The way to obtain the isomers of phthalic acid with a high degree of purity

 

(57) Abstract:

Usage: as a monomer for polymer materials. The inventive product of terephthalic, isophthalic and phthalic acid with a high degree of purity without purification stages hydrogenation. Reagent 1: isomer of xylene. Reagent 2: oxygen-containing gas. Reaction conditions: after the 1-St and 2-nd stage of oxidation of the precipitate was separated from the solvent and then the process is returned to the cycle solvent, then the resulting slurry is heated to a high temperature for extraction of impurities, after cooling and process air and catalysts on the 3rd stage of oxidation. Distinguishing characteristics: a) the modified catalytic system consisting of a conventional catalyst Co/Mn/Br and additives of Nickel, chromium, zirconium or cerium, taken separately or in mixture with each Doug, which leads to selective acceleration of the oxidation reaction, (b) pre-heating and a special method of feeding the reaction mixture to ensure uniform oxidation rate throughout the reaction volume, and c) moderate temperatures and relatively short reaction time. 3 C. p. F.-ly, 1 table. 1 Il.

This invention relates to organic chemistry, namely usovershenstvoval acid (FA), an important monomers and intermediates in polymer chemistry to obtain plastics, chemical fibers, films, paints and dyes, and this method ensures that the receipt of these compounds with a high degree of purity.

Terephthalic acid, the original connection for obtaining polyester films and fibers, usually receive a so-called SD-method, consisting in the oxidation of p-xylene with molecular oxygen in the presence of catalysts containing heavy metals in the environment acetic acid as solvent.

However, terephthalic acid, obtained by the SD method, contains a large number (1000-3000 hours per million 4-carboxyanhydride (4-KBA), which is not suitable for obtaining polyester films and fibers.

Therefore, the preferred method of obtaining dimethylterephthalate interaction of terephthalic acid with methanol, the exporter can be cleaned easily and reacts with the glycol to form a polyester. Another, more common method of purification of terephthalic acid is dissolving terephthalic acid in water at high temperatures and pressures and the processing solution with hydrogen over a catalyst based on a noble metal is and a million 4-KBA. However, both these methods have drawbacks. The first method of cleaning that uses terephthalate, accompanied by release of methanol upon receipt of the polyester. The second method is characterized by the use of different solvents, catalysts and options stages of oxidation and purification and, therefore, requires the use of two independent units.

To overcome these shortcomings of the commonly used methods have been proposed other methods.

An example of this method is the oxidation of p-xylene with molecular oxygen in the presence of a heavy metal and bromine compounds, dissolved in acetic acid with receiving TC with the degree of conversion of more than 90% of Untreated TC obtained by this reaction, crushed in the acetic acid medium at 140-230aboutIn the presence of molecular oxygen to reduce the average particle diameter is more than 20% of the Sludge generated at this stage of treatment, is oxidized in the second stage at a temperature of at least 10aboutWith higher than the temperature in the first stage or in the range of 180-300aboutWith get purified TC, suitable as monomer [1]

For the implementation of this method requires individual p is kosorotov mixing when using the mixer for grinding and in addition, according to this method, it is difficult to obtain terephthalic acid with high purity, containing less than 25 hours per million 4-KBA.

As an example cleaning TC can lead the way to handle oxygen-containing gas crude product, obtained by liquid-phase catalytic oxidation of p-xylene in an acetic acid medium in the presence of catalysts comprising compounds of cobalt, manganese, chromium, cerium, lead or mixtures thereof in an amount of 0.01 to 5.0% by weight of the TC, which was subjected to purification [2] the Process is carried out at 250aboutC for 1 h, the Disadvantage of this method is the large duration of contact of the reactants at high temperature, which leads to oxidation as impurities, and acetic acid.

The closest in technical essence is a method of obtaining terephthalic acid, consisting of four successive stages of liquid-phase oxidation of p-xylene in acetic acid medium oxygen-containing gas in the presence of catalysts based on cobalt-manganese-bromine [3] In the first stage p-xylene is oxidized at 180-230aboutWith over 40-150 minutes until a degree of conversion of greater than 95% At the second stage, the temperature at 2-30aboutWith lower than perpetuity stage proceeds at 260aboutC. TC obtained by this method, a 0,027% (270 hours per million) 4-KBA and therefore has a limited ability to be used in the production of polyester fibers and films.

The main disadvantages of this method are:

a) the use of high temperature (about 260about(C) at the stage of additional oxidation of the impurities (the second and fourth stage) leads to oxidation not only impurities but also acetic acid and, thus, to reduce the technical and economic indicators of the process;

b) pretty much the duration of the first stage of oxidation of p-xylene (90 min), which reduces the performance of the process;

C) a high content of 4-KBA 270 h per million (0,027%) at TC.

Therefore, this method is not only effective, but also the quality of the LC worse than the quality of TC obtained by the method comprising purification stage catalytic hydrogenation.

The invention relates to a method for the isomers of phthalic acid with a high degree of purity of the three-stage liquid-phase oxidation of xylene isomers, which improves the efficiency of the process and to improve the quality of the target product through the application of new catalytic systray Truelove acid and carboxybenzaldehydes (KBA) in target products at moderate temperatures, and to achieve a rapid, almost instantaneous mixing of the reactants in the reaction zone with an ideal distribution in the reaction space of the nutrient mixture, which comes in the form of restricted flows (submerged in liquid jets) with a high degree (6-30 m/s) countercurrent with respect to the direction of the circular rotation of the reaction mixture.

It was established that the purpose of the invention can be achieved step-by-step liquid-phase oxidation of xylene isomers oxygen-containing gas in the environment of the lower aliphatic acid in the presence of a catalyst containing cobalt salts, manganese and bromine compounds at elevated temperature and pressure, and the oxidation is carried out in three stages at 150-230aboutIn the presence of a catalyst, optionally modified with additives, heavy metals, including Nickel, chromium, zirconium or cerium, taken separately or in mixture with each other, the concentration of the modifying additive is 0.05-0.1 of the total concentration of cobalt and manganese, and the ratio of the concentrations of the modified catalyst in the first, second and third stages is 1:0.5 and 0.9:0,01-0,20 respectively. The total concentration of additives is 30-300 hours mil is p xylene and the catalyst, served in the reaction zone of the first stage with an initial speed of 6-30 m/s in countercurrent with respect to the direction of rotation of the reaction mixture and process air. The resulting reaction product is optionally oxidized in the second stage, the mixture of air and gas emerging from the first stage, and treat phlegm from the mold, located after the second stage reactor. The concentration of water in the reaction zone is maintained equal to 6-12% Of the slurry leaving the second reaction zone at least 60% of the solvent is replaced by the solvent is a lower aliphatic acid coming from the washing units in the third stage of the oxidation product. The resulting slurry isomer of phthalic acid is heated at 200-250aboutC, kept at this temperature for 5-60 min, and the third stage is treated with oxygen-containing gas. The content of the KBA in the isomers of phthalic acid is 25 hours in a million.

The advantages of this method are as follows.

At each stage of oxidation the use of integrated Co, Mn, Br-catalyst modified by additions of Nickel, chromium, zirconium or cerium, accelerates the oxidation reaction on the limiting stages, namely the conversion of isomers Truelove sour is the reaction zone due to the uniform distribution in the reaction volume of the nutrient mixture, entering into the reaction zone at a high speed (6-30 m/s) leads to the selective oxidation of xylenes and subsequent oxidation of the intermediate products with minimal loss of solvent is a lower aliphatic acid. In addition, to achieve high product quality and the acceleration response at each stage.

Heating nutritious reaction mixture to a temperature approaching the temperature of the oxidation process (reaction temperature 150-230aboutC) eliminates the temperature gradient in the reaction zone and in combination with rapid mixing provides a stable reaction in full.

The complex influence of the composition and concentration of the modified catalyst in each stage and the combination of oxidation processes with partial (second stage) or complete dissolution of the crystallized impurities (third stage) also increases the efficiency of the process and improves the quality of the product.

The drawing shows a reaction scheme according to this invention.

The invention is illustrated by the following examples.

P R I m e R 1. The reaction of the nutrient mixture is prepared in a vessel made of titanium and equipped with a stirrer and a jacket for heating.

In a vessel with a useful volume of 10 m3download p-xylene, catalyst and solvent in a quantity kg: p-xylene 1734; (SLA)24H2About 31,5; Mn(OAc)24H2O 26,7; HBr(100%) 23,15; N2ABOUT 210,05; CH3COOH 8174; Ni(OAc)24H2O 3,0.

The prepared solution nutrient mixture has the following composition, acetic acid 80,63; p-xylene 17,00; 0,0732; Mn 0,0588;Ni 0,0070; water 2.0; Br 0,2270.

Nutrient mixture in an amount 3672 kg/h is fed to the centrifugal pump through the heating elements and 4 nozzles in the oxidation reactor (V=10 m3), equipped with two turbine agitators mounted on a common shaft. Nourishing the reaction mixture is introduced into the reaction volume with a linear speed of 20 m/s at a temperature in the zone of distribution of the jet 160aboutC.

The reaction is carried out at 198aboutC and a pressure of 18 kg/cm2within 40 minutes TC isolated from the mixture contains 1250 h per million (0,1250%) 4-KBA and has an index of color 16aboutN. The loss of acetic acid due to the oxidative decarboxylation of the first stage is 68 kg/t TC.

The product obtained in the first stage, is fed into the reactor in the second stage, where it is treated with a gas containing molecular ncentratio water in the second stage of oxidation of the support equal to 10%

The quality of LC separated from the product obtained in the second stage oxidation: the content of 4-KBA 1.9 times less, 1.3 times better index color.

The reaction mixture is fed to the third stage of oxidation, prepared in a vessel with a useful volume of 16 m3equipped with a mixer. TC isolated from the reaction product of the second stage of oxidation with residual moisture 15% served in a number 2659 kg in the reaction vessel, where at the same time from the installation of the regeneration of the solvent serves 96% acetic acid in the amount of 7977,8 kg

Received a 25% suspension of TC, in which 85% aqueous solvent is replaced by a fresh 96% acetic acid, in the amount of 3600 kg/h is fed by a pump into the heater where it is heated to 230aboutAnd then in the collection, provided with a stirrer and elements that support a constant temperature.

In the third stage reactor oxidation serves a gas containing molecular oxygen in the gas mixture leaving the first reactor stage and air), and 736 kg/h of a solution of Hydrobromic acid in acetic acid of the following composition, acetic acid 95; water 4,875; Hydrobromic acid 0,125.

In the third stage reactor oxidation also serves Koba is in, TC 20; Co+Mn 0,0132; H2O 7; Br 0,0212, the third stage of the oxidation is continued for 20 minutes

After the reaction, the reaction mixture is discharged into the collection, working with stirring, where dissolved TC crystallizes at 105aboutAnd atmospheric pressure. The hot suspension is separated in the centrifuge, the precipitate washed with fresh acetic acid and dried in the dryer. From 1734 kg source p-xylene get 2661 kg net TC, which corresponds to 98% of final output.

TC after the third stage of oxidation meets all the requirements of the monomer with a high degree of purity: the contents of the main impurity 4-KBA is 25 hours per million (0,0025%), index of color 8aboutN. The total duration of oxidation on the first, second and third stages is 80 min, the loss of acetic acid 73,9 kg/t TC.

Thus, the use of effective methods for rapid equalization of temperature and concentration of reagents in the reaction zone provides selective sequential oxidation of xylene isomers in the target products with a high degree of purity (content of 4-KBA less than 25 hours per million (0,0025%) and the index of the color 4-6aboutN) and leads to the intensification of the process 2 times.

P R I m m e R 2. The process is Zr and 40 hours a million CE. The resulting product (net TC) contains 15 hours per million 4-KBA and has an index of color 4aboutN. The process parameters and the results are shown in the table.

P R I m e R 3. The process is carried out as in example 1, but 70 hours per million replace Ni 120 hours per million Zr. Net TC contains 24 hours in a million 4-KBA and has an index of color 8aboutN. The conditions of the reaction and the results are shown in table;

P R I m e R 4. The process is conducted as in example 1, but instead of 70 hours per million Ni injected 120 per million hours CE. Net TC contains 22 hours per million 4-KBA has index color 7aboutN. The process conditions and results are shown in table.

P R I m e R 5. The process is conducted as in example 1, but the number of Ni increased from 70 hours per million to 100 hours in a million. Net TC contains 20 hours per million 4-KBA has index color 7aboutN. The process conditions and results are shown in table.

P R I m e R 6. The process is conducted as in example 1, but instead of 70 hours per million Ni take 50 hours per million of Ni and 50 per million hours CE. Net TC contains 25 hours per million 4-KBA and has an index of color 5aboutN. The process conditions and the results are shown in TA is n Ni. The obtained TC contains 25 hours per million 4-KBA, but the index color is very high 46aboutN. The process conditions and results are shown in table.

P R I m e R 8 (comparative). The process is conducted as in example 7, but the initial feed rate of the reaction mixture is reduced from 28 m/s to 1 m/s Obtained TC contains 650 hours in a million 4-KBA, index color 26aboutN. Process conditions and results are shown in table.

P R I m e R 9 (comparative). The process is conducted as in example 1, but instead of 70 hours per million Ni add 50 hours per million of Ni and 50 hours per million Cr and reduce the concentration of the catalyst in the third stage (metal instead 132-21 hours per million; Br instead 212 32 hours per million). The obtained TC contains 421 hours in a million 4-KBA and has an index of color 9aboutN. The process conditions and results are shown in table.

P R I m e R 10 (comparative). The process is conducted as in example 1, but exclude from the reaction mixture to 70 hours per million Ni, serves the reaction mixture was heated to 60aboutWith instead of 160aboutC and heating temperature and the reaction in the third stage is set to 180aboutInstead of 230 and 200aboutS, respectively. The obtained TC contains 222 hours in a million 4-KBA and has an index is sustained fashion). The process is conducted as in example 1, except that reduce the concentration of Co and Mn, and the concentration of the additive increases. The obtained TC contains 480 hours in a million 4-KBA and has an index of color 42aboutN. The process conditions and results are shown in table.

P R I m e R 12 (m-xylene). The process is conducted as in example 1, except that the oxidation is subjected to m-xylene instead of p-xylene and instead of 70 hours per million Ni add 50 hours per million of Ni and 50 hours per million Cr. Obtained pure isophthalic acid contains 25 hours per million 3-KBA and has an index of color 10aboutN. The process conditions and the results are shown in the table.

P R I m e p 13 (m-xylene). The process is conducted as in example 1, except that instead of p-xylene oxidation is subjected to m-xylene. Obtained pure isophthalic acid contains 15 hours per million 3-KBA and has an index of color 10aboutN. The process conditions and the results are shown in the table.

P R I m e R 14 (comparative). The process is conducted as in example 13, except that one of the catalyst components, 70 hours per million Ni, exclude from the reaction mixture, reduce the initial feed rate Pete is phthalic acid contains 160 part per million 3-KBA and has an index of color 48aboutN. The process conditions and the results are shown in the table.

P R I m e R 15 (o-xylene). Repeat example 1, except that instead of p-xylene oxidation is subjected to o-xylene and instead of 70 hours per million Ni enter 40 hours per million Ni, 20 hours per million Cr, 30 hours per million Zr and 40 per million hours CE. Net phthalic acid contains 20 hours per million 2-KBA and has an index of color 20aboutN. The process conditions and the results are shown in the table.

P R I m e R 16 (comparative). Repeat example 1, except that instead of p-xylene oxidation is subjected to o-xylene and the reaction mixture was fed at a rate of 1 m/s (instead of 20 m/s). Received phthalic acid contains 28 hours per million 2-KBA and has an index of color 20aboutN. The process conditions and the results are shown in the table.

1. The way to obtain the isomers of phthalic acid with a high degree of purity by sequential liquid-phase oxidation of xylene isomers with molecular oxygen or oxygen-containing gas in the environment of the lower aliphatic acid with stirring and at a speed of certain temperature intervals at each stage, in the presence of catalysts, ri stage so what preheated nourishing the reaction mixture containing the isomers of xylene, lower aliphatic acid and a catalyst, is fed into the reaction zone of the first stage of oxidation with an initial speed of 6 to 30 m/s in countercurrent with respect to the direction of rotation of the reaction mixture, the resulting reaction product is oxidized in the second stage, the mixture of air and gas emerging from the first stage and treat phlegm from the mold, located after the second stage reactor, with subsequent crystallization and recovery of the products of oxidation, which, after squeezing the handle returned in the cycle, the solvent is a lower aliphatic acid, extracted in a solution of impurities from solids at 200 - 250oC for 5 to 60 minutes, and spend the third stage of oxidation, and used in the process, the catalyst further comprises modifying additives of heavy metals, including Nickel, chromium, zirconium or cerium, taken separately or in mixture with each other, the concentration of the modifying additive is 0.05 to 0.1 of the total concentration of cobalt and manganese, and the ratio of the concentrations of the modified catalyst in the first, second and third stages is 1 0,5 0,6 0,01 0,20 sootvetstvuyuthimi in the first stage reactor, carried out to a temperature below the temperature of oxidation.

3. The method according to p. 1, characterized in that the first stage of the oxidation is carried out at 150 to 230oWith, and the second and third stage of oxidation at a temperature of at least 2 80oWith lower temperature extraction.

4. The method according to p. 1, characterized in that the treatment of the sludge after the second stage of oxidation is returned into the cycle solvent displace at least 60% of the original solvent.

 

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SUBSTANCE: invention relates to a continuous method for preparing highly pure terephthalic acid. Method involves oxidation of p-xylene with oxygen-containing gas in acetic acid medium in the presence of catalyst comprising heavy metal salts, such as cobalt and manganese and halide compounds under increased pressure and temperature up to the definite degree of conversion of para-xylene to terephthalic acid at the first step and the following two-step additional oxidation of prepared reaction mixture and isolation of the end product. Mixing time of reagents is <25 s, oxidation at the first step is carried out at temperature 180-200°C up to conversion degree of p-xylene 95%, not above, oxidation at the second step is carried out at temperature 175-185°C and before feeding to the third step of oxidation the reaction mass is heated to 200-260°C, kept for 8-12 min and oxidized at temperature 180-200°C in the presence of catalyst comprising Ni and/or Zr salts additionally. As halide compounds method involves using XBr or XBr + XCl wherein X is H, Na, Li followed by isolation of solid products of oxidation after the third step and successive treatment with pure acetic acid and water in the mass ratio terephthalic acid : solvent = 1:3. Invention provides intensification of process and to enhance quality of terephthalic acid.

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EFFECT: the invention ensures production of the target product in the improved crystalline form.

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FIELD: chemical industry; petrochemical industry; methods of extraction of the unreacted xylene from the acetic acid at production of the terephthalic or isophthalic acid.

SUBSTANCE: the invention is pertaining to the field of production of the terephthalic or isophthalic acid by oxidation of the corresponding alkyl benzene, in particular, to the stage of separation of the reaction mixture including the acetic acid in the capacity of the dissolvent. The method is intended for extraction of the unreacted para-xylene or meta-xylene at the regeneration of the acetic acid using isobutyl acetate as the azeotropic agent for dehydration of the acetic acid. From the azeotropic distillation column at the temperature of 94-100°С separate the fraction containing the para-xylene or meta-xylene, which is fed into the run-down tank, where separate the aqueous phase from the organic phase. In the azeotropic section of the azeotropic distillation column determine the ratio of the para-xylene or meta-xylene and the isobutyl acetate in the stored fraction of the organic phase and periodically remove the accumulated part of the organic phase until the mass ratio of the concentrations of the para-xylene or meta-xylene and the azeotropic agent attains the interval from 0.5 up to 6. As the version of realization of the method route the circulation of the part of the accumulated fraction of the organic phase from the run-down tank to the azeotropic column. The technical result of the invention is upgrade of the production process of regeneration of the acetic acid and the unreacted alkylbenzene using the phase of the azeotropic distillation of xylenes from the acetic acid.

EFFECT: the invention ensures the upgrade of the production process of regeneration of the acetic acid and the unreacted alkylbenzene using the phase of the azeotropic distillation of xylenes from the acetic acid.

8 cl, 4 tbl, 5 dwg

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to an improved method for synthesis of halogenphthalic acid. Method involves mixing from 3 to 7 weight parts of acetic acid with 1 weight part of halogen-ortho-xylene, with from 0.25 to 2 mole% of cobalt source as measured for above said halogen-ortho-xylene, with from 0.1 to 1 mole% of manganese source measured for above said halogen-ortho-xylene, with from 0.01 to 0.1 mole% of metal source as measured for above said halogen-ortho-xylene wherein this metal is chosen from zirconium, hafnium and their mixtures, with from 0.02 to 0.1 mole% of bromide source as measured for above said halogen-ortho-xylene wherein halogen-ortho-xylene is represented by the formula (IV): wherein X represents halogen atom. Method involves holding the reaction mixture under pressure 1600 KPa, not less. At temperature 130-2000C, addition of molecular oxygen-containing gas to the reaction mixture in consumption 0.5 normal m3 of gas/h per kg of halogen-ortho-xylene in the reaction mixture for time sufficient for 90% conversion of halogen-ortho-xylene to yield halogenphthalic acid. Also, invention relates to a method for synthesis of halogenphthalic anhydride by distillation and dehydration of halogenphthalic acid, and to a method for synthesis of polyesterimide that involves interaction of halogenphthalic anhydride with 1,3-diaminobenzene to yield bis-(halogenphthalimide) of the formula (II): wherein X means halogen atom, and interaction of bis-(halogenphthalimide) of the formula (II) with alkaline metal salts of dihydroxy-substituted aromatic hydrocarbon of the formula (IV): OH-A2-OH wherein A2 means a bivalent radical of aromatic hydrocarbon to yield polyesterimide.

EFFECT: improved method of synthesis.

20 cl, 2 tbl, 5 ex

FIELD: process for continuous production of terephthalic or isophthalic acid by liquid phase oxidation of respective aromatic dialkyl hydrocarbon.

SUBSTANCE: in order to prepare reaction solvent at least part of mother liquor separated from produced acid is used. Oxidation catalyst concentration in mother liquor is measured beforehand and then oxidation catalyst concentration is continuously corrected due to direct control (regardless of water content). Predetermined quantities of solvent and aromatic hydrocarbon as raw material are continuously supplied to oxidizing reactor for oxidizing aromatic hydrocarbon by means of molecular oxygen. Water concentration in condensate returned from reactor is measured and controlled by means of discharged quantity of returned condensate for stabilizing water concentration in reaction system in order to obtain in the result dicarboxylic acid. Oxidation temperature is sustained stable due to controlling pressure; oxygen concentration in exhaust gas is sustained stable due to controlling feed of oxygen containing gas.

EFFECT: production of stable quality acid, rational consumption of resources, power and water for performing process.

FIELD: chemistry.

SUBSTANCE: invention pertains to improved method of lowering content of 4-carboxybenzoldehyde and p-toluic acid in benzenedicarboxylic acid, which is terephtalic acid. Method involves: (1) supplying (i) p-xylene (ii) water acetic acid reaction medium, containing oxidation catalyst, containing source of cobalt, manganese and bromine source, dissolved in it, and (iii) acid containing gas in the first oxidation zone at high pressure, in which there is liquid phase, exothermal oxidation of p-xylene. In the first reactor, oxidation at high temperature and pressure is maintained at 150-165°C and 3.5-13 bars respectively; (2) removal from the upper part of the first reactor of vapour, containing water vapour, acetic acid reaction medium and oxygen depleted gas, and directing the vapour into the column for removing water; (3) removal from the lower part of the column for removing water of liquid, containing partially dehydrated acetic acid solution; (4) removal from the lower part of the first reactor of the oxidation product, containing (i) solid and dissolved terephtalic acid, 4-carboxybenzaldehyde and p-toluic acid, (ii) water acetic acid reaction medium, containing oxidation catalyst dissolved in it; (5) supplying (i) product of oxidation from stage (4), (ii) oxygen containing gas and (iii) solvent in vapour form, containing acetic acid, obtained from a portion of partially dehydrated acetic acid solvent from stage (3) into the second oxidation zone high pressure, in which there is liquid phase exothermal oxidation of 4-carboxybenzaldehyde and p-toluic acid, where temperature and pressure in the second reactor of oxidation at high pressure is maintained at 185-230°C and 4.5-18.3 bars respectively; (6) removal from the upper part of the second reactor of vapour, containing water vapour, acetic acid reaction medium, and oxygen depleted gas; (7) removal from the lower part of the second reactor of the product of second oxidation, containing (i) solid and dissolved terephtalic acid and (ii) water acetic acid reaction medium; and (8) separation of terephtalic acid from (ii) water acetic acid reaction medium from stage (7) with obtaining of terephtalic acid. The invention also relates to methods of obtaining terephtalic acid (versions). The obtained product is terephtalic acid, with an overall concentration of 4-carboxybenzaldehyde and p-toluic acid of 150 ppm or less.

EFFECT: improved method of lowering content of 4-carboxybenzoldehyde and p-toluic acid in benzenedicarboxylic acid and obtaining terephtalic acid.

13 cl, 1 dwg, 1 ex

FIELD: process engineering.

SUBSTANCE: invention relates to removal of impurities and mother solution and wash filtrate extraction from oxidising reactor discharge flow formed in synthesis of carboxylic acid, usually, terephthalic acid. Proposed method comprises: (a) directing oxidised flow in zone of enrichment by solid particles to settle solid particles and form dumping flow suspension via cooling it, adding settling agent, removing solvent or combining said cooling and adding; (b) separating dumping flow suspension in separation zone to form filter pad and mother solution and forced flushing of said filter pad at high pressure in said separation zone by flushing fluid flow comprising water and, not obligatorily, solvent to form washed pad. Note here that said separation zone comprises at least one filter device operated at pressure and comprising at least one filter cell. Note also that said filter cell accumulates layer of filter pad with depth of at least 0.635 cm (0.25 inch), "c" directing at least a portion of flushing filtrate and at least a portion of mother solution to oxidising zone.

EFFECT: higher efficiency.

44 cl, 4 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to methods of producing aromatic carboxylic acids. The method involves the following, for example: bringing material which contains at least one substituted aromatic hydrocarbon, in which the substitutes can be oxidised to carboxyl groups, with oxygen gas in a liquid-phase oxidation reaction mixture which contains monocarboxylic acid as a solvent and water, in the presence of a catalyst composition meant for oxidising the substituted aromatic hydrocarbon to an aromatic carboxylic acid, containing at least one heavy metal, in a reaction section at high temperature and pressure sufficient for preservation of the liquid-phase oxidation reaction mixture and formation of an aromatic carboxylic acid and impurities containing by-products of the reaction, dissolved or suspended in the liquid-phase oxidation reaction mixture and a high-pressure vapour phase which contains a solvent - monocarboxylic acid, water and small quantities of the initial aromatic hydrocarbon and by-products of oxidation of the initial aromatic hydrocarbon and the solvent - monocarboxylic acid; moving the high-pressure vapour phase from the reaction section to a separation section in which the solvent - monocarboxylic acid, water and oxidation by-products are separated into at least one first liquid phase rich in the solvent - monocarboxylic acid and at least one second liquid phase rich in water, and at least one second high-pressure vapour phase stripped of the solvent - monocarboxylic acid, which contains water vapour, so that by-products of oxidation of the initial aromatic hydrocarbon are preferably in the first liquid phase and by-products of oxidation of the solvent - monocarboxylic acid are preferably in the second high-pressure vapour phase; and removal from the separation section in separate streams of the first liquid phase which is rich in the solvent - monocarboxylic acid, and the second liquid phase rich in water, which contains less than 5 wt % solvent - monocarboxylic acid and by-products of its oxidation, and the second high-pressure vapour phase which virtually contains less than 2 wt % by-products of oxidation of the initial aromatic hydrocarbon.

EFFECT: invention relates to an apparatus for producing aromatic carboxylic acids.

45 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of recovering energy during production of aromatic carboxylic acids via liquid phase oxidation of aromatic hydrocarbons wherein vapour containing reaction solvent and water forms in the top part of the reactor, and the method comprises the following steps: a) high efficiency separation of the vapour from the top part of the reactor to form at least a high-pressure gas stream containing water and organic impurities; b) recovering heat of the high-pressure gas stream via heat exchange with a heat sink, where a condensate forms, said condensate containing approximately 20-60 wt % water, present in the high-pressure gas stream, and high-pressure exhaust gas containing approximately 40-80 wt % water present in the high-pressure gas stream, remains uncondensed and temperature or pressure of the heat sink increases; and c) expansion of the high-pressure exhaust gas which is uncondensed at step (b), containing approximately 40-80 wt % water, present in the high-pressure gas stream, in order to recover energy of the high-pressure exhaust gas in form of work; and d) directing the heat sink, whose temperature and pressure increases at step (c), to another step of the method for heating or using outside the method. The invention also relates to a method of producing aromatic carboxylic acids with energy recovery and a device for recovering energy.

EFFECT: invention significantly lowers power consumption during production of aromatic carboxylic acids.

16 cl, 3 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to improved methods of producing aromatic carboxylic acids, involving bringing material containing at least one initial substituted aromatic hydrocarbon, where the substitutes are oxidisable to carboxylic acid groups, with oxygen gas in a liquid-phase oxidation reaction mixture containing a monocarboxylic acid as a solvent and water, in the presence of a catalyst composition containing at least one heavy metal, which is effective for catalysing oxidation of the substituted aromatic hydrocarbon to an aromatic carboxylic acid, in a reaction section at high temperature and pressure, effective for keeping the liquid-phase oxidation reaction mixture in a liquid state and forming an aromatic carboxylic acid, and impurities containing by-products of oxidation of the initial aromatic hydrocarbon, which are dissolved or suspended in the liquid-phase oxidation reaction mixture, and a high-pressure vapour phase containing a solvent - monocarboxylic acid, water and small amounts of the initial aromatic hydrocarbon and by-products; transferring the high-pressure vapour phase from the reaction section into a separation section sprinkled by a liquid reflux containing water and capable of almost completely separating the solvent - monocarboxylic acid and water in the high-pressure vapour phase to form a liquid rich in solvent - monocarboxylic acid and depleted of water, high-pressure gas containing water vapour; transferring the high-pressure gas containing water vapour from the separation section without processing to remove organic impurities into a condensation section and condensation of the high-pressure gas to form a liquid condensate containing water and exhaust gas from the condensation section under pressure, containing non-condensed high-pressure gas components, transferred into the condensation section; removal from the condensation section of a liquid condensate containing water and suitable for use without further processing as at least one liquid containing water in a method of purifying aromatic carboxylic acids; and feeding the liquid condensate containing water removed from the condensation section during purification of aromatic carboxylic acids in which at least one step includes: (a) preparing a purification reaction solution containing an aromatic carboxylic acid and impurities which are dissolved or suspended in a liquid containing water; (b) bringing the purification reaction solution containing aromatic carboxylic acid and impurities in the liquid containing water, at high temperature and pressure, into contact with hydrogen in the presence of a hydrogenation catalyst to form a liquid purification reaction mixture; (c) separating the solid purified product containing carboxylic acid from the liquid purification reaction mixture containing aromatic carboxylic acid and impurities in the liquid containing water; and (d) using at least one liquid containing water to wash the obtained purified solid aromatic carboxylic acid separated from the liquid purification reaction mixture containing aromatic carboxylic acid, impurities and the liquid containing water; such that the liquid containing water on at least one step of the purification method contains a liquid condensate containing water and which needs processing to remove organic impurities.

EFFECT: invention also relates to apparatus for producing aromatic carboxylic acids.

44 cl, 2 dwg

FIELD: chemistry.

SUBSTANCE: invention relates to a method of processing polyethylene terephthalate wastes. The method involves ethanolysis of polyethylene terephthalate (PET), in which material containing PET reacts with ethanol. Ethylene glycol and an aromatic diethyl ester, such as diethyl isophthalate and/or diethyl terephthalate, are separated. PET or a terpolymer containing a terephthalate monomer and ethylene glycol monomers react with ethanol and ethanol, diethyl terephthalate, ethylene glycol and optionally diethyl isophthalate are separated. The separated diethyl components can undergo liquid-phase oxidation to obtain an aromatic carboxylic acid. Acetic acid can also be obtained via liquid-phase oxidation of the separated diethyl components. Aromatic carboxylic acid can be used to obtain polymers. The invention also describes apparatus for processing polyethylene terephthalate wastes. The apparatus includes a reactor, a distillation column operating at atmospheric pressure and a vacuum distillation column.

EFFECT: high efficiency of the method.

29 cl, 1 dwg, 8 tbl, 8 ex

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