Description of the drawings:
Fig. 1 is a schematic MP installation for the implementation of the preferred form of this invention related to obtaining as terephthalic and isophthalic acid;
Fig. 2 is a schematic MP installation for the implementation of another preferred form of this invention relating to the production of terephthalic acid;
Fig.3 - dependence of the solubility of TPA, IPA, and 4-CBA from temperature and solvent.

Description of the preferred embodiments Yes is auchenia as terephthalic, and isophthalic acid, shown in Fig.1.

With regard to Fig.1, the crude terephthalic acid with a plot of the oxidation reactor (not shown) containing approximately 95% of terephthalic acid, 5% isophthalic acid and a small amount of other impurities (4-carboxybenzoyl, 3-carboxybenzoyl, p-Truelove acid, m-Truelove acid and so on), served in the first tank to dissolve 100 through the pipeline 1 to be mixed with the mother liquor from the filter II 105 (line 7) and the sludge from the filter 113 IV (line 19). The temperature in the first tank to dissolve 100 support level from 160 to 180oFor complete dissolution of the solids and evaporation of essentially all of the methanol flowing through the pipeline 19.

Then a saturated solution from the first tank to dissolve 100 continuously fed to the first cooling crystallizer 101 through the pipeline 2 to obtain crystals of salt of terephthalic acid at a temperature of from 30 to 50oC. a Slurry containing crystals of salt of terephthalic acid, leaves the first cooling crystallizer 101 via line 3 in the I filter 102, where the crude crystalline residue is removed and served in the second tank to dissolve 103 to line 4. In the second VAT on the system for recovering solvent. The temperature in the second tank to dissolve 103 is again supported at the level of from 160 to 180oWith to completely dissolve the salt crystals of terephthalic acid. A saturated solution from the second tank to dissolve 103 continuously served by pipeline 5 second flash crystallizer 104, where the temperature of the support at the level of at least 60oIn order to prevent the formation of salt crystals of terephthalic acid. The degree of lowering the temperature in the crystallizer is controlled by the number of N-methylpyrrolidone, quickly evaporated from the mold by reducing the pressure. The evaporated N-organic re circulate in the first tank to dissolve 100 pipeline 36.

The sludge from the second mold 104 serves to filter II 105 via the pipeline 6, where the solid residue purified terephthalic acid restores and serves on the installation for washing the precipitate 106, while the mother liquor recycle in the first tank to dissolve 100 through the pipeline 7. Installation for washing the precipitate 106 total weight of residual N-methylpyrrolidone remove countercurrent washing with water, and the washed precipitate is served by pipeline 10 in coking (camera) 107 to remove the final traces of N-methylpyrrole does not contain N-methylpyrrolidone, filter in the filter III 108 and dried in the dryer I 109 receiving end of terephthalic acid.

The mother liquor from filter 102 I served on the pipeline 15 in the apparatus for deposition of 112, while the mother liquor passes through the oxidizing apparatus 111 used for the implementation of the related inventions described and claimed in the concurrently pending application, U.S. serial 09/098 060, entitled "Method of reducing the content of isomers carboxyanhydride in terephthalic or isophthalic acid," owned by the same assignee as this application, and cited in this description as a reference for various purposes. Methanol served in apparatus for deposition on the pipe 16, causing complete the precipitation (or crystallization) of terephthalic acid and a slight deposition of isophthalic acid from the mother liquor. The sludge from the apparatus for deposition of 112 serves to filter IV 113 via the pipeline 18 for removing the bulk of the mother liquor from the slurry prior to its recycling in the first tank to dissolve 100 through the pipeline 19.

The mother liquor from the filter 113 IV served in the evaporating device 114 to remove N-methylpyrrolidone and methanol by heat and vacuum evaporation thus, Thu first mold 115 isophthalic acid to crystallization at a temperature of from 30 to 50oIn the cooling or rapid evaporation. The vaporized N-organic and methanol from the evaporator 114 is served in the distillation column 110, receiving N-organic from the bottom, and methanol from the top of the column. The flow of methanol recycle in apparatus for deposition 112 through the pipeline 16, while a stream of N-methylpyrrolidone served in the second tank to dissolve 103 through the pipeline 35. The sludge from the first mold 115 isophthalic acid serves to filter V 116, give crude residue of isophthalic acid and mother liquor. The mother liquor is fed into the apparatus for the deposition 112 through the pipeline 17, however, the portion of the stream 17 are drawn through the pipe 37 to prevent the accumulation of impurities and coloring matter.

The precipitate from the filter V 116 is then applied on the pipe 25 in the tank to dissolve 117 isophthalic acid, where the crude is dissolved in methanol at a suitable temperature and pressure. A saturated solution of isophthalic acid is filtered in the filter 118 VI to remove traces of insoluble substances to blowing pipe 28. Free from solids solution serves on the pipe 29 into the second mold 119 for isophthalic acid, getting her crystals by fast IP is Levoy acid serves on the pipeline 30 to the filter 120 VII, to recover and wash the crystals of purified isophthalic acid to a final drying in the dryer II 121. getting end-isophthalic acid, while the mother liquor from the filter 120 VII recycle in evaporating device 114 through the conduit 31.

Another preferred implementation of the present invention relating to the production of terephthalic acid, illustrated in Fig. 2. Crude terephthalic acid containing from about 90 to 99% of terephthalic acid and from 1 to 10% of isophthalic acid) served in a tank for dissolving 200 I through the pipeline 201 to be mixed with the mother liquor M/L-2 from the filter II 206 (recycled pipeline 220) and recycled sludge from the filter V 215 (recycled pipeline 221). The temperature in the tank to dissolve the support level from 140 to 200oC to dissolve essentially all solids. A saturated solution is then served by pipeline 222 in the first mold 202, where the temperature is reduced to a level of from 30 to 60oWith, by cooling or solvent evaporation (pressure drops) to ensure the growth of crystals of terephthalic acid.

The sludge from the first mold 202 podutil to wash skinny or saturated N-methylpyrrolidone, to remove the mother liquor from the precipitate before filing the pipeline 224 in the tank to dissolve II 204, where the sludge is mixed with quickly evaporated N-organic pipeline 225 and evaporated N-organic pipeline 226 and 227. The temperature in the tank to dissolve II 204 is again supported at the level of from 140 to 200oC to dissolve essentially all solids. A saturated solution served by pipeline 228 in the second mold 205, where the temperature is reduced to a level of from 30 to 60oWith, by cooling or solvent evaporation (pressure drops) to ensure the growth of crystals of terephthalic acid.

The sludge from the second mold 205 is again served by pipeline 229 in the filter II 206 to recover the precipitate, which is then served by pipeline 230 in a counter-current contactor 207 for washing with water to remove the total mass of the free N-methylpyrrolidone of sediment. Water-washed solids are served by pipeline 231 in making (camera) 208 to remove traces of residual N-methylpyrrolidone of purified solid terephthalic acid by partial or complete dissolution of the solids in the reaction chamber 208 at a temperature o water are removed by pipeline 232, and the residue of terephthalic acid is served by pipeline 234 for drying in the dryer, getting the final purified terephthalic acid.

The mother liquor M/L-1 I filter 203 is sent by pipeline 235 evaporating device 210 I to remove significant amounts of N-methylpyrrolidone. A concentrated solution served by pipeline 236 in the mold III 211 to cause the growth of crystals of terephthalic acid low purity. The crystals are then recovered from the filter IV 212 and recycle tank for dissolving 200 I by pipeline 237. The mother liquor M/L-3 from the filter IV 212 serves on the pipeline 238 in evaporating apparatus II 213, then the mold IV 214 and the filter V 215 for the regeneration of the residual terephthalic acid low purity, sent to Chan for dissolving 200 I by the pipe 239. The final mother liquor M/L-4 of the filter V 215, containing mainly isophthalic acid, N -, an organic and a small amount of terephthalic acid, passes through the pipe 240 and subject to the further regeneration of N-methylpyrrolidone by mixing with water before utilitarianism.


Claims

1. The method of purification of crude terephthalic acid (TPA) from a liquid dispersion, siderastrea crude terephthalic acid in a selective crystallization solvent at a temperature of about 50 250oTo obtain a solution, (b) crystallization of the purified acid from this solution by reducing the temperature and/or pressure, (c) the Department specified crystallizing purified terephthalic acid from the solution, (d) re-dissolving the specified separated purified terephthalic acid in a selective crystallization solvent to obtain a second solution, (e) crystallization of purified terephthalic acid from the second stage from the specified second solution by reducing the temperature and pressure sufficient to rapid evaporation of the solvent from the specified terephthalic acid specified in the second solution, not specified cooling the solution below the 50o(F) the Department indicated purified terephthalic acid from the second stage from the specified second solution, (g) washing the specified separated purified terephthalic acid from the second stage of water, (h) impregnation specified washed separated purified terephthalic acid from the second stage of water at a temperature of approximately 150 - 300o(I) filtering and drying the specified moistened with water, purified terephthalic acid from the second stage (j) adding antibacterial to the specified filtered is traveling acids from the specified solution of stage (j) and the connection specified precipitated terephthalic acid with a specified source of crude terephthalic acid to process stage (a), (l) the evaporation of solvents from the specified filtered solution not containing terephthalic acid, at stage (k) for crystallization of terephthalic acid at a temperature of approximately 5 - 100o(M) the Department specified crystallized crude isophthalic acid from this solution in stage (1),(n) re-dissolving the crude terephthalic acid in a selective crystallization solvent at a temperature of about 50 250oWith to obtain a second solution, (about) the crystallization of purified isophthalic acid from the specified second solution of stage (n) by reducing the temperature and pressure sufficient to rapid evaporation of the solvent from the specified isophthalic acid specified in the second solution, not specified cooling the solution below about 50oWith, and (b) separating and drying the indicated purified isophthalic acid from the second stage of the specified second solution.

2. The method according to p. 1, in which the specified dispersion contains up to 20% isophthalic acid (IPA), a small amount of 4-carboxaldehyde, 3-carboxyaldehyde and impurities selected from unreacted starting materials, solvents, products of side reactions and/or other undesirable metaethical acid selected from the group consisting of N-methylpyrrolidone (NMP), N,N-dimethylacetamide, N,N-dimethylformamide, N-formylpiperidine, N-alkyl-2-pyrrolidone, N-mercaptoethyl-2-pyrrolidone, N-alkyl-2-cooperalion, N-oxoalkyl-2-pyrrolidone, morpholine, carbitols, C1-C12alcohols, ethers, amines, amides and esters, and mixtures thereof.

4. The method according to p. 3, wherein said selective crystallization solvent for the purification of terephthalic acid is a N-organic or N,N-dimethylacetamide.

5. The method according to p. 4, wherein said selective crystallization solvent for the purification of terephthalic acid is a N-organic.

6. The method according to p. 1, wherein said antibacterial to precipitate terephthalic acid from the solution of terephthalic and isophthalic acids are selected from the group consisting of methanol, water, methyl ethyl ketone, acetone, C1-C12alcohols, carbitols, esters, ethers, C1-C12carboxylic acids, and mixtures thereof.

7. The method according to p. 6, wherein said antibacterial to precipitate terephthalic acid from the solution of terephthalic and isophthalic acids represents methanol or water.

8. The method according to p. 7, in atoilet represents methanol.

9. The method according to p. 1, wherein said selective crystallization solvent for re-crystallization of terephthalic acid selected from the group consisting of methanol, water, methyl ethyl ketone, acetone, C1-C12alcohols, carbitols, esters, ethers, C1-C12carboxylic acids, and mixtures thereof.

10. The method according to p. 9, wherein said selective crystallization solvent for re-crystallization of purified isophthalic acid is a methanol or water.

11. The method according to p. 1, wherein said antibacterial contains in relation to antibacterial/solution of 0.1 to 10.0 to precipitate terephthalic acid.

12. The method according to p. 11, in which the ratio of antibacterial/solution is preferably 0.5 to 3.

13. The method of purification of crude terephthalic acid (TPA) from a liquid dispersion containing terephthalic and isophthalic acid obtained by oxidation of a mixture of xylenes, comprising: (a) dissolving crude terephthalic acid in a selective crystallization solvent at a temperature of about 50 250oTo obtain a solution, (b) crystallization of the purified acid from this solution by Sneezy from the specified solution, (d) re-dissolving the specified separated purified terephthalic acid in a selective crystallization solvent to obtain a second solution, (e) crystallization of purified terephthalic acid from the second stage from the specified second solution by reducing the temperature and pressure sufficient to flash evaporation of solvent from the specified terephthalic acid specified in the second solution, not specified cooling the solution below the 50o(F) the Department indicated purified terephthalic acid from the second stage from the specified second solution, (g) washing the specified separated purified terephthalic acid from the second stage of water, (h) impregnation specified washed separated purified terephthalic acid from the second stage of water at a temperature of approximately 50 to 300o(I) filtering and drying the specified water-soaked purified terephthalic acid from the second stage, (j) the concentration specified in the filtered solution from step (C) by evaporation and cooling of the concentrated solution for crystallization of terephthalic acid and a small part of isophthalic acid, (k) the Department specified precipitated terephthalic acid and a small part of isophthalic AI (a),(l) the concentration specified in the filtered solution from step (k) by the second evaporation and cooling of the concentrated solution for further crystallization of terephthalic acid and a small part of isophthalic acid, (m) the Department specified crystallized terephthalic acid and a small part of isophthalic acid from this solution in (1) and recycling solid mixture for processing in stage (a) and (n) the supply of the specified filtered solution from step (m) in a device for processing waste or for further processing.

14. The method according to p. 13, in which the specified dispersion contains up to 20% isophthalic acid (IPA), a small amount of 4-carboxaldehyde (4-CBA), 3-carboxyaldehyde (3-CBA) and impurities contained in the unreacted raw materials, solvents, products of side reactions and/or other undesirable materials.

15. The method according to p. 13, wherein said selective crystallization solvent for the purification of terephthalic acid selected from the group consisting of N-methylpyrrolidone (NMP), N, N-dimethylacetamide, N,N-dimethylformamide, N-formylpiperidine, N-alkyl-2-pyrrolidone, N-mercaptoethyl-2-pyrrolidone, N-alkyl-2-cooperalion, N-oxoalkyl-2-pyrrolidone, morpholine, carbitols, C1-C12alcohols, ethers, amines, amides and esters, and mixtures thereof.

16. The method according to p. 15, wherein said selective crystallization solvent for cleaning terephthaloyl selective crystallization solvent for the purification of terephthalic acid is a N-organic.

18. The method of purification of crude terephthalic acid (TPA) and isophthalic acid (IFC) of the liquid dispersion containing terephthalic, isophthalic acid and other impurities resulting from the oxidation of a mixture of xylenes, comprising (a) dissolving crude terephthalic acid in a selective crystallization solvent at a temperature of about 50 250oTo obtain a solution, (b) crystallization of the purified acid from this solution by reducing the temperature and/or pressure and the Department specified crystallizing purified terephthalic acid from the solution, (c) adding antibacterial to the specified solution, from which it is separated by the specified crystallizing purified terephthalic acid to precipitate essentially all of terephthalic acid remaining in the specified solution, (d) the Department specified precipitated terephthalic acid, (e) evaporating the solvent from a solution obtained by adding antibacterial and removal of precipitated terephthalic acid, crystallization of terephthalic acid, thereby purifying and removing the purified isophthalic acid.

19. The method according to p. 18, further including the dissolution and crystallization specified is which this dispersion contains up to 20% of isophthalic acid (IFC), small amounts of 4-carboxaldehyde (4-CBA), 3-carboxyaldehyde (3-CBA) and impurities contained in the unreacted raw materials, solvents, products of side reactions and/or other undesirable materials.

21. The method according to p. 18, wherein said selective crystallization solvent for the purification of terephthalic acid selected from the group consisting of N-methylpyrrolidone (NMP), N, N-dimethylacetamide, N,N-dimethylformamide, N-formylpiperidine, N-alkyl-2-pyrrolidone, N-mercaptoethyl-2-pyrrolidone, N-alkyl-2-cooperalion, N-oxoalkyl-2-pyrrolidone, morpholine, carbitols, C1-C12alcohols, ethers, amines, amides and esters, and mixtures thereof.

22. The method according to p. 18, wherein said antibacterial to precipitate terephthalic acid from the solution of terephthalic and isophthalic acids are selected from the group consisting of methanol, water, methyl ethyl ketone, acetone, C1-C12alcohols, carbitols, esters, ethers, C1-C12carboxylic acids, and mixtures thereof.

23. The method according to p. 18 which further includes repeating the specified dissolution and crystallization of terephthalic acid, if necessary, to obtain purified of tereta the

 

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