KR20010101068A - Process of purifying and producing high purity aromatic polycarboxylic acids and derivatives thereof - Google Patents

Abstract

The present invention provides a process for solvent extraction purification for aromatic polycarboxylic acids or derivatives that meet or exceed polymer grade specifications. The method comprises dissolving the crude aromatic polycarboxylic acid or derivative in a base compound; Removing impurities and excess base compound; And removing residual base compounds while preparing the purified product. The purification process not only removes impurities from the crude acid or derivative, but also removes residual base compounds from the final product that would otherwise contaminate the product. Salts in the cake are converted to the product by acid substitution, pyrolysis, or electrolysis. The method uses a base extraction solvent to extract base compounds and impurities from salts. The residual base compound in the recovered product is then removed by leaching, stripping, thermal disturbance using electromagnetic waves, or pyrolysis and evaporation. The purification method allows removal of the crystallization device for crystallization and the drying and pneumatic conveying device. Finally, the purification process is combined with conventional oxidation and solvent recovery using only one set of process steps instead of two sets to produce aromatic polycarboxylic acids or derivatives.

Description

Process for Purifying and Producing High Purity Aromatic Polycarboxylic Acids and Derivatives thereof {PROCESS OF PURIFYING AND PRODUCING HIGH PURITY AROMATIC POLYCARBOXYLIC ACIDS AND DERIVATIVES THEREOF}

Background of the Invention

Aromatic polycarboxylic acids have been prepared by oxidizing the corresponding alkyl groups with molecular oxygen. Examples of such acids are pure terephthalic acid (PTA), isophthalic acid (IPA), trimellitic acid (TMA), 2,6-naphthalene dicarboxylic acid (2,6-NDA), 2,7-naphthalene dicarboxylic acid (2,7-NDA), and other acids. Since PTA is the most typical method, it will be used as an example in the present invention. However, the purification and production process of the present invention is applicable to all aromatic polycarboxylic acids and derivatives thereof.

A conventional method of preparing PTA consists of the following steps of preparing crude terephthalic acid (CTA).

1) Oxidation: The reaction of p-xylene (PX) with air is carried out in liquid phase using cobalt-manganese-bromine as a catalyst and acetic acid as a solvent at 150 to 230 ° C and 150 to 425psia.

2) Crystallization: The effluent from the reactor is crystallized by three to five large crystallizers at reduced pressure and temperature to precipitate terephthalic acid from the mother liquor.

3) Filtration: The crude acid is separated from the mother liquor by centrifugation / filtration. The treated or untreated mother liquor is recycled to the oxidation step.

4) Drying: Blowing inert gas to dry the crude acid, then acetic acid carried by the inert gas is recovered by scrubber. The dried crude terephthalic acid is pneumatically delivered to silos or storage bins that require large amounts of nitrogen flow or, for some PTA plants, an air separation plant.

5) Solvent and Catalyst Recovery: The solvent and catalyst are recovered by various methods.

The CTA containing about 0.5% impurity is then purified by a hydrogenation process to contain about 25 ppm 4-carboxybenzaldehyde (4-CBA), 150 ppm p-toluic acid, and about 0-50 ppm benzoic acid. Create a graded PTA. Similar to CTA, purified PTA from the hydrogenation unit undergoes another set of process steps: crystallization; percolation; And drying as described above. Thus, to remove impurities at about 0.5% from the reactor effluent to about 0.025% of the purified product, a conventional method uses the following expensive steps:

1) Two sets of process steps are required for crystallization, centrifugation / filtration, drying, and pneumatic conveying devices.

2) An expensive purification method by chemical reaction is used. Although neglecting the higher capital cost of the hydrogenation unit, high production costs are required because they work under high temperatures and pressures using expensive precious metals as catalysts under high temperatures and pressures.

3) Long residence times are required for crystallization. To recover the product from the mother liquor, about 3 to 5 CTAs and about 5 large crystallizers are used. In addition, because of the highly corrosive bromine-acetic acid environment, some crystallization devices may require the use of expensive corrosion resistant materials, such as titanium-lined devices.

4) Dry and pneumatic conveyance is required to produce the final product.

5) Meets the polymer grade specification, but the product still contains about 0.01% impurities.

High purity PTA, or derivatives thereof, are required to be suitable for producing polyester fibers, films, and molding resins. Terephthalic acid is difficult to purify because of its low solubility in most solvents, high boiling point, and similar physical and chemical properties to the impurities present.

One alternative method is to remove impurities by solvent extraction. Solvent extraction approaches are interesting because they are less expensive. This can be traced back to 1953 (US Pat. No. 2,664,440), or earlier. Initially, the solvents presented were unstable, reactive with the product, toxic or unable to purify CTA to the desired level. Later, Iwane (US Pat. No. 5,344,969) and Hirowatari (US Pat. No. 5,565,609) disclosed methods using more stable solvents. The following is a summary of these methods.

1) Dissolution of Crude Acid: Aromatic polycarboxylic acids form salts with many base compounds, which salts are soluble in water or soluble solvents such as alcohols at elevated temperatures.

2) Impurity Removal: Some impurities, like activated carbon in the case of colorants, can be easily removed by solution pretreatment. Impurities with acid-like properties are separated from the mother liquor by crystallization by cooling above 30 ° C.

3) Product Recovery: Hirotari thermally decomposes the pretreated solution by heating or by contacting the concentrated solution with steam in the presence of alkylene glycol. Relaxation precipitates and washes the salt and then pyrolyzes it or converts it to a purified product by adding an acid substitution solvent that substitutes for the acid, the product in the salt. Relaxation also recovers the product by adding an acid substituted solvent directly to the solution.

Both relaxation and Hiwartari use amine compounds consisting of nitrogen as the only heteroatom, such as aliphatic, cycloaliphatic, aromatic, or heterocyclic amines. Relaxation uses alcohol as a soluble solvent for the purification of crude NDA obtained from oxidation. Hiwartari uses water as the soluble solvent for recovering aromatic dicarboxylic acid from the hydrolyzed polyester resin. In its approach, purified salts are not prepared because impurities consist only of additives and colorants which can be simply removed by activated carbon. Thus, this method is suitable for purifying hydrolyzed resins already containing high purity PTA with a colorant or additive that is easily separated, but is applied to crude aromatic dicarboxylic acids obtained from oxidation containing impurities that are difficult to separate. Not suitable for

In pyrolysis, the relaxation adds heat to salts that can be dispersed in paraffin, alkylbenzene, alkylnaphthalene, or alkylbiphenyl, and does not use steam for heating. The solvent selected will have a high boiling point and will be present as other contaminants in the final product. Hiwartari decomposes the preheated aqueous solution with reflux to decompose the amine salt, or concentrate the solution by distillation and then contact with steam to decompose and remove the amine compound. Alkylene glycol is used to raise the reflux temperature. Reflux increases the base content in the final product, and distillation requires evaporation of at least 50% of water, which requires significant energy.

Relaxation claims to improve the purity of 2,6-NDA from 97.2% to about 99.8%, and Hiwartari recovers the hydrolyzed resin to 99.9% PTA. Relaxation applies its method to crude NDA obtained from reactor effluents at a purity level of less than CTA to purify only to levels similar to CTA. Both approaches improve product purity, but they still deviate from the specification of polymer grade PTA (> 99.98%).

Another approach is the method of Lee (US Pat. No. 5,767,311) using N-methyl pyrrolidone (NMP) to dissolve CTA at 140-190 ° C. without using a soluble solvent. The solution is cooled to 5-50 ° C. to crystallize. Filtration and washing of the precipitate produces PTAs that conform to polymer grade specifications without using any means to recover the product from the salt. However, experiments using this method show that unconverted salts contaminate the final product. This contamination may be due to the failure to recognize the presence of salts formed by NMP and PTA in the process. Li identified precipitate from solution as PTA, but this is actually a salt. The salt is converted to the product during washing by some washing solvent such as methanol. However, no significant salt is converted since washing alone is not sufficient to convert all salts into products. The dissolution process and solvent recovery of the process are expensive. Compared with amine compounds or morpholines, NMP is about 2 to 3 times more expensive and requires 3 to 5 hours more to dissolve crude acid. In addition, it is more expensive to recover by heating a high boiling point solvent. In addition, Lee's claim that CTA can be dissolved in a non-aqueous morpholine solution is incorrect. If water is not present, solubility is negligible regardless of the solution temperature. Although morpholine can dissolve CTA, the final product is a salt, not PTA, because methanol cannot convert the morpholine salt to PTA. The difference between NMP and morpholine salts will be discussed later and used by the present invention. The present invention uses new crystallization processes and washing solvents to improve the product quality of this process.

Regardless of the advantages, purification by solvent extraction in commercial applications is not known. The main problem is due to the fact that the residual base compound remaining in the final product becomes the contaminant itself. All proposed organic base compounds contain nitrogen which causes coloring and other problems in the preparation of polyesters, which have not been discussed in the prior art with respect to the above problem, and have not been taught how to remove the base compound from the final product. .

Crystals always contain residual solvent by inclusion during crystallization. If known methods are used, the crystals may contain at least 0.1% residual base compound similar to the impurity level of CTA. To be suitable for preparing polyesters, residual base compounds must be removed at several ppm, similar to the impurity levels of PTA. Thus, conventionally known prior art solvent extraction removes impurities from the crude acid, but introduces residual base compounds as contaminants in the product, making the product unsuitable for producing the polyester.

Known methods have not attempted to remove residual base compounds from the final product. Relaxation teaches the use of acid solvents, Hirotari teaches the use of water to wash base compounds from the final product filter cake, and Lee uses NMP, p-xylene, acetone, methyl ethyl to wash the filter cake. Teach using ketones or methanol. In an experiment in which the cake was washed and leached for about 10 hours using water at a ratio of 100: 1, a purified product still containing a significant amount of base compound was produced. This indicates that the base compound is difficult to remove once it is included in the product crystals. This problem is not known because it has not been addressed in the published literature, or is known to those skilled in the art but remains unresolved.

Prior art solvent extraction purification methods clearly or implicitly suggest replacement of the hydrogenation unit and use CTA as feed except li. Li's claim that the high rate of CTA can be recovered directly by filtering the reactor effluent without using crystallization or other means is misleading. Since most of the CTA remains in the mother liquor of the reactor effluent, a long residence time is required to settle the CTA. Thus, conventional methods use three to five large crystallizers to recover the CTA. The present invention proposes to use flashing and evaporation to reduce residence time.

Since the purification method itself requires another set of process steps for crystallization, filtration, drying, and pneumatic transport, the prior art also requires two sets of process steps to produce PTA. Thus, using known solvent extraction methods to produce aromatic polycarboxylic acids has the following disadvantages:

1) Introduce a base compound that contaminates the final product.

2) Two sets of process steps are required for crystallization, centrifugation / filtration, drying, and pneumatic conveying devices.

3) Significant detectable impurities remain in the final product.

4) Because of the long residence time required for crystallization, several large crystallizers are required.

5) Dry and pneumatic transport is required to produce the final product.

Accordingly, several objects of the present invention are as follows:

1) To provide a solvent extraction purification method that removes impurities from crude acids to meet or exceed the specifications of polymer grade aromatic polycarboxylic acids.

2) To remove the base compound from the purified product so that the purified product is suitable for polyester fibers, films, molding resins, or other applications.

3) to provide a process for producing polymer grade aromatic polycarboxylic acids, requiring only one set of process steps to substantially reduce capital and production costs.

4) To reduce the number of crystallization devices required for crystallization or to remove the crystallization devices.

5) to produce aromatic polycarboxylic acids that can be used for direct polyester preparation without the need for drying and pneumatic conveying steps.

Additional objects and advantages will be surprisingly surprising from the solvent extraction methods disclosed herein that remove impurities to levels not detected by current standard HPLC measurements.

Field of invention

The present invention relates to an improved process for the purification and production of aromatic polycarboxylic acids and derivatives thereof, especially derivatives such as aromatic polycarboxylic acids, or esters in high purity.

Summary of the Invention

The present invention provides a solvent extraction purification method for aromatic polycarboxylic acids, or polymers thereof, that meet or exceed polymer grade specifications. The method comprises the steps of dissolving a derivative such as crude aromatic polycarboxylic acid or methyl ester in the base compound; Removing impurities and excess base compound; And removing residual base compounds while preparing the purified product. The purification process not only removes impurities from the crude acid or derivative, but also removes residual base compounds from the final product that would otherwise contaminate the product. The salt in the cake state is converted to the product by acid substitution, pyrolysis or electrolysis. The method uses a base extraction solvent to extract base compounds and impurities from salts. The residual base compound in the recovered product is then removed by leaching, stripping, thermal agitation using electromagnetic waves, or pyrolysis and evaporation. The purification method allows removal of the crystallization device for crystallization and the device for drying and pneumatic conveying. Finally, the purification method uses only one set of process steps instead of two sets to produce aromatic polycarboxylic acids or derivatives in combination with prior art oxidation and solvent recovery, with substantially reduced capital and production costs. do.

Detailed description of the invention

The present invention provides a solvent extraction purification method for aromatic polycarboxylic acids, or polymers thereof, that meet or exceed polymer grade specifications. The method applies to any polycarboxylic acid such as PTA, IPA, TMA, 2,6-NDA, 2,7-NDA, and other acids. The invention also applies to acid derivatives comprising esters such as dimethyl terephthalate (DMT), dimethyl-2,6-naphthalene dicarboxylate (NDC), hydrolyzed polyester, or the like. The method comprises the steps of dissolving a derivative such as crude aromatic polycarboxylic acid or methyl ester in the base compound; Removing impurities and excess base compound; And removing residual base compounds while preparing the purified product. The base compound preferably contains both oxygen and nitrogen as heteroatoms, such as morpholine or NMP. Additional base compounds are discussed in more detail below. The salt in the cake state is then converted to the product by acid-substituted solvent, thermal decomposition, or electrolysis.

In addition to removing impurities from the crude acid or derivative, the method uses a base-extraction solvent to extract base compounds and impurities from salts and recovered products. Residual base compounds in the recovered product are removed by leaching, stripping, thermal disturbance using electromagnetic waves, or thermal decomposition and evaporation. Residual base compounds are not impurities but contaminants introduced by the purification process. The method reduces the cost by eliminating the crystallization apparatus for crystallization and the drying and pneumatic conveying apparatus. Finally, the purification process uses only one set of process steps instead of two sets to produce aromatic polycarboxylic acids in combination with prior art oxidation and solvent recovery.

Crystals of aromatic polycarboxylic acids purified by solvent extraction typically include adsorption mechanisms on the crystal surface, namely cracks, cracks, and entrapment in lumps; And base compounds and other solvents by inclusion of liquid pockets. The base compound in the crystal is not present as a liquid, but as a solid salt formed with product crystals or acid substituted solvents. Washing and pyrolysis can remove the adsorbed or trapped portion, but not the contained solids that are masked by the product crystals with sublimation temperatures of about 300 to 425 ° C. For this reason, it is extremely difficult to remove residual base compounds from product crystals.

In the prior art, the oxidation of the base compound is prevented by performing in an inert atmosphere to prevent deterioration of the color of the product which masks the presence of the base compound. Standard HPLC analysis techniques used to measure impurities cannot detect nonaromatic base compounds; If the compound is not intentionally oxidized to demonstrate the presence of the compound, then the base compound cannot be detected by color measurement of the purified product. A simple technique for detecting the presence of residual base compounds is to burn the final product in a color other than white at high temperatures for a long time in air. The presence of residual base compounds can be detected by comparing the degree of white to that of PTA purified by hydrogenation, or using existing colorimetric techniques.

In the purified salt, the base compound which is not bound to the carboxylic acid functional group is an excess base compound. Removal of excess base compound from the salt is inevitable in contact of the recovered product with the base compound, since the compound is a component of the salt. Thus, additional steps are required to remove residual base compounds contained within the recovered product crystals, which is difficult and unclear.

The present invention reveals a base extraction solvent that extracts both base compounds and impurities from the purified salt and recovered products. Suitable base extraction solvents have low solubility for the crystals of interest or have the ability to convert salts to product acids; Has high solubility for base compounds and impurities; Any non-nitrogen containing compound that is easy to separate or does not need to be separated from the final product. The solvent may contain hydroxyl, carbonyl, ether, ketone, ester, or other functional groups.

If a solvent extraction method is not explicitly specified, the method is carried out at a temperature range from the freezing point of the solution to the highest boiling point at a predetermined pressure, preferably at the highest boiling point temperature range from the cold water temperature. Working pressure is not particularly limited; It can vary in the absolute air pressure range of 0 to 1000, preferably 0.001 to 5.

Purification methods for removing impurities and residual base compounds include the following process steps.

Dissolution of Crude Acid or Derivative

The crude aromatic polycarboxylic acid or derivative is dissolved in the base compound by salt formation. If the salt can be dissolved in the solvent for dissolution, the solvent for dissolution is used to increase the solubility and the cost of dissolution is reduced. If the salt is not soluble in the solvent for dissolution, no solvent for dissolution is used. This also includes the rare case where the crude acid or derivative is dissolved in the base compound without salt formation.

Crude aromatic polycarboxylic acids or derivatives can be obtained from any source containing any kind of impurities. The crude acid or derivative may be, for example, in the middle of an oxidation reactor such as in the production of dimethyl terephthalate (DMT) or dimethyl-2,6-naphthalene dicarboxylate (NDC), hydrolyzed polyester, or other compounds. Obtained from the final production stream. Base compounds include oxygen-containing base compounds and non-oxygen-containing base compounds. Oxygen containing base compounds include any compound having oxygen and nitrogen as heteroatoms, such as morpholine compounds, amide compounds, inorganic bases and other compounds. Non-oxygen containing base compounds include amine compounds and ammonia. Base compounds include aliphatic, cycloaliphatic, aromatic, and heterocyclic compounds. The amount of base compound used is from 0.5 to 100 moles per mole of carboxyl or substituted carboxyl functional groups of aromatic polycarboxylic acids or derivatives, preferably from 1 to 2 moles per mole of carboxyl functional groups of crude aromatic polycarboxylic acids. . Solvents for dissolution include water, alcohols, ethers, ketones, and esters. The amount of the solvent for dissolution may vary from 0 to 100 moles, preferably 1 to 10 moles per mole of carboxyl functional groups of the crude aromatic polycarboxylic acid.

The prior art uses conventional heating methods that dissolve crude acids by transferring energy from solvent molecules to salt ions to overcome attraction. In addition to the use of conventional heating, the present invention can dissolve crude acids or esters by thermal disturbances under electromagnetic waves. Thermal disturbance of the ionized solution under electromagnetic waves is different from conventional heating or microwave heating. The electromagnetic waves provide thermal disturbances to both solvent molecules and salt ions. However, the ions receive more energy, so that the ions heat the solvent molecules, as opposed to other heating. Thus, it has distinct features such as solubility, solvent evaporation, and crystallization. For example, this may be due to different solubility, since salt ions receive more energy for dissolution but can be pyrolyzed and returned to the acid or ester; Better crystallization efficiency because of higher evaporation and less crystallization solvent; And because high energy ions can be used to pyrolyze a portion of the salt to produce the product acid or ester. The main advantage is the significant savings in melting energy and time. Less dissolution time reduces the decomposition of the solvent or the reaction with impurities.

Relaxation and Hiwartari use non-oxygen containing amine compounds, and Li use alicyclic amide compounds having properties of pyrrolidone compounds, carbonyl and amine functional groups. Other preferred oxygen containing base compounds are morpholine compounds having the properties of ether and amine functional groups. Oxygen-containing organic base compounds have significantly different properties from non-oxygen-containing organic base compounds in hygroscopicity by basicity, dielectric constant, dipole moment or solvent. The present invention utilizes these properties to remove base compounds and impurities from the purified product.

Oxygen containing salts are referred to as basic salts and non-oxygen containing salts are referred to as normal salts. Most salts are soluble in many solvents such as water and alcohols. Salts containing ether groups are referred to as ether basic salts, although they are soluble in water, many are insoluble in other solvents such as alcohols. Salts containing carbonyl groups are referred to as carbonyl basic salts, which are insoluble in most solvents, including water and alcohols. Solvents that have low solubility in salts or can be converted back to acids, but still have high solubility for impurities and base compounds, are used as base extraction solvents for purifying salts or products. According to the present invention, it is found that the carbonyl basic salt is weakly bound. Thus, it is easier to recover salts to products and remove base compounds from products, but it is more difficult and expensive to form salts. The opposite holds true for ether basic salts. Thus, the base compound removes impurities from the crude acid and the base extraction solvent removes base compounds and impurities from the purified salts and the final product.

More specifically, aromatic polycarboxylic acids are those having one or more condensed rings, in which two or more carboxylic acid groups may be present at any position of the aromatic ring (s), and any hydrogen is replaced by another functional group. It can be. Examples of the monocyclic aromatic dicarboxylic acid include, but are not limited to, terephthalic acid, isophthalic acid, orthophthalic acid, trimellitic acid, hemimelitic acid, trimesic acid, pyromellitic acid, and melic acid. no. Examples of two ring aromatic polycarboxylic acids are 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, 1,7-naphthalene dicarboxylic acid, 1,8-naphthalene dicarboxylic acid Acids, 2,3,6-naphthalene tricarboxylic acid, 1,4,5,8-naphthalene tetracarboxylic acid, and 2,3,6,7-naphthalene tetracarboxylic acid, but are not limited thereto. It doesn't happen. Examples of aromatic polycarboxylic acids of three condensed rings are 2,6-anthracene dicarboxylic acid, 2,7-anthracene dicarboxylic acid, 2,8-anthracene dicarboxylic acid, 2,9-anthracene dica Leric acid, 1,9-anthracene dicarboxylic acid, 2,3,6-anthracene tricarboxylic acid, 1,4,5,8-anthracene tetracarboxylic acid, and 2,3,6,7-anthracene Tetracarboxylic acid, but is not necessarily limited thereto. Aromatic polycarboxylic acids include mixtures of aromatic polycarboxylic acids, for example 2,6-naphthalene dicarboxylic acid, and mixtures in any proportion of 2,7-naphthalene dicarboxylic acid.

In the base compound, the nitrogen atom in the base compound may have a trivalent or pentavalent. Base compounds include all combinations of heteroatoms and carbon atoms at different positions of the compound, and saturated and unsaturated compounds with one or more hydrogen atoms may be ammonium salts substituted with or derived from alkyl, aryl, or acyl groups . If the base compound is in a solid or gaseous state under conventional conditions, its aqueous solution may be used. The base compound may be a mixture in any proportion. The inorganic base may be sodium hydroxide, potassium hydroxide and the like.

Morpholine compounds include morpholine, N-methylmorpholine, N-ethylmorpholine, N-propylmorpholine, N-isopropylmorpholine, N-methylmorpholine oxide, N-phenylmorpholine, 4-morpholine pro Pionitrile, 1-morpholine-1-cyclohexene, or other compounds. Other base compounds containing ether groups include single-heterocyclic compounds containing 3 to 8 atoms with nitrogen and oxygen in the ring, including oxazocin, oxazine, oxazole, isoxazole, oxadiazet, Oxaziline and the like.

Amide compounds include aliphatic amides such as dimethylformamide, dimethylacetamide, ethaneamide, acetamide, and other compounds. Alicyclic amides include pyrrolidone, N-methyl-pyrrolidone, N-ethyl-pyrrolidone, N-alkyl-2-pyrrolidone, N-mercaptoalkyl-2-pyrrolidone, N-mercapto Ethyl-2-pyrrolidone, N-alkyl-2-thiopyrrolidone, N-methyl-2-thiopyrrolidone, N-hydroxyalkyl-2-pyrrolidone, and N-hydroxyethyl-2 -Pyrrolidone, lactam, and the like. Aromatic amides include phenylacetamide, phenylene terephthalamide, and the like.

Aliphatic amines are methylamine, dimethylamine, trimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, n-propylamine, di-n-propylamine, tri-n-propylamine, isopropylamine, di Isopropylamine, triisopropylamine, ethylenediamine, N-methylethyleneamine, N, N-dimethylethylenediamine, N, N'-dimethylethylenediamine, N, N, N'-trimethylethylenediamine, N, N, N ', N'-tetramethylethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, monoethanolamine, diethanolamine, triethanolamine, dimethylacetamide, dimethylformamide and the like. Alicyclic amines are methylcyclohexylamine, N-methylcyclohexylamine, N, N-dimethylcyclohexylamine, ethylcyclohexylamine, N-ethylcyclohexylamine, N, N-diethylcyclohexylamine, isopropylcyclo Hexylamine, N-isopropylcyclohexylamine, N, N-diisopropylcyclohexylamine, ethylene imine, propylene imine and the like. Aromatic amines include N, N-dimethylaniline, N, N-diethylaniline, N, N-dibutylaniline, N, N-dimethyltoluidine, N, N-diethyltoluidine and the like. Heterocyclic amines include pyridine, piperidine, N-methylpiperidine, N-methylpyrrolidine and the like.

Preferred base compounds are morpholine, N-methyl-pyrrolidone, trimethylamine, triethylamine, or triethanolamine.

Alcohols are methanol, ethanol, n-propanol, isopropanol, n-butyl alcohol, isobutyl alcohol, secondary-butyl alcohol, tert-butyl alcohol, n-amyl alcohol, isoamyl alcohol, secondary-amyl alcohol, tertiary Aliphatic monohydric alcohols such as amyl alcohol, neopentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, and decyl alcohol; Alicyclic monohydric alcohols such as cyclopentyl alcohol and cyclohexyl alcohol; Aliphatic linear diols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, and pentanediol; Alicyclic diols such as 1,2-cyclopentanediol, 1,3-cyclopentanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, and 1,4-cyclohexanediol; And aliphatic polyols such as glycerol and pentaerythritol. Preference is given to aliphatic monohydric alcohols having up to 3 carbon atoms and diols having up to 4 carbon atoms. The alcohol may be a mixture of any proportion thereof. Preferred alcohols are methanol, ethanol, or alkylene glycols.

Ethers are dimethyl ether, diamyl ether, diethyl ether, isopropyl ether, n-butyl ether, n-hexyl ether, chlorodimethyl ether, phenyl methyl ether, dibenzyl ether, ethylene oxide, dioxane, trioxane, furan, Tetrahydrofuran, methyl tetrahydrofuran, tetrahydropyran, methyl tetrahydropyran and other compounds. Ketones are acetone, methyl ethyl ketone, methyl n-propyl ketone, methyl n-butyl ketone, methyl amyl ketone, methyl acetone, 2-methyl cyclopentanone, methyl n-butyl ketone, methyl amyl ketone, methyl acetone, 2-methyl Cyclopentanone, cyclopentanone, cyclohexanone, cyclohexanol and other compounds. Esters are ethylene glycol methyl ether, diethylene glycol methyl ether, ethylene glycol ethyl ether, diethylene glycol ethyl ether, ethylene glycol butyl ether, ethylene glycol ethyl ether, ethylene glycol benzyl ether, diethylene glycol, triethylene glycol, alkyl formate , Alkyl acetates, alkyl propionates, oxalates, alkyl lactates, carbonates, benzoates, and other compounds.

Removal of impurities and excess base compounds

This step removes impurities by pretreating, settling, separating and washing the cake. Impurities can be removed by crystallization by solution pretreatment and cooling as taught in the prior art. The present invention also provides a new method for removing both impurities and excess base compounds from the washed cake.

Solution pretreatment involves the removal of impurities that can be easily separated from the solution, for example, colorants or additives by activated carbon, insolubles by filtration, or suspensions by overflowing or scraping. To remove it. Methods of separating impurities of this kind are already well known and the present invention is not limited to any particular one. If the crude contains no impurities of this kind, no solution pretreatment is necessary.

Crystallization is difficult to separate and removes impurities with similar physical and chemical properties as the product. The solubility of impurity salts is lower or higher than product salts at predetermined temperatures and solution compositions. By changing the solution temperature and / or composition, impurities with lower solubility precipitate out and separate before others. Precipitation of the product salt separates the product salt by leaving those with higher solubility in the mother liquor.

The prior art uses crystallization by cooling to separate impurities and the salts are separated by conventional methods such as filtration or centrifugation. Since long residence times are required to grow crystals from the mother liquor, several large crystallizers are required for crystallization. An alternative method is to crystallize by adjusting the composition with cooling to reduce residence time requirements. Prior to crystallization after complete dissolution of the crude acid, a predetermined amount of solvent is removed by conventional methods such as evaporation or distillation so that the cooled slurry still contains sufficient mother liquor to separate impurities. This reduces the residence time which is significant for crystallization but still requires it.

In the prior art, since the solvent for dissolution immediately dissolves the salt, a base compound is commonly used to wash the filtered salt. However, due to the low viscosity of the salt, the cleaning efficiency is low. In addition, this saturates salts with excess base compound and increases the content of base compound in the final product. Other prior art teaches the use of aliphatic hydrocarbons or aromatic hydrocarbons as washing solvents. It simply replaces the solvent in the crystal and does not provide extraction power and may be present in the final product as other contaminants.

The present invention uses a base extraction solvent to remove all excess base compound and impurities from the salt. This new method involves washing and leaching with a base extraction solvent, crystallization of the salt in the presence of a base extraction solvent, precipitation of the product in the presence of a base extraction solvent, crystallization by direct extraction from the salt, crystallization by resaltting, and Base substitutions.

Most base extraction solvents do not convert salts to acids. However, this may be the case when pure solvents are used to wash the filtered carbonyl basic salts, in which mixing the base extraction solvent for converting salts with the base compound in an appropriate proportion reduces the salt conversion. For example, mixing methanol with 50% NMP to wash the filtered salt significantly reduces salt conversion. The washed cake is preferably kept as a salt.

More specifically, base extraction solvents are water, hydrogen peroxide, alcohols, ethers, phenols, ketones, esters and other compounds. Alcohols, ethers, ketones, and esters are defined above. The base extraction solvent may be used alone or as a mixture of any ratio of two or more solvents, and the solvent may be used in liquid or vapor state. Preferred base extraction solvents are water, methanol, ethanol, alkylene glycol, acetone, tetrahydrofuran, or tetrahydropyran. Since the target crystal in this step is a purified salt, the solvent for dissolution used is excluded. In the next step, the crystal of interest is a product acid or derivative which may comprise the solvent for dissolution used.

The color of most impurity salts is not white, the odor of excess base compounds is ammonia, and using base extraction solvents to wash or leach the filter cake is comparable to salts washed with other solvents such as base compounds or hydrocarbons. Thereby significantly improving the salt in both color and odor. By definition, leaching is distinct from washing filter cakes (Perry's Chemical Engineering Handbook, 6 ^th Edition page 19-48). Washing and leaching methods are very well known and the invention is not limited to any particular one.

The base extraction solvent may be added to the solution after completely dissolving the crude acid. The presence of base extraction solvent during crystallization reduces the inclusion of base compounds while simultaneously extracting impurities and base compounds from salts. In addition, the presence of a base extraction solvent in solution changes the crystallization mechanism such as shape, size, and rate. For example, adding methanol, acetone, or tetrahydrofuran changes the shape and increases the size of the crystals from the NMP-PTA salts.

The purified product can be precipitated by adding an acid substitution solvent to the solution in the presence of a base extraction solvent. The presence of the base extraction solvent extracts impurities and base compounds from the precipitation. According to the invention, water precipitates the product directly from the saturated solution, but since other base extraction solvents, such as methanol, precipitate salts that are in a range of solution compositions, water is the base extraction solvent and also the acid for the carbonyl basic salt. It turns out that it is a substitution solvent. However, the solubility of 4-CBA and NMP salts in water is about 10 times lower than methanol. Compared to washing to convert salts in the prior art, precipitation of the product in the presence of a base extraction solvent provides better control of salt conversion and crystal size by adjusting temperature, stirring, composition, and residence time. In the prior art, acid substituted solvents are added to precipitate the product in the absence of a base extraction solvent. However, product purity is low because most impurities precipitate with the product.

Most or all solvents are removed from the solution by evaporation or flashing to give a solid or slurry of salt. Since impurities do not vaporize under normal operating conditions, they all remain with the salt. This is a condition to be avoided in the prior art crystallization in which impurities are retained in the mother liquor for separation. However, according to the present invention it has surprisingly been found that base extraction solvents can extract most impurities and excess base compounds from salts. Thus, this crystallization process completely removes the residence time requirement for crystallization. Product recovery efficiency depends on the solubility of the salt in the base extraction solvent and the amount of solvent for dissolution remaining in the slurry. Unlike the crystallization of the prior art, crystallization by extraction directly from the salt does not cool the solution for crystallization. The mother liquor in the slurry may or may not be separated from the salt prior to adding the base extraction solvent. The extracted solution is then separated from the salt by conventional separation methods.

Re-dissolution of the precipitate in the solvent or base compound for dissolution and recrystallization of the solution for at least 1 hour can result in the removal of impurities to levels undetectable by current standard HPLC methods or the determination of polymer grade specifications for crude acids with higher concentrations of impurities. Removed to meet. Thus, crystallization by resalting may include crystallizing salts from a solution of crude acid; Separating, washing and re-dissolving salts; Recrystallizing the salt from the solution; And separating and washing the salt in a conventional manner. Preferably, the salt is completely dissolved before recrystallization. If the washed cake contains product acid by using electromagnetic waves or by washing with a salt conversion base extraction solvent, the acid may or may not be separated from the salt, or redissolved or redissolved by the base compound for resalting. You can't let that happen. Any of the crystallization methods discussed above can be used for crystallization and reprecipitation. However, preference is given to using crystallization by direct extraction from salts for crystallization and recrystallization. If precipitation of the product in the presence of a base extraction solvent is used, it is preferably the final crystallization step. The number of resalting treatments is not particularly limited and is preferably 1 to 2 times.

The base extraction solvents used in the methods discussed above to remove impurities may or may not be the same. The amount used is 0.1 to 100 moles, preferably 1 to 10 moles per mole of carboxyl functional groups. For ether basic salts, the preferred base extraction solvent is methanol or ethanol. For carbonyl basic salts, alkylene glycols, acetone, tetrahydrofuran, or tetrahydropyran are also preferred.

Salt base substitution is a method of increasing product recovery by replacing the base compound of the original salt with the base compound of another salt. As discussed above, preparing carbonyl basic salts is more difficult and expensive, but recovery is easier and cheaper. For example, preparing NMP-PTA salts is several times more expensive than morpholine-PTA salts, but the salts can be recovered with less expensive water. According to the present invention, it is found that the base compound of the salt can be replaced by another base compound having a higher boiling point, so that the ether basic salt or the conventional salt can be converted into the carbonyl basic salt. Thus, salts can be prepared with more economical base compounds and converted to other salts for more economical product recovery. The salt to be converted is mixed with a substituted base compound in the presence or absence of a solvent for dissolution. Substituted base compounds and / or solvents for dissolution are then removed from the solution by conventional separation methods such as evaporation or distillation, using conventional heating or electromagnetic waves. Substituted salts are prepared by precipitation from the solution by cooling in the presence or absence of a base extraction solvent or by direct extraction from the salt. Solvent solvents, such as water, are used to dissolve unconverted salts that are recycled or converted in a series of steps. Salt base substitutions include changing salt crystals, such as shape or size, in the presence of other base compounds. The amount of substituted base compound used may vary from 0.1 to 100 moles, preferably 1 to 10 moles per mole of carboxyl functional groups.

In addition to washing with a non-salt converting base extraction solvent, the filter cake may be washed with a salt converting base extraction solvent or an acid substituted solvent. This can be thought of as a combination of washing and the next step, acid substitution, which is Li's approach. However, washing gives little control over salt conversion and product properties. The present invention prefers to precipitate the purified product during crystallization prior to filtration or to separate the precipitate as a salt to be converted in the next step, both of which are salt conversion, extraction of base compounds and impurities from the recovered product, and product particle size This is because it is better controlled. For some basic salts, the product particle size can be influenced by salt particle size, which can be controlled by adjusting spray drying, composition, residence time, temperature, agitation and others.

Thus, the method of removing impurities includes pretreatment of the solution, crystallization by cooling, crystallization by control of the composition with cooling, crystallization of the salt in the presence of the base extraction solvent, precipitation of the product in the presence of the base extraction solvent, extraction from the salt directly. Crystallization, crystallization by resalting, salt base substitution, washing with base extraction solvent, leaching with base extraction solvent, or any possible combination of these methods. In addition to removing impurities from the crude acid or derivative, excess base compound is also removed from the washed cake, thereby reducing the content of base compound in the final product produced by the next step.

Removal of Residual Base Compounds During Preparation of Purified Product

This step recovers the product from the salt in the washed cake when the amount of salt is significant, and / or removes residual base compounds prior to preparation of the final product. Methods for recovering the product from the purified salts include acid substitution; pyrolysis; Or electrolysis. Preferably, the product is recovered in the presence of a base extraction solvent. Since solution composition and temperature, agitation, and residence time can affect the particle shape and size of the product, they are preferably optimized for extraction of base compounds and impurities.

Acid substitution

To convert the salt to the product, acid substitution solvent is added to displace the product acid and precipitate. The salt can be mixed with the base extraction solvent. It is preferred to completely dissolve the ether basic salts and conventional salts before adding the acid substitution solvent, with preferred solvents being water, methanol, ethanol, alkylene glycol, or mixtures thereof. Carbonyl basic salts are insoluble in most solvents and water is a preferred acid substituted solvent. Water is preferably added in the presence of a base extraction solvent such as methanol, ethanol, acetone, tetrahydrofuran, or tetrahydropyran. Acid substitution can be performed under electromagnetic waves. Acid substitution with the base extraction solvent reduces the inclusion of base compounds and impurities in the recovered product.

Acid substitution solvents are aliphatic carboxylic acids, inorganic acids, water, or other compounds. Aliphatic carboxylic acids may be formic acid, acetic acid, propionic acid, butyric acid, glycolic acid, lactic acid, malic acid, tartaric acid, mesotartaric acid, citric acid, monochloroacetic acid, monobromoacetic acid, mononitroacetic acid, trifluoroacetic acid, and trichloroacetic acid There is; The inorganic acid can be nitric acid, hydrochloric acid, hydrogen bromide, hydrogen iodide, sulfuric acid, phosphoric acid, and perchloric acid. As discussed above, the water and base extraction solvents can be acid substitution solvents for the carbonyl basic salts. The acid substitution solvent may be a mixture of any ratio of these acids, or a mixture of these acids and a solvent for dissolving or a base extraction solvent in a ratio of at least 1% by weight of acid.

For ether basic salts or conventional salts, preferred acid substitution solvents are aliphatic carboxylic acids, most preferred is acetic acid. For carbonyl basic salts, water is preferred. The amount of acid substitution solvent added is 0.5 to 100 moles per mole of carboxyl functional groups in aromatic polycarboxylic acids. It is usually added in slightly larger amounts than the mole portion of the carboxyl functional groups.

pyrolysis

Heat is applied to the purified salt to thermally decompose the base compound in the temperature range of 50 to 350 ° C. The salt may be mixed with a base extraction solvent having the desired boiling point which may be adjusted by pressure. Preferred base extraction compounds are water, steam, or alcohols. Heat can be applied by heat transfer, or by heat transfer such as direct contact with a heating medium.

In addition to conventional heating methods, salts can be pyrolyzed under electromagnetic waves. Preferably, the salt is mixed with a base extraction solvent, such as water, steam, or an alcohol, in any proportion capable of absorbing waves to dissolve or acid-substitute the salt and aid decomposition. The wave heats up the molecules to separate them from the product crystals that are permeable to the wave and break down the solution into a mixture of recovered product and unconverted salt. Maintaining the proper solvent concentration and temperature causes the solution to be continuously degraded by waves. Base extraction solvent can be added to the mixture in a series of steps for further decomposition. The unconverted salt can be separated from the recovered product by dissolving in a solvent, and the filtrate is recycled or thermally disturbed by waves in a series of steps. Thus, the method can be used in batch or continuous processes. Pyrolysis by electromagnetic waves requires significantly less energy and residence time than conventional processes. For example, residence times are expected to be about 0.04 to 0.6 hours as compared to about 2 to 12 hours of conventional processes. In addition, heating from the inside reduces the likelihood of incorporating base compounds in the recovered crystals.

The decomposed base compound is preferably separated from the product recovered by conventional processes such as evaporation, suction under vacuum, distillation, adsorption, transport by inert gas, vapor, or solvent for dissolution, and the like.

For carbonyl basic salts, it is preferable to use water or steam as the base extraction solvent to directly contact the salts with steam or to pyrolyze them by electromagnetic waves, since they simultaneously pyrolyze and acid-substitute the salts. The product particle size is determined by the particle size of the salt, which is easier to control. In addition, this eliminates the filtration step and the pneumatic conveying and drying step by pyrolysis and evaporation of residual salts and solvents in alkylene glycols.

Electrolysis

Current is applied to the solution formed by dissolving the purified salt in the base extraction solvent to concentrate the basic cation on the negative electrode, while concentrating the acidic anion on the positive electrode. The product acid precipitates around the anode if the applied current is large enough. An alternative method is to add an acid substitution solvent or heat around the desired electrode to precipitate the product acid while keeping the basic cations separated under a moderate electric field to reduce the inclusion of the base compound. The electrodes are separated in a conventional manner to minimize interference of ions around other electrodes. Electrolysis is similar to the production of metal elements by well known electrolysis, and the present invention is not limited to any particular electrolysis method. The magnitude of the current used is not particularly limited, and ions are separated depending on the desired production rate or electric field. The electrode can be made of a material that does not react with ions and dissolves itself in solution to contaminate the product, or a material capable of depositing basic cations on the separation electrode. Preferred base extraction solvents are methanol, ethanol, alkylene glycols, or mixtures thereof.

The recovered product crystals can be separated by conventional methods and the filter cake is washed with a base extraction solvent, an acid substitution solvent, or any proportion of solvent mixture. Some recovered product can be processed directly by the next step without separation.

The prior art uses only washing to remove residual base compounds or convert salts to products, which is insufficient to remove base compounds to a satisfactory level. The final product has a high content of residual product, which means that the washed cake contains a significant excess of base compound, the product is recovered without extraction of the residual base compound from the crystals, and the purified solution containing excess base compound is pyrolyzed. This is because the base compound is directly refluxed into a pyrolyzed solution, or unwashed salts remain in the product to use a wash for salt conversion.

On the other hand, the present invention seeks to reduce residual base compounds by removing excess base compounds from salts and extracting residual compounds from recovered products. However, it is unavoidable that the recovered product comes into contact with the base compound because it is a component of the salt. Thus, these efforts can reduce but not completely remove residual base compounds from the recovered product. Some of the previous steps for removing the base compound can be removed by having more residual base compound in the recovered product. Removing residual base compounds is a difficult process. Therefore, it is desirable to minimize the residual base compound in the recovered product.

The present invention provides the following new method for removing the residual base compound from the recovered product to produce a final product suitable for polyester production. This new method leaches; Stripping; Thermal disturbance by electromagnetic waves; Pyrolysis and evaporation; Or combinations of these methods.

The recovered product may be leached by mixing with the base extraction solvent at a predetermined amount and temperature and refiltered for at least 1 hour. Leaching methods or methods for stripping traces of solvent from the filter cake are well known and the present invention is not limited to any particular method. Leaching or stripping merely removes base compounds that are adsorbed or trapped but not contained.

Thermal disturbance by electromagnetic waves applies the wave to the recovered product or mixture of product and base extraction solvent. This method is similar to pyrolysis by electromagnetic waves, emphasizing the removal of residual salts contained in the recovered product. Waves are selectively absorbed by residual base compounds and solvents that cause thermal disturbances to heat and drive ions, which are adsorbed on the surface or embedded within the crystals from the crystals passing through the waves. The decomposed base compound and other solvents are then separated as a vapor, as a liquid by an adsorbent, or are leached by a base extraction solvent surrounding the crystal. Base extraction solvents can be added continuously or continuously to the cake for a predetermined period or time to assist in the decomposition of the trace salts. This method removes residual base compounds and at the same time dries the product crystals.

Pyrolysis and evaporation evaporate residual solvents such as water or acetic acid and thermally decompose the residual base compound at 50 to 350 ° C, and preferably at 90 to 210 ° C. The recovered product is mixed at elevated temperatures with a monomer such as alkylene glycol, an oligomer varying from 1 to 100 basic units obtained by reacting the product acid with the monomer, or a base extraction solvent such as water. The high boiling point of alkylene glycols or oligomers is used to pyrolyze residual salts and to evaporate residual solvents from solution. In addition, alkylene glycol is a structural unit of polyester, and a solution or filter cake can be used directly to produce the polyester. This makes the drying and pneumatic conveying step unnecessary. If the purification plant is not integrated in the polyester plant, this method can be carried out elsewhere. In order not to introduce other components, it is preferable to use heat transfer or heat disturbance under electromagnetic waves. Evaporated residual solvent is removed by suction or other suitable method. The preferred amount of alkylene glycol is the amount needed to polymerize so that the treated solution can be used directly to prepare the polyester. This step may be used in conventional methods to eliminate the drying and pneumatic conveying steps by mixing the final product before drying with alkylene glycol. The treated solution differs from a solution which contains a significant amount of base compound and other solvents and which is degraded upon product recovery which is unsuitable for producing the polyester.

The base extraction solvent used for product recovery, washing, leaching, stripping, thermal disturbance using electromagnetic waves, or pyrolysis and evaporation may or may not be the same. The amount of base extraction solvent used is not particularly limited, and 0.5 to 1000 moles per mole of carboxyl functional groups are preferred.

Pyrolysis and evaporation with alkylene glycol is not used to remove residual base compounds, or if necessary, the purified product is dried by blowing an inert gas to remove residual solvent as in conventional methods. Alternatively, drying is carried out using electromagnetic waves as described above.

The purification process by solvent extraction can be carried out under atmospheric pressure of a reducing gas, such as inert gas such as air, steam, nitrogen, argon, or helium, hydrogen or lower hydrocarbon gas. This method can be used for batch, semi-batch, or continuous processes.

Recycling improves the efficiency of product recovery and solvent use. For example, the filtrate can be recycled or used to the previous step for washing or leaching to reduce solvent requirements and improve product recovery. The recycle filtrate can be treated or untreated. The filtrate can be treated by any suitable method such as distillation, filtration, centrifugation, sedimentation, evaporation, cooling, further addition of solvent, or any combination of these methods. Recycling methods to improve efficiency are already well known and are not limited to any particular one.

Impurities in the disclosed methods are unexpectedly surprisingly not detected by current standard HPLC methods. Compared to the product purity in the prior art, the difference is about 2 times. The color of the sample intentionally fired meets the current standard, which means that the base compound has been removed to a satisfactory level. PTAs with less impurities offer many possible advantages: greater molecular weight in the polymerization, stronger and finer fibers, less oxygen permeation through the bottle, faster spinning rates for fiber production, and many more benefits to be discovered. field.

Description of Preferred Methods for Producing High Purity Aromatic Polycarboxylic Acids or Derivatives

The new combination of the purification methods discussed above and the prior art oxidation and solvent and catalyst recovery provide a method with significantly lower capital and production costs. This method can be applied to all aromatic polycarboxylic acids produced by oxidation of the corresponding alkyl group with molecular oxygen. Examples of such acids are PTA, IPA, TMA, 2,6-DNA, 2,7-DNA, and other compounds. Since PTA is the most common, we will use it as an example.

The combination method reduces two sets of process steps to one set to produce high purity aromatic polycarboxylic acid. This is accomplished by utilizing the following features and advantages found in the disclosed purification methods.

1) In addition to CTA, the purification process can directly select reactor effluent as feed without separating CTA. The effluent contains a catalyst (including catalyst promoter) and other substances that can be separated from the product in the purification process, such as acetic acid. This reduces the two sets of process steps in a typical process to one set, significantly reducing capital and production costs.

2) The prior art should take into account factors such as viscosity, particle size, product recovery, and inclusion of impurities which can be avoided by the proposed method of crystallization by direct extraction from salt. Base extraction solvents can also be used to adjust the viscosity of the slurry for separation and transport.

3) This purification method can remove more impurities than the hydrogenation unit in a conventional process. This allows the oxidation reactor to operate at more economical conditions, for example, with significantly lower hydrocarbon combustion and catalyst consumption.

4) The purification method does not require a crystallizer for crystallization.

5) Purification methods can use pyrolysis and evaporation with alkylene glycol to eliminate the dry and pneumatic conveying steps.

6) Purification methods use physical separation rather than chemical reactions to remove impurities, which requires less capital and production costs for purification.

7) Purification methods result in significantly higher product purity than conventional processes. This offers many advantages as described above.

The present invention has these synergistic and non-obvious features to provide an unproposed combination method that requires significantly less capital and production costs. This combination method involves oxidation; Dissolution of crude acid; Removal of impurities and base compounds from the purified salts; Removal of residual base compounds while recovering purified acid from salts; And recovery of solvent and catalyst. These process steps are described as follows.

Oxidation

This step oxidizes the corresponding alkyl groups with molecular oxygen to produce aromatic polycarboxylic acids. Oxidation of aromatic polycarboxylic acids has been extensively studied over the last 50 years, and the present invention can use any conventional technique known previously, and is not limited to any particular one.

The method developed by Mid-Century is a widely selected oxidation method, comprising acetic acid as a solvent to aid slurry mixing and circulation; Heavy metals as catalysts such as cobalt and manganese; And bromine-containing compounds as promoters. The reaction conditions are generally in the range of 175 to 230 ° C and 1500 to 3000 Pa.

The feed comprises dissolving a catalyst, a reactor solvent, or a salt formed by a crude acid and a base compound in a solvent for dissolution; Removing impurities and base compounds from the purified salts; And a recycle containing the intermediate product from the steps of recovering the solvent and the catalyst.

Dissolution of Crude Acid or Derivative

Dissolution of crude aromatic polycarboxylic acids or derivatives in base compounds has already been described. As discussed above, the purification process may select reactor effluent or CTA as a crude acid in a conventional process. Thus, there are many alternatives between the two extreme methods for preparing crude acid. For example, when a slurry from a flashed reactor effluent is used as crude acid, the reactor solvent and catalyst will be present in the filtrate containing impurities which can be subsequently recovered in the solvent and catalyst recovery steps. Alternatively, in previously known prior art such as flashing, evaporation, heating / cooling, crystallization, filtration, centrifuge, distillation, fractionation column, fluid hydrocyclone, cyclone separator, sedimentation, mother liquor with water, membrane The reactor solvent and catalyst are separated from the crude acid by the taught method, or from any intermediate step of producing CTA in a conventional process. The separated mother liquor is recycled to the reactor or sent to the solvent and catalyst recovery stage. The present invention is not limited to any particular process for separating reactor effluents. However, one of the preferred separation processes is to evaporate most of the mother liquor from the flashed reactor effluent and to recycle a small portion of the mother liquor containing the catalyst separated from the crude acid. Evaporation may or may not be performed under electromagnetic waves. This approach recovers most of the crude acid from the reactor effluent without using crystallization.

Other sources of crude acid can be obtained from recycled treated or untreated filtrates or from recovering solvents and catalysts.

Removal of impurities and excess base compounds

Removal of impurities has been described above. As discussed above, crystallization by controlling the composition with cooling can reduce the number of crystallizers, and crystallizing by direct extraction from salt eliminates the crystallization device for crystallization.

The filtrate can be recycled to another stage, treated or untreated, or sent to a solvent and catalyst recovery stage. Some impurities must be removed from this step to avoid accumulation, which can be achieved by any suitable method. One example is the evaporation of the solvent from selected filtrates containing a significant amount of impurities, followed by a product recovery step to recycle the sediment directly or to convert the salts to impurities prior to recycling.

Removal of Residual Base Compounds During Preparation of Final Product

This step has been described above. When pyrolysis and evaporation with alkylene glycols are used to remove residual base compounds, the drying and pneumatic conveying steps of the prior art processes become unnecessary.

Particle sizes obtained from acid substitutions are generally finer than those obtained from conventional PTA processes, but more uniform. If alkylene glycol is used to remove trace base compounds, the mixture can be used directly to prepare PET. However, if necessary, the apparent density of the PTA can be adjusted by re-dissolution and recrystallization. This can be accomplished by many methods used in existing manufacturing plants. Recrystallized PTA not only resembles the apparent density of current commercial PTAs, but also is further purified to contain less impurities.

Solvent and Catalyst Recovery

In addition to the use of previously known techniques for recovering the reactor solvent, water, and catalyst, this step may comprise a base compound; Base extraction solvents; Acid substituted solvents when acid substituted solvents are used to recover the product and are different from the reactor solvent; And when a solvent for dissolution is used and is different from water, solvent for dissolution is also recovered. In addition, residual impurities and products are likely to emerge from the direct recycle of the filtrate from the purification step.

Not all components need to be recovered in pure form. Some may be recovered as a mixture. For example, in the step of dissolving the crude acid, the base compound and the solvent for dissolution can be used as a mixture. In addition, if the mixture contains some acid substitution solvent, this does not significantly affect the efficiency of the purification.

Among the solvents, some may form eutectic mixtures. If acid substitution is used to recover the product, the base compound and acid solvent may form an electrolyte. However, methods for separating such components are already present, such as, for example, distillation, filtration, centrifugation, sedimentation, evaporation, pyrolysis, cooling, membranes, strong base substitution, strong acid substitution, addition of other components to decompose the eutectic mixture, and the like. It is well known. In addition, the present invention may use electromagnetic waves for evaporation, distillation, and pyrolysis.

conclusion

Thus, the purification process of the present invention provides a method of removing impurities from crude aromatic polycarboxylic acids or derivatives, as well as removing base compounds used in purification, which if not removed, contaminate the final product. The present invention solves unresolved or unknown problems and makes purification by solvent extraction practical.

Purification methods reduce or eliminate the total number of crystallizers for crystallization. Using alkylene glycols to remove residual base compounds eliminates the drying and pneumatic conveying steps required in the prior art.

Compared to the purity in the prior art, the improvement in product purity is about 2 times for impurities not detected by standard HPLC measurements. This offers many possible advantages, such as the production of new, stronger and thinner fibers, increased PET fiber production at higher spinning rates, the application of PET bottles to new applications by decreasing oxygen permeability, and more advantages to be revealed. .

Using some of the features and advantages found in the purification process, combining this purification method with the prior art in oxidation and solvent and catalyst recovery reduces two sets of process steps to one set in conventional processes. This non-combined method of combination significantly reduces the capital and production costs for producing high purity aromatic polycarboxylic acids.

In addition to aromatic polycarboxylic acids, purification methods can be used to purify organic acids or derivatives having similar physical and chemical properties. Derivatives include different numbers of acid functional groups; Acid groups substituted by other functional groups; Acid functional groups at different positions; Or may have the same acid group at the same position but substituted with another functional group such as methyl or the like.

Accordingly, the scope of the invention should not be determined by the illustrated embodiments, but rather by the appended claims and their legal equivalents. The invention is further illustrated by the following examples.

Reference Example

A sample of crude terephthalic acid (CTA) with impurity levels shown in Table 1 obtained from the PTA manufacturer was used for the experiment:

4-CBA Benzoic acid p-toluic acid PTA (ppmw) 2436 1097 515

Where ppmw means weight ppm.

Comparative Example 1

CTA having a composition similar to that in Table 1 was purified by conventional hydrogenation purification methods discussed in the prior art to give PTA products with impurities at the levels shown in Table 2.

4-CBA Benzoic acid p-toluic acid PTA (ppmw) 15 Not detected 141

Similarly, PTA products from other sources contained the levels of impurities shown in Table 3.

4-CBA Benzoic acid p-toluic acid PTA (ppmw) 25 52 150

Impurity levels in the purified product usually represent commercially available polymer grade terephthalic acid.

Comparative Example 2 (removal of non-base compound impurities)

The 150 g sample of CTA described in Table 1 was mixed with 198 g of morpholine and 180 g of water. The solution was warmed up to 100 ° C. to completely dissolve the CTA and then cooled to room temperature to precipitate. The slurry was filtered off from the mother liquor and the filter cake was subsequently washed with morpholine to give 196 g of a wet cake. The recovered solid was then mixed with 84 g of water and 22 g of morpholine. The solution temperature was then raised to 110 ° C. to evaporate concentrate 57c.c., and the solution was then cooled to room temperature to precipitate. The filter cake was subsequently washed with morpholine to yield 145 g of purified salt. The salt was then mixed with 235 g of acetic acid and 14 g of water to precipitate PTA. The filter cake was washed with about 600 g of water. The wet cake was then dried in an oven at about 275 ° C. for 4 hours to give 40 g of dry purified terephthalic acid. Analysis by HPLC shows impurities in Table 4. However, the measured B-value representing the color of the cake was 6.5, more than four times the standard value of 1.6. This indicates that PTA contained a significant amount of morpholine.

4-CBA Benzoic acid p-toluic acid PTA (ppmw) Not detected Not detected Not detected

Comparative Example 3 (Product Precipitation by Direct Addition of Acetic Acid)

The 3 g sample of CTA described in Table 1 was completely dissolved in a solution containing 5.010 g of triethylamine and 9.047 g of methanol at room temperature. Thereafter, 7.570 g of acetic acid was added to precipitate the crystals, which was then filtered and dried to yield 2.179 g of terephthalic acid. Analysis by HPLC showed that the acid contained impurities as shown in Table 5.

4-CBA Benzoic acid p-toluic acid PTA (ppmw) 2471 844 471

Example 1 (crystallization by direct extraction from the precipitate with leaching)

The 40 g sample of CTA described in Table 1 was mixed with 52 g of morpholine and 48 g of water. The solution was heated to 110 ° C. to dissolve the CTA and evaporate the concentrate 29c.c., which was then cooled to room temperature and precipitated. The filter cake was subsequently washed and leached with methanol to afford 55 g of a wet cake. Thereafter, the wet cake was mixed with 30 g of methanol, and then 85 g of acetic acid was added to the solution to precipitate terephthalic acid. The wet cake was washed with 35 g of methanol and leached three times with 35 g of methanol to give 31.5 g of a wet cake. The wet cake was then dried in an oven at 250 ° C. for 4 hours to allow 24 g of the dried cake. The B-value of the cake was still 2.73 higher than the standard, and HPLC analysis showed that the PTA contained the impurities of Table 6.

4-CBA Benzoic acid p-toluic acid PTA (ppmw) 20.8 Not detected Not detected

Example 2 (crystallization by resalting with evaporation and pyrolysis)

The 925 g sample of CTA described in Table 1 was dissolved in 1103 g of morpholine and 1205 g of water. The solution was heated to 110 ° C. and evaporated to a concentrate of about 404 c.c. and stopped before rapid crystallization. The solution was cooled to room temperature for 4 hours to precipitate crystals. 250 g of ethanol was added to dilute the slurry, and then the filter cake was washed and leached with about 750 g of ethanol to give 1455 g of salt. 1005 g of salt was dissolved in 465 g of water. The solution was heated to 109 ° C. and the concentrate about 280c.c. evaporated and then rapidly crystallized. The salt was leached with 650 g of ethanol and the slurry was filtered and washed with 250 g of ethanol to give 702 g of purified salt. 35 g of salt was dissolved in 40 g of water and 40 g of ethanol, and then 60 g of acetic acid was added to the solution to precipitate the product crystals. The filter cake was washed and leached with about 200 g of water to give 27.5 g of wet cake, which was then mixed with 130 g of EG. The solution was heated to about 150-165 ° C. under normal pressure until the brown liquid was no longer concentrated and separated from the solution. Thereafter, the thermal solution was immediately filtered, washed with about 300 g of water and leached to give 15.4 g of a wet cake. Thereafter, the cake was dried at a medium power level for 20 minutes with an adsorbent under the cake in a microwave oven, and then the cake was dried at about 250 ° C. for 4 hours in an oven to give 11.6 g of dry cake. The B-value of the cake was 1.58 which met the standard, and analysis by HPLC showed that the PTA contained the impurities of Table 7.

4-CBA Benzoic acid p-toluic acid PTA (ppmw) Not detected Not detected Not detected

Example 3 (simulating reactor effluent conditions with leach)

The 150 g sample of CTA described in Table 1 was dissolved at room temperature in a solution having a composition similar to the flashed reactor effluent composition. The solution contained 202 g of morpholine, 191 g of water, 29 g of 48% hydrobromic acid, 0.23 g of cobalt acetate tetrahydrate, 0.3 g of magnesium acetate tetrahydrate, and 60 g of acetic acid. The temperature of this solution was raised to 110 ° C. to dissolve CTA and evaporate concentrate 79c.c. The solution was then precipitated by cooling to room temperature and subsequently the filter cake was washed and leached with methanol to yield 278 g of a wet cake. The wet cake was then mixed with 133 g of water, then the solution temperature was raised to 110 ° C. to evaporate concentrate 88c.c., and then the solution was allowed to cool to room temperature to precipitate. The filter cake was washed and leached with methanol to yield 160 g of wet cake. Thereafter, the wet cake was mixed with 160 g of methanol, and 180 g of acetic acid was added to the solution to precipitate terephthalic acid. The wet cake was washed and leached with 500 g of water and leached three times with 35 g of methanol to give 123 g of the wet cake. The wet cake was dried at medium power level for 20 minutes with the adsorbent under the cake in a microwave oven, then the cake was dried at about 250 ° C. for 4 hours in an oven to give 73 g of dry cake. The B-value of the cake was 2.22, all metal contents were below the standard specification, and analysis by HPLC showed that the PTA contained impurities in Table 8.

4-CBA Benzoic acid p-toluic acid PTA (ppmw) Not detected Not detected Not detected

Example 4 (pyrolysis by microwave)

A 10.05 g sample of the purified salt of Example 2 was dissolved in 6 g of water. The solution was heated in a 600 watt microwave oven for 3 minutes and the residual mixture contained about 9.29 g of solids. The solid was then mixed with 6.27 g of water and heated in the oven for 3 minutes to yield 8.82 g of the solid. Thereafter, the solid was mixed in 6.66 g of water and heated for 3 minutes to obtain 8.49 g of the solid. The solid was then mixed with 10.85 g of water and heated in an oven for 4 minutes to give 8.14 g of solid. Thereafter, the solid was mixed in 9.59 g of water and heated in an oven for 3 minutes to obtain 7.82 g of a solid. In each step, the reduction in weight is due to the degraded salts.

Example 5 (crude NDC)

150 g samples of crude 2-6 and 2-7 dimethyl naphthalene dicarboxylate (NDC) were mixed with 161 g of morpholine and 180 g of water. The temperature of this solution was raised to 110 ° C. and the solvent was evaporated to 86c.c. Thereafter, the solution was cooled to precipitate crystals, and then filtered to separate from the mother liquor. The filter cake was subsequently washed with a 10% by weight water mixture in morpholine to yield 186 g of wet cake. The wet cake was then redissolved in 72 g of water and 18 g of morpholine, then the solution was heated to evaporate concentrate 35c.c. The solution was cooled to precipitate, filtered and washed with a solvent mixture containing 10% by weight water in morpholine to give 158 g of a wet cake. Thereafter, a mixture of 16 g of water and 158 g of acetic acid was added to the purified salt to precipitate the product acid. This was then filtered, washed with water and dried to give 85 g of purified acid. Crude NDC was purified to 99.993%. The analysis of crude acid by capillary electrophoresis revealed that (8.86, 3.824), (8.92, 2.891), (8.92, 5.518), (9.06, 10.038), (9.18, 36.226), (9.45, 18.536), (9.52, 13.944), (9.57, 8.298), (11.87,0.106) and (11.99, 0.598). Electrophoresis of the purified acid showed two peaks at (9.49, 99.993) and (9.55, 0.007) over time and area.

Example 6 Dissolution by Microwave and Crystallization in Ethanol Using NMP

The 12.5 g sample of CTA described in Table 1 was mixed with 60 g of NMP preheated in a 600 watt-microwave oven for 30 seconds. A low power level oven was used to completely dissolve the CTA for 3.5 minutes. 13 g of ethanol was added to the solution during crystallization by cooling the solution in an ice bath for about 60 minutes. The salt was then filtered and washed with a solvent mixed with 50% ethanol and 50% NMP to give 26.2 g of salt. The salt was mixed with 31 g of NMP and redissolved for 2.7 minutes using low power levels in a microwave oven. 15 g of ethanol was added to the solution during crystallization by cooling the solution in an ice bath for about 60 minutes. The salt was then filtered and washed with a solvent mixed with 50% ethanol and 50% NMP to give 16 g of purified salt. 3 g of purified salt was placed between the stacks of filter papers immersed in water. The microwave oven was set at a low power level to pyrolyze the purified salt until there was no weight variation to yield 1.2 g of PTA. Table 9 shows the impurities analyzed by HPLC.

4-CBA Benzoic acid p-toluic acid PTA (ppmw) Not detected Not detected Not detected

The foregoing examples are provided to facilitate understanding of the methods of the invention and are not intended to limit the scope of the invention to specific compounds or process steps. The scope of the invention is defined by the claims.

Claims (38)

Dissolving the crude organic acid or derivative thereof in the base compound; Removing impurities; And A method of making a purified organic acid, or derivative thereof, comprising removing the residual base compound while recovering the purified organic acid or derivative thereof. The method of claim 1, wherein the crude organic acid or derivative is dissolved by thermal disturbance under electromagnetic waves. The method of claim 1 wherein the crude organic acid or derivative is a crude aromatic polycarboxylic acid. The method of claim 1 wherein the crude organic acid or derivative is dissolved in a base compound and a solvent for dissolution. The method of claim 1 wherein excess base compound is removed during removal of impurities. Dissolving the salt formed by the crude organic acid or derivative thereof and a base compound; Pretreatment, crystallization by cooling, crystallization by control of composition with cooling, crystallization of salts in the presence of base extraction solvent, precipitation of product in the presence of base extraction solvent, crystallization by direct extraction from salt, crystallization by resalting treatment, Removing impurities and excess base compounds from salts of crude organic acids or derivatives using one or more processes selected from the group consisting of salt base substitution, washing with base extraction solvent, and leaching with base extraction solvent; And A process for preparing a purified organic acid or derivative thereof, comprising removing the residual base compound while recovering the purified organic acid or derivative from the salt. The method of claim 6 wherein the crude organic acid or derivative is a crude aromatic polycarboxylic acid. 8. The process of claim 7, wherein the crude aromatic polycarboxylic acid is terephthalic acid or isophthalic acid. 8. The method of claim 7, wherein the crude aromatic polycarboxylic acid is a mixture of 2,6-naphthalene dicarboxylic acid, 2,7-naphthalene dicarboxylic acid, or naphthalene dicarboxylic acid. 7. A method according to claim 6, wherein the salt is dissolved by thermal disturbance under electromagnetic waves. 7. The method of claim 6, wherein the base compound is an oxygen containing base compound. The method of claim 6 wherein the salt is dissolved in a base compound and a solvent for dissolution. The method of claim 6 wherein the base compound is morpholine and the salt is dissolved in water. The method of claim 6 wherein the base compound is trimethylamine, triethylamine, or triethanolamine and the salt is dissolved in water or alcohol. 7. The method of claim 6, wherein the base compound is an amide compound. The method of claim 15 wherein the amide compound is N-methyl-pyrrolidone. 7. The method according to claim 6, wherein the base compound is an amide compound and the salt is dissolved in a solvent for dissolution. 7. The method of claim 6 wherein the impurities are removed with a base extraction solvent and the base extraction solvent comprises water, methanol, ethanol, alkylene glycol, acetone, tetrahydrofuran, or tetrahydropyran. 8. The process of claim 7, wherein the step of recovering the purified organic acid from the salt is by addition of an acid substitution solvent in the presence of a base extraction solvent. 8. The method of claim 7, wherein the step of recovering the purified organic acid from the salt is by pyrolysis under electromagnetic waves. 8. The method of claim 7, wherein the residual base compound is removed from the organic acid purified by one or more processes selected from the group consisting of leaching, stripping, thermal disturbance by electromagnetic waves, and pyrolysis and evaporation. Dissolving the salt formed by the crude organic acid or derivative thereof and a base compound; Crystallization by direct extraction from salt, crystallization of salt in the presence of base extraction solvent, precipitation of product in the presence of base extraction solvent, crystallization by resalting with base extraction solvent, salt base substitution, and leaching with base extraction solvent A method of making a purified organic acid or derivative thereof, comprising the step of removing impurities from salt using one or more processes selected from the group. The method of claim 22 wherein the crude organic acid or derivative is a crude aromatic polycarboxylic acid. 23. The method of claim 22, wherein the salt is dissolved by thermal disturbance under electromagnetic waves. 23. The method of claim 22 wherein the salt is dissolved in a solvent for dissolution. 23. The method of claim 22, wherein the base compound is an oxygen containing base compound. The method of claim 22, further comprising recovering the purified organic acid or derivative from the salt by acid substitution, pyrolysis or electrolysis. 28. The method of claim 27, wherein the remaining base compound is removed using at least one process selected from the group consisting of leaching, stripping, thermal disturbance by electromagnetic waves, and pyrolysis and evaporation during recovery of the purified organic acid or derivative from the salt. Method further comprising a. A process for preparing a purified solution composed of an aromatic polycarboxylic acid or a derivative thereof and a monomer or oligomer for producing a polyester, Mixing an aromatic polycarboxylic acid or derivative containing a residual solvent with a monomer or oligomer; And Increasing the temperature to 50 to 350 ° C. to remove residual solvent. 30. The method of claim 29, wherein the monomer is alkylene glycol. 30. The method of claim 29, wherein removing residual solvent is performed under electromagnetic waves. Preparing a crude aromatic polycarboxylic acid or derivative by oxidizing an alkyl group on an aromatic compound with molecular oxygen in the presence of a catalyst and a solvent; Dissolving the salt formed by the crude aromatic polycarboxylic acid or derivative and the base compound; Removing impurities from salts of crude aromatic polycarboxylic acids or derivatives; While recovering the purified aromatic polycarboxylic acid or derivative from the salt, removing the residual base compound; And Recovering the solvent and the catalyst, to produce a purified aromatic polycarboxylic acid or derivative thereof. 33. The method of claim 32, wherein the salt is dissolved in a base compound and a solvent for dissolution. 33. The process of claim 32, wherein the crude aromatic polycarboxylic acid or derivative is prepared by flashing and evaporation. Dissolving the crude organic acid or derivative containing impurities in the base compound by thermal disturbance under electromagnetic waves; And A method for preparing a purified organic acid or derivative thereof, comprising removing impurities. 36. The process of claim 35 wherein the crude organic acid or derivative is dissolved in a base compound and a solvent for dissolution. 36. The method of claim 35, further comprising recovering the purified organic acid or derivative. 37. The method of claim 36, wherein the residual base compound is removed during recovery of the purified organic acid or derivative.