Method for preparation of aromatic carboxylic acids and the method of obtaining purified naphthaleneboronic acid
(57) Abstract:The invention relates to a method for producing an aromatic carboxylic acid, which comprises oxidizing in the liquid phase source of aromatic compounds containing at least one capable of oxidation of alkyl or acyl group, oxygen-containing gas in a solvent containing a low molecular weight carboxylic acid, in the presence of an oxidation catalyst containing heavy metals, when 121-232oC with formation of a reaction mixture of oxidation products containing the obtained aromatic carboxylic acid. The reaction mixture is heated oxidation products at temperatures from at least 228-368oC to obtain a second reaction mixture of oxidation products, which then emit an aromatic carboxylic acid. 2 C. and 7 C.p. f-crystals, 1 Il., 13 table. This invention relates mainly to a method for producing aromatic carboxylic acids. More specifically the present invention relates to an improved process for the preparation of aromatic carboxylic acids, such as natalijagolosova acid by liquid phase oxidation of alkyl - or allsamsung aromatic source soedineniya acids are very important organic compounds. Some of them are used as intermediates in the production of other organic compounds, and some serve as monomers in the production of polymeric materials. For example, terephthalic acid is used for the production of polyethylene terephthalate, commonly used polyester material, and naphthaleneboronic acid (for example, naphthoic acid) are used to produce chemicals for pictures and dyes. In addition, naphthalenesulphonate acid can be used for various polyester and polyamide compositions.One of naphthalenesulphonic acid - 2,6-natalijagolosova acid is a particularly important aromatic carboxylic acid, as it may interact with the ethylene glycol with the formation of poly(ethylene-2,6-naphthalate) (PENG). Derived from PAN fibers and films possess high strength and better thermal properties compared to other polyester materials, for example, in comparison with the polyethylene terephthalate. High-strength fibers derived from PAN, can be used for the manufacture of cord tires, and the film obtained from PENG, mainly used for the manufacture of magnetic tapaculo quality most appropriate for use in the above cases, it is desirable to use purified 2,6-naphthaleneboronic acid. Similarly, it is desirable to use purified form and other aromatic carboxylic acids, if they are used in the above cases.Aromatic carboxylic acids and especially 2,6-naphthaleneboronic acid usually get liquid-phase catalyzed by metal by oxidation of the alkyl - or allsamsung aromatic compounds. In the process of oxidizing an alkyl group (e.g. methyl, ethyl or ISO-propyl group) or an acyl group is oxidized to a carboxyl group. Although this reaction is an efficient oxidation reaction, however it has some disadvantages. For example, when oxidation is subjected to 2-alkyl - or 2-acetamidino connection itself naphthalene ring is sensitive to oxidation, which leads to the formation trimellitic acid. In case of incomplete oxidation of a methyl group instead of a carboxyl group is formed aldehyde group. Moreover, when using liquid-phase oxidation promoter, such as bromine, are formed brominated aromatic carboxylic sour the AK as it tends to form stable complexes with metal oxidation catalyst. Such complex metals are difficult to remove from aromatic carboxylic acids and, in addition, the reaction streams containing trimellitic acid is difficult to return in the reaction mixture for oxidation, as trimellitate acid is bound in a complex with a metal catalyst and, therefore, disables it. This recycle stream can be obtained from the mother liquor of the reaction mixture, which is separated from the aromatic carboxylic acids by oxidation of alkyl or acyl group. On recycling can also return the wash stream, which is formed when washing aromatic carboxylic acid with a suitable solvent. Therefore, you need a way that ensures the extraction of aromatic carboxylic acid with reduced content trimellitic acid and/or other impurities, so that it can be more effectively implemented recycling the oxidation reaction mixture. The present invention provides such a method.This invention is a method of obtaining an aromatic carboxylic acid, which comprises: (a) liquid-phase oxidation of aromatic compounds containing at least one capable of Kislinsky molecular weight in the presence of an oxidation catalyst on the basis of heavy metal and at a temperature of about 250 450oF, with formation of a reaction mixture of oxidation products containing aromatic carboxylic acid; b) heating the reaction mixture of oxidation products at temperatures of at least 500oF with the formation of the second mixture of reaction products; and (C) the selection of the second mixture of the reaction products of aromatic carboxylic acids.In the method of the present invention, the aromatic compound containing at least one is able to oxidize the alkyl or acyl group, is oxidized at least 90 mol.% and preferably almost all is able to oxidize the alkyl or acyl group are oxidized to carboxyl groups in the resulting aromatic carboxylic acid. At the next stage, the reaction mixture is heated to a temperature of at least approximately 500oF. Unexpectedly, it was found that this technique leads to a more pure form aromatic carboxylic acids secreted from the reaction mixture of oxidation products. In addition, the mixture remaining after separation of the desired aromatic carboxylic acid, which is usually referred to as the mother liquor, or has a low content of impurities and by-products is when you recycle in liquid-phase oxidation reaction, as a result it facilitates recycling the mother liquor to the reaction mixture of liquid-phase oxidation. The return of the mother liquor is desirable, as it contains useful metal oxidation catalyst and also because it contains an intermediate oxidation products, which can be oxidized to the desired aromatic carboxylic acid.The method of the present invention is particularly suitable for oxidation dialkyl-, alkyl-acyl - or deacylation to the appropriate naphthaleneboronic acid. Catalyzed by heavy metals liquid-phase oxidation of such derivatives of naphthalene usually requires a high content of metal catalysts and oxidation reaction as a by-product of the oxidation reaction is formed trimellitate acid. The method of the present invention, however, leads to a significant reduction in the content of trimellitic acid in the reaction mixture of oxidation products that allows you to send a greater amount of the mother liquor back to the oxidation reaction. Recycled mother liquor contains - in addition to precious metal oxidation catalyst - fine particles naphthalenemethanol acids, intermediates of oxidation, which can the t to preserve these valuable components, and also solves the problem of waste disposal. In addition, natalijagolosova acid obtained by the method of the present invention, contains fewer unwanted impurities and by-products, and 2,6-natalijagolosova acid obtained by the method of the present invention, has a large particle size, which provides a more efficient filtration and washing of this product. Finally, the method of the present invention allows more flexibility in the choice of the composition of the reaction mixture oxidation and conditions of the oxidation reaction used in the oxidation of alkyl - or accelerations compounds to the corresponding aromatic carboxylic acid. For example, the conditions of the oxidation reaction, which were previously considered unacceptable, because it led to the formation of a considerable amount trimellitic acid can now be used as the method of the present invention enables the effective removal of such trimellitic acid to recirculatory the mother liquor after the oxidation reaction on the oxidation reaction.In Fig. 1 presents the flow diagram in the embodiment of the present invention, which shows an integrated way, vlachoyiannopoulos acid, and phase separation.The reaction mixture oxidation products, used in the method of the present invention, is formed by liquid-phase catalyzed by heavy metals by oxidation of the alkyl - or allsamsung aromatic compounds. Such aromatic compounds include any acyl and/or alkyl substituted aromatic compound in which the acyl and/or alkyl group may be oxidized to a carboxylic acid. In accordance with the present invention formyl group can also be oxidized and is considered equivalent to the acyl group. In particular, acceptable original aromatic compounds are compounds that have the formula
< / BR>where n takes integer values from 1 to 8, preferably from 1 to 4, more preferably n takes on the values 1 or 2;
the substituent R is independently selected from the group comprising alkyl groups containing from 1 to 6 carbon atoms, inclusive, and acyl groups containing from 1 to 6 carbon atoms inclusive. Preferably the substituent R represents a methyl, ethyl, isopropyl, acetyl or formyl.Examples of acceptable aromatic starting compounds are o-xylene, m-is diphenyl ether, dissimilar, 3,3', 4,4'- tetraalkylammonium, where the alkyl group contains preferably from 1 to 4 carbon atoms, inclusive, and more preferably where the alkyl group is a methyl. Examples of the source of aromatic compounds based on naphthalene are: 1-methyl - and 2-methylnaphthalene, 1-ethyl-2-ethylnaphthalene, 1 - isopropyl - 2-isopropylnaphthalene; 2,6-dialkyl - or 1-acyl-6-alkylnaphthalene, such as 2,6-dimethyl-, 2,6-diethyl - 2,6-diisopropylnaphthalene; 2-acetyl-6-methylnaphthalene, 2-methyl-6-ethylnaphthalene, 2-methyl-6-isopropylnaphthalene and similar compounds. Preferred aromatic compounds for this method are p-xylene, m-xylene and 2,6-dimethylnaphthalene that the oxidation converted into terephthalic acid, isophthalic acid and 2,6-naphthaleneboronic acid, respectively.In U.S. patent 5034561, 5030781 and 4950825 (Sikkenua et al.) disclosed is a method of obtaining dimethylnaphthalene. In Pat. USA 5026917 (Hagen et. al.) describes the method of obtaining 2-methyl-6-acetylation, and in U.S. Pat. USA 4873386 a way of producing 2,6-deatination.The most preferred source of aromatic compound to oxidation according to the method of the present invention is 2,6-dimethylnaphthalene. 2,6-Nai monomer in the production of PAN, high quality polyester. Moreover, 2,6-dimethylnaphthalene is preferable, for example, 2,6-diethyl - or 2,6-diisopropylnaphthalene, because it has a lower molecular weight and the yield of 2,6-naphthaleneboronic acid on the specific weight of 2,6-dealkylation above, 2,6-dimethylnaphthalene than for 2,6-diethyl - or 2,6-diisopropylnaphthalene.Methods of liquid-phase catalyzed by heavy metals oxidation of alkyl - or allsamsung aromatic compounds to the corresponding aromatic carboxylic acids are well known. For example, in U.S. Pat. USA 4950786, 4933491, 3870754 And 2833816 described such methods of oxidation. In General acceptable oxidation catalysts based on heavy metals are metals having atomic number from about 21 to 82, inclusive, preferably a mixture of cobalt and manganese. The preferred solvent for oxidation is a monocarboxylic acid with a low molecular weight, containing from 2 to 6 carbon atoms inclusive, preferably acetic acid or a mixture of acetic acid and water. The reaction temperature is usually about 300 - 450oF, and the reaction pressure should be such that the reaction is rim weight, containing from 2 to 6 carbon atoms or a low molecular weight aldehyde containing from 1 to 6 carbon atoms. Can also be used brominated promoting compounds known in this field, such as hydrogen bromide, molecular bromine, sodium bromide.Particularly acceptable method of oxidation of 2,6-dialkyl or 2-acyl-6-alkylnaphthalene to 2.6-naphthaleneboronic acid described in U.S. Pat. USA 4933491 (Albertins and others ). Acceptable solvents for such liquid-phase oxidation reactions of 2,6-dialkyl or 2-acyl-6-alkylnaphthalene are benzoic acid, any aliphatic C2-C6- monocarboxylic acids, such as acetic acid, propionic acid, n-butyric acid, ISO-butyric acid, n-valeric acid, trimethylhexane acid, hexanoic acid and water. The preferred solvent is a mixture of water and acetic acid, and in such a mixture preferably contains 1 to 20% water. The source of molecular oxygen used in such liquid-phase oxidation reactions of 2,6-dialkyl or 2-acyl-6-alkylnaphthalene, can serve as oxygen contained in air and oxygen gas. For reasons of economy, the preferred source of molecular Keene includes promotergene connection and at least one cobalt - and mn containing compound. Preferably the catalyst contains cobalt-, manganese - and brominated compounds. The ratio of cobalt (based on elemental cobalt) in the cobalt component of the catalyst to 2,6-dialkyl or 2-acyl-6-alkylnaphthalene liquid-phase oxidation is in the range from about 0.1 to 100,0 milligram-atoms (mg) per gram-mole of 2,6-dialkyl or 2-acyl-6-alkylnaphthalene. The ratio of manganese (calculated on an elemental manganese) in the manganese component of the catalyst to cobalt (based on elemental cobalt) in the cobalt component of the catalyst for liquid-phase oxidation is in the range from about 0.1 to 10.0 mg-1 mg-and cobalt. The ratio of bromine (based on elemental bromine) in bromoderma component of the catalyst to the total content of cobalt and manganese (calculated on an elemental cobalt and manganese) in the cobalt and manganese components of the catalyst for liquid-phase oxidation is in the range from about 0.1 to 1.5 mg-and mg-and cobalt and manganese.Each of cobalt and manganese component of the catalyst may be provided by any of the known ionic or mixed forms, which constitute soluble forms of cobalt, manganese and bromine in rastvoritelya and/or manganese, acetate tetrahydrate and/or bromide. The ratio of bromine to the total of cobalt and manganese from 0.1:1.0 to 1.5:1.0 get when using a suitable source of bromine, such as elemental bromine (Br2or bromine in the ionic form (for example, HBr, NaBr, KBr, NH4Br and others) or an organic bromide, which are known to provide bromide ions at the operating temperatures at which carry out the oxidation (e.g., brombenzene, benzyl bromide, tetrabromoethane, ethylenedibromide and others). The total content of bromine in the molecule bromide or bromide ion is used to determine how the ratio of elemental bromine: cobalt+magnesium corresponds to the interval from 0.1:1.0 to 1.5:1.0 in. Bromide ion released from organic bromides in the conditions of the oxidation reaction, can be easily determined by known analytical techniques. Tetrabromide, for example, at the operating temperature of 335oF, as installed, allocates approximately 3 effective gram-atom per gram-mole.When working minimum pressure in the oxidation reactor is maintained so, in which 2,6-dialkyl or 2-acyl-6-alkylnaphthalene and at least 70% of the solvent are in the liquid phase. Evaporated 2,6-dialkyl or 2-acyl-6-alkylnaphthalene and the solution of the population. When the solvent used is a mixture of acetic acid and water, an acceptable pressure in the oxidation reactor is a pressure in the range of approximately 0 to 35 kg/cm2or the pressure is from about 10 to 30 kg/cm2. The range of temperature in the oxidation reactor is generally from about 250oF, preferably 350 - 450oF, preferably up to 420oF. At temperatures above 450oF there's a lot of "burning" of a solvent and/or naphthalene derivatives. The residence time of the solvent in the oxidation reactor is generally about 20 to 150 minutes, and preferably 30 to 120 minutesThe oxidation process can be carried out periodic, continuous or semi-continuous manner. With continuous way 2,6-dialkyl or 2-acyl-6-alkylnaphthalene, the solvent and the components of the catalyst are introduced in portions into the reactor and the temperature and pressure in the reactor increased to the desired value, at which to start the oxidation reaction. Air is introduced into the reactor continuously. After completion of the oxidation reaction, for example, after all of 2,6-dialkyl or 2-acyl-6-alkylnaphthalene fully introduced into the reactor, the temperature of the contents Reichstag, the solvent and catalyst are continuously introduced into the oxidation reactor and a stream of reaction products containing 2,6-naphthaleneboronic acid and catalyst components dissolved in the solvent exits the reactor. By semi-continuous method, the solvent and the catalyst are introduced into the reactor and then 2,6-alkyl - or 2-acyl-6-alkylnaphthalene and the air continuously the floor in the reactor. The above-described method of oxidation 2.6-dialkyl or 2-acyl-6-alkylnaphthalene can be used for oxidation of other alkyl - and/or allsamsung aromatic compounds, for example, in the oxidation of p-xylene to terephthalic acid or m-xylene to isophthalic acid.In industrial large-scale production of the preferred continuous method of oxidation. With this method, which is used as starting compound 2,6-dimethylnaphthalene, the weight ratio of monocarboxylic acid used as a solvent to 2,6-dimethylnaphthalene is preferably about 2:1 to 12:1, mg-and-the ratio of manganese to cobalt is in the range from 5:1 to 0.3:1, mg-and-the ratio of bromine to the total of cobalt and manganese is approximately 0.3:1-0,8:1, and the total content of cobalt and manganese (rarities, the temperature of the reaction is maintained in the range from about 370 to 420oF. Acetic acid is the most suitable solvent for carrying out considered continuous oxidation of 2,6-declination.Depending on the reaction conditions selected source of aromatic compounds, oxidation catalyst and the content of the selected catalyst, the reaction mixture obtained in the oxidation process contains, in addition to the target aromatic carboxylic acid, the number of impurities and by-products of the reaction. For example, when the oxidation reaction as a source of aromatic compounds used 2,6-dealkylation, the reaction mixture coming directly from the reactor oxidation (also called the General stream exiting the reactor or ISD) contains a solvent, which is typically a mixture of acetic acid and water, the target 2,6-naphthaleneboronic acid and promise, including trimellitic acid (TMLC), bromo-2,6-naphthaleneboronic acid (Br-2,6-NIR), 2-formyl-6-naphthoic acid (2-opt), 2-naphthoic acid (2-NK), a number of other impurities, as well as cobalt and manganese components of the catalyst. Acetic acid and is of the STATCOM. The analysis of this solid residue allows you to evaluate all the stronghold of the components present in the reaction mixture, and, therefore, to assess the yield of the target product and by-products of the reaction. Usually in the oxidation of 2,6-dimethylnaphthalene content trimellitic acid in the solid products of the oxidation reaction mixture may reach 5%, typically about 3-4%. The number of 2-formyl-6-naphthoic acid can be up to 1%, typically about 0.5%. The number bromo-2,6-naphthaleneboronic acid can reach up to 3%, typically about 0.2-1 wt. %. The total content of cobalt and manganese in the solid portion of the reaction mixture, the oxidation can be up to 4 wt.%. Although the target 2,6-natalijagolosova acid generally not soluble in the reaction mixture oxidation, especially after cooling the reaction mixture to a temperature below the reaction temperature and can be easily separated from the reaction mixture, selected 2,6-natalijagolosova acid is also contaminated trimellitic acid, 2-formyl-6-naphthoic acid, bromo-2,6-naphthaleneboronic acid, other organic impurities and by-products of the reaction, as well as cobalt and manganese oxidation catalyst. Sledovatel the temperature and even when separated 2,6-natalijagolosova acid is washed with fresh solvent at elevated temperature with removal of the remaining mother liquor, selected 2,6-natalijagolosova acid still contains a significant quantity of the above-mentioned impurities and side products of the reaction that you want to delete from the resulting 2,6-naphthaleneboronic acid.However, we found that the content of undesirable impurities in the process of liquid-phase oxidation source alkyl - or allsamsung aromatic compounds can be significantly reduced by heating a reaction mixture of oxidation products (total reaction stream exiting the reactor, ISD) at a temperature of at least approximately 500oF, preferably at least at 550oF and most preferably at least approximately at 600oF. Although the reaction temperature above approximately 600oF, for example, 650oF, have a beneficial effect, it is preferable not to raise the temperature to more than 700oF. it is Important that the high-temperature stage of the present invention after a stage of oxidation, in which almost all is able to oxidize the alkyl or acyl group in the aromatic ring are oxidized to carboxyl groups. In addition, the phase of the high-temperature treatment is regular oxygen from an external source.When heating a mixture of oxidation products at the above elevated temperature of at least approximately 500oF, it is desirable to maintain at least 50 wt.% and preferably almost all of the solvent in the liquid phase, to prevent its loss. Therefore, it is desirable to use the apparatus under pressure to low molecular weight carboxylic acid, which is the solvent in the oxidation remained in the liquid phase. Acceptable pressure for the heat treatment is pressure from about 200 psig to 3000 psig. The desired pressure is needed to correlate with the selected temperature and the vapor pressure of water and low molecular weight carboxylic acid used as the solvent for the oxidation reaction. In addition, a mixture of oxidation products can be smashana more low molecular weight carboxylic acids, water or another solvent to conduct high-temperature treatment at approximately 500oF. Acceptable low molecular weight carboxylic acids are acids containing from 1 to 8 carbon atoms. Preferably it is an aliphatic monocarboxylic acid and most preferably COI the course of the oxidation. The amount of solvent that is present at the stage of heat treatment according to the method of the present invention may correspond to the amount needed to dissolve almost all of the present aromatic carboxylic acid. However, a complete or almost complete dissolution is not required. For example, stage heat treatment of the present invention is effective when at least 10 wt.%, preferably 20 wt.% the aromatic carboxylic acid is in solution. Acceptable weight ratio of solvent-aromatic carboxylic acid is at least about 2:1, preferably 3:1 to 10: 1. If the aromatic carboxylic acid is a 2,6-naphthaleneboronic acid, the preferred solvent for high temperature processing is acetic acid, and probably contain about 2 to 50 wt.% water.At the stage of high temperature treatment according to the method of the present invention, the reaction mixture oxidation products is maintained at a temperature of at least approximately 500oF in a period of time sufficient to reduce the content of undesirable impurities and by-product of zivaetsja at a temperature of at least 500oF is at least 0,1 min, preferably at least about 1 min, and most preferably at least 10 minutes After conditioning at a temperature of at least approximately 500oF the content of undesirable impurities in the reaction mixture of oxidation products is reduced. For example, if the reaction mixture of oxidation products contains trimellitic acid content trimellitic acid is reduced if the reaction mixture of oxidation products contains formulating acid, the content of formulating acid is reduced if the reaction mixture of oxidation products contains one or more bromofluorocarbons acids, the content of brominated acids decreases. Reduced content of impurities in the reaction mixture after carrying out heat treatment in accordance with the method of the present invention leads, for example, to a more pure form 2,6-naphthaleneboronic acid, when 2,6-natalijagolosova acid is separated from the mother liquor of the reaction mixture oxidation subjected to heat treatment. In addition, the mother liquor of the reaction mixture after oxidation heat treatment according to the method of the present invention otozureru in the oxidation reaction, because it contains less trimellitic acid, which forms a complex with a metal oxidation catalyst and deactivates it. For example, when the reaction mixture is formed by oxidation the oxidation of 2,6-dimethylnaphthalene or other 2,6-dealkylation and the reaction mixture oxidation contains bromo-2,6-naphthalenesulphonate acid, 2-formyl-6-naphthoic acid and trimellitic acid content bromo-2,6-naphthaleneboronic acid in the reaction mixture, the oxidation can be reduced by at least about 20% and preferably approximately 50%. The number of 2-formyl-6-naphthoic acid can be reduced by at least 15%, preferably at least 30%, and the number trimellitic acid can be reduced at least about 20% and preferably at least about 50%. Preferably in the oxidation reaction mixture used at the stage of high temperature treatment according to the method of the present invention, contains acetic acid, water, cobalt and manganese, 2,6-natalijagolosova acid, trimellitate acid, 2-formyl-6-naphthoic acid and bromo-2,6-naphthalenesulphonate acid.At the stage temperature orbolato, can be processed by one or more oxidizing, reducing, or other cleansing agents to further improve the purity allocated aromatic carboxylic acid and an additional removal of undesirable components, such as aldehydes and brominated aromatic compounds from the mother liquor of the reaction mixture oxidation. For example, the reaction mixture oxidation (either before or after selection of the target aromatic carboxylic acid) by heating at a temperature of at least approximately 500oF can be processed by one or more oxidizing agents such as manganese dioxide, bromoviridae acid, hydrogen peroxide or other peroxide-like compounds. On the other hand, and preferably it can be treated with a reducing agent such as hydrogen gas. Hydrogen gas is the preferred reagent and acceptable partial pressure of hydrogen gas is approximately 5-500 psig. When using gaseous hydrogen is also preferable to use one or more standard hydrogenation catalysts. Such hydrogenation catalysts are noble catalysts of hydrogenation. For example, such a catalyst is at least one metal from among platinum, palladium, rhodium, ruthenium or rhenium supported on a carrier such as alumina or charcoal. The preferred hydrogenation catalyst is platinum, ruthenium or palladium deposited on charcoal. The weight ratio of the hydrogenation catalyst to the reaction mixture, the oxidation is preferably from about 0.001:1 to about 0.5:1, preferably from about 0.005: 1 to 0.05:1 based on the total weight of the catalyst, including the material of the carrier, if it is used. When using as a catalyst of a noble metal of group VIII noble metal present in the catalyst is usually in the amount of approximately from 0.1 to 5 wt.% based on the total weight of the catalyst. The preferred catalyst is palladium, ruthenium or platinum on charcoal, and metal is contained in an amount of from about 0.1 to 1.0 wt.% based on the weight of the catalyst.When using hydrogen at the stage of heat treatment according to the method of the present invention together with a hydrogenation catalyst, it is desirable to operate at temperatures and the ratio of solvent to aromatic the awn is in solution. Under such conditions it is possible to skip the mother liquor of the oxidation reaction containing contaminated aromatic carboxylic acid, through a fixed bed of hydrogenation catalyst. However, the use of hydrogen is not necessary that all of the aromatic carboxylic acid was in solution. For example, the hydrogenation catalyst may be contained on one side of a screen or filter, or other barrier that is permeable dissolved aromatic carboxylic acid, other dissolved components and hydrogen, but does not let the material in the form of particles, such as undissolved components of the reaction mixture oxidation, including undissolved aromatic carboxylic acid. When using this type of equipment, the hydrogenation reaction can be performed without exposing the catalyst for the hydrogenation of the effects of insoluble components in the reaction mixture of oxidation, which can clog the catalytic hydrogenation. However, as mentioned above, when using hydrogen when carrying out high-temperature processing, it is desirable to operate under conditions when the aromatic carboxylic acid is almost completely and preferably is completely in solution. In the C zone of the oxidation reaction, may not contain sufficient quantities of low molecular weight carboxylic acid and/or water for dissolving an aromatic carboxylic acid at a temperature that is used during high-temperature processing. Therefore, it may be desirable to add a solvent such as water or low molecular weight carboxylic acid, to the reaction mixture for dissolving an additional amount of aromatic compounds and preferably to dissolve all of the aromatic carboxylic acid. One of the possible sources of such a solvent is a mixture of low molecular weight carboxylic acids and water, which is formed from vapor oxidation reaction mixture, which must be condensed and at least partially returned to the reaction mixture oxidation. However, a certain amount or all the resulting condensate can be added to the reaction mixture at the stage of high-temperature processing in order to dissolve the aromatic carboxylic acid. In the example below 10 presents data on the solubility of 2,6-naphthaleneboronic acid in water and in acetic acid. These data can be used to estimate the amount of acetic acid, assusyhoido for dissolving 2,6-naphthaleneboronic acid at a certain temperature reactions.When using gaseous hydrogen at carrying out high-temperature treatment according to the method of the present invention the removal of 2-formyl-6-naphthoic acid and bromo-2,6-naphthaleneboronic acid from the reaction mixture and oxidation of 2,6-naphthaleneboronic acid isolated from the reaction mixture, the oxidation is facilitated. For example, when using gaseous hydrogen and acceptable hydrogenation catalyst during thermal processing of the oxidation reaction mixture obtained by oxidation of 2,6-dimethylnaphthalene, hydrogen contributes to the destruction of 2-formyl-6-naphthoic acid and bromo-2,6-naphthaleneboronic acid. In addition, 2-formyl-6-naphthoic acid into products, which when returned to the oxidation reactor into 2,6-naphthaleneboronic acid. Interaction bromo-2,6-naphthaleneboronic acid with hydrogen conducts to 2,6-naphthaleneboronic acid. This prevents the loss of valuable project. Consequently, the use of hydrogen during high temperature processing of the reaction mixture oxidation is possible to use the reaction mixture, which contains a larger number of 2-formyl-6-naphthoic acid and bromo-2,6-naphthalenedione thus, to obtain a higher content of 2-formyl-6-naphthoic acid and/or bromo-2,6-naphthaleneboronic acid. This is an advantage, because the methods of the prior art it was necessary to use more stringent conditions of oxidation, in order to achieve complete oxidation of 2-formyl-6-naphthoic acid, 2,6-naphthaleneboronic acid. However, under oxidizing conditions, which is achieved by a low content of 2-formyl-6-naphthoic acid, observed the formation of large quantities of trimellitic acid. Thus, the method of the present invention, in which the high-temperature processing is hydrogen, allows for a greater flexibility in terms of oxidation for the formation of aromatic aldehydes and brominated aromatic compounds as the subsequent treatment with hydrogen facilitates the removal of such compounds from the reaction mixture of oxidation.After high temperature treatment of the reaction mixture oxidation using hydrogen or without it, or using another cleansing agent it is usually cooled for crystallization of the target aromatic carboxylic acid. The degree of cooling depends on variables such as as solvent, the temperature at which was carried out high-temperature processing, and on the desired degree of purity of the aromatic carboxylic acid. However, usually the reaction mixture is cooled to a temperature not higher than 450oF, preferably to a temperature of approximately 100 - 400oF, more preferably about 150 to 350oF. If the aromatic carboxylic acid is a 2,6-naphthaleneboronic acid, then the reaction mixture is preferably cooled to a temperature less than approximately 500oF, more preferably to a temperature of from approximately 200oF to about 450oF.Although the reaction mixture can be cooled relatively quickly using, for example, one or more quick mold, it is preferable to slow cooling. Slow cooling leads to a product with a large particle size and can provide a more pure aromatic carboxylic acid. Preferably the cooling rate is not more than approximately 80oF/min, more preferably not more than 50oF/min is preferable cooling rate is between about 1oR) and also contains a significant amount of very small particles, for example, about 20-40 wt.% the particles have a size of less than 11 microns. In the above-described method of the invention, however, is obtained 2,6-natalijagolosova acid having an average particle size of at least about 40 microns, more preferably at least 60 μm and, very importantly, only a small percentage of 2,6-naphthaleneboronic acid is in the form of very small particles, for example, not more than 15 wt.% 2,6-naphthaleneboronic acid has a particle size of less than 11 μm, more preferably not more than about 10%. According to the above method are 2,6-naphthaleneboronic acid having an average particle size of 100 μm or more.The aromatic carboxylic acid with a large particle size, in particular 2,6-naphthaleneboronic acid is desirable because large particles of aromatic carboxylic acids by lastwritetime to remove the last traces of mother liquor. In addition, the presence of very small particles of aromatic carboxylic acids leads to clogging of filters and other devices used to separate aromatic carboxylic acid from the mother and the leaching solutions.After stage heat treatment in accordance with the method of the present invention with stage cooling with or without solid aromatic carboxylic acid, and preferably 2,6-natalijagolosova acid is separated, that is separated from the mother liquor of the reaction mixture oxidation. At the stage of separation can be used by any acceptable method, such as filtration, centrifugation, sedimentation and similar methods. The mother liquor of the oxidation reaction, separated from the aromatic carboxylic acid, contains valuable oxidation catalyst and, as described above, is normally returned, at least partially, in the reaction mixture oxidation. To recycle a certain amount or all low molecular weight carboxylic acid used as a solvent, can be removed. Aromatic carboxylic acid collected in the equipment used for the separation of aromatic carboxylic acid from the high-temperature reaction. Such a solvent may be water, low molecular weight carboxylic acid containing from 1 to 6 carbon atoms, preferably acetic acid, mixtures of such low molecular weight carboxylic acid with water, and any other acceptable solvent, such as toluene, xylene, C9aromatic solvent and the like solvents. The weight ratio of the leaching solvent to aromatic carboxylic acid is usually about 0.2:1 to 3:1. When the aromatic carboxylic acid is a 2,6-naphthaleneboronic acid, the preferred proryvnym solvent is acetic acid or its mixture with water, wherein the water is present in amount of from about 5 to 95 wt.% and in which the weight ratio of acetic acid or mixtures of acetic acid with water to 2,6-naphthaleneboronic acid is about 0.2:1 to 2:1. Moreover, it is preferable that the washing solvent was heated to a temperature of preferably 200 to 450oF. Although usually just one stage of leaching, can be used and an additional step of washing.After separation of the aromatic carboxylic acid from the high temperature of the reaction mixture or the settlement of ritel. Dried aromatic carboxylic acid is used as described above, or additionally cleaned using one or more methods of treatment.Although it is preferable to carry out stage heat treatment of the present invention to the separation of aromatic carboxylic acids, are also useful thermal treatment of the mother liquor obtained after the separation. Therefore, another embodiment of the method of the present invention is in the primary Department of the aromatic carboxylic acid from the oxidation reaction mixture with subsequent high temperature processing of the selected stock solution described above.Another objective of the present invention is a method of cleaning naphthaleneboronic acid by contacting contaminated naphthaleneboronic acid with a cleaning solvent at an elevated temperature for a time sufficient to reduce the content of impurities in the contaminated naphthaleneboronic acid.At such high temperature the way contaminated natalijagolosova acid obtained liquid-phase catalyzed by heavy metals by oxidation of the alkyl - and/or allesammen in the liquid phase to a temperature of at least 500oF with the formation of a mixture of products. Purified natalijagolosova acid then is released from the mixture. Unexpectedly, it was found that in this process trimellitate acid is transformed into other compounds such as ortho-phthalic acid, terephthalic acid and isophthalic acid. High temperature provides a cleaner naphthaleneboronic acid, such as phthalic acid do not form like trimellitic acid strong complexes with metal oxidation catalyst such as cobalt or manganese, workflows, obtained after thermal processing, can be returned to the oxidation reactor, as they contain fewer trimellitic acid. Besides reducing the content trimellitic acid in contaminated naphthaleneboronic acid, described here, high temperature leads to reduction in the content of other undesirable impurities, such as formulationa acid and bromofluorocarbons acid.Naphthalenesulphonate acid, which can be cleaned using this method include 1,2-, 1,3-, 1,4-, 1,5-, 1,6-, 1,7-, 1,8-, 2,3-, 2,6- and 2.7-naphthalenesulphonate acid. This method is especially the m oxidation of 2,6-alkyl-, preferably 2,6-dimethyl-substituted naphthalene in the presence of low molecular weight aliphatic acid as solvent, air, and oxidation catalyst based on cobalt, manganese and bromine, as described above.Cleaning solvents that can be used in the present method, are solvents that are at least partially dissolve naphthaleneboronic acid at elevated temperatures and which do not react with naphthaleneboronic acid, and which do not decompose at elevated temperatures used in this process and therefore do not lead to contaminants. For example, solvents containing reactive groups such as amines, alcohols, phenols and thiols, usually cannot be used as solvents in the present case. Acceptable solvents, however, are water, low molecular weight carboxylic acid, and especially mixtures of water and low molecular weight carboxylic acids. Preferably, such low molecular weight carboxylic acids contain from about 1 to 8 carbon atoms, and preferably represents a monocarboxylic acid. Low molecular weight carboxylic who atoi communication. Examples of acceptable low molecular weight carboxylic acids, which can be used as solvents are acetic acid, propionic acid, ISO - and ad-butyric acid, benzoic acid, fluoro-, bromo-, Chloroacetic acid, and similar compounds. The most preferred acetic and propionic acid. Due to the availability and low cost, and also because this acid was also used in the above liquid-phase catalyzed by metal oxidation catalyst, acetic acid is the most preferred low molecular weight carboxylic acid for use as a cleaning solvent. When using mixtures of water and low molecular weight carboxylic acid, the weight ratio of water and carboxylic acid may be in the range of about 1:99 to 99:1, respectively, preferably about 2:98 - 96:2. The preferred solvent is a mixture of water and low molecular weight carboxylic acid, preferably acetic acid, and the acid number is from about 5 to 20 wt.% based on the weight of the solvent. Such mixtures facilitate the removal of metal oxidation catalyst. In addition,the number, for example, from 0.01 to about 10 wt.% strong acids, such as hydrochloric acid, sulfuric acid, Hydrobromic acid, triperoxonane acid, etc. Such strong acids also facilitate the removal of the metal catalyst for the oxidation of naphthaleneboronic acid.The amount of cleaning solvent used in this method of treatment should be sufficient to dissolve at the reaction temperature of at least part naphthaleneboronic acid in the reaction mixture. The preferred amount of solvent used is that amount which will dissolve the most part and more preferably almost the entire naphthaleneboronic acid in the reaction mixture. However, treatment of contaminated naphthaleneboronic acid occurs when at least 10 wt.%, more preferably 20 wt.% naphthaleneboronic acid remains in solution under the reaction conditions of high temperature method. The weight ratio of solvent to naphthaleneboronic acid is typically at least about 1:1, more preferably at least 2:1 and most preferably at least 2.5:1. Usually ve the reaction is an essential characteristic of high-temperature method of the present invention when using cleaning solvent. Unexpectedly, we found that high-temperature processing naphthaleneboronic acid containing impurities such as trimellitate acid, 2-formyl-6-naphthoic acid and bromo-2,6-natalijagolosova acid leads to a decrease of the content of these impurities. This reduction is not a simple separation of impurities from contaminated naphthaleneboronic acid, as would be expected in the normal process of recrystallization, and due to the transformation of impurities in the other compounds. The result can be obtained more pure natalijagolosova acid and, very importantly, workflows, remaining after the allocation naphthaleneboronic acid, have low content of trimellitic acid, which makes them acceptable for return to the reaction mixture of oxidation.The temperature of the reaction at such a high temperature cleaning method using a cleaning solvent, is at least approximately 500oF, more preferably about 550oF and most preferably at least approximately 600oF. the Period of time during which the reaction mixture is maintained at these temperatures, represents the time, MESI, due to transformation into other compounds. This period of time is in the range from about 0.1 min to several hours depending on the selected temperature, impurity content in the contaminated naphthaleneboronic acid, as well as from the desired degree of purification. The combination of temperature and reaction time should be sufficient to reduce the content trimellitic acid present in the reaction mixture by at least 40%, more preferably at least 60%. In most cases, the reaction time is about 1 minute, preferably at least about 5 minutes the temperature of the high temperature process preferably should not exceed approximately 700oF. At temperatures above 700oF may be excessive decomposition naphthaleneboronic acid, such as 2,6-natalijagolosova acid. If you select a cleaning solvent has a low vapor pressure at the temperature selected for carrying out high-temperature cleaning process, it will be necessary to carry out the reaction in the apparatus under pressure so that the solvent was in a liquid state. Therefore, the pressure of such a process delicieuse solvent in the reaction mixture is in a liquid state. For example, if you use the preferred solvents, such as water, low molecular weight carboxylic acids and mixtures of water with low molecular weight carboxylic acids, the pressure should reach approximately 3000 pounds per square inch, more preferably 2000 pounds per square inch. Preferably, the pressure was at least 200 pounds per square inch.After high-temperature processing using cleaning solvent, the reaction mixture of products subjected to a separation process in which the resulting purified natalijagolosova acid is separated from the used solvent. To separate the solid product from the liquid at this stage of separation can be used any way. For example, can be used to filter (vacuum, atmospheric or high pressure, sedimentation or centrifugation. You can also use combinations of these methods of separation. Also, it is preferable to rinse the cleaned naphthaleneboronic acid solvent after its separation from the cleaning solvent used in high temperature processing.Before the separation of the purified naphthaleneboronic acid from established, to cause crystallization naphthaleneboronic acid. However, it can be expected that cooling will lead to crystallization of not only the target naphthaleneboronic acid, but also to the precipitation or crystallization of impurities. Therefore, an acceptable temperature for the Department naphthaleneboronic acid from the reaction mixture is temperature, which leads to naphthaleneboronic acid the desired degree of purity with the desired output naphthaleneboronic acid. For example, before the separation naphthaleneboronic acid from the reaction mixture may be cooled to a temperature below the reaction temperature of about 20 to 400oF, more preferably at 200 - 350oF. More preferably before the separation naphthaleneboronic acid from the reaction mixture, the latter is cooled to a temperature of from about 100 to 400oF. in Addition, it is desirable that the reaction mixture was cooled slowly. Slow cooling of the reaction mixture results in naphthaleneboronic acid, having a larger average particle size and naphthaleneboronic acid containing fewer particles with very small size. Naphtaline sticy not clog or "no shade" filter elements or basket centrifuges at carrying out filtration and/or centrifugation. In addition, natalijagolosova acid with large particles preferred in obtaining PAN, as in this case, you have fewer glycol to obtain suspensions naphthaleneboronic acid and ethylene glycol, which can be transported by means of pumps. The rate of cooling of the reaction mixture should not exceed 50oF/min, more preferably 40oF/min and most preferably 10oF/min When carrying out this method according to the continuous scheme to obtain a low cooling rates can be used tubular heat exchanger with the surface being cleaned. When using high-temperature method of the present invention can be obtained 2,6-natalijagolosova acid with an average particle size, measured by the analyzer Microtrac particleTMat least 100 μm, preferably at least 125 μm. In addition can be obtained 2,6-natalijagolosova acid with an average particle size of at least about 200 microns. Moreover, 2,6-natalijagolosova acid, obtained by heat treatment of the present invention using cleaning solvent, characterized by a very low content of Melkite approximately 2%.In one of the embodiments of the high-temperature method, which uses the solvent, during the stage of heating is used inert atmosphere. For example, a gas, such as nitrogen, helium or argon or a mixture of one or more gases, is added to the reaction apparatus for removing or reducing the amount of oxygen that is present in the air.In another embodiment of the present high-temperature method, the reaction mixture containing naphthaleneboronic acid and a cleaning solvent, may be treated with hydrogen in the presence of iodine or more hydrogenation catalysts. This treatment leads to a significant reduction of impurities such as 2-formyl-6-naphthoic acid, in purified 2,6-naphthaleneboronic acid. In addition, the use of hydrogen facilitates the removal of the bromine-naphthalenesulphonic acids and turns bromo-2,6-naphthaleneboronic acid naphthaleneboronic acid. When using hydrogen, the preferred solvent is water and low molecular weight carboxylic acids, such as acetic acid. Can also be used a mixture of low molecular weight carboxylic acids. Acetic acid is the most is) the amount of water ranges from about 2 to about 98%. The most preferred solvent is a mixture of water and acetic acid, the water is present in amount of about 5 to 95 wt.%, more preferably 15 to 85%. When using hydrogen, the amount of solvent preferably should be a number that is almost completely dissolves naphthaleneboronic acid at a temperature at which do the cleaning.When using hydrogen, the latter preferably represents a hydrogen gas at a partial pressure of from about 1 to 10 pounds per square inch, and preferably 5 are 300 pounds per square inch. In a mixture with hydrogen may be used an inert gas, such as nitrogen, helium or argon. As the hydrogenation catalyst can be any catalyst which catalyzes the interaction of hydrogen with impurities and removes the formyl naphthoic acid and bromo-naphthaleneboronic acid in purified naphthaleneboronic acid. The preferred catalyst for the hydrogenation are representatives of the noble metals of group VIII, which are platinum, palladium, rhodium, ruthenium, osmium, irdieden method of the present invention using a cleaning solvent. The above-mentioned metals of group VIII can be used deposited on a suitable material, or can be used without coating. As the material of the carrier may be used such materials as aluminum oxide, aluminosilicate, silicon dioxide, clay, zirconium dioxide. It is especially good to use as a base material charcoal and/or charcoal. The number of one or more metals of group VIII on a carrier, preferably on coal and/or charcoal, is approximately 0.1 - 5.0 wt.%, based on the weight of the catalyst. The amount used of the catalyst is a function of variables such as reaction temperature, concentration of impurities in naphthaleneboronic acid and the aging time of the reaction. However, in General the weight ratio of contaminated naphthaleneboronic acid to the active component of the hydrogenation catalyst is from about 200: 1 to 30,000:1, more preferably from 2000: 1 to 20000: 1. The preferred catalyst is a catalyst comprising a 0.03-1.0 wt.% palladium on carbon with a large surface area. Such catalysts offer the company Engelhard. Corp., Edison, N. J.; Degussa Corp., South Plainfield., N. Y; Aldrich. Chemical Co., Milwa isdi naphthaleneboronic acid, will vary depending on the amount of used catalyst for the hydrogenation, the hydrogen concentration and temperature. However, in the General case, the aging time or hourly space velocity of the reaction mixture in contact with a hydrogenation catalyst is from about 200 to 200,000 g of reaction solution per 1 g of the active component of catalyst per hour. More preferably this amount is from about 100 to 100,000.After treating the reaction mixture with hydrogen, the reaction mixture is separated from the hydrogenation catalyst. If is a continuous method in which the reaction mixture passes over or through a fixed bed of the catalyst hydrogenation, such phase separation is not required. However, if you are using the periodic method, in which the catalyst added to the reaction mixture, for example, in pellet form, the hydrogenation catalyst must be separated from the reaction mixture using one or more methods, such as filtration, settling or centrifugation. When using the catalyst in such a dispersed form, it is desirable that the conditions were those in which naphthalenesulphonate, in order to facilitate the separation of the reaction mixture from the hydrogenation catalyst. However, when working in conditions where natalijagolosova acid not all is in solution, the hydrogenation catalyst may be located on one side of a screen or filter or other barrier which prevents the passage of dissolved naphthaleneboronic acid, dissolved impurities and gaseous hydrogen, but does not allow undissolved particles naphthaleneboronic acid and insoluble impurities. When using such equipment, the hydrogenation reaction can be carried out in such a way that the hydrogenation catalyst is not exposed to insoluble components, which can deactivate it.In another embodiment of the high-temperature method, especially when the cleaning solvent is water or a mixture of water with low molecular weight carboxylic acid, to improve the degree of purification of the resulting carboxylic acid can be added activated charcoal. The use of activated charcoal is especially suitable for conditions where natalijagolosova acid when carrying out high-temperature processing is almost completely dissolved. When grief is next cooled observed crystallization of purified naphthaleneboronic acid. The weight ratio of activated carbon to contaminated naphthaleneboronic acid typically ranges from about 0.005: 1 to 0.06: 1, more preferably from about 0.01:1 to 0.03:1.In addition, high-temperature method of the present invention for cleaning naphthaleneboronic acid using cleaning solvent does not require the receipt and use of mono - and/or di-alkali metal salts, or other soluble salts or soluble esters or anhydrides. Contaminated natalijagolosova acid, downloadable for carrying out the cleaning process, as well as natalijagolosova acid present in the cleaning process, is mainly in the protonated acid form, that is, when the carboxyl group is protonated form or hydrogen form, more preferably, when at least 90 mol.% naphthaleneboronic acid is in the protonated form, and most preferably, when almost all natalijagolosova acid is in the protonated or hydrogen form, and not in the form of a salt, ester or other derivative.In addition to the above-described method and methods, the present invention relates to 2,6 sustained fashion at least 175 μm, more preferably at least about 200 microns, and more preferably to approximately 1000 μm, more preferably up to about 800 microns, preferably such a 2.6-natalijagolosova acid contains less than 5% of particles having a particle size of up to 11 μm, preferably less than 2% of particles having a particle size of less than 11 μm, moreover, such a 2,6-natalijagolosova acid preferably has a 95% purity, more preferably at least 98% purity. The present invention also includes compositions containing a physical mixture of 2,6-naphthaleneboronic acid having an average particle size of at least about 100 microns, preferably at least about 125 microns, and preferably to approximately 1000 μm, more preferably up to about 800 microns and a glycol containing from 2 to about 6 carbon atoms, and preferably ethylene glycol, in which the molar ratio of glycol to 2,6-naphthaleneboronic acid is from about 1:1 to about 10:1, preferably from 1:1 to 4:1, respectively, and preferably less than 5 wt.% particles 2,6-naphthaleneboronic acid has a particle size below 11 microns.plants using cleaning solvent, contains a very small amount trimellitic acid, for example, less than about 0.5%, a very small amount of 2-formyl-6-naphthoic acid, for example, less than approximately 0.1 wt.%, and a very small number bromo-2,6-naphthaleneboronic acid, for example, less than 0.05 wt.%.The advantage of the present invention is that the resulting aromatic carboxylic acid is more acceptable to obtain esters. This is because the aromatic carboxylic acid is cleaner than it would be when receiving it in another way, and in the process of obtaining and purifying air more than pure aromatic carboxylic acid contributes a smaller amount of impurities that must be removed when cleaning the air. For example, the preferred method of obtaining dialkylamide ether 2,6-naphthaleneboronic acid is in the handling of 2,6-naphthaleneboronic acid molar excess of the alcohol, preferably methanol, at an elevated temperature. For example, the weight ratio of alcohol to 2,6-naphthaleneboronic acid is about 1: 1 to 10:1, and the temperature lies in the range of approximately 100 - 700oF. If necessary, there may be used a catalyst for etete approximately 0.1 - 10.0 wt. % based on the weight of 2,6-naphthaleneboronic acid, or one or more catalysts based on metals described in British patent 1437897. After the esterification reaction mixture is cooled to the crystallization of ether. The ether is preferably crystallized in methanol or in an aromatic solvent such as toluene or xylene, and the recrystallized product may be subjected to distillation distillation under reduced pressure, preferably using a high efficiency distillation column, to obtain the purified dimethyl-2,6-naphthaleneboronic acid. Upon receipt and clearance of this ether, as well as other esters of aromatic carboxylic acids, formed a number of working threads containing concentrated impurities. For example, when crystallization is carried out of the ether mother liquor obtained in the esterification reaction, contains impurities, such as fully or partially esterified oxidized impurities. This stream after removal of practically all of the alcohol may be returned to the reaction mixture oxidation or preferably it may be returned to stage high-temperature processing method of the present invention. Similarly ameriface is whether the aromatic solvent can be recycled in the reaction mixture oxidation or preferably a high-temperature stage of the process of the present invention. In addition, if the ether is distilled, then the VAT residue contains concentrated impurities and this VAT residue or part of it may be returned to the reaction mixture oxidation or, preferably, high-temperature stage of the process of the present invention. Therefore, the present invention relates to dimethyl-2,6-naphthalenecarboximides obtained by the esterification of 2,6-naphthaleneboronic acid obtained in accordance with the present invention.High-temperature processing and the method of the present invention can be implemented as periodic and continuous schemes.Figure 1 is a diagram of one method of implementing the present invention using as a starting compound in the oxidation of 2,6-dimethylnaphthalene. Liquid-phase catalytic oxidation of 2,6-dimethylnaphthalene flows in the reactor section 1. For the filing, respectively, 2,6-dimethylnaphthalene, acetic acid (solvent at the stage of oxidation), catalyst (i.e. bromine, cobalt and manganese component) and air in the oxidation reactor used supply line 2-5. The total flow from the reactor oxidation (i.e. contaminated 2,6-naftalinescu reactions and impurities) is fed into the reactor 20 of high temperature treatment on line 15. In the reactor high-temperature processing, the total flow from the oxidation reactor is heated to a temperature of at least 500oF in order to reduce the content of impurities and by-products in the mother solution, which leads to an increase in the purity of 2,6-naphthaleneboronic acid and increases the size of its particles. This reactor can be, for example, a reactor with stirring or sectional reactor. Hydrogen gas can be fed into the reactor high-temperature processing on line 25, and an acceptable catalytic hydrogenation can also be served in the reactor high-temperature processing. The mixture of products after reactor high-temperature processing is cooled in the mold 35. Cooling is accompanied by a decrease in pressure, allowing the mixture to cool by evaporation of the solvent with decreasing pressure. If you want a slower cooling, can be used cascade mold in order to lower the temperature stepwise. On the other hand, the gradual cooling of the mixture can be used tubular heat exchanger with clean walls. Slow cooling promotes the formation of large crystals of 2,6-naphthalenemethanol to adultsa on the device for the separation system, the solid-liquid 45. Device for separating solid-liquid can be a rotary filter, a centrifuge or a vessel for deposition. Collected 2,6-naphthaleneboronic acid optionally washed, for example, acetic acid or a mixture of acetic acid with water. Rinsing liquid, it is possible at elevated temperatures, flows through line 50 to a device for the separation system, the solid-liquid. Solid wet 2,6-natalijagolosova acid on line 55 is sent to the dryer 60 which removes the residual amount of solvent. The liquid separated from the reaction mixture in the device for the separation system, the solid-liquid and used for flushing solvent through line 70 is directed to the apparatus for separation of the mother liquor 75. The part of the mother liquor, which may have at least a small number of remote water is returned to the oxidation reactor through line 80. The remaining portion, for example 5 to 50% of the mother liquor, on the line 90 is fed into the machine allocation solvent 95. Apparatus for the selection of the solvent is usually a multi-stage apparatus for distillation, in which water is separated from the acetic acid. Dedicated acetic acid is on the line 98. When carrying out the oxidation of the condenser exhaust fumes 110 condenses and cools the mixture of vapors of acetic acid and water formed by ekzotermicheskie oxidation reactions that enter the condenser through line 115. The cooled condensate is partially returned to the reactor through line 120 to control the temperature of the oxidation reaction. Part of the condensate, which is enriched in water compared with the mixture of solvents oxidation reaction, is also fed into the reactor high-temperature processing 20 through line 130. Part of the condensate is returned to the reactor in comparison with a portion directed to the reactor high-temperature processing, depends on the content of the solvent, which is preferably in the reactor high-temperature processing. The ability to add a condensate after the oxidation reaction in the reactor high-temperature processing allows you to provide a lower water content in the oxidation reactor. Lower water content in the oxidation of 2,6-dimethylnaphthalene to 2.6-naphthaleneboronic acid leads to a low content of oxidized impurities and side products of the reaction.The invention is better understood from the following examples. However, it should be understood that e is th as examples, limiting the scope of invention.Examples
For oxidation of 2,6-dimethylnaphthalene 2.6-naphthaleneboronic acid according to examples 1 and 2 were used following the General methods of oxidation.Installation oxidation consisted of one litre titanium reactor top outlet, equipped with water-cooled titanium condenser, the case for thermocouples, line input air line supply and pressure regulator. As a solvent in the oxidation used acetic acid as the oxidation catalysts used acetate tetrahydrate cobalt (II) acetate tetrahydrate manganese (II). Source of bromine for oxidation reactions served as aqueous Hydrobromic acid. The condenser is designed for cooling and return to the reactor and the condensed solvent, evaporating due to heat when the reaction of oxidation. During the oxidation reaction in the reactor served in both the air and 2,6-dimethylnaphthalene with a slight excess of air in order to provide 6% oxygen content in the exhaust gas. Upon completion of the oxidation reaction of the supply and the air flow block and the contents of the reactor through an overflow line is transferred into a collection of what I acetic acid at atmospheric pressure.The particle size was measured using a standard size analyzer Microtrac IITMcompany Leeds and Northrup Go. (St. Petersburg, Florida). As the circulating fluid suspension of particles 2,6-naphthaleneboronic acid used methanol (or water). This method is based on the scattering of laser light and allows to measure both the average and median particle size. By this method you can also determine the weight percent of 2,6-naphthaleneboronic acid having a particle size of less than 11 microns. Organic components were analyzed using liquid chromatography. Metals and bromine was measured using x-ray fluorescence spectroscopy or analysis inductively coupled plasma (MOS).In the following examples and tables 2,6-natalijagolosova acid identified as 2,6-NIR; 2,7-natalijagolosova acid as 2,7-NIR; trimellitate acid as TMLC; 2-formyl-6-naphthoic acid as a 2-FNK; 2-naphthoic acid as a 2-NK; bromo-2,6-natalijagolosova acid as Br-2,6-NIR; terephthalic acid as TC and isophthalic acid as IR. BUT or value of 0.00 means "not determined".The values in the tables and examples related to the "normalized 2,6-NDK" obtained by dividing p is needful "total" values and multiplying by 100. Because of the magnitude of the signal component 2,6-NIR really get the magnitude is less accurate concentration measurement. Therefore, this value is normalized as described above. Value of 0.00 in the tables indicate that the content of the component is not determined by the method of analysis.Example 1
Table 1 shows the results of five oxidation reactions, each of which uses the same ratio of solvent oxidation and the supply flow 2,6-dimethylnaphthalene. For experiments 1 and 3 oxidation conditions selected to minimize the number of 2-formyl-6-naphthoic acid in the product. It is desirable for the conventional process, as 2-FNK difficult to separate and it is an undesirable component in 2,6-NIR used to obtain PENG and other polyesters. However, as indicated by the data of table 1, the conditions under which produces a minimal number of 2-FNK, also cause the formation trimellitic acid and oxidation of the solvent, acetic acid, as evidenced by the large amount of carbon dioxide. For experiments 2, 4 and 5 conditions selected to reduce the number TMLC and/or carbon dioxide, which usually leads to a higher yield of 2,6-NIR, but also to Avelino in the following examples, method of high-temperature heating of the present invention can be used to reduce the levels of 2-opt in the oxidation reaction mixture. In addition, when using hydrogen under heat 2-FNK, apparently, is transformed into an intermediate product which is then recirculated oxidative reaction mixture is oxidized to 2,6-naphthaleneboronic acid.Example 2
In table II, experiments 1-3, presents data on the oxidation of 2,6-dimethylnaphthalene 2.6-naphthaleneboronic acid when the reaction described in the weight relationship of the solvent to 2,6-dimethylnaphthalene. Low solvent supplied to the raw materials necessary, because in this case can be obtained a greater amount of 2,6-NIR based on the size of the oxidation reactor, and presents the data show that a low solvent-raw materials lead to particularly good results. In addition, the amount of by-product, such as bromo - 2,6-natalijagolosova acid formed at a lower relationship solvent to 2,6-dimethylnaphthalene, can be reduced, and in some cases the presence of such a product may be excluded, if use is more low quantity of solvent in the reaction mixture of oxidation.In table II, experiments 4-6 show that the use of a higher content of bromine in the reaction of oxidation can lead to the desired reduction of the number of oxidizing acetic acid, which is established by the formation of carbon dioxide. However, the increase of bromine in the reaction mixture oxidation increases the number of generated bromo-2,6-naphthalenesulphonic acids. However, as described above and as shown hereinafter, the method of the present invention can be implemented with the aim of reducing the amount bromo-2,6-naphthalenesulphonic acids in the reaction mixture of oxidation products. In addition, when using hydrogen bromo-2,6-natalijagolosova acid into 2,6-naphthaleneboronic acid.The following examples 3, 4 show the use of high temperature processing of the present invention. These examples were carried out using crude 2,6-naphthaleneboronic acid, obtained under conditions of continuous liquid-phase oxidation of acetic acid as solvent and catalyzed by cobalt, manganese and bromine. This 2,6-natalijagolosova acid contains most of the impurities and by-products, which were Nai is example 3
Table III presents the experiments 1-8, which are carried out in the reactor pressure vessels of 50 ml, equipped with an internal thermocouple and containing solvents and crude 2,6-naphthaleneboronic acid having specified in table III composition. Into the reactor was introduced a metal mesh basket containing the catalyst, such as granules of 0.5% Pd on coal. The catalyst was pre-heated in a solvent at 530oF for 72 h for "aging" and give more stability to the catalyst. And, finally, the reactor was purged with hydrogen to remove oxygen and was raised pressure, feeding the required amount of hydrogen and sealing the reactor.The reactor was placed in a device for stirring and stirred the contents of the reactor at a shaking speed of 360 cycles per min. In the process of shaking the reactor was partially immersed in a sand bath to maintain the required temperature, which is measured using a thermocouple. Continuing the shaking, the reaction temperature was maintained for 30 min, as indicated in table III. Upon completion of the reaction, the reactor was removed from the sand bath, cooled to room temperature, was determined by the weight of the contents of the reactor and transferred into the Cup for drying in a vacuum customary analyzed.Experiments 1-3, are shown in table III, was performed using a mixture of 85% acetic acid and 15% water at different hydrogen pressures. This attitude of solvents is similar to the ratio of solvents, which is expected in the stream leaving the oxidation reactor. In all cases we achieved 100% conversion of the bromo-2,6 NIR, 62-72% conversion TMLC and 61-71% conversion of 2-FNK. Number 2-NK formed by the decomposition of 2,6-NIR, lay in the interval from 0.0 to 0.06 wt.%. The number of decarboxylation increased with increasing hydrogen pressure and ranged from 0.02 to 0.14%. Therefore, there has been a high degree of conversion of the impurities along with low by-product formation. The increase in the normalized content of 2,6-NIR indicates that some impurities (such as bromo-2,6-NIR) is converted into 2,6-NIR.In experiments 4-6 used a mixture of acetic acid-water 50/50. The conversion of the bromo-2,6-NIR was 100%, as in the case of 85% acetic acid. Turning TMLC and 2-FNK in some cases was higher than when using 85% acetic acid. However, the number of 2-NK and tetralin was higher than when using 85% acetic acid. In experiments 7 and 8 as the solvent used water conducted two comparative experience in a large reactor high pressure with stirring at the same loading source 2,6-NIR, catalyst and under the same pressure of hydrogen. In experiment 1 as a solvent used water, as in experiment 2 - a mixture of 90% acetic acid and 10% water. Both experiment was carried out in the same conditions, except that in experiment 2 reaction time was doubled to obtain higher conversion of 2-FNA and study the formation of unwanted side products. One of the advantages of the use of acetic acid in comparison with water is that the vapor pressure of acetic acid below that allows you to run at a lower pressure, 500 psig at a temperature of 590oF. Upon completion of the reaction, the reaction mixture of both experiments was cooled to 300oF and filtered through a sieve at the bottom of the reactor. The precipitate was washed into the reactor with 300oF 400 g of the same solvent and obtained by filtering the mother liquor was added to the first stock solution.The mother solution and the precipitate was dried in a vacuum dryer at 175 - 195oF, separately mixed to obtain homogeneous samples and each sample was analyzed using liquid chromatography for the determination of organic components and using x-ray fluorescence spectroscopy for the determination of metals. For opredeleniiakh and the composition of the filtrate and the precipitate was used for calculation of the composition of the total product, which are presented in table IV in the column "joint product".Comparison of "joint products" in table IV shows that the conversion of 2-opt and TMLC higher in experiment 2 (90% acetic acid) than in experiment 1. This can be explained by a longer reaction time in example 2. However, despite the longer the reaction time, the formation of 2-NK was lower in experiment 2.The metal content in the two sediments were significantly different. When using as solvent water, the number of remaining metal was almost 3 times higher than in the sediment obtained using 90% acetic acid. The particle size obtained using each solvent, was significantly higher than in the case of a simple separation of the solid product from the suspension.Example 5
For evidence that the treatment of the bromo-2,6-NIR hydrogen on Pd/C will be accompanied by the formation of 2,6-NIR, spent experience with the original product containing 2,6-NIR high purity by adding 4.3% bromo-2,6-NIR (approximately 2-10 times higher are usually formed by oxidation). After treatment for 10 min at 600oF the entire reaction mixture was dried and the dry product contained only 0.02 loss bromo-2,6-NIR and the emergence of 2,6-NIR. It was not observed in other new components. This example confirms the mentioned advantage of the present invention a method of increasing the yield of 2,6-NIR with greater flexibility in the choice of conditions under oxidation. The results are presented in table V.Example 6
In this example, used after cooling, the total flow leaving the oxidation reactor (the RESPONDENTS), but without any separation, concentration or dilution. So, WHICH contained acetic acid/water as solvent and about 25 wt.% solid components. The sample, WHICH was dried in a vacuum dryer; the composition of the solid components is given in table VI. In the autoclave of 300 ml was loaded, WHICH together with the catalyst 0.5% Pd/C in the basket of wire mesh. To remove oxygen, the autoclave was purged with helium, and then using the hydrogen raised the pressure to 300 psig. With stirring, the autoclave was rapidly heated to the required temperature and held at this temperature for a set time. Upon completion of the reaction, the heating was stopped and the autoclave was cooled to 400oF for 3 min and then quickly cooled to room temperature. The contents of the reactor were unloaded, the solvent of variography.Experiment 1, conducted at 600oF, shows that high conversion TMLC, bromo-2,6-NIR and 2-opt can be achieved in a short period of time, about 10 minutes, at 600oF if you are using fresh hydrogenation catalyst. This is true, despite the high solids content (25%), which may prevent the complete dissolution of all solids in a single operation. The crystalline product has a large average particle size with a small content of fine particles. Less than 20% of the bromine is lost in the form of HBr, although achieved 90% conversion of the bromo-2,6-NIR. Not detected education 2-NK due to decarboxylation.Experiment 2 was carried out at a lower temperature using already used catalyst and at a longer reaction time. The obtained results similar to the results of experiment 1 to a high degree of conversion TMLC and bromo-2,6-NIR, but sometimes received a lower conversion of 2-FNK. At lower temperatures the loss of bromine were lower.Work at lower temperatures reduces the pressure in the reactor and the rate of corrosion. However, complete dissolution of the solid components, is probably not achieved. When using a reactor with the catalyst.In the following examples 7-9 were using the same reactor as in example 3, and the total flow leaving the reactor, which was used in all these examples, was obtained under the conditions of oxidation of 2,6-dimethylnaphthalene 2.6-naphthaleneboronic acid in a solvent mixture of acetic acid-water catalysis by cobalt, manganese and bromine.Example 7
In table VII presents the results of heating of the RESPONDENTS at 575 - 650oF for or 1 or 30 min, as shown in experiments 1-6. When hydrogen was not used. Overall, the reaction product was dried to remove solvent and analyzed. The results show that trimellitate acid is mainly converted into terephthalic acid (TC) and ISO-phthalic acid (MK). In addition, when heat treatment is observed transformation bromo-2,6-NIR and mostly 2-FNK.Example 8
In example VIII presents data from a series of high-temperature treatments of the total reaction product without the use of hydrogen, which are applied in a hot filtration, and the filter product is washed with 200oF a mixture of 85% acetic acid and 15% water. These data show that under different conditions 2,6-naphthalenyl, bromine and some organic impurities. Of great importance is the fact that particle size 2,6-naphthaleneboronic acid was significantly larger than the size of the particles in the stream exiting the reactor.Example 9
In table IX presents the results of high-temperature processing General reaction of the oxidation product in accordance with the method of the present invention, where, after high temperature treatment of 2,6-naphthaleneboronic acid was filtered hot from the reactor and used washing. The obtained data show that high-temperature processing facilitates the removal TMLC, bromo-2,6-NIR and 2-opt out of the final product. It is important to note that "dry the filtrate, which contains the catalyst of the oxidation reaction, characterized by low content TMLC, which means that this material can be returned to the oxidation reaction without adding unwanted TMLC.Example 10
Below presents data on the solubility of 2,6-naphthaleneboronic acid in distilled water and in acetic acid (see table. A).Example 11
In the following table X shows the overall methodology of the experiments 1-7:
Into the reactor under pressure to 5 ml with internal thermocouple, and have been fitted the Wallpaper 2,6-NIR, obtained when catalyzed by cobalt, manganese and bromine liquid-phase oxidation of 2,6-dimethylnaphthalene, and contained metal and organic impurities listed in table X. After purging the reactor with helium to remove oxygen, the reactor was sealed and the contents mixed with traucki at a speed of 360 cycles/min (kg/min). When shaken with such speed the reactor was immersed in a heated bath of fluidized bed of sand, for heating the reaction mass to the required temperature within 30 min After conditioning at a fixed temperature for a certain period of time the reactor was removed from the sand bath and cooled, still shaking. The cooling rate was regulated by the amount of air directed to the external surface of the reactor.After the reaction and cooling of the reaction mixture, the reactor was weighed to determine the weight change due to leakage (see "Weight of the product" in table X). The product was unloaded from the reactor at room temperature using cold distilled water to facilitate unloading. The mixture was filtered and the precipitate from the filter and the filtrate was dried in a vacuum dryer at 85oF for 4-8 hours, dry Weight Peavy balance exceeded 95% and in most cases - 98% of the original load.The solid product from the filtrate and filter were analyzed using liquid chromatography. In table X presents the calculated total number of the product by combining the weights of each component in the sediment and dry the filtrate. Liquid chromatography gives the most accurate results, although the Mac. % the content of 2,6-NDA ("2,6-NDA" (as defined in the table) is usually less accurate due to the size of the signal detector in liquid chromatography. Partial correction is obtained by normalizing the magnitude of 2,6-NIR by dividing the total received wt.% content and multiplying by 100, which is shown in the table in column 2,6-NDA (% of total)". In any case, found no evidence of decomposition 2,6-NIR excess of approximately 1%. Particle size was determined as described above, by using MicrotracTM.Experiments 1-3, shown in the table, was performed using the same 2,6-NIR, temperature and time of curing reaction, but at different cooling rates. All three experiences show that the conversion TMLC is about 69%, and the conversion of the bromo-2,6-NIR is about 56%, whereas the formation of 2,6-NIR was less than 0.2%. Lower sorostitutes to increase the size of the particles of the average size of 54 μm at a faster cooling rate 125oF/min to medium size 207 microns at a speed of 6.5oF/min At all cooling rates, the percentage of particles less than 11 microns (fine particles) was significantly reduced from 40% in raw 2,6-NIR to less than 3% in the final product. This reduction in small particles leads to a significant improvement of devices for separation systems solid/liquid in the separation of purified 2,6-naphthaleneboronic acid from the mother liquor of the reaction mixture.Experiments 1-3 are presented in table X, show that to obtain a high conversion rate, and the highest particle size is desirable to carry out more than slow cooling. These experiments also show an unexpected characteristic of the present invention, when TMLC and bromo-2,6-NDA when carrying out high-temperature treatment of the present invention are the corresponding transformations.Experiments 4-6, shown in table X, carried out under conditions similar to the conditions of experiments 1-3, except that the reaction temperature was changed from 600oF, as in experiment 4, up to 540oF experience 6. The result of reducing the temperature was reduced as the conversion of impurities and reducing the size of the particles. When more nigeriana small particle size of less than 11 μm was 18%. Although both of these values show an improvement in comparison with the original 2,6-NIR, they also show that the cleanup is not complete within 10 min of the reaction. A longer reaction time may be expected to lead to improved results at 540oF. the Results obtained at 540oF, show that the preferred temperature is the temperature of at least about 550oF.In experiment 6, table X were used less water and more 2,6-NIR to increase the ratio of solvent/solid component is from 5:1 (16.7% solids) to 4:1 (20% solids). Heating at 600oF with moderate cooling rates similar to the rates used in experiment 4, results in a product similar to the product experience 4 with a high degree of conversion of the bromo-2,6-NIR, moderate conversion TMLC and with the formation of 2-NK less than 0.2%.Example 12
Experience 8 in table XI were conducted to determine the degree of formation of impurities during the high temperature processing of the initial 2,6-NIR, not containing metals and containing a small amount of organic impurities. In this experiment, which used the same reactor as in experiments 1-7 in example 11, ipshita 2,6-NIR contained 1.4 wt. % ether. The product after thermal treatment contained 0.3% of ether and 0.5% of other unidentified impurities, which were determined using liquid chromatography, which shows that the decomposition of 2,6-NIR slightly.Example 13
In experiments 9 and 10 in table XII high-temperature processing of crude 2,6-NIR was carried out to a greater extent than in experiments 1-8 of example 11, in order to provide hot filtration of the product at temperatures above the temperature of the water.Experience 9 were carried out in an autoclave of 300 ml Raw materials served as 2,6-NIR in the form of a wet sludge separated from the oxidation reactor. This wet precipitate contained 20.2 g of solid product, 6 g of acetic acid and 1 g of water. The wet precipitate was added to 93 g of water. After high temperature treatment in special conditions, the reactor was cooled to room temperature, and at the bottom of the reactor was placed a filter in stainless steel. The reactor was again heated to 400oF for 10 minutes, then give liquid to flow from the reactor through the filter. Added an additional 40 ml of water and was altered for 5 min, the filtrate was again removed through the filter. Sediment and combined filters were dried and analyzed, the results are presented in table II.The results is istratii, leads to a product with a very low content TMLC and 20-NK, 88% increase decrease amount bromo-2,6-NIR, a 50% increase decrease 2-FNK, undetectable amount of cobalt and manganese, and 84% increase decrease in the total content of bromine. In addition, the particle size was increased almost 10 times, and excluded the presence of small particles with size less than 11 microns.Almost 74% TMLC present initially becomes "other" components (mainly ISO-phthalic and terephthalic acid), which are mainly in the filtrate. This transformation TMLC makes vintage solution is potentially more good material to return to the oxidation reactor where TMLC, as we know, reduces the activity of the oxidation catalyst. 1.49 g of solid products, the mother liquor contains only about 21% of 2,6-NIR, which is less than 2% of the total number of source 2,6-NIR.Example 14
In a high pressure autoclave with a 300 ml, equipped with equipment for mixing, internal thermocouple, pressure gauge, as well as incoming and outgoing lines, downloaded 100 g of water and 20.02 g of impure 2,6-NIR (powder with very small particles of light-yellow color), the results of which are presented in ISE stirrers, but below the surface level of the liquid. After cleaning the reactor from oxygen with helium in the reactor was filed hydrogen to 300 pounds per square inch (72oF).Under stirring at low speed (250 rpm) reactor heated for 20 min to 600oF and this temperature was kept for 30 minutes the pressure in the reactor, as noted, was 1510 psig at 600oF. the Reactor was then cooled to 600oF to 400oF for 35 min, and then with 400oF to 77oF for 70 minutes At 77oF adding in the reactor was 210 pounds per square inch at the expense of the remaining hydrogen. The reactor was opened and for the analysis of the selected sample mixed solid product. It is established that the solid products in the reactor was white with a faint greenish tinge. Studies using the electron microscope show that the product sample consists of a crystalline material with a certain number of crystals with a maximum length of more than 700 microns. After drying, the solid product was a colorless crystals, analysis of which is given in table XIII.Although this represents only some embodiments of the present invention, alternative embodiments and various modifications will be about what their alternative embodiments are considered equivalent and meet the spirit and scope of the present invention. 1. Method for preparation of aromatic carboxylic acids by liquid phase oxidation of the corresponding aromatic compounds containing at least one capable of oxidation of alkyl or acyl group, oxygen-containing gas in a solvent containing a low molecular weight carboxylic acid, in the presence of an oxidation catalyst containing heavy metals, at 121 - 232oC with formation of a reaction mixture of oxidation products containing the obtained aromatic carboxylic acid, which is subjected to further processing, characterized in that the treatment is that the reaction mixture is heated oxidation products at temperatures from at least 228 to 368oC to obtain a second reaction mixture of oxidation products, which then emit an aromatic carboxylic acid.2. The method according to p. 1, characterized in that the reaction mixture of oxidation products is heated to at least 315oC.3. The method according to p. 1, wherein the aromatic compound is a 2,6-dimethylnaphthalene.4. The method according to p. 1, characterized in that the aromatic carboxylic acid is recovered from the reaction mixture products ocil rasaut on the stage of oxidation.5. A method of obtaining purified naphthaleneboronic acid through liquid-phase oxidation of dialkyl or diacyl-, or alkylarylsulfonates compounds oxygen-containing gas in a solvent containing a low molecular weight carboxylic acid, in the presence of an oxidation catalyst containing heavy metals, when heated with the formation crude naphthaleneboronic acid, which is subjected to further processing, characterized in that the treatment is that raw natalijagolosova acid in contact with a cleaning solvent that contains water, low molecular weight carboxylic acids or mixtures thereof, with at least 260oC for a time sufficient to reduce the concentration present in trimethylsilanol acid by at least 40%, followed by separation of the resulting mixture of products purified naphthaleneboronic acid.6. The method according to p. 5, characterized in that the acid is a 2,6-naphthaleneboronic acid.7. The method according to p. 5, characterized in that the raw natalijagolosova acid comes in contact with the cleaning solvent in the presence of gaseous hydrogen and a hydrogenation catalyst.the Oh of the acid.9. The method according to p. 5, characterized in that the separation of the purified naphthaleneboronic acid from the resulting mixture of products is carried out at a temperature which is approximately 10 - 210oC lower than the temperature of contact of the acid with the solvent.
FIELD: organic chemistry, chemical technology.
SUBSTANCE: invention relates to the improved method for preparing 2-keto-L-gulonic acid. This compound is an intermediate substance in synthesis of vitamin C. Method involves oxidation of L-sorbose in the presence of platinum-containing polymeric catalyst applied on Al2O3 in medium with the equimolar content of NaHCO3 under atmosphere pressure, at the rate stirring 870-1 000 rev/min and bubbling pure oxygen as an oxidizing agent. Reaction is carried out in medium water : ethyl alcohol 7-10 vol. %, in the concentration of L-sorbose 0.29-0.6 mole/l, on spherical microparticles of catalyst in the amount 20-40 g/l with ultra-thin layer of polydiallyldimethylammonium chloride as cationic polyelectrolyte with platinum nanoparticles formed on it. The content of platinum in catalyst is 1-2%. The feeding rate of oxidizing agent is 400-450 ml/min. The end product is obtained with high yield 97-99%.
EFFECT: improved preparing method, enhanced yield of product.
7 cl, 1 tbl, 1 sch, 7 ex