Method (variants) and a device for producing aromatic carboxylic acids

 

(57) Abstract:

The invention relates to a method for producing aromatic carboxylic acids by exothermic liquid-phase oxidation reaction of the corresponding alkylaromatic parent compound in the liquid-phase reaction mixture consisting of water, low molecular weight monocarboxylic acid as a solvent, the oxidation catalyst on the basis of heavy metal and a source of molecular oxygen in the reaction conditions leading to the gaseous exhaust stream of high pressure water-containing gaseous by-products and gaseous low molecular weight monocarboxylic acid, followed by distillation of the aromatic carboxylic acid and separation of the exhaust flow high pressure, while the exhaust flow high-pressure direct high-performance distillation column to remove at least 95 wt.% low molecular weight monocarboxylic acid from the waste stream, with the formation of the second exhaust flow high-pressure containing water and gaseous by-products formed in the oxidation process, and then the second exhaust flow high-pressure direct funds in termicheskogo liquid-phase oxidation of alkylaromatic compounds in the reaction mixture, containing acetic acid as solvent, water, gaseous products and gaseous acetic acid, comprising the reaction vessel suitable for oxidation, high efficiency distillation column, means for directing a gaseous exhaust stream, the means for removal of combustible materials from the vapor, means for the release of energy from the steam coming out of the distillation column after removal of combustible materials. The technical result is an improvement of the method of receipt. 3 S. and 14 C.p. f-crystals, 1 Il.

The invention relates to a method for producing aromatic carboxylic acids by exothermic liquid-phase oxidation of aromatic starting compound. More specifically, this invention relates to a method for producing aromatic carboxylic acids by exothermic liquid-phase oxidation of aromatic starting compound, in which the energy released during the exothermic oxidation, effectively returns. This invention also relates to an effective method of treatment of wastewater generated during the extraction of aromatic carboxylic acids.

Aromatic carboxylic acids are useful chemical unique scale in number, more than 10 billion pounds per year. One factory can produce from 100,000 to more than 750,000 metric tons of TC per year. TC is used, for example, to obtain polyethylene terephthalate (PET), raw materials for the production of polyester fibers for the textile and polyester films for packaging and containers. TC can be obtained by an exothermic oxidation under high pressure suitable aromatic starting compound, for example, paraxylene, in liquid environment using air or other source of molecular oxygen as oxidant and one or more compounds of heavy metals as a catalyst, and one or more promoting compounds. Methods of oxidation of paraxylene and other aromatic compounds using such liquid-phase oxidation reactions are well known. For example, in U.S. patent 2833816 described by way of the oxidation of aromatic starting compounds to their corresponding aromatic carboxylic acids.

Key in these ways of producing aromatic carboxylic acids is the use of liquid-phase reactions using low molecular weight carboxylic acids, e.g. acetic, as the creation of water, and water is also formed in the reaction of oxidation.

In the oxidation process also forms the reaction waste gas, which typically contains carbon dioxide, carbon monoxide and, depending on the promoter used, can contain bromide. In addition, when the source of molecular oxygen using air, the reaction waste gas contains nitrogen and unreacted oxygen. Although for regulating the temperature of the highly exothermic oxidation reaction can be used various means, usually most convenient to remove heat by evaporation of the solvent, i.e., the boiling point of the latter during the oxidation reaction.

Evaporated the solvent, which is typically a mixture of water and low molecular weight carboxylic acids, still condensed in one or more of the partial capacitors, and then the condensate is returned to the reaction mixture. However, because water also contains at least part of the condensate is usually sent to the device for the separation, typically distillation column for the separation of water from low molecular weight aliphatic acid, a solvent so that the concentration of Uvalda or passed through an oxidizer for combustion by-products and waste form product it does not harm the environment.

Exhaust the high pressure gas contains a significant amount of energy. Although the known method, to some extent, used a small amount of energy contained in the exhaust gas by passing the gas through, for example, the expander or turbine, the known methods are not fully utilized the energy of exhaust gas of high pressure. In the known methods of removing heat from the reaction mixture was carried out by condensation of part of the steam distilled to obtain a pair of moderate pressure.

Pairs of moderate pressure, in particular, used for energy recovery steam turbine and the part used for the separation of water from acetic acid by distillation.

Therefore, you must create an improved method for the preparation of aromatic carboxylic acids, in which the energy liberated in the process is highly exothermic oxidation reactions under high pressure, can be effectively utilized.

Patented continuous preparation of aromatic carboxylic acids by exothermic liquid-phase oxidation reactions of aromatic starting compound, in which the ethical energy of the initial compounds to aromatic carboxylic acids in the liquid phase, water-containing, low molecular weight carboxylic acid as solvent, the oxidation catalyst on the basis of heavy metal and a source of molecular oxygen, under reaction conditions which produce a gaseous exhaust stream of high pressure water-containing gaseous by-products and gaseous low molecular weight carboxylic acid, which solvent;

b) removing in a highly efficient separating device, at least about 95 wt.% low molecular weight carboxylic acid from the waste stream to obtain a second exhaust mixture high pressure, containing no low molecular weight carboxylic acid, a solvent containing water, and gaseous by-products formed during the oxidation reaction; and

in the direction of the second exhaust mixture of high pressure in the means for the regeneration of energy from the second exhaust mixture high pressure.

In addition to providing efficient energy return, obtained by the exothermic oxidation of aromatic starting compound, the use of high efficiency separation devices, for example, distillation columns, provides the acid. This water may be returned in the form of distillate in the distillation column. Any residual aromatic carboxylic acid in water, as well as intermediate oxidation products, therefore, returned to the reactor and stand out as a useful product.

In addition, return to the water cycle for cleaning reduces or even eliminates the need for water treatment in the plant for wastewater treatment. Thus the load on the plant for wastewater treatment is significantly reduced. Thus, this invention relates also to a method for producing aromatic carboxylic acids by the exothermic oxidation reactions in the liquid phase aromatic starting compound, which includes the oxidation of aromatic starting compound to an aromatic carboxylic acid in a liquid phase reaction mixture comprising water, a low molecular weight carboxylic acid, which is the solvent, the oxidation catalyst on the basis of heavy metal and a source of molecular oxygen under reaction conditions which produce a gaseous waste stream containing water, gaseous by-products and gaseous low molecular weight carboxylic acid, which is the Rast is Blarney carboxylic acid from the waste stream with the formation of the second exhaust flow high pressure, containing water and gaseous by-products formed during the oxidation of: separating the aromatic carboxylic acid from the reaction mother liquor formed by liquid-phase oxidation with obtaining the crude aromatic carboxylic acid; purification of crude aromatic carboxylic acid at elevated temperature and pressure in the environment of the cleaning solvent containing water, with formation of a mixture of purified aromatic carboxylic acid and the mother liquor from the stage of purification, containing water; and separating the purified aromatic acid from the mother liquor and returning at least part of the mother liquor from the stage of purification in a highly efficient distillation column.

This invention also relates to a reactor suitable for the conversion of the aromatic starting compound in an aromatic carboxylic acid by liquid-phase oxidation of aromatic starting compound in the reaction mixture containing a low molecular weight aliphatic carboxylic acid and water, and efficient energy return, obtained by oxidation reaction, which contains the reaction vessel suitable for the implementation of liquid-phase oxidation of aromatic starting compound with improved water and thus that the steam coming out of the distillation column contained less than about 1.0 wt.% acetic acid, and means for directing steam, obtained by liquid-phase oxidation reactor, distillation column.

The drawing shows the circuit implementation of the method according to the invention.

In the method according to this invention of the original aromatic compound is oxidized in the process exothermic liquid-phase oxidation reaction to aromatic carboxylic acids, and the energy released during this vysokotekhnologicheskoi oxidation, now returned and is used, for example, to generate electricity or other useful forms and transmitted energy.

Aromatic original connection, suitable for implementing the method according to the invention, is any aromatic compound, which is oxidized substituents, which may be oxidized to a carboxyl group, for example, oxidizing the Deputy may be an alkyl group, e.g. methyl, ethyl or isopropyl. This may be partially oxidized alkyl group, for example, an alcohol group, aldehyde group or ketone group.

Aromatic portion of the aromatic ishodnoj/P> The number of oxidizable substituents in the aromatic part of the aromatic starting compound may be equal to the number of available positions in the aromatic part of the aromatic starting compound, but typically less than and preferably equal to 1 to 4, more preferably 2 or 3. Thus, examples of suitable aromatic starting compounds in the method according to this invention include toluene, ethylbenzene, o-xylene, m-xylene, p-xylene, 1-formyl-4 - methylbenzol, 1-hydroxymethyl-4-methylbenzol, 1,2,4-trimethylbenzene, 1-formyl-2,4-xylene, 1,2,4,5-tetramethylbenzene, alkyl-, hydroxymethyl-, formyl - and acetamidine naphthalene compounds, for example, 2,6 - and 2,7-dimethylnaphthalene, 2-acyl-6-methylnaphthalene, 2 - formyl-6-methylnaphthalene, 2-methyl-6-ethylnaphthalene, 2,6-deethylation etc.

Paraxylene, for example, by oxidation of terephthalic acid, from metaxalona obtained isophthalic acid and 2,6 - dimethylnaphthalene obtained 2,6-natalijagolosova acid.

As indicated above, methods of oxidation of aromatic starting compound to the corresponding aromatic carboxylic acid using liquid-phase oxidation reaction, catalyzed by heavy metals is well known. For example, in the patent is about the preferred method of oxidation of 2,6-dimethylnaphthalene to 2,6-naphthalene-dicarboxylic acid described in U.S. patent 5183933. However, in General, a suitable oxidation catalysts based on heavy metals include metals having an atomic number from about 21 to about 82, inclusive, preferably, a mixture of cobalt and manganese. The preferred solvent in the oxidation is a low molecular weight aliphatic monocarboxylic acid containing 2 to 6 carbon atoms, inclusive, or its mixture with water.

Preferred is acetic acid or a mixture of acetic acid and water.

Typical is the reaction temperature from about 145oC to about 235oC and pressure such that the reaction mixture is in the liquid phase. You can also use a promoter, for example, low molecular weight ketone containing 2-6 carbon atoms or a low molecular weight aldehyde containing 1-6 carbon atoms. Can also be used as a promoter bromine compounds known from the prior art, for example, hydrogen bromide, molecular bromine, sodium bromide, etc.

Also need a source of molecular oxygen and usually it is the air. For the conversion of the paraxylene in Trefoleva acid content of molecular oxygen can vary from 10% to gaseous oxygen. Air yavlyaetsya, oxygen-containing gas fed to the reactor should provide education flue gas-steam mixture containing from 0.5 to 8% vol. oxygen (measured in the absence of solvent). For example, the feed rate of oxygen-containing gas sufficient to provide oxygen in an amount of from 1.5 to 2.8 moles on methyl group, will result in oxygen content (measured in the absence of a solvent) in the exhaust gas mixture is equal to that of 0.5-8% vol.

The catalyst used in stage oxidation to obtain crude terephthalic acid preferably contains cobalt, manganese and bromine, and may additionally contain accelerators, known from the prior art. The ratio of cobalt (calculated as elemental cobalt) in the cobalt component of the catalyst to p-xylene in the process of liquid-phase oxidation is in the range from about 0.2 to about 10 milligram atoms (mg-a) g-mol of p-xylene. The ratio of manganese (calculated as elemental manganese) in the manganese component of the catalyst to cobalt (calculated as elemental cobalt) in the cobalt component of the catalyst in the process of liquid-phase oxidation is in the range from about 0.2 to about 10 mg-and mg-and cobalt. the obsession of cobalt and manganese (calculated as elemental cobalt and elemental manganese) in the cobalt and manganese components of the catalyst in liquid-phase oxidation is in the range from about 0.2 to about 1.5 mg and mg and the total content of cobalt and manganese.

Each of the cobalt and manganese components may be represented in any of the known ionic or United forms, which constitute soluble forms of cobalt, manganese and bromine in a solvent in the reactor.

For example, when the solvent is acetic acid, it is possible to use carbonates, tetrahydrate, acetates, and/or bromides of cobalt and/or manganese.

The ratio of bromine to the total content of cobalt and manganese, equal to from 0.2: 1.0 to 1.5:10 mg, is provided with a suitable source of bromine. Such sources of bromine include elemental bromine (Br2or bromine ion (for example, HBr, NaBr, KBr, NH4Br and so on), or organic bromides which are known to provide bromine ions at the operating temperature of the oxidation (e.g., benzylbromide, mono - and dibromohexane acid, bromoacetamide, tetrabromide, ethylenedibromide and so on). The total content of bromine in molecular bromine and bromide ion is used to meet needs in the elementary bromine in ensuring the relationship of elemental bromine to the total of cobalt and manganese, equal to from 0.2:1.0 to 1.5:1.0 mg. Ion bromine released from organic bromides under operating conditions of oxidation, may be Le is lots minimum pressure, when running the reactor oxidation is the pressure, which ensures the presence of a liquid phase p-xylene and solvent. When the solvent is a mixture of acetic acid - water, a suitable gauge pressure in the oxidation reactor is in the range from about 0 kg/cm2to about 35 kg/cm2and is usually from about 10 kg/cm2up to about 20 kg/cm2. The temperature in the oxidation reactor is usually from about 120, preferably from about 150oup to about 240oC, preferably to about 230o. The residence time of the solvent in the oxidation reactor is generally from about 20 to about 150 minutes and preferably from about 30 to about 120 minutes

The process conditions described above for the oxidation of paraxylene to terephthalic acid, may also be used for oxidation of metaxalone in isophthalic acid.

For oxidation of 2,6-dimethylnaphthalene to 2.6-naphthaleneboronic acid weight ratio of monocarboxylic acid, a solvent, 2,6-dimethylnaphthalene, preferably, is from about 2:1 to about 12: 1, the ratio in mg-and manganese to cobalt is from about 5:1 to about 0.3: 1,the content of cobalt and manganese in the calculation of elemental cobalt and manganese care at least about 0.40% of the weight of the solvent, and the temperature of the oxidation reaction is approximately 185-220oC. Acetic acid is the most suitable solvent for oxidation of 2,6-dimethylnaphthalene.

The reaction vessel used for carrying out liquid-phase oxidation of aromatic starting compound to an aromatic carboxylic acid is any reaction vessel, which is designed for operation in the conditions used for the reaction of the liquid-phase oxidation. Typically, these reactors are made of inert material, for example, titanium and lined with an inert material such as glass or titanium.

If the oxidation reaction is carried out at elevated pressure, the reactor must be designed to withstand the pressure used for the reaction of oxidation.

The reactor may also be equipped with one or more agitators.

Typically, the reactor has a cylindrical shape and is oriented vertically.

As described above, the heat generated during the liquid-phase oxidation is dissipated by evaporation of the solvent from the reaction mixture together with water, in the reaction mixture. Poskytovatel by adjusting the pressure. When the reaction pressure is from about 7 to about 21 kg/cm2the temperature of the reaction mixture comprising acetic acid as solvent, and the pair obtained approximately 170-210oC. Thus, the high temperature, high pressure steam generated in the process of liquid-phase oxidation, are a significant source of energy, especially when taking into account the amount of the vapor produced in large scale in a factory producing 200000-750000 metric tons of aromatic carboxylic acids in the year.

According to the method according to this invention, the evaporated solvent is directed into the apparatus, for example, highly efficient distillation column that can separate a solvent, usually a low molecular weight aliphatic carboxylic acid from the water formed in the oxidation process.

For the reasons discussed in more detail below, the apparatus used for separating water from the solvent must be capable of separation so that at least about 95%, more preferably about 98% and most preferably at least about 99% by weight of low molecular weight carboxylic acid solvent in parool the speaker of the apparatus for separation, contains a very small amount of solvent and, in addition to oxides of carbon, nitrogen and oxygen and by-products, is essentially high-pressure steam. For example, if the solvent is a low molecular weight carboxylic acid, e.g. acetic acid, steam, supplied to the device for separation, is a mixture of acetic acid and water at a weight ratio of acetic acid to water is from about 20:1 to about 3:1, and steam escaping from the apparatus for the separation, usually contains less than about 0.5 weight. % acetic acid, more preferably, less than about 0.1 wt.% acetic acid and most preferably less than about 0.05 wt.% acetic acid.

Although the apparatus used to carry out this separation, can be any device that can separate the water from the solvent, the preferred apparatus or means for carrying out such separation, is a distillation column, preferably, highly efficient distillation column. You can use any efficient distillation column, however, the preferred columns contain highly effective nozzle, for example, Koch Flexipac, etc., or contain / tube sheet climatically plates, more preferably, at least about 50 theoretical plates.

The distillation column should provide the Department so that at least 95%, more preferably about 98% and most preferably at least about 99 wt.% low molecular weight carboxylic acid, a solvent, in the vaporous exhaust stream is removed. As indicated above, in these waste streams, the ratio of low molecular weight monocarboxylic acid, for example acetic acid, to water by weight is generally from about 20:1 to about 2:1.

Preferably, the apparatus for the separation is to separate the solvent from the water at high pressure. Apparatus for separating, preferably working under pressure equal to or slightly less than the pressure of the reaction liquid-phase oxidation.

For directions a couple formed by liquid-phase oxidation, in the apparatus for separation, you can use any tool. For example, you can use the pipeline or other suitable channel. In addition, the device for separating, for example, distillation column, can be directly connected to the reaction vessel used for carrying out the side of gaseous products, formed as a result of oxidation, carbon oxides formed during the oxidation and, if as the source of molecular oxygen is air, nitrogen is passed through the apparatus for the separation to remove most of the reaction solvent. The gas discharged from the device for separation, typically contains water (steam), oxides of carbon, nitrogen, unspent molecular oxygen and by-products of oxidation, for example, methyl bromide. It is important that the gas discharged from the device for separation, is still under high pressure and, therefore, is a valuable source of energy. Although this exhaust gas from the device for separation, you can skip to the means for energy recovery, for example, defender, it is preferable to first remove corrosive and/or combustible by-products from the exhaust gas of high pressure before submitting it to defender or other means for energy recovery. Although removal of combustible materials from the exhaust gas is any suitable means, the preferred device for catalytic oxidation, for example, thermal oxidizer, in which the exhaust gas is in contact with a suitable catalyst at high and combustible by-products in the exhaust gas is subjected to catalytic oxidation to substances, not detrimental to the environment. Such catalytic oxidation can lead to reduction or elimination by oxidation of any residual reaction solvent contained in the exhaust gas, and it can lead to oxidation by-product, for example, methyl.

However, in the method according to this invention used the device for the separation allows you to remove a large part of the reaction solvent from the exhaust gas.

Thus, the exhaust gas flowing into the catalytic oxidation of the exhaust gas contains a small amount of the reaction solvent, so that the load on the catalytic oxidation is small.

The high content of the reaction solvent in the catalytic oxidation of exhaust gas would lead to an extremely large temperature rise in the catalytic oxidation. Further, the combustion reaction of the solvent will be a great loss from the economic point of view, since it is desirable to save and return to the cycle as much as possible of the solvent used in the oxidation reaction.

Typically, the gas discharged from the installation of cat and hydrogen bromide. Bromine and hydrogen bromide formed during the catalytic oxidation of bromide. Oxidation catalysts for such off-gases are available, for example, from Engelhard Corp. or allied signal Inc.

The high-pressure gas exiting the catalytic oxidation and scrubber, it is preferable to send in a pre-heater for increasing temperature of exhaust gas and converting the condensed water, which can be paired. The flow of dry gas of high pressure coming out of the preheater, is sent to defender or other means for energy recovery, the bearer of which is the flow of high pressure gas.

A means for energy recovery from waste gas of a high pressure, for example, defender, connected with an electric generator and/or other equipment requiring mechanical energy, for example, a compressor. The electric power generated by the generator, can be used to control equipment used at the plant for the production of aromatic carboxylic acids, for example, it can be used when the compressor to inject air for the reaction of liquid-phase oxidation, and any excess electricity is estvo energy, returned in accordance with this invention, is at least about 0.3, and more preferably at least about 0.35 kW.hour per pound (0.4 kg) obtained terephthalic acid.

After exiting defender exhaust gas condensate, and produced water is suitable for other processes at the plant. This water is relatively pure, containing only a small amount of dissolved gases. For example, the condensed water can be used as the distillate to the distillation column that is used as the device for highly efficient separation. Water obtained by condensation of the flue gas can also be used as solvent at the stage of purification, where the crude aromatic carboxylic acid, process for obtaining purified aromatic carboxylic acid. Thus, the water formed by condensation of the flue gas can be used as a solvent in the recrystallization or as a solvent for carrying out one or more chemical and/or physical treatments of crude aromatic carboxylic acid. One such method of purification consists in contacting an aqueous solution or suspension of the crude aromatic the deposits. This method is disclosed in U.S. patent 3584039. In the case of purifying terephthalic acid as an example of this method of cleaning is carried out at elevated temperature and pressure in a fixed bed of catalyst. You can use the reactor with a flow of up and down. Crude terephthalic acid which is to be cleaned, dissolved in water or a mixture of water and any other polar solvent, for example, C1-C4 aliphatic carboxylic acid.

The temperature in the reactor and, consequently, the temperature of the slurry of terephthalic acid in the cleaning time can be in the range from about 100 to about 350oC. the Preferred temperature range is from about 275 to about 300oC.

The pressure in the reactor depends primarily on the temperature at which the cleaning. As soon as the temperature at which substantial amounts of contaminated terephthalic acid can dissolve exceed the boiling point of the solvent under normal conditions, the pressure is substantially above atmospheric pressure to maintain the aqueous solution in the liquid phase.

In General, the reactor pressure during the hydrogenation may be in the range of from about 200 UP> (6205-8273 kPa).

The partial pressure of hydrogen is usually in the range from about 30 to about 200 F./inch2(206,8-1379 kPa).

The catalyst used at this stage of treatment, represents one or more metals, catalytic hydrogenation, for example, ruthenium, rhodium, palladium or platinum, on a suitable carrier, for example, coal or titanium dioxide.

A suitable carrier is active carbon, usually obtained from coking coal in the form of granules having a surface area of from 600 to 1500 m2/,

The metal content on the media is about 0.01 to 0.02 wt.%. Suitable materials for obtaining purified aromatic carboxylic acids from crude aromatic carboxylic acids are described in U.S. patent 5256817 and in the application for U.S. patent 029037, filed March 10, 1993

After passing through the reactor for purification of aromatic carboxylic acid a solution of an aromatic acid in an aqueous solvent is cooled to precipitate the purified aromatic carboxylic acid.

The temperature to which a cooled solution is that a large part of the purified aromatic carboxylic acid crystallizes. Kristalizovyvatsja for the separation system, the solid-liquid for example, a centrifuge or a filter. The residue purified aromatic carboxylic acid may be washed with clean water, dried and sent to storage or packaging and dispatch.

The aqueous mother liquor separated in the centrifuge or filter contains a number of impurities, intermediate reaction products, and also contains suspended and dissolved aromatic carboxylic acid. In the known methods this thread was transferred to the effluent treatment plant. However, in the method according to this invention the main portion of this mother liquor can be returned in a device for the separation used to separate the reaction solvent from the water, resulting in the oxidation process. Thus, impurities, intermediates and reaction by-products of the aromatic carboxylic acid is returned to the reaction mixture.

Impurities are oxidized further, the intermediate products are converted into a useful product, and aromatic carboxylic acid is recycled for reuse. Such recycling of the mother liquor from stage hydrogenation is especially useful if a device for the separation used to separate water from the reaction solvent is a distillation column. Vosvrda is also effective to add the liquor from the stage of purification in the reaction mixture. Thus, the method according to the invention provides the exception of the greater part of the flow of wastewater, which would otherwise have gone to the plant for treatment of sewage.

Before returning the flow of liquor in the distillation column, it can be treated to remove suspended substances, if they are. For example, it can be subjected to filtration or centrifugation, or it can pass through a hydrocyclone to remove suspended particles. Prior to this treatment to remove suspended particles, the mother liquor can be processed, for example, cooling, removal of dissolved substances, which otherwise can cause fouling of distillation columns.

The drawing shows a diagram of a preferred variant of the method according to the invention. In the oxidation reactor 10 under stirring paraxylene reacts with air in the presence of acetic acid and water as a solvent, cobalt and manganese and one or more bromine compounds, for example, hydrogen bromide, as a promoter of oxidation. The oxidation reaction is carried out at a temperature of from about 170 to about 210oC and a pressure of from about 7 to about 21 kg/cm2. The heat released Ave is natural with gaseous by-products, oxides of carbon, nitrogen Ezy air supplied into the reactor and unreacted oxygen pass through the pipe 12 to a distillation column high pressure 20 containing about 45 theoretical plates. In the distillation column, the solvent is acetic acid is separated from the flue gas. The distillation column is designed and operates in such a way that at least 99% acetic acid to remove from the flue gas. Acetic acid from the bottom of the distillation column is sent to the drum 30 through the pipe 25.

From the drum 30 acetic acid, which may contain some amount of water is returned to the reactor 10 through the pipe 35. The number of returned solvent is controlled so as to maintain the desired amount of solvent in the oxidation reactor.

The reaction of the exhaust gas discharged from the upper part of the distillation column 20 through the pipe 38, contains less than about 0.1 wt.% acetic acid and is mostly water (steam), and also contains nitrogen and gaseous intermediate products, for example, methyl bromide. The exhaust gas from pipe 38 enters the catalytic oxidation 40, where intermediate products, napryajennogo oxidation 40 is also provided with a water scrubber to remove bromine from waste gas, coming out of the catalytic oxidation. If acetic acid is not completely removed from the exhaust of the reaction stream, it will be oxidized in the catalytic oxidation, resulting in reduced losses. The exhaust gas from the catalytic oxidation 40 is directed into the pipe 42. Part of the exhaust gas pipe 42 is directed into the pipe 43 and then to the condenser 45, where water from the flue gas condenses. The cooled exhaust gas is supplied into the drum 50 through the pipe 46. The gas, containing no water, out of the loop pipe 51. Water from the drum 50 is directed into the vessel 110 with a suspension of terephthalic acid.

The flue gas that is mainly water vapor, the pipe 42 is directed in the pre-heater 60 through the pipe 55. The heater 60 of the exhaust gas is heated to a temperature of from about 200 to about 235oC, which is sufficient to prevent condensation of the flue gas, from which removed acetic acid, defendere 70. Preheated flue gas enters defender 70 pipeline 65. Defender 70, which takes away energy from the exhaust gas, controls the operation of the compressor 75, national generator 80, which generates electricity for use at the plant, producing TC, and at the local power plant.

Expanded exhaust gas exits defender 70 pipeline 72 and enters the condenser 90, where the water in the expanded gas is condensed. Condensed water from the condenser 90 is directed into the drum 100 through the pipeline 92. Water from the drum 100 is sent to a distillation column high pressure 20 pipeline 102 and 200. This water is returned to the column, serves as a distillation for the column. Water from the drum 100 is also supplied into the vessel 110 with a suspension of terephthalic acid by pipeline 105.

The reaction mixture containing crude thereforewe acid, water, acetic acid, catalytic metals, the intermediate products of the oxidation reaction and by-products, out of the oxidation reactor 10 through pipe 115 and is directed into the vessel 120, where the temperature of the reaction mixture decreases for crystallization of dissolved terephthalic acid.

The vessel 120 may be provided with means to supply air to continue the oxidation reaction. Exhaust gases from the vessel 120 is directed into the vessel 130 through the pipeline 128 where additional cooling is a device for separating 135 pipeline 132. A device for the separation 135 typically represents one or more centrifuges or filters.

In the device for the separation 135 crude terephthalic acid is separated from the mother liquor. The mother liquor exits the device to divide 135 by pipeline 138 and enters the drum for Queen cells 140. The main part of the mother liquor containing the catalyst and acetic acid, is recycled to the oxidation reactor 10 through line 145. The other part of the mother liquor is fed to the Stripping column 150 through the pipeline 148, where acetic acid is removed and sent to the vessel 130 through the pipe 152, the residue from the Stripping column is directed to flow along the pipeline 154.

The slurry of crude terephthalic acid and the water from the drum with a suspension of terephthalic acid 110 is sent to a hydrogenation reactor 160 pipeline 158.

In the reactor 160 crude terephthalic acid is dissolved in water, treated with hydrogen at an elevated temperature, for example, about 260-290oC, and increased pressure for the purification of crude terephthalic acid, for example, by reducing the concentration of 4-carboxybenzene.

The reaction mixture from the hydrogenation reactor 160 enters the vessel for crystallization 170 on trubor the I in a device for the separation of 180 pipeline 175. Purified terephthalic acid is released from the device to divide 180 by pipeline 190. A device for the separation of 180 is typically a centrifuge or a rotary vacuum filter.

The mother liquor from the device 180, which contains water, dissolved and suspended purified terephthalic acid and various intermediate and by-products, recycled into the upper part of the distillation column high pressure 20 in the pipeline 200. The return of the mother liquor from the device for separation of 180 in the distillation column high pressure 20 to return the intermediate and by-products in the mother liquor in the oxidation reactor, where they are oxidized or converted into terephthalic acid. It also provides recycling valuable terephthalic acid, which otherwise would have done on the wastewater treatment or for regeneration it would require costly methods, and it allows to eliminate the processing of large volumes of wastewater plants for wastewater treatment.

1. Method for preparation of aromatic carboxylic acids by the exothermic oxidation of the corresponding alkylaromatic parent compound in the liquid phase of the reaction mixture, Astashova heavy metal and a source of molecular oxygen, under reaction conditions, leading to the gaseous exhaust stream of high pressure water-containing gaseous by-products and gaseous low molecular weight monocarboxylic acid, followed by distillation of the aromatic carboxylic acid and separation of the exhaust flow high pressure, characterized in that the exhaust flow high-pressure direct high-performance distillation column to remove at least 95% by weight of low molecular weight monocarboxylic acid from the waste stream, with the formation of the second exhaust flow high-pressure containing water and gaseous by-products formed in the oxidation process, then the second exhaust stream of high pressure is directed to the means for the release of energy from the second exhaust stream.

2. The method according to p. 1, characterized in that the high efficiency distillation column has at least about 30 theoretical plates.

3. The method according to p. 1, characterized in that the means for the release of energy from the second exhaust flow high pressure is defender.

4. The method according to p. 1, characterized in that defender associated with electric generc a paraxylene and aromatic carboxylic acid is terephthalic.

6. The method according to p. 1, characterized in that the low molecular weight monocarboxylic acid, which solvent is an acetic acid.

7. The method according to p. 1, characterized in that the water contained in the second outgoing stream of high pressure, used for purification of aromatic carboxylic acids.

8. Method for preparation of aromatic carboxylic acids by the exothermic oxidation of the corresponding alkylaromatic parent compound in the liquid-phase reaction mixture consisting of water, low molecular weight monocarboxylic acid as a solvent, the oxidation catalyst on the basis of heavy metal and a source of molecular oxygen in the reaction conditions leading to the gaseous exhaust stream of high pressure water-containing gaseous by-products and gaseous low molecular weight monocarboxylic acid and the reaction mother liquor containing aromatic carboxylic acid, characterized in that

a) the exhaust gas stream is directed into a high efficiency distillation column to remove at least 95 wt.% low molecular weight monocarboxylic acid from waste pot is FL, formed in the oxidation process;

b) separating the aromatic carboxylic acid from the aqueous reaction mother liquor, with the formation of crude aromatic carboxylic acid;

C) purify the crude carboxylic acid by hydrogenation at elevated temperature and pressure in the cleaning solvent containing water, with formation of a mixture of purified aromatic carboxylic acid and aqueous mother liquor;

d) separating the purified aromatic carboxylic acid from the mother liquor and returning at least a portion of the mother liquor into a high efficiency distillation column.

9. The method according to p. 8, wherein the alkylaromatic the original compound is a para-xylene and the aromatic carboxylic acid is terephthalic.

10. The method according to p. 9, characterized in that the low molecular weight monocarboxylic acid, which solvent is an acetic acid.

11. The method according to p. 8, characterized in that the high efficiency distillation column has at least about 30 theoretical plates.

12. The method according to p. 8, characterized in that the cleaning solvent is the FDS is an efficient distillation column.

14. Device for producing aromatic acids by exothermic liquid-phase oxidation of alkylaromatic compounds in the reaction mixture containing acetic acid as solvent, water, gaseous products and gaseous acetic acid, comprising the reaction vessel suitable for the implementation of liquid-phase oxidation alkylaromatics compounds at elevated temperature, characterized in that it includes:

a) high efficiency distillation column capable of separating a mixture of acetic acid and water so that the steam escaping from the distillation column contains less than about 0.5 wt.% acetic acid;

b) means for directing gaseous exhaust stream into a high efficiency distillation column;

(C) means for removal of combustible materials from the vapor emerging from the highly efficient distillation columns;

d) a means for the release of energy from the steam coming out of the distillation column after removal of combustible materials.

15. Installation according to p. 14, characterized in that the high efficiency distillation column has at least about 30 theoretical plates.

16. Installation on p. on p. 16, characterized in that defender connected to an electric generator.

 

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