Purification of carboxylic acids through complexing with selective solvents

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of purifying carboxylic acid from a mixture which contains one or more carboxylic acids selected from a group consisting of terephthalic acid, isophthalic acid, orthophthalic acid and their mixtures, and also contains one or more substances selected from a group consisting of carboxybenzaldehyde, toluic acid and xylene. The method involves: bringing the mixture into contact with a selective solvent for crystallisation at temperature and in a period of time sufficient for formation of a suspension of a complex salt of carboxylic acid with the selective solvent for crystallisation without complete dissolution of the complex salt of carboxylic acid; extraction of the complex salt and decomposition of the complex salt in the selective solvent for crystallisation in order to obtain free carboxylic acid. The mixture containing unpurified carboxylic acid is brought into contact with the selective solvent for crystallisation in order to form a suspension of a complex salt of carboxylic acid with the selective solvent for crystallisation. The complex salt is extracted and, if desired, processed for extraction of free carboxylic acid.

EFFECT: methods are especially suitable for purifying aromatic dibasic carboxylic acids such as terephthalic acid, and also enables reduction of the degree of contamination of phthalic acids with carboxybenzaldehyde isomers.

22 cl, 3 tbl, 1 dwg, 3 ex

STATEMENT of GOVERNMENT INTEREST

This invention was made with government support under grant DOE Grant N DE-FC36-011D14085. Essentially, the government has certain rights in this invention.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is not temporary in respect of the provisional application N 60/561000 dated April 9, 2004, the full contents of which are incorporated herein by reference.

The technical FIELD TO WHICH the INVENTION RELATES.

The invention relates to the purification of carboxylic acids. More specifically, the disclosed method and equipment for purification of aromatic dicarboxylic acids by complex formation and crystallization with a selective solvent for crystallization.

The prior art TO WHICH the INVENTION RELATES.

Purified carboxylic acid and, especially, aromatic dicarboxylic acids are important from the point of view of industry. For example, purified terephthalic acid (TPA) is a starting material for the formation of polyester resins, which, in turn, used for the manufacture of many commercial products have a number of useful properties. Traditionally purified terephthalic acid is obtained from the "raw" terephthalic acid through a number of cleaning methods, often with the help of the cat is of catalysts. Many of the currently available methods of purification of crude terephthalic acid are not fully satisfactory either from an engineering or economic point of view. In addition, the purity of terephthalic acid is an important determining factor in the formation of polyester resin.

Many of the problems existing and previous systems for obtaining purified terephthalic acid derived from the difficulties operating in the economic mode of the reaction system to obtain the crude terephthalic acid with good outputs. These problems are exacerbated by difficulties in the purification of crude terephthalic acid to remove impurities and unwanted components in order to obtain purified terephthalic acid suitable as starting substances for the production of polyester. Related problems of prior systems include high capital investment required for plants for the production of TPA, the rigidity of the working conditions of the preceding processes as to obtain the crude terephthalic acid and its treatment, and the need to possess, to a certain extent, the ability to deal with a catalytic systems and solvents for the reaction, as well as by-products of the reaction so as to minimize problems from easiest to the environment, and to control the loss of substance.

One important factor in obtaining purified terephthalic acid is the formation of crystals having a size and shape that contributes to their good characteristics in respect of the treatment, the ability to clean and filterability during the production of TPA, and also make easier handling and better processability in the production of polyesters.

The US patent No. 2949483 published authors Ham et al. (Ham with co-authors), describes the dissolution of the terephthalic acid in N-methyl-2-pyrrolidinone, then the deposition of ' complex salt containing terephthalic acid and N-methyl-2-vinylpyrrolidone. The solid is washed with water to remove N-methyl-2-vinylpyrrolidone and get purified TPA. Claimed in the patent, the degree of extraction is from about 60% to 95% by weight of the crude terephthalic acid.

The US patent No. 5840968 published authors Lee et al. (With co-authors), describes a method and equipment for purification of crude terephthalic acid from a liquid dispersion containing impurities of unreacted starting substances, solvents, products of side reactions and/or other undesirable substances. The method uses the stage filtration dispersion for the formation of a filter cake of crude terephthalic acid, RA is the creation of the elevated temperature of the filter cake in a selective solvent for crystallization to form a solution, crystallization of the purified terephthalic acid from solution in the solvent for crystallization by lowering the pressure and temperature of the solution and selection zakristallizuetsya purified terephthalic acid from the solution. Selective solvent for crystallization is anhydrous, non-caustic and, significantly, directionspanel with respect to terephthalic acid. Examples of selective solvents for crystallization are N-organic or dimethylacetamide.

The US patent No. 5929274 published authors Lamshing et al. (Lansing with co-authors), describes a method of reducing the content of isomers carboxyanhydride in the crude terephthalic and/or isophthalic acid (IPA). The crude TPA or IPA is dissolved in N-methylindoline and then injected into the reaction with the oxidant, mainly, such as anhydrous hydrogen peroxide, for turning isomer carboxyanhydride (4-CBA, or 3-CBA) in TPA or IPA at moderate temperature and pressure.

The US patent No. 6054610, published with co-authors, describes a method and equipment for production of purified terephthalic acid and optionally isophthalic acid from mixed xylenes. The method consists in the cleaning liquid industrial waste oxidation reactor containing a mixture of terephthalic acid and isophthalic acid, and the e small quantities of 4-carboxyanhydride (4-CBA), 3-carboxyanhydride (3-CBA) and isomers Truelove acid for the production of terephthalic acid and, if desired, purified isophthalic acid within a single process.

The US patent No. 6140534, published with co-authors, describes a method of obtaining isophthalic acid from metaxalona and, especially, purification of crude isophthalic acid (IPA), produced in this way, or from their liquid dispersion also containing unreacted educt, solvents, products of side reactions and/or other undesirable substances. Step of the method, svjazanny with cleaning, involves the following stages (1) filtering the dispersion for the formation of the filter cake from raw IPA, (2) dissolving at an elevated temperature of the filter cake in a selective solvent for crystallization to form a solution, (3) crystallization of purified IPA from solution in the solvent for crystallization by lowering the temperature or pressure of the solution, or lowering both of these parameters, (4) selection zakristallizuetsya purified IPA from solution and (5) reconstitution or soaking the washed cake of purified IPA at elevated temperature to remove residual traces of solvent for crystallization and obtain the desired size and shape of the particles. Selective solvent for crystallization usually represent an N-organic.

The INVENTION

The present invention provides a method and equipment for purification of carboxylic acids from a mixture containing one or more carboxylic acids and possibly other substances. According to a particular method of implementation of the carboxylic acid is a terephthalic acid (TPA) and other substances as raw materials, by-products, contaminants, etc. that are present in industrial liquid waste generated during the production of terephthalic acid. Carboxylic acid cleaned by contact of the mixture with a selective solvent for crystallization at a temperature and for a time effective to form a suspension of the complex salt of carboxylic acid with a selective solvent for crystallization and extraction of the complex salt. The complex salt may be used in this form as it is, or it can be processed further to obtain the free carboxylic acid. To extract the free acid complex salt can be subjected to decomposition in the selective solvent for crystallization at the stage of secondary crystallization and recrystallizing to obtain the free acid.

The present invention also provides a method and equipment for oxidation products of partial oxidation, present is in liquid industrial waste in the production process, terephthalic acid, such as carboxybenzaldehydes. The present invention also provides a method and equipment for the separation of terephthalic acid and isophthalic acid. The present description describes these and other aspects of the invention.

BRIEF DESCRIPTION of DRAWINGS

The drawing is a simplified schematic illustration of the method of the invention.

DETAILED description of the INVENTION

The present invention provides a method of purification of carboxylic acids from a mixture containing one or more carboxylic acids and possibly other substances. The term clean, used here, means the processing mixture comprising one or more carboxylic acid, to obtain a mixture which is enriched in the desired carboxylic acid as compared with other carboxylic acids and/or other substances that were present in the original mixture. The mixture can be solid, liquid or suspension. According to a particular method of implementation of the carboxylic acid is a dicarboxylic acid, for example, terephthalic acid (TPA), and other substances are a source of substance by-products, impurities, etc. that are present in industrial liquid waste generated during the production of terephthalic acid. On the other hand, the carboxylic acid can in order to represent isophthalic acid, orthophthalic acid or other industrially useful carboxylic acids and/or mixtures of these acids.

There are several reaction systems to obtain the crude TPA from a number of starting materials. The present invention can be used, essentially, with any of these reaction systems. The usual reaction system involves the oxidation of paraxylene (p-xylene). Traditional TPA production process requires a relatively high purity p-xylene (99,7+ %) to achieve a suitable quality product at a suitable price. This is because such processes are known to the prior art use hydrogenation as the primary method of purification of crude TPA produced during oxidation process. Although the method is the selective hydrogenation to remove basic impurities, 4-carboxybenzene (4-CBA), by converting it into n-Truelove acid, this method only works with a very small amount of 4-CBA (preferably less than 3000 ppm). Traditional manufacturing processes TPA is not able to separate TPA from its isomers, such as isophthalic acid (IPA) and phthalic acid (PA).

The present invention provides a method and equipment for production of purified TPA and, optionally, isophthalic acid, from mixed xylenes. It is important that according to the invention can about ISAT liquid industrial waste oxidation reactor, containing terephthalic acid and isophthalic acid, and small amounts of 4-carboxyanhydride (4-CBA), 3-carboxyanhydride (3-CBA) and isomers Truelove acid, and other impurities. In the course of carrying out the invention to produce purified terephthalic acid and, if desired, purified isophthalic acid within a single process. These products are suitable for production of fibers, films, plastic bottles and structures on the basis of polyester resins, often reinforced by other materials, such as fiberglass.

According to the method of the invention, the mixture containing the carboxylic acid is in contact with a selective solvent for crystallization. The term selective solvent for crystallization, used here, refers to a solvent capable of forming adducts or complex salts with carboxylic acid. Typical solvents include N,N-dimethylacetamide, N,N-dimethylformamide, N-formylpiperidine, N-alkyl-2-pyrrolidone, N-mercaptoethyl-2-pyrrolidone, N-alkyl-2-cooperalion, N-hydroxyalkyl-2-pyrrolidone, morpholines, carbitol, C₁-C₁₂alcohols, ethers, amines, amides, esters and mixtures of two or more of these solvents. Extremely suitable selective solvent for crystallization is N-organic.

The US patent No. 294948, published ham with co-authors, the full content of which is incorporated here by reference, describes a method of purification of TPA using N-methylpyrrolidone. According to ham terephthalic acid is completely dissolved in N-methyl-2-pyrrolidinone at a temperature in the range from 50°C to 130°C. the Solution is cooled to a temperature in the range from 10°C to 45°C and the precipitated solid. The solid in this case is not terephthalic acid, and represents "a complex salt containing terephthalic acid and N-methyl-2-pyrrolidinone. Ham found that salt contains two mol of N-methyl-2-pyrrolidinone for each mol of terephthalic acid. Solid salt formed at a low temperature, filtered and washed with N-methyl-2-pyrrolidinone to remove adhering impurities. Then the salt is washed with water with a temperature between 10°C and 100°C. As N-methyl-2-pyrrolidinone completely miscible with water at all temperatures, salt is destroyed, as the water washes away the N-methyl-2-pyrrolidinone of salt. The remaining terephthalic acid is filtered and dried. Ham stated that the degree of extraction is from about 60% to 95% by weight of the crude terephthalic acid.

The process of ham is not practical for the purification of TPA for the production of polyesters. Even if TPA reaches the desired purity, sedimentation, op is lackawana, filtration and drying TPA, as described by ham, extremely difficult. The crystals of terephthalic acid formed by these salts, are extremely small, so that the ratio of surface area/volume is too large for effective drying. These small crystals form a solid cake or block during filtration. Once formed a solid cake or block, it is very difficult to process the matter further. Even the reconstitution unit in another solvent is the problem. Because of these shortcomings, this process is not commercially feasible.

The US patent No. 5767311, published with co-authors, the full content of which is incorporated here by reference, describes multitudinis the crystallization process. In the first crystallizer crude terephthalic acid is dissolved in N-methyl-2-pyrrolidinone at a temperature in the range of from 140°to 190°C., then cooled to a temperature in the range from 10°C to 20°C, to form a salt. Salt is filtered and washed with pure N-methyl-2-pyrrolidinone. Then salt pererastayut in N-methyl-2-pyrrolidinone in the mould for the second stage at a temperature in the range of from 140°to 190°C. the Solution is cooled to a temperature in the range from 30°C to 60°C to salt formed again. Salt is washed with pure N-methyl-2-pyrrolidinone at 45°C for replacement of the remaining m the exact solution on the surface and then washed with low-boiling solvent, such as methanol, to the destruction of the salts, and the substitution of N-methyl-2-pyrrolidinone. Purified crystals of terephthalic acid formed as a result of the destruction of salts, are still small, however, when used as a washing liquid low-boiling solvent instead of water, fine particles are easier to dry and easier to extract purified terephthalic acid.

The US patent No. 6054610, published with co-authors, the full content of which is incorporated here by reference, describes additional physical properties of the salt of terephthalic acid - N-methyl-2-pyrrolidinone. For example, Lee showed that salts are shiny, transparent and slightly whitish crystals, which can easily be distinguished from opaque, white crystals of terephthalic acid. On the empirical molar ratio of N-methyl-2-pyrrolidinone/terephthalic acid salt is changed from 2.04 to 3.11 points instead of 2, as proposed by the ham, since the solvent can be captured by the crystal during the formation of salt crystals. Lee also showed that with increasing temperature the salt crystals begin to decompose at approximately 50°C. This means that salt is stable below about 50°C, unstable between 50°C and 60°C and the crystals of terephthalic acid stable above 60°C. based On these observations, the cleaning process has been improved else. According to Whether the crude terephthalic acid is first dissolved in N-methyl-2-pyrrolidinone in the cooling mold in the temperature range from 140°C to 200°C. Then the mold is cooled to a temperature in the range from 30°C to 50°C to achieve adequate removal of impurities using the selective formation of salts. The resulting salt was filtered and washed using pure N-methyl-2-pyrrolidinone. Suspension of salt then pererastayut at a temperature in the range from 140°C to 200°C and served on a number of flash crystallizers for the second stage, where the temperature and the pressure is reduced step by step to the final temperature being in the range from 50°C to 60°C, at which salt should not be formed. Flash crystallizers are used to obtain crystals of appropriate size and shape. Then the crystals of purified terephthalic acid is filtered and washed with pure N-methyl-2-pyrrolidinone and water, and then dried.

The drawback of the method according to Lee, described in the previous paragraph, is that the first stage of crystallization requires that the crude TPA was completely dissolved in the solvent for crystallization at elevated temperature, and the second stage of crystallization includes flash-crystallization. Both these stages give the process a significant energy costs. A feature of the way is westline of the present invention is that it does not require the same high energy costs, since it does not require complete dissolution of the TPA. According to the method of the invention, the mixture containing the carboxylic acid is in contact with a selective solvent for crystallization at a temperature and for a time effective to form a suspension of the complex salt of carboxylic acid with a selective solvent for crystallization. Specialist with this area is understandable the fact that the formation of the suspension means that the complex salt is fully dissolved in the selective solvent for crystallization. According to one method of implementation of a complex salt is formed by heterogeneous complexation, resulting in solid and liquid to give a solid product. The process occurs at lower temperatures and therefore requires much less added externally energy than the previously described processes. For example, the temperature may be any temperature above the melting point of the solvent for crystallization and below the temperature at which the complex salt is destroyed. According to one method of implementation, the temperature may be from about 0 to about 65°C. the Mixture may be contacted with a selective solvent for crystallization during any period of time, dostat knogo, to allow complex salt to be formed. If the kinetics of formation of the complex salt is very fast, instantaneous contact of the mixture with the solvent for crystallization or contact for a few seconds may be sufficient. On the other hand, the mixture may be contacted with the solvent for crystallization over a long period of time, for example, from about 30 seconds to about 24 hours or from about 1 minute to about 5 hours. If the mixture containing the carboxylic acid is a solid or suspension, it may be preferable to process solid or slurry to obtain small particle sizes prior to contact of the mixture with a selective solvent for crystallization. For example, solid or untreated slurry can chop or stir to obtain particles of small size.

According to the method of the invention, the complex salt is extracted, for example, by filtration to obtain a filter cake containing complex salt and the mother solution containing the solvent and possibly excess crude carboxylic acid, the starting materials, impurities, etc. According to one method of implementation of the thus extracted complex salt of carboxylic acid may be used without further lane is processing or with minimal further processing, such as rinsing with a solvent, drying, etc. Some relevance to industry processes, will allow to use as starting material a complex salt of carboxylic acid instead of the free carboxylic acid. For example, if the production process of the polyester has a high tolerance to the solvent used for the purification of TPA, a complex salt TPA can be entered directly in the process of production of polyesters without removing free TPA.

On the other hand, a complex salt can be processed further to extract the free carboxylic acid. For example, a complex salt can be secretariaat during one or more stages of secondary crystallization to obtain the free carboxylic acid. According to the method of the invention, the filter cake containing complex salt, decompose in a selective solvent for crystallization. According to one method of implementation of a complex salt, essentially completely dissolve during this stage, the secondary crystallization (and any subsequent stages of secondary crystallization, if they are present). The temperature of the phase(s) secondary crystallization is usually higher than the temperature of the first stage of crystallization, in order to facilitate complete dissolution of the complex salt. The temperature of stage(is) secondary crystallization can be any temperature, in which soluble complex salt, however, the final temperature should be above the temperature at which decomposes a complex salt in order to obtain the free carboxylic acid. On the other hand, a complex salt can be decomposed without complete dissolution of the complex salt, i.e. by a heterogeneous process, in suspension of the complex salt. According to one method of implementation of the secondary crystallization temperature may be in the range from about 65°to about 300°C. alternatively, the temperature may be in the range from about 65°to about 200°C., Or the temperature may be in the range from about 65°to about 150°C.

Crystallization of the free carboxylic acid at the stage(s) secondary crystallization can be achieved, for example, by lowering the temperature of the suspension or solution and/or reduce the volume of solvent. At lower temperatures it is desirable that the temperature remained above the temperature at which decomposes a complex salt. For example, the temperature can be lowered to a temperature in the range from about 60°to about 185°C. or to a temperature in the range from about 60°to about 100°C. the Amount of solvent can be reduced, for example, by vacuum or by passing a stream of the inert gas, such as nitrogen, over or through the solvent. On the other hand, the free carboxylic acid can be secretariaat by adding a precipitant to the stage(s) of secondary crystallization. Examples of suitable precipitants include water, methanol, ethanol and other alcohols, acids, amines, ethers, and aromatic hydrocarbons.

It may be desirable to provide external power stage(s) of secondary crystallization, for example, by mixing or stirring, in order to obtain a suitable morphology of crystals of the free carboxylic acid. For example, a desirable processability in the production of polyesters requires TPA crystals were strong, had good rheological characteristics and possessed of such size that it can easily achieve their subsequent dissolution. Generally speaking, both strength and good rheological characteristics predstavlyaet the characteristics of the crystals, which are spherical or globular, and not have a rod-like or needle-like shape. The term "globular", as used here will refer to crystals that have good rheological characteristics and durability. The term "globular" does not limit the crystal of a specific aspect ratio and can the t to cover the crystals, which have a spherical, oblong and kartofeleochistkoy form, in contrast to the needle-like or rod-like form.

To obtain a filter cake containing free carboxylic acid, a free carboxylic acid, zakristallizuetsya during phase(s) secondary crystallization, can be collected, for example, by filtration. For example, if the carboxylic acid is a TPA, the filter cake obtained in the stage(s) of secondary crystallization, contains purified TPA. This filter cake can be extracted at this stage or rinse/be recrystallized from water or other solvent, as described below. From this moment purified TPA easy to handle thanks to an appropriate morphology of the crystals obtained at the stage(s) secondary crystallization.

According to an alternative method of performing the carboxylic acid is a mixture of terephthalic acid and one or more other acids, such as isophthalic acid. The method of the invention includes a process of separating terephthalic acid from isophthalic acid and/or other carboxylic acids. The process of separating terephthalic acid and isophthalic acid is described in US patent N 6054610, published with co-authors, the full content of which is incorporated here by reference. Briefly, tadia(and) secondary crystallization further divided into early stage, where TPA is selectively crystallized and recovered, and isophthalic acid and/or other acid is crystallized from the remaining depleted TPA solution during one or more subsequent(their) stages(s) of crystallization. According to an alternative way of making the mother liquor, which is formed by the extraction of the complex salt as described above, contains terephthalic acid and isophthalic acid. According to one method of implementation of the terephthalic acid can be precipitated from the mother liquor to obtain depleted terephthalic acid stream and then depleted of terephthalic acid stream can be precipitated isophthalic acid.

The filter cake containing free carboxylic acid obtained in stage(s) of secondary crystallization, it can be washed with a suitable solvent to remove any adhering solvent for crystallization and to facilitate drying of solvent. Suitable solvents for washing are water, methanol, ethanol and other alcohols, acids, amines, ethers, and aromatic hydrocarbons. Extremely suitable solvent for rinsing is water. Rinsing may be briefly washing the free acid solvent for rinsing, soaking the free acid or is even complete dissolution of the free acid in the solvent for rinsing and crystallization of the free acid from it.

Traditional TPA production process requires a relatively high purity p-xylene (99,7+%) due to the fact that these processes typically use hydrogenation as the primary method of purification of the crude TPA. Although the method of hydrogenation is very selective for removal of the impurities, 4-carboxybenzene (4-CBA), through its conversion into p-Truelove acid, the method only works with a very small amount of 4-CBA (preferably less than 3000 ppm). The method of implementation of the present invention provides a method of purification of liquid industrial waste oxidation reactor containing small additions of 4-carboxyanhydride (4-CBA), 3-carboxyanhydride (3-CBA) and isomers Truelove acid, by including the stage of oxidation of the CBA in the process stream. According to the method of implementation of the oxidizing agent added to the stock solution or part of the mother liquor obtained(oops) by filtration of liquid industrial waste resulting from the crystallization of the complex salt, which(th) usually contains a number of CBA. Oxidation step allows you to oxidize part of this CBA to dicarboxylic acid and returning the mother liquor back to the stage crystallization of a complex salt, thereby increasing the total efficiency of the process. It may be desirable about the regulation of the concentration CBA oxidized in the mother solution, for example, by purging part of the mother liquor and returning back part of the stock solution so that the concentration of CBA in the remaining fallopian solution remains within the desired concentration range. According to the implementation method for the concentration of impurities is possible to drive away the pure solvent from the mother liquor. Optionally, impurities in the concentrated mother solution can be precipitated and return back to the first mold. According to the method of the invention, the range of concentrations of the CBA in the concentrated mother solution support in the range of between about 100 ppm and about 50%, preferably between about 1 and about 10% and most preferably about 5%.

Examples of suitable oxidants include air, enriched air, pure oxygen, hydrogen peroxide, aqueous solution of hydrogen peroxide, hydrogen peroxide in an organic liquid, ozone, carbon tetrachloride, trichloroacetaldehyde, hexamine, acetone, cyclohexanone, benzophenone, cinnamic aldehyde, dimethyl sulfoxide, sulfide, chiral oxidants, glyoxal, organic peroxyacids, such as nagarajuna acid, peracetic acid, natantia acid, nodropina acid, nadalina acid, and naftalina acid. According to one method of implementation of pH on the stage of the R CBA is from about -2 to about 6, preferably from about -1 to about 4, and more preferably from -1 to approximately 2.1. The pH during the oxidation process CBA can be adjusted by adding organic or inorganic acids. Examples of suitable acids include chromic acid, hydrofluoric acid, adnovate acid, hydrochloric acid, sulfuric acid, nitric acid, selenic acid, picric acid, trinitrophenol (2,4,6-) acid, naphtalenesulfonic acid, benzosulfimide acid, trichloroacetic acid, oxalic acid, dichloracetic acid, trihydroxy (2,4,6-) benzoic acid, cyclopropane-1:1-dicarbonyl acid, acetic acid, maleic acid, dihydroxypregna acid, dihydroxybenzoic acid, dichloracetic acid, 2,4-pyridylcarbonyl acid, o-nitrobenzoic acid, γ-cyanomelana acid, cyanopropionic acid, zanoxolo acid, o-aminobenzenesulfonic acid, quinolinic acid, bromoxynil acid, dinicotinate acid, α-chloropropionic acid, malonic Kyoto, bramantino acid, Chloroacetic acid, o-identify acid, α-Harmelen acid, o-phthalic acid, fermenting acid, o-chlorbenzol acid, p-cyanogenesis acid, dihydroxybenzoic (2,2-) acid, formic acid, dihydroxybenzoic (2,5-) acid, o-guide is oxybenzoic acid, on-cyanogenesis acid, and α-tartaric acid.

The method of implementation of the present invention provides a processing device for implementing the process described above. A simple schematic of this setup is shown in the drawing. It should be understood that, in reality, piping design, when the threads, and that, if not stated, the threads are implied when mention substances. Moreover, under regulating flow valves regulating the temperature of the devices, pumps, compressors and the like understand the collected and working in normal relation with respect to the main parts of the equipment shown on the drawings and discussed further in this document with reference to a continuously working process according to this invention. All these valves, instruments, pumps and compressors, and heat exchangers, accumulators, capacitors and the like are included in the term "accessory". Providing, as necessary, such auxiliary equipment in the context of the present invention is quite accessible to the specialist in this field.

In respect of the drawing, the mixture containing the crude carboxylic acid, is fed into the tank 1, thread 2, and thread 3 serves a selective solvent for crystallization. Re ervoir 1 may be any suitable reservoir, known in this field. Tank 1 preferably includes a portion for contacting a mixture containing carboxylic acid with a selective solvent for crystallization to form a suspension of the complex salt and is designed for the separation of complex salt from the mother liquor. On the other hand, these two actions can be performed using equipment consisting of many devices. The complex salt is transferred to the reservoir 4 via stream 5, and the mother liquor is transferred to the tank 6 via stream 7. The complex salt is rinsed in the tank 4 rich selective solvent for crystallization, served with a thread 8, and/or clean a selective solvent for crystallization, served with a thread 9. In the depicted implementation method of the pure solvent serves as a reusable solvent from the reservoir 6. On the other hand, the solvent can be added from an external source, such as conforming solvent.

The complex salt is transferred into the tank 10 through stream 11, where it is dissolved in a selective solvent for crystallization. Selective solvent for crystallization, already containing complex salt and, if desired, other solvents can be submitted via stream 12. Pure selective solvent DL the crystallization served with a thread 13. In the depicted implementation method of the pure solvent serves as a reusable solvent from the reservoir 6. On the other hand, the solvent can be added from an external source, for example, as a standard solvent. The temperature of the contents of the tank 10 is supported such that the complex salt as a whole, in essence, decomposes or dissolves. According to one method of implementation, the temperature of the contents of the tank 10 may be from about 65°to about 300°C. To facilitate crystallization of the free carboxylic acid can reduce the temperature of the tank 10 and/or can reduce the amount present in the tank 10 solvent or you can add the precipitator into the tank 10. For example, the amount of solvent can be reduced by passing over the surface of the solution or through the solution of a current of inert gas, for example, N₂. Similarly, you can reduce the temperature, but it is preferable that the temperature remained above the temperature at which decomposes a complex salt. For example, the temperature can be reduced to a temperature in the range of from about 60°C. to 100°C. According to one method of implementation to the tank 10 bring energy, for example, by mixing or stirring. Preferably, the energy was such that the resulting crystal is free carboxylic acid was globular, i.e. have the desired rheological properties and technological characteristics. The tank 10 may be any suitable reservoir, known in the field, and, preferably, provides a means for dissolving the complex salt in a solvent, mixing the solution, in order to provide adequate energy to obtain the desired size and shape of the crystals, extraction of solid crystals of free acid and, if desired, the supply of additional solvents or precipitants. All of these actions can be performed using a single device processing plant or processing plant, consisting of many devices. The drawing depicts the installation is equipped with one storage tank 10 to the secondary crystallization, however, an alternative method of implementation is an installation equipped with many devices for the secondary crystallization.

Selective solvent for crystallization is recycled back into the vessel 1 for the initial crystallization using a stream 15 or, if desired, return back to the vessel 4 for the first rinsing, or, if desired, it can be directed into the reservoir 6 to extract the solvent. Extracted free acid is transferred into the tank 16 where it is rinsed one or more rinsing solvent, p is given by the thread 17. Depicts a method of performing 17 shows the flow supplied from an external source, but the solvent can serve as a reusable solvent from the reservoir 6. The free carboxylic acid can be rinsed by brief contact with a rinsing solvent, through prolonged or soaking in the rinsing solvent, or by dissolving the free acid in the rinsing solvent and crystallization of the free acid. The free acid obtained in stage rinsing, leaves the process via stream 18. Rinsing solvent from the reservoir 16 can, if desired, to extract in the tank 6 or reuse in the tank 1, or, if desired, reused in the tank 4.

The mother liquor from the tank 1 is transferred to the tank 6 via stream 7, and a selective solvent for crystallization from the tank 4 is transferred to the tank 6 via stream 19. For this reason, the contents of the tank 6 contains a selective solvent for crystallization, and probably one or more of the crude free acid starting material, the products of partial oxidation and by-products of the process of formation of acid, and possibly other impurities. In the method of the invention, use is used for the purification of TPA, obtained by oxidation of p-xylene (or mixed xylenes), the primary products of partial oxidation are 4-carboxybenzene (4-CBA), 3-carboxybenzene (3-CBA, derived from m-xylene, isomers Truelove acid, and 4-CBA is apparently the main one. In this way the implementation of the concentration of the product of partial oxidation can be adjusted by changing the amount of pure solvent extracted from the reservoir 6 (as extract a greater amount of clean solvent, more impurities are concentrated in the concentrated mother solution). Taking into account the material balance, a certain amount of the concentrated mother liquor from the tank 6 can be removed with cleansing stream 20. Remaining concentrated mother liquor is transferred into the reservoir 21 via stream 22. According to one method of implementation of a content stream 22 may have a tendency to sedimentation. According to one method of implementation of such deposited substances can be removed from the stream 22 or re-used, for example, in thread 1. The pH value of the content stream 21 can, if desired, be adjusted by adding regulating the pH of the reagents with the help of flow 23. Suitable regulating pH reagents include acids, such as the organic and inorganic acids, for example, chromic acid, hydrofluoric acid, adnovate acid, hydrochloric acid, sulfuric acid, nitric acid, selenic acid, picric acid, trinitrophenol (2,4,6-) acid, naphtalenesulfonic acid, benzosulfimide acid, trichloroacetic acid, oxalic acid, dichloracetic acid, trihydroxy (2,4,6-) benzoic acid, cyclopropane-1:1-dicarbonyl acid, acetic acid, maleic acid, dihydroxypregna acid, dihydroxybenzoic acid, dichloracetic acid, 2,4-pyridylcarbonyl acid, o-nitrobenzoic acid, γ-cyanomelana acid, cyanopropionic acid, zanoxolo acid on-aminobenzenesulfonic acid, quinolinic acid, bromoxynil acid, dinicotinate acid, α-chloropropionic acid, malonic acid, o-bromobenzoyl acid, Chloroacetic acid, o-identify acid, α-Harmelen acid, o-phthalic acid, fermenting acid, o-chlorbenzol acid, p-cyanogenesis acid, dihydroxybenzoic (2,2-) acid, formic acid, dihydroxybenzoic (2,5-) acid, o-hydroxybenzoic acid, o-cyanogenesis acid, and α-tartaric acid. Used for pH control acid can, if desired, to extract from the stream 27 and reuse. The contents of the tank 21 is transferred into the PE ervoir 24 via stream 25. The contents of the tank 24 are oxidized by the oxidant supplied via stream 26, and then transferred into the tank 1 via stream 27. Suitable oxidants include air, enriched air, pure oxygen, hydrogen peroxide, aqueous solution of hydrogen peroxide, hydrogen peroxide in an organic liquid, ozone, carbon tetrachloride, trichloroacetaldehyde, hexamine, acetone, cyclohexanone, benzophenone, cinnamic aldehyde, dimethyl sulfoxide, sulfide, chiral oxidants, glyoxal, organic peroxyacids, such as nagarajuna acid, peracetic acid, natantia acid, nodropina acid, nadalina acid, and naftalina acid. Oxidizing agents and by-products of oxidation can, if desired, to extract from the stream 27 and reuse.

EXAMPLES

Example 1: Remove 4-CBA due to the purification of the complex salt

Suspensions received in three chemical glasses by adding 28 g of the crude TPA (containing 2.5% 4-CBA) to 100 g of NMP. The temperature of the three suspensions during mixing is maintained approximately 41 to 46°C. the Samples were filtered and rinsed with saturated solution of TPA/NMP at 40°C. the Concentration of 4-CBA was determined using gas chromatography. The results are shown in Table 1.

Example 2: remove the 4-CBA due to the purification of the complex salt at different temperatures

Suspensions received in three chemical glasses by adding 28 g of the crude TPA (containing 2.5% 4-CBA) to 100 g of NMP by mixing for 30 minutes. The temperature of the three suspensions during mixing is maintained constant. Then, each sample was filtered and rinsed with saturated solution of TPA/NMP at its own temperature. The concentration of 4-CBA was determined using gas chromatography. The results are shown in Table 2.

Example 3: Oxidation of 4-CBA in various who's the pH values

This example illustrates the effect of pH on the oxidation of 4-CBA using H₂O₂. The oxidation was carried out at 25°C for 300 minutes. The results are shown in Table 3. The results show that the decrease in pH leads to a much stronger oxidation.

1. The method of purification of carboxylic acids from a mixture that includes one or more carboxylic acids selected from the group consisting of terephthalic acid, isophthalic acid, orthophthalic acid, and mixtures thereof, and optionally including one or more substances selected from the group consisting of carboxymethylthio, Truelove acid and xylene, and the method includes:
contacting the mixture with a selective solvent for crystallization at a temperature and for a time effective to form a suspension of complex salts of carboxylic sour the s with a selective solvent for crystallization without complete dissolution of the complex salts of carboxylic acids;
removing the complex salt and
the decomposition of the extracted complex salt in a selective solvent for crystallization to obtain the free carboxylic acid.

2. The method according to claim 1, in which the selective solvent for crystallization is chosen from the group consisting of N,N-dimethylacetamide, N,N-dimethylformamide, N-formylpiperidine, N-alkyl-2-pyrrolidone, N-mercaptoethyl-2-pyrrolidone, N-alkyl-2-cooperalion, N-hydroxyalkyl-2-pyrrolidone, morpholine, carbitols, amines, and mixtures thereof.

3. The method according to claim 1, in which the selective solvent for crystallization is an N-organic.

4. The method according to claim 1, in which the temperature at the stage of contacting the mixture with a selective solvent for crystallization is from about 0 to about 65°C.

5. The method according to claim 1, in which the time at the stage of contacting the mixture with a selective solvent for crystallization is from about 1 min to about 5 hours

6. The method according to claim 1, in which the extracted complex salt is dissolved in the selective solvent for crystallization.

7. The method according to claim 1, in which the extracted complex salt forms a suspension in a selective solvent for crystallization.

8. The method according to claim 1, further comprising mixing the selective solvent with sufficient energy to flow Krista the implementation carboxylic acid, the crystals which have a globular shape.

9. The method according to claim 1, further comprising lowering the temperature of the selective solvent at the stage of decomposition of the extracted complex salt in a selective solvent for crystallization.

10. The method according to claim 1, further comprising reducing the amount of selective solvent by evaporation of part of the selective solvent for crystallization at the stage of decomposition of the extracted complex salt in a selective solvent for crystallization.

11. The method according to claim 1, additionally comprising adding a precipitant to a selective solvent for crystallization at the stage of decomposition of the extracted complex salt in a selective solvent for crystallization.

12. The method according to claim 1, in which the extraction of complex salts leads to the formation of the mother liquor, which is enriched in one or more substances selected from the group consisting of carboxymethylthio, Truelove acid and xylene, and the method further includes adding an oxidant to the portion of the mother liquor.

13. The method according to item 12, in which the oxidizing agent is chosen from the group consisting of air, enriched air, pure oxygen, hydrogen peroxide, aqueous solution of hydrogen peroxide, hydrogen peroxide in an organic liquid, ozone, carbon tetrachloride, tri gazetelere, hexamine, acetone, cyclohexanone, benzophenone, cinnamic aldehyde, dimethyl sulfoxide, sulfide, chiral oxidants, glyoxal, organic peroxyacids, such as nagarajuna acid, peracetic acid, natantia acid, nodropina acid, nadalina acid, and naftalina acid.

14. The method according to item 12, in which the pH of the above-mentioned part of the mother liquor is from about 1 to about 7.

15. The method according to item 12, in which the pH of the above-mentioned part of the mother liquor is brought to a value of - 1 to about 7, by adding acid to the above stock solution.

16. The method according to item 12, further comprising cleaning an additional carboxylic acid of the above part of the mother liquor by contact of the above part with a selective solvent for crystallization at a temperature and for a time effective to form a suspension of complex salts of additional carboxylic acid with a selective solvent for crystallization, and extraction of the complex salt.

17. The method according to claim 1, wherein the mixture comprises terephthalic acid and isophthalic acid and in which the extraction of the above complex salts leads to the formation of the mother liquor, and the method further includes the precipitation of the terephthalic acid and the mother liquor, to get depleted terephthalic acid stream, and then the deposition of isophthalic acid depleted terephthalic acid stream.

18. The method according to claim 1, wherein the mixture comprises terephthalic acid and isophthalic acid, and the method further includes lowering the temperature and reducing the amount of solvent for the secondary crystallization or adding a precipitant in the first phase to the solvent for the secondary crystallization for selective removal of free terephthalic acid and to obtain depleted terephthalic acid solution and then lowering the temperature and reducing the amount of depleted terephthalic acid solution in the second phase for selective extraction of isophthalic acid.

19. The method according to claim 1, in which the carboxylic acid is chosen from the group consisting of terephthalic acid, isophthalic acid, orthophthalic acid, and mixtures thereof, in which the mixture additionally contains one or more substances selected from the group consisting of carboxymethylthio, Truelove acid, and xylene, in which the extraction of the above complex salts leads to the formation of the mother liquor enriched in one or more of the above substances, and in which the selective solvent for crystallization is chosen from the group consisting of N,N-d is methylacetamide and N-methylpyrrolidone, the method further includes:
the decomposition or dissolution of the above complex salt in a selective solvent for crystallization for the formation of the secondary suspension or solution and precipitation of the free carboxylic acid of the above secondary solution with stirring the above-mentioned secondary solution with sufficient energy to flow crystallization carboxylic acid, the crystals which have a globular shape, and adding an oxidant to the above stock solution, where the oxidant is chosen from the group consisting of air, enriched air, pure oxygen, hydrogen peroxide, an aqueous solution of hydrogen peroxide, hydrogen peroxide in an organic liquid, ozone, carbon tetrachloride, trichloroacetaldehyde, hexamine, acetone, cyclohexanone, benzophenone, cinnamic aldehyde, dimethyl sulfoxide, sulfide, chiral oxidants, glyoxalic, organic peroxyketal, such as nagarajuna acid, peracetic acid, natantia acid, nodropina acid, nadalina acid, and naftalina acid.

20. The method according to 17, further including adjustment of the pH of the part of the mother liquor to a value from about 1 to about 7 and adding an oxidant to the above part of the mother liquor, in which the oxidizing agent chosen by the group, consisting of air, enriched air, pure oxygen, hydrogen peroxide, an aqueous solution of hydrogen peroxide, hydrogen peroxide in an organic liquid, ozone, carbon tetrachloride, trichloroacetaldehyde, hexamine, acetone, cyclohexanone, benzophenone, cinnamic aldehyde, dimethyl sulfoxide, sulfide, chiral oxidants, glyoxalic, organic peroxyketal, such as nagarajuna acid, peracetic acid, natantia acid, nodropina acid, nadalina acid, and naftalina acid, and returning the above part of the mother liquor in the tank for initial crystallization.

21. The method of extraction of purified terephthalic acid from liquid industrial waste in the production process, terephthalic acid, and the method includes:
the contacting liquid industrial waste with a selective solvent for crystallization in the tank for the initial crystallization to obtain a suspension of the complex salt of terephthalic acid with the solvent for crystallization without complete dissolution of the complex salts of terephthalic acid,
filtering the above suspension to obtain a solid complex salt and the mother liquor,
the decomposition or dissolution of the solid complex salt with a selective solvent for crystallization in R is serveware for secondary crystallization at a temperature of from about 65°to about 300°C. to obtain a suspension or solution for the secondary crystallization,
lowering the solution temperature for the secondary crystallization to a value of from about 60°to about 185°C for crystallization of free terephthalic acid and
removing the free terephthalic acid.

22. The method of extraction of the carboxylic acid in the form of its complex with the salt from a mixture that includes one or more carboxylic acids selected from the group consisting of terephthalic acid, isophthalic acid, orthophthalic acid, and mixtures thereof, and optionally including one or more substances selected from the group consisting of carboxymethylthio, Truelove acid and xylene, and the method includes:
contacting the mixture with a selective solvent for crystallization at a temperature and for a time effective to form a suspension of the complex salt of carboxylic acid with a selective solvent for crystallization without complete dissolution of the complex salts of carboxylic acids; and
removing the complex salt.