Method of producing crude aromatic dicarboxylic acid for hydrogenation purification

FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of producing crude terephthalic acid for use at a hydrogenation purification step via liquid-phase oxidation with an oxygen-containing gas in an oxidation reactor fitted with a mixer, using as the starting material para-xylene in a solvent - acetic acid, in the presence of a metal-containing catalyst which contains cobalt (Co), manganese (Mn) and bromine (Br) as an oxidation promoter, where the oxidation reaction temperature is controlled such that is lies in the interval from 185 to 197°C, average dwell time of the starting mixture in the reactor for liquid-phase oxidation ranges from 0.7 to 1.5 hours, content of water in the reaction solvent is controlled such that it ranges from 8 to 15 wt %, and the composition of the catalyst in the solvent is controlled in a range defined depending on the reaction temperature such that it includes: (1) a catalytically active metal (Co+Mn) in amount of 2650 ppm or less and in amount equal to or more than a value determined by the following relationship: (Co+Mn) = -0.460(t-185)3+18.4(t-185)2-277.5(t-185)+2065, in which (Co+Mn) is the content of (Co+Mn) in ppm, t is the reaction temperature (°C) (temperature range from 185 to 200°C), (2) weight ratio Mn/Co is controlled in a range from 0.2 to 1.5, preferably from 0.2 to 1; (3) content of Br is equal to or less than 1.7, if represented by a value Br/(Co+Mn) in form of weight ratio, and in amount equal to or greater than a value given by the equation: Br/Mn = -0.00115(t-185)3+0.0362(t-185)2-0.5803(t-185)+5.18, in which Br/Mn is weight ratio Br/Mn (wt/wt), and t is reaction temperature (°C) (temperature range from 185 to 200°C), and crude terephthalic acid is obtained with content of 4-carboxybenzaldehyde in amount from 2000 to 3500 ppm as an intermediate product of liquid-phase oxidation. The method provides cheap production of crude terephthalic acid for use in hydrogenation purification and use of a controlled amount of oxidation catalyst, which does not have undesirable effect on the life of a hydrogenation purification catalyst, as well as conditions for carrying out the corresponding reaction.

EFFECT: obtaining terephthalic acid during liquid-phase oxidation of the corresponding dialkylated aromatic hydrocarbon using a solvent, acetic acid, carried out by reducing the oxidised amount of acetic acid lost during oxidation, limiting formation of ash in the obtained terephthalic acid, and enabling control of the composition of the oxidation catalyst depending on reaction temperature.

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The technical field to which the invention relates.

The present invention is a method of obtaining a crude aromatic dicarboxylic acid, which is preferred for use in the hydrogenation purification upon receipt of an aromatic dicarboxylic acid high purification by hydrogenation purification after receiving the crude aromatic dicarboxylic acid by liquid phase oxidation dialkylamino aromatic hydrocarbon with a gas containing oxygen.

Specifically, the method of obtaining an aromatic dicarboxylic acid by liquid-phase oxidation refers to the composition of the catalyst of liquid-phase oxidation and reaction conditions that produce crude aromatic dicarboxylic acid with high efficiency liquid-phase oxidation, revealing the performance of the hydrogenation catalyst in the implementation of hydrogenation treatment in the form of an aqueous solution of the crude aromatic dicarboxylic acid obtained a more economical way.

Background of invention

Method for preparation of aromatic dicarboxylic acids from dialkylamino aromatic hydrocarbon used as a starting material, such as para-xylene or meta-xylene by assests is of liquid-phase oxidation of oxygen-containing gas in the presence of a catalyst, including cobalt (Co), manganese (Mn) and bromine (Br) in the solvent is acetic acid is used in industry on a large scale and has practical application.

As the aromatic dicarboxylic acid obtained by the above method includes an intermediate oxidation products, such as 4-carboxybenzene (4-KBA) and 3-carboxybenzene (3-KBA), as well as colored products, such as biphenyls and fluorenone, aromatic dicarboxylic acid is dissolved in water, conduct the reaction of the hydrogenation catalyst based on a noble metal deposited on a carbon carrier, in order to remove or reduce the content of impurities, thus receive the purified aromatic dicarboxylic acid is intended for use as a starting substance for the preparation of aromatic polyesters.

This method is used to convert the intermediate product and the colored material that is not suitable for the preparation of aromatic polyesters intended, for example, to obtain fibers, easily soluble in water material via hydrogenation reactions with subsequent removal of hydrogenated impurities by dissolving them in an aqueous solvent with the crystallization and isolation of the aromatic dicarboxylic acid.

On the other hand, have conducted a study on the conditions the reaction and the composition of the catalyst in liquid-phase oxidation reactions of oxygen-containing gas in a solvent - acetic acid, to obtain a high-purity aromatic dicarboxylic acid capable of direct polymerization glycols without additional purification stages in hydrogenation reactions.

As shown in the patent is 1 (JP-B No. Sho 45-36732), patent document 2 (JP-B No. Sho 53-30700) and patent document 3 (JP-B No. Sho 56-21015), they are designed to present ways to improve the reaction temperature and catalyst composition for oxidation reactions and the production of high-purity aromatic dicarboxylic acid at a lower concentration of aromatic aldehyde monocarboxylic acids, for example 4-KBA, and painted materials in the form of impurities; purity acid sufficient for direct polymerization after conducting a single stage reaction, namely the oxidation.

Accordingly, since the patent document 4 (JP-B No. Sho 34-2666) on the catalyst comprising a heavy metal and bromine", no bids are received on the way to obtain the crude aromatic dicarboxylic acids suitable for hydrogenation purification, as part of the improvements to the composition of the catalyst oxidation catalytic compositions intended to obtain the crude aromatic dicarboxylic acid, aromatic dicarboxylic acid not having high purity) realiabilty dialkylamino hydrocarbon as a starting material, since the removal of impurities strongly depends on the stage hydrogenation treatment, held next after the oxidation stage.

Patent document 1: JP-B No. Sho 45-36732

Patent document 2: JP-B No. Sho 53-30700

Patent document 3: JP-B No. Sho 56-21015

Patent document 4: JP-B No. Sho 34-2666

Patent document 5: JP-B No. Sho 53-24057

Patent document 6: JP-A No. Hei 11-228492

Detailed description of the invention

The problem, which is solved by this invention

The process of obtaining a purified aromatic dicarboxylic acid, which is currently used in industry, are presented in figure 1 the process of obtaining purified terephthalic acid, which is divided into two stages: the stage of obtaining the crude terephthalic acid (NTC) and cleaning stage to obtain purified terephthalic acid (TCI).

That is in the process of obtaining the crude terephthalic acid (NTC) para-xylene as a starting substance, acetic acid as solvent and catalyst (Co, Mn, Br) served in the oxidation reactor 1, in which the mixing takes place at high temperature (from 180 to 210°C) and high pressure (10 to 20 kg/cm2(Rel.)), as well as serving the air in the lower part of the reactor 1 for the continuous carrying out oxidation reactions. Flue gas with low oxygen content due to assests the deposits of the oxidation reaction out of the upper part of the reactor 1 together with the vapors of the solvent. The exhaust gas containing vapors of the product is passed through a cooler-condenser 2, which are capable of condensation components condense and separate to form a liquid condensate and flue gas reactions in the separator gas and liquid 3. A large portion of the liquid condensate is returned to the reactor 1, but the part is extracted to regulate the concentration of water in the solvent in the reactor.

The reaction product is removed from the bottom of the reactor, adjusting the liquid level, and a pre-defined reaction volume in the secondary oxidation reactor (not shown in figure 1, this additional reactor as the reactor, equipped with stirrer, condenser, cooler, separator gas and liquid) and it serves oxygen-containing gas, e.g. air, to complete the oxidation reaction. Obtained after completion of the oxidation reaction the reaction product is transferred into the mold 4 at a lower pressure and is cooled by evaporation under pressure; the resulting terephthalic acid precipitated and get the suspension with the solvent. The resulting suspension is separated and washed in the separator, the solids and liquid 6, for example, in the filter device, and produce crystals of terephthalic acid. They are then dried in the dryer with obtaining the crude terephthalic acid (NTC).

<> Then at the stage of obtaining purified terephthalic acid (TCI) the dried crude terephthalic acid (NTC) and water quantitatively loaded into a vessel for the preparation of suspensions 10, to prepare aqueous suspensions of pre-set concentration (from 20 to 33 wt.%). The suspension is also quantitatively transferred into the heater 12 and the vessel for dissolving 11 at high pressure (60 to 80 kg/cm2(Rel.)) and terephthalic acid is dissolved by heating in aqueous solution, and then sent to the reactor for hydrogenation purification 13. In the hydrogenation reactor 13 cleaning at high temperature (from 260 to 290°C) and high pressure (60 to 80 kg/cm2(Rel.)) download activated carbon catalyst containing a noble metal such as palladium, an aqueous solution of terephthalic acid containing impurities, simultaneously serves hydrogen and put it through a catalyst bed, thereby conducting the reaction of hydrogenation of impurities.

An aqueous solution of terephthalic acid, processed in hydrogenation reactions, as described above, is cooled using equilibrium evaporation when manual pressure a few molds are combined in series (from 3 to 6 stages) (set of molds in figure 1 not shown) to deposition of crystals of terephthalic the th acid. The purified suspension, which crystallized terephthalic acid is separated and washed in the separator solids and liquids, for example in a centrifuge, with the aim of identifying crystals of terephthalic acid. Then the purified terephthalic acid is dried using the dryer and get at this stage in the form of the product (OTC).

Accordingly, since the cleaning process at the stage hydrogenation purification works effectively, requires fewer requirements to the stage of obtaining the crude aromatic dicarboxylic acid, the previous stage hydrogenation treatment, and there are no proposals for phase oxidation reaction, suitable for hydrogenation treatment, including both phases of the oxidation reaction and hydrogenation treatment.

Specifically, as for the catalyst of the reaction liquid-phase oxidation in the process of obtaining the crude aromatic dicarboxylic acid, there are no suggestions for the improvement of the catalyst composition including Co, Mn and Br, since the publication of the patent document 4 described above, and describes the implementation of liquid-phase oxidation with molecular oxygen in the presence of a heavy metal and bromine".

In addition, in the patent containing the sign of the regulation of the relations of the component parts of a catalyst in quantitative interval is e, for example, the relation Mn/With or relationship Br/With the Co concentration in the solvent for the reaction of oxidation, introduced in the present description by reference (patent documents 1 to 3 described above), described that the terephthalic acid of high purity can be obtained by reduced amounts of impurities (4-KBA as an intermediate product) to about 500 ppm million or less.

However, although improvements can provide high purity aromatic dicarboxylic acid as a starting material for the production of aromatic polyesters without the use of stage hydrogenation purification as the subsequent stage, the loss of the oxidation of the solvent (acetic acid)that occur during oxidation together with the reaction of deep oxidation, can be approximately 0.2 as the basic unit of acetic acid (mass ratio of the consumed in the oxidation of acetic acid per mass of the obtained terephthalic acid), as shown in the example of patent document 3 described above, and therefore this method is not superior from an economic point of view by the way.

Further, also in the other patents described above (patent documents 1 and 2 described above), although the amount consumed in the oxidation of acetic acid is not specifically listed, as this venture is the FDS includes obtaining terephthalic acid, containing the same amount of 4-KBA, as in the above patent publication, it is believed that in this case, the oxidation consumes about the same amount of acetic acid.

On the other hand, at the stage hydrogenation purification of impurities, for example, the intermediate reaction products contained in the crude aromatic dicarboxylic acid, hydronauts obtaining soluble in water products.

For example, the stage hydrogenation purification is performed on the basis of the fact that the intermediate product of the reaction, the aldehyde aromatic monocarboxylic acids, for example 4-KBA, becomes methylated aromatic monocarboxylic acid, such as para-Truelove acid, and colored impurities, such as fluorine, subjected to hydrocracking and their content in the purified crystals of the aromatic dicarboxylic acid is strongly reduced during its crystallization and selection.

Among these reactions in the hydrogenation purification from aldehyde aromatic monocarboxylic acid (4-KBA) the reaction of hydrogenation of the aldehyde aromatic monocarboxylic acid (4-KBA, a molecular weight of 150) in methylated aromatic monocarboxylic acid (para-tolarova acid, molecular weight 136) proceeds almost quantitatively (91 wt.% in the calculation of the molecular weight), and because methylated aromatic monocarboxylic acid (para-tolarova acid) is found after hydrogenation reactions in almost the same amount (about 90 wt.%), as the aldehyde aromatic monocarboxylic acid (4-KBA) in the crude aromatic dicarboxylic acid, the reaction is carried out as a method of producing purified terephthalic acid, the crystals of which the content of para-Truelove acid does not exceed 150 ppm million, using an improved method of crystallization from aqueous solution gidrirovannoe terephthalic acid, as shown in patent document 4 (JP-B No. Sho 53-24057) and patent document 5 (JP-A No. Hei 11-228492). As other impurities can easily be removed by recrystallization after the reaction through the course of hydrocracking, etc., improved crystallization method was performed by treating it as a critical stage in the reduction of the content of methylated aromatic monocarboxylic acid (para-Truelove acid) during treatment.

The improved method is a method of recovering aldehyde aromatic monocarboxylic acid (4-KBA)contained in the crude aromatic dicarboxylic acid, hydrogenation reactions to methylated aromatic monocarboxylic acid (para-Truelove acid), and then implement the successful crystallization in the system of multi-stage evaporation pressure drops (evaporative cooling with discharge pressure) so that the methylated aromatic monocarboxylic acid para-tolarova acid) is captured by the selected crystals.

In accordance with this, in the patent JP-B No. Sho 53-24057 described, which is enough to get crystallized terephthalic acid with impurities not exceeding 150 ppm million through a multistage evaporation pressure drops with the number of stages 5 to 8 of terephthalic acid containing from 2000 to 6000 ppm million pair-Truelove acid, based on terephthalic acid. Then, in the above example, terephthalic acid content of 2,500 ppm million pair-Truelove acid, dissolved in water, and carry out multi-stage evaporation pressure drops with obtaining crystallized terephthalic acid, the impurities content is 150 ppm million or less.

Further, in the example shown in JP-A 11-228492, terephthalic acid, containing 3000 ppm million pair-Truelove acid, dissolve in water to obtain crystallized terephthalic acid with a content of 150 ppm million or less para-Truelove acid.

In accordance with this, the content of aldehyde aromatic monocarboxylic acid (4-KBA) in the aromatic dicarboxylic acid (NTC), obtained by oxidation of the aromatic dicarboxylic acid (NTC), suitable for hydrogenation purification, greatly exceeds the number of methylated aromatic monocarboxylic acid (para-Truelove acids is), contained in the purified aromatic dicarboxylic acid. However, this does not require the aromatic dicarboxylic acid (NTC) of such high purity that the content of aldehyde aromatic dicarboxylic acid (4-KBA) was 500 ppm million or less, as proposed in patent documents 1 to 3 described above, and it is possible to make such an oxidation reaction, as obtaining the crude aromatic dicarboxylic acid (NTC)that contains about 3000 frequently./million aldehyde aromatic monocarboxylic acid (4-KBA).

For this purpose, suppose that there must be some way to mild oxidation in the liquid phase dialkylamino hydrocarbons, suitable as a preliminary stage before stage hydrogenation treatment, different from the proposals described above (patent documents 1 to 3).

For the crude aromatic dicarboxylic acid (NTC), intended for use in hydrogenation purification, suppose that the content of aldehyde aromatic monocarboxylic acid (4-KBA), which is an impurity, preferably ranges from 2000 to 3500 ppm million, and the object of the present invention are components of the catalyst (Co, Mn and Br) and the reaction conditions required for the reaction mild oxidation, which forms the I of the crude aromatic dicarboxylic acid (NTC), containing from 2000 to 3500 ppm million aldehyde aromatic monocarboxylic acid (4-KBA).

Ways to solve problems

The authors of the present invention conducted a thorough investigation of the reaction temperature and oxidation catalyst (Co, Mn, Br), intended for the reaction mild oxidation with obtaining the crude aromatic dicarboxylic acid containing from 2000 to 3500 ppm million aldehyde aromatic monocarboxylic acid. Specifically, they found that lowering the reaction temperature and the decrease in the content of bromine (Br), which is the most sensitive instrument for the regulation of reactivity in the oxidation reaction, affects the catalyst for hydrogenation treatment on the subsequent stage, and examined the change in the composition of the oxidation catalyst and the reaction temperature as a way to obtain the crude aromatic dicarboxylic acid, intended for hydrogenation treatment.

The authors of the present invention have found that the amount of solvent, acetic acid (the main component of acetic acid), lost in the oxidation taking place along with the formation of aromatic dicarboxylic acids by the oxidation reaction, is compensatory correlation with the number of aldehyde aromatic monocarboxylic acid (4-KBA)is contained in the resulting aromatic dicarboxylic acid, and the impact on the number of oxidized acetic acid (the main component of acetic acid) is lower at lower reaction temperature, with the same content of aldehyde aromatic monocarboxylic acid (4-KBA) in the obtained aromatic dicarboxylic acid; and the amount of oxidized acetic acid is not reduced even if the temperature is reduced to 185°C or below. Then it was confirmed that the amount of oxidized acetic acid (the main link acetic acid) ranges from 37 to 45 kg per tonne received dicarboxylic acid, which is significantly lower compared to the example given in the patent (reference to patent document 3) (0,2 approximately 200 kg/t).

In accordance with this to obtain an aromatic dicarboxylic acid containing from 2000 to 3500 ppm million aldehyde aromatic monocarboxylic acid (4-KBA), intended for hydrogenation purification, it has been found that the reaction temperature should be preferably from 197 to 185°C.

However, although consider it necessary to increase the quantity of catalyst (Co, Mn, Br), necessary for the preparation of aromatic dicarboxylic acids with the same content of aldehyde aromatic monocarboxylic acid (4-KBA) to reduce the reaction temperature, if the content of Br in the oxidized catalyst is I'm down in accordance with the requirements for example, in order to achieve a lower activity in the reaction and suppress corrosion of the equipment, it was found that this leads to a clogging layer of catalytic hydrogenation in the subsequent stage, so you are forced to abort the operation and affects the activity of hydrogen on stage hydrogenation treatment (comparative example 1). At the same time, it has been found that this is due to the ash content in the formed aromatic dicarboxylic acid; the Mn content in the ash is extremely high, which occurs due to the decrease of the ratio of bromine to the amount of manganese (Br/Mn). Further, it was found that the ratio Br/Mn, is able to limit the ash content depends on the reaction temperature, i.e. it is inversely proportional to the reaction temperature in the following equation (2). Accordingly, it was found that it is necessary to increase the content of bromine and reduce the manganese content, as well as to reduce the reaction temperature.

I believe that the reason is to reduce the impact of Co, Mn as catalysts and Br as a promoter and regenerating agent in the reaction liquid-phase oxidation, therefore, the automatic regeneration of the manganese to form manganese oxide leaking can't. Further, while it is usually assumed that the catalyst activity of the hydrogen on isdi decreases with aggregation and loss of active metal and sticking to it of impurities, since the deposition of the oxide of manganese causes a decrease in the hydrogenating activity to contamination of the layer of catalyst, ash should be avoided to save the active lifetime of the catalyst.

Further, the regulation of the amount of catalyst (Co, Mn, Br), which is required along with a decrease in the reaction temperature, increases with increasing mass relations Br/(Co+Mn); it was also found that when the mass ratio of Br/(Co+Mn) is increased to a value of 1.7 or more at the reaction temperature, component 185°C, it has no effect on the content of aldehyde aromatic monocarboxylic acid (4-KBA) in the aromatic dicarboxylic acid (NTC). Then it was found that when the reaction temperature greater than 185°C., a sufficient amount of bromine is determined by the mass ratio of Br/(Co+Mn), amounting to 1.7.

Accordingly, it is preferable to limit the number of bromine was regulated so that the minimum ratio Br/Mn calculated in accordance with equation (2), correlated with each reaction temperature, and the maximum number was determined by the ratio of Br/(Co+Mn) in the catalyst composition, the components of 1.7.

Based on the discoveries described above, to obtain a crude aromatic dicarboxylic acid, intended for hydrogenation purification, with what uranium aldehyde aromatic monocarboxylic acids, components from 2000 to 3500 ppm million, you can get the most economical of the crude aromatic dicarboxylic acid and to provide a method of obtaining a crude aromatic dicarboxylic acid capable of ensuring the efficiency of the catalyst for hydrogenation treatment in the long period of time by obtaining a catalytic composition for the oxidation catalyst, which contains (1) a catalytically active metal (Co+Mn) in the amount of 2650 frequent./million or less and in a quantity equal to or greater than the content represented by the equation according to:

(in which (Co+Mn) is the content of (Co+Mn) in part./million, t is the reaction temperature (°C) (temperature interval from 185 to 200°C)),

(2) the mass ratio of Mn/Co is adjustable from 0.2 to 1.5, preferably from 0.2 to 1

(3) bromine content is 1.7 or less in mass ratio of Br/(Co+Mn) and at least equal to or above equation according to (2)

in which Br/Mn represents the mass ratio of Br/Mn (weight/weight), t is the reaction temperature (°C),

while the oxidation reaction is carried out at a reaction temperature of liquid-phase oxidation component from 185 to 197°C., preferably from 185 to 195°C.

Eff the CT of this invention

The present invention can provide the components of the catalyst (Co, Mn and Br) and the reaction conditions required for the reaction mild oxidation, is capable of producing crude aromatic dicarboxylic acid (NTC)containing aldehyde aromatic monocarboxylic acid (4-KBA) in an amount of from 2000 to 3500 ppm million, which represents a typical impurities contained in the crude aromatic dicarboxylic acid (NTC), the most suitable for carrying out hydrogenation treatment.

The best way practical implementation of the present invention

In the present invention, the aromatic dicarboxylic acid containing from 2000 to 3500 ppm million aldehyde aromatic monocarboxylic acids intended for hydrogenation purification, is obtained by oxidation dialkylamino aromatic hydrocarbon as a starting material in the liquid phase oxygen-containing gas in a solvent, acetic acid, in the presence of a catalyst comprising Co, Mn and Br.

As the source dialkylamino aromatic hydrocarbon used para-xylene or meta-xylene, and the solvent used in the reaction of acetic acid. In the oxidation catalyst, prepared in acetic acid as solvent, the amount contained (Co+Mn is the maximum 2650 frequent./million, the content is 2065 frequent./million at 185°C, and is regulated within the intervals of the amount calculated by the equation (1), that is, the content decreases with increasing reaction temperature.

The amount of catalyst (Co+Mn)of 2650 frequent./million, gives the opportunity to obtain an aromatic dicarboxylic acid containing about 2000 ppm million aldehyde aromatic monocarboxylic acid with a ratio of Br/(Co+Mn)=1,7 (wt./wt.) at the reaction temperature of 185°C, the content of the catalyst has a reduced impact on the content of bromine with increasing ratio of Br/(Co+Mn) is more than the value of 1.7. Further, when the content of the catalyst is no need to increase its activity in the reaction by increasing the content of Co+Mn (since there is no need to reduce the aldehyde content of monocarboxylic acid to below 2000 ppm million).

In addition, the number of Co+Mn, calculated by equation (1)represents a content of the catalyst, wherein the reaction of oxidation is formed of an aromatic dicarboxylic acid containing a maximum of about 3500 ppm million aldehyde aromatic monocarboxylic acid, and the amount of Co+Mn represents the minimum quantity of catalyst that is required when adjusting (increasing) the number compared with the value calculated on the basis of the AI of equation (1) for each reaction temperature under the condition of reducing the amount of aldehyde aromatic monocarboxylic acid or quantity of bromine. Accordingly, it is preferable that the amount of Co+Mn in acetic acid used as solvent, was regulated within the range of values between two specified contents of Co+Mn.

Further, in the oxidation reaction, for example, in the applications described in patent documents 1 to 3 described above, the ratio of Mn/(mass ratio) is adjusted within the range from 0.2 to 1.5, preferably from 0.2 to 1, in accordance with the influence of manganese as socializaton on a cobalt catalyst. Preferably, the ratio of Mn/(mass ratio) decreased with decreasing reaction temperature, due to restrictions on the reaction temperature and the ratio Br/Mn (mass ratio), and the ratio of Mn/Co is preferably adjusted so that it was 0.49 or less, due to restrictions in relation Br/Mn at the reaction temperature, component 185°C.

Then, as the number of Br should increase with decreasing reaction temperature, increasing its content higher values of Br/(Co+Mn)=1,7 at the reaction temperature of 185°C less effect on the content of aldehyde aromatic monocarboxylic acid (4-KBA) as the reaction product. Sufficient throttling is achieved by increasing temperature and regulating the ratio of Br/(Co+Mn) at the level of 1.7 or less. Accordingly, catalyzatoroprovod so, to its composition was regulated in the range of, at least, the amount of which is calculated by the equation (2) or more relating to the content of manganese in order to limit the formation of ash in the final aromatic dicarboxylic acid with a maximum content of bromine, which is regulated by the ratio of Br/(Co+Mn)=1,7.

That is, the amount of bromine in the catalyst is at least corresponds calculated by equation (2) or more, in order to avoid the formation of ash and entering the aromatic dicarboxylic acid that is used for hydrogenation treatment, and the number of bromine at the reaction temperature of 185°C was such that the ratio (Br/Mn) was 5,18. This number corresponds to control the ratio of Mn/Co average of 0.49 and provides the catalyst with a ratio of Br/(Co+Mn)=1,7.

Acetic acid as solvent, prepared as described above, served in a quantity of 2.5 to 4 times the amount (by weight) dialkylamino aromatic hydrocarbon, which serves as the source material in the oxidation reactor, and served in the reactor oxygen-containing gas, e.g. air, in order to conduct the oxidation reaction. Flue gas depleted in oxygen consumed in the oxidation reaction, and contains a pair dissolve what I take away from the upper part of the reactor, solvent vapours condense in the condenser-cooler 2, then the liquid condensate is separated using the separator gas/liquid 3 and return to the reactor. The oxygen concentration in the exhaust gas of the reaction, separated from the liquid condensates, measured, and then the gases produced from the reaction system at a regulated pressure. The temperature in the reactor, i.e. the reaction temperature, adjust range from 185 to 197°C., preferably from 185 to 195°C. by regulating the steam generation using pressure adjustment (from 11 to 18 kg/cm2(Rel.)).

Then fed to the reactor, the amount of oxygen-containing gas is adjusted so that the oxygen concentration in the exhaust from the reaction gases ranged from 2.5 to 4%vol.

In addition, part of the recirculating liquid condensate is removed for the purpose of regulating the water content in the solvent during the reaction, so that it ranged from about 8 to 15 wt.%, preferably from 10 to 13 wt.%. To regulate the amount of water in the reactor serves the solvent, acetic acid (containing no catalyst)in an amount corresponding to a remote amount of liquid condensate so as to maintain constant the concentration of the oxidation catalyst used in the reaction solvent.

The reaction product obtained upon completion of the reaction soft OK the comprehension, you want to remove from the bottom of the reactor for the regulation of liquid level or while maintaining a constant reaction volume. The reaction volume corresponds to the residence time in the reactor is supplied to the reaction mixture, it is preferably adjusted so that it ranged from 0.7 to 1.5 hours, more preferably from 1 to 1.3 hours.

In the oxidation reaction, which is carried out as described above, the solvent is acetic acid, which is consumed by the reaction of decomposition of gaseous carbon dioxide (including carbon monoxide) and water flowing parallel to the oxidation of the original dialkylamino aromatic hydrocarbon. The reaction of co oxidation acetic acid flowing in this case, determines the loss on the oxidation of acetic acid; in industry these losses count and take into account as losses on the oxidation of acetic acid in the calculation of the obtained aromatic dicarboxylic acid (the basic unit of acetic acid, kg/t).

Suppose that the number of oxidized acid depends on the stiffness of the conditions of the oxidation reaction and is a compromise relation to the content of aldehyde aromatic monocarboxylic acid remaining in the obtained aromatic dicarboxylic acid, that is equal to this value, multiplied by a coefficient. According to the respectively, the content of aldehyde monocarboxylic acid (4-KBA) (from 2000 to 3500 ppm million) in accordance with the method of the present invention, differs from the content of the aldehyde aromatic monocarboxylic acid (4-KBA) (500 ppm million or less) in accordance with patent document 3 described above, so that the amount of oxidized acetic acid significantly different for the oxidation process in accordance with the present invention is intended to obtain an aromatic dicarboxylic acid. The reaction conditions of oxidation, which are the subject of the present invention differ from the conditions proposed in patent document 3 described above. Further, the amount of oxidized acetic acid described in this description of the method is greatly reduced, which increases the efficiency of the method of producing an aromatic dicarboxylic acid in accordance with the present invention.

However, even if the oxidation reaction produces the same amount of aldehyde aromatic monocarboxylic acid (4-KBA), the amount of oxidized acetic acid (the basic unit of acetic acid) is reduced when carrying out the oxidation reaction at lower temperatures, and, in addition, the degree of decrease with decreasing temperature decreases as it approaches to a temperature of 180°C. Then, when the temperature is round reaction, component 180°C, the amount of oxidized acetic acid (the basic unit of acetic acid) practically coincides with the number oxidized at a temperature of 185°C.

Accordingly, if the oxidation reaction in the process according to the present invention is carried out at a temperature of 185°C or above, or at a temperature of 197°C or below, the amount of oxidized acetic acid (the basic unit of acetic acid) is almost 45 kg/t or below, resulting in an aromatic dicarboxylic acid containing aldehyde aromatic monocarboxylic acid (4-KBA) in the range from 2500 to 3500 ppm million to obtain the purified aromatic dicarboxylic acid is even more greatly improved quality, it is preferable to carry out the oxidation reaction in the temperature range from 185 to 195°C.

Further, the oxidation of the solvent include acetic acid, followed by reaction of co oxidation of acetic acid and the source of the reacting substances in the reactor. The content of aldehyde aromatic monocarboxylic acid (4-KBA) is measured and, in so far as this content, the residence time of the reactants in the reactor make as short as possible, i.e. from 0.7 to 1.5 hours To obtain an aromatic dicarboxylic acid containing aldehyde aromatic monocarboxylic acid (4-KBA) in an amount of from 2000 to 350 ppm million, and stabilization of the oxidized amount of acetic acid, it is preferable to carry out the oxidation reaction at the time of stay in the reactor comprising from 1 to 1.3 hours.

The reaction mixture containing the product formed as described above, is removed from the reactor in the advanced oxidation reactor, it serves oxygen-containing gas and completes the reaction of the source materials and intermediate reaction product remaining in the reaction mixture. Then the mixture containing the reaction product is transferred to the mold 4 and cooled, and the resulting aromatic dicarboxylic acid is crystallized, and then the suspension is passed through a stage of separation of solid and liquid components, remove the acetic acid by washing and dried to obtain powder of the crude aromatic dicarboxylic acid containing from 2000 to 3500 ppm million aldehyde aromatic monocarboxylic acid.

Then the crude aromatic dicarboxylic acid, obtained as described above is fed to a purification stage; after the conversion of the crude aromatic dicarboxylic acid in an aqueous solution, as described above, it serves to hydrogenation purification using a palladium catalyst deposited on activated carbon at high temperature and high pressure, with the purpose under which the actual content of the activity in the hydrogenation in a long time (from 1 to 3 years). Then it is crystallized in a multi-stage cooling with decreasing pressure, is subjected to separation into solid and liquid components, washed with water and dried to obtain a crystalline powder of purified aromatic dicarboxylic acid, in which the content of the methyl derivative of the aromatic monocarboxylic acid is 150 ppm million or less, that is purified aromatic dicarboxylic acid has properties that allow to use it as a starting substance for the preparation of aromatic polyesters.

Examples

The method in accordance with the present invention will be further described in detail for a specific preferred options with reference to examples, comparative examples and the reference examples.

Examples 1 to 4 and comparative examples 1 to 2

The scheme of obtaining the crude terephthalic acid (NTC) is shown in figure 1, the oxidation reaction to obtain the crude terephthalic acid was used as starting material para-xylene.

As the equipment for the reaction of the applied oxidation reactor for high pressure (internal volume was approximately 48 m3), equipped with a rotary mixer; in the reactor was filed para-xylene as a starting reagent, reaction solvent, stereodigitalization and air under pressure; acetic acid was applied separately to regulate the water content in the reaction solvent.

Then mixed with pairs of exhaust gas reaction, which was formed as a result of the oxidation reaction were removed from the upper portion of the oxidation reactor was passed through a condenser - cooler 2, which is capable of condensing the components of the mixed exhaust gas is condensed and cooled, with the purpose of separation of the liquid condensate which is returned to the oxidation reactor.

Portion of the liquid condensed for return to the reactor were removed through the outlet in the circuit and thus regulate the water content in the solvent during the reaction.

Further, the exhaust gas of the reaction, is separated from the liquid condensate introduced into the gas absorber (not shown) at high pressure and unloaded through the washing treatment with acetic acid and water.

On the other hand, reacted and formed the final suspension was transferred in the secondary oxidation reactor (not shown), and after additional oxidation reaction was processed in the mold 4 and the separator of solid and liquid products 6 (separation of solids from liquid and washing the precipitate with getting wet pressed sludge end of terephthalic acid. Then, after drying in sushi is the LCA 7, received crude terephthalic acid (NTC).

The oxidation reaction was carried out at a feed of acetic acid containing a catalyst, in an amount which is three times more by weight per 100 parts per hour of the original para-xylene, compressed air, regulating the pressure of exhaust gas at the outlet of the reactor in order to achieve the appropriate temperature reactions, and injecting air in such quantity that the concentration of gaseous oxygen in the exhaust gas was about 3.5% vol. and facilitated oxidation reactions. Then the reaction product was transferred in the secondary oxidation reactor, the fluid level control was carried out using x-rays, so that the residence time in the reactor was about 70 minutes the water Concentration in the reaction mixture during the reaction was regulated so that it was approximately 11.5 wt.% (the water in the mother liquor of the reaction).

For this example, the reaction temperature, the content of catalyst (Co, Mn, Br) in the feed solvent is acetic acid, and the content of 4-KBA in the crude terephthalic acid are shown in tables 1 through 6. At the same time was measured content of gaseous carbon dioxide (CO2) and carbon monoxide (CO) in the exhaust gas, determined the amount of oxidized acetic acid (the main is dinica acetic acid) and calculated the ratio of the number of oxidized acetic acid to the amount of terephthalic acid filed on para-xylene (kg/t TC), these data are also shown together in tables 1 through 6.

Table 1
Example 1. The reaction temperature of 195°C
The concentration of catalystThe content of Co+MnContents 4-KBAThe amount of oxidized acetic acid
From (common./million)Mn (part./million)Br (part./million)(part./million)(part./million)(kg/t terephthalic acid)
4452251155670351040,2
48023512107153050of 40.9
5002451265745280041,9
540 2651370805250043,3
5652781435843230044,5
6353101600945195047,0

Table 2
Example 2. The reaction temperature of 197°C
The concentration of catalystThe content of Co+MnContents 4-KBAThe amount of oxidized acetic acid
From (common./million)Mn (part./million)Br(part./million)(part./million)(part./million)(kg/t terephthalic acid)
43521011006452900 43,3
4852351225720250045,2

Table 3
Example 3. The reaction temperature of 190°C.
The concentration of catalystThe content of Co+MnContents 4-KBAThe amount of oxidized acetic acid
From (common./million)Mn (part./million)Br (part./million)(part./million)(part./million)(kg/t terephthalic acid)
71536518601080347038,0
74036218701102325038,1
8103952055 1205270039,6
865425219512802450of 40.9
95446624151420210043,2
102050025851520190044,9

685
Table 4
Example 4. The reaction temperature of 185°C
The concentration of catalystThe content of Co+MnContents 4-KBAThe amount of oxidized acetic acid
From (common./million)Mn (part./million)Br (part./million)(part./million)(part./million)(kg/t terephthalic acid)
138035402085345037,4
147072037202190320037,1
1556762394023182800of 37.8
166081542102475245039,4
1720842435525622250of 40.9
177086744852637210042,0

The content of Co+Mn
Table 5
Comparative example 1. The reaction temperature of 200°C
The concentration of catalystContents 4-KBAThe amount of oxidized acetic acid
From (common./million)Mn (part./million)Br (part./million)(part./million)(part./million)(kg/t terephthalic acid)
320170865490345045,1
377185956562290046,4
4001951020595260047,9
4232071070630245048,9
4852371225722205051,9
5602751420835170055,8
6072951535902155057,7

Table 6
Comparative example 2. The reaction temperature 180°C
The concentration of catalystThe content of Co+MnContents 4-KBAThe amount of oxidized acetic acid
From (common./million)Mn (part./million)Br (part./million)(part./million)(part./million)(kg/t terephthalic acid)
462092594305545295037,4
49009801001058802600 a 38.5

The correlation between the content of 4-KBA in the resulting terephthalic acid and oxidized by the amount of acetic acid is shown in figure 2.

It was found that the amount of oxidized acetic acid is in the compensation ratio with 4-KBA, and the amount of oxidized acetic acid at a lower temperature of the reaction was reduced with the aim of obtaining terephthalic acid with the same contents 4-KBA in this oxidation reaction, and, in addition, the number of oxidized acetic acid is not reduced even when the temperature drops to values below 185°C.

Further, with regard to the relationship between the metal content in the catalyst (Co+Mn) and the reaction temperature, it is necessary to reduce the number of Co+Mn at lower temperature; the content of Co+Mn required to obtain terephthalic acid containing about 3500 ppm million (from 3450 to 3510 frequent./million) and about 2000 ppm million (from 1900 to 2100 ppm million) at each temperature of the reaction depending on the reaction temperature (from 185 to 200°C) is shown in figure 3 (◦and •).

In this reaction to produce NTC intended for hydrogenation treatment, the content of Co+Mn in the solvent are doing so that it fell in the area of compositions in figure 3, which is contained between two lines, grades 4-KBA, components of 3500 and 2000 ppm million at each temperature the reaction is AI.

Then, since the reaction is carried out at a ratio of Br/(Co+Mn)=1,7 if it is carried out in the range of higher temperatures (190, 195°C)NTC for use in hydrogenation purification can be obtained by increasing the content of Co+Mn and reducing the ratio of Br/(Co+Mn). For this curve, denoted by the symbol ◦ in figure 3, determines the control amount of the catalyst with a minimum content of Co+Mn at each temperature.

Further, the curve represented by the symbol ◦ in figure 3, is described below formula

in which t is the reaction temperature (°C)and the temperature range is from 185 to 200°C.

Because the decrease in the content of bromine in the reaction temperature of 185°C causes the formation of ash and because it is difficult to reduce the content of bromine below the number defined by the ratio of Br/(Co+Mn)=1,7, control the amount of catalyst (the amount of Co+Mn equal to 2650 frequent./million) at 185°C under the reaction conditions with the aim of obtaining terephthalic acid containing 2000 ppm million 4-KBA (curve marked with • in figure 3) represents the maximum content of the catalyst in this reaction.

In accordance with this, the amount of catalytically active metal (Co+Mn) in the solvent for the oxidation reaction, intended to obtain NTC (contents 4-KBA from 2000 to 3500 ppm million), plagiarisation purification in the preparation of the catalyst ask this, as the amount of Co+Mn calculated by the equation described above, or more, and the content of the catalyst support such that the content of Co+Mn was at the control level in 2650 frequent./million or less (within the range specified by bold dashed line shown in figure 3).

A basic example 1

In accordance with the scheme of obtaining purified terephthalic acid, are presented in figure 1, receipt of crude terephthalic acid (NTC) and obtaining purified terephthalic acid (OTC) hydrogenation purification carried out using as starting material para-xylene.

The conditions of the oxidation reaction in the production of NTC are identical to those described in examples 1, 2, 3 and 4, in which the reaction solvent was filed in the amount three times greater than the mass number of the original para-xylene, the air was filed so that the concentration of oxygen (O2) in the exhaust gas was about 3.5 vol.%, and the reaction was carried out in a continuous mode at a temperature of 193°C. Removal of the formed reaction product and a liquid condensates, subsequent processing of remote products, etc. carried out in the same way as in the above examples.

To prepare supplied to the reaction of catalytic composition comprising Co, Mn and Br in the solvent for the reaction, a solution of a catalytically asset is s metals (Co, Mn), Hydrobromic acid and acetic acid served as the source material using separated from the reaction mother liquor. As the solvent for the reaction were prepared to refrain from adding excess amount of bromine in obtained by separation from the product uterine fluid, but only to reimburse the quantity consumed in the reaction, but mostly I added a catalytically active metals (Co, Mn) and measured the content of 4-KBA, and on the basis of measurements of added Co and Mn in such amounts that the content of 4-KBA in the resulting NTC was approximately 2500 ppm million the Content of cobalt, manganese and bromine was measured in the corresponding process, as shown in figure 4 (the increase of the cobalt and manganese, and a decrease in the content of bromine).

NTC, which was obtained in this way contained from 1800 to 3300 ppm million 4-KBA.

Then, with the purpose of hydrogenation purification thus obtained NTC in accordance with the scheme in figure 1, it was mixed with water to form a water suspension containing about 27 wt.% NTC, and was dissolved by heating (285°C), and then fed into the reactor for hydrogenation purification, containing solid catalyst (0.5% of Pd catalyst deposited on activated carbon), and hydrogenation was performed cleaning NTC.

In the reactor hydrogenise the ion cleaning pressure was maintained at a level of 70 kg/cm 2(Rel.) as the supply of hydrogen gas in the reactor was filed NTK number, which is three times exceeded (wt./wt. per hour) number of Hydrotreating catalyst, in aqueous solution in the portion of the reactor, which is located above the layer of catalyst for hydrogenation treatment. Then the reaction mixture was applied to the mold 14 and was carried out in five stages evaporative cooling taking place under the influence of manual pressure relief in the mold 14, the deposited crystals of purified terephthalic acid (TCI).

The resulting suspension of crystals TCI filed in the separator solids and liquids 15 to isolate crystals of QCD, which was dried to obtain the product purified terephthalic acid.

As the process pressure difference before and after catalyst for hydrogenation treatment (differential pressure) was increased only for half of the month (14 days), the pressure of the feed water solution was raised to 75 kg/cm2(Rel.) or higher, and increased the pressure fluctuations so that the supply of water and the solution was interrupted and hydrogenation purification stopped. After washing the hydrogenation reactor 13 cleaning water when the temperature and the pressure was decreased to values, allowing us to open the reactor, it was observed that the PSS is the catalyst entire small black resinous substance especially in the lower part of the layer. The results of measuring the differential pressure at the exit/entrance to the layer of the solid catalyst (differential pressure Δ) are presented in figure 5. Also, figure 5 shows measured values of ash content in the feed to the purification of the STC.

Based on the above results suggest that the sharp increase in differential pressure Δ in the layer of catalyst depends on the ash content in the feed in the reaction NTC.

On the basis of ash content, measured as described above (after 1, 25, 13, 25 days), the results for the fall of the metal content is presented in the following table 7.

The results show that the ash content is determined by the components of the catalyst; with the increasing content of fly ash, the amount of manganese in its composition increases unusually quickly (after 13, 25 days the ratio of Mn/Co is 8.3), while the composition of the catalyst receiving STC ratio of ingredients is quite another (Mn/Co=0,49), i.e. the ash formed by precipitating manganese. It has been suggested that the reason is to reduce the concentration of bromine in the catalyst receiving NTC.

Table 7
The content of the AOR is s and the content of metals
The pattern, number of work daysThe ash content (part./million)From (common./million)Mn (part./million)Fe (part./million)Mn/Co (-)
1,2593.81,90,10,5
13,25825,142,10,28,3

Basic examples 2 to 4, examples 5 through 14 and comparative examples 3 through 11

Used the device for carrying out oxidation reactions containing the reactor pressure vessels (internal volume of 20 l), equipped with a stirrer, a heater and a reflux condenser, and an opening for introducing a source material, an opening for feeding oxygen-containing gas, and an outlet for removal of reaction product; 8 kg of solvent to the reaction mixture, acetic acid, which was dissolved cobalt acetate, manganese acetate and Hydrobromic acid were loaded into the reactor was purged with gaseous nitrogen, and then raised the temperature to 200°C and pressures up to 19 kg/cm2(Rel.) when the AC is shivani.

Through hole for supplying the source material was continuously applied 2 kg/h of steam-xylene through hole for supplying oxygen-containing gas was applied continuously the flow quantity and pressure of the air is regulated so that the oxygen concentration in the exhaust gas from the upper hole for the waste gas in the reflux was about 4 vol.%, the temperature was set at specified levels (200, 195, 185°C) and reaction was performed for 1 hour.

Next, while maintaining the respective temperatures of the reaction described above, and the continued supply of para-xylene and air, began to apply the reaction solvent (solvent, which was prepared with the catalyst) at a rate of 7.5 kg/h through the opening for introducing the source material, and the reaction product was removed through the opening for removal of the reaction product in the receiver for the product under the regulation of the liquid level so that the internal volume of the liquid was 9 sheets Simultaneously recirculating liquid was removed with a speed of 1.5 kg/h of the lateral drainage reuse of liquid condensate to the reaction proceeded in a continuous mode. Therefore, the average dwell time of the initial reaction mixture is regulated so that it was approximately 1.1 hours.

Then ran a continuous reaction; through t the hour supply of para-xylene, the reaction solvent and removal of the products, as well as the recirculation of liquid condensates stopped, the air supply is maintained for a further one minute and then stopped.

After the reaction and cooling the reaction product remaining in the reactor to about 70°C., it was removed from the reactor and filtered, then washed 6 kg of acetic acid and dried in a dryer to obtain the final product of terephthalic acid (about 3 kg).

The content of catalyst (Co, Mn, Br), prepared in a solvent, and the relationship of the components of the catalyst components (the ratio of Mn/Co and Br/Mn) at each reaction temperature are presented in tables 8 through 11. The content of catalyst (Co, Mn, Br) in the reaction solvent is about 1.25 times higher than the amount shown in tables 8 through 11 (because the recirculated liquid was removed with a speed of 1.5 kg/h).

We measured the content of 4-KBA in terephthalic acid and ash content obtained under appropriate reaction conditions, these values are given in tables 8 through 11.

To regulate the amount of catalyst in the reaction solvent examples, in which the content of 4-KBA in the obtained terephthalic acid ranged from 2300 to 2800 ppm million

Table 8
The reaction temperature of 200°C
ExampleThe content of catalystThe relationships of the elements in the compositionTerephthalic acid
No.From (common./million)Mn (part./million)Br (part./million)Mn/Co (-)Br/Mn (-)4-KBA (part./million)Ash (part./million)
A basic example 26052952700,490,9223305,0
A basic example 33405104251,500,8326405,0
A basic example 46203052300,490,75 27204,5
Comparative example 36303101900,490,6126308,0
Comparative example 44704701901,000,40272018
Comparative example 53755651901,510,34261021

Table 9
The reaction temperature of 195°C
ExampleThe content of catalystThe relationships of the elements in the compositionTerephthalic acid
No.From (common./million)Br (part./million)Mn/Co (-)Br/Mn (-)4-KBA frequent./million)Ash part./million)
Example 544522011250,495,1124905,0
Example 66253059300,493,0523505,0
Example 73833839961,002,6025704,5
Example 87453656650,491,8226805,0
Comparative example 6775380 5800,491,5325607,0
Comparative example 75455456501,001,19270028

Table 10
The reaction temperature of 190°C
ExampleThe content of catalystThe relationships of the elements in the compositionTerephthalic acid
No.From (common./million)Mn (part./million)Br (part./million)Mn/Co (-)Br/Mn (-)4-KBA (part./million)Ash (part./million)
Example 990544517550,493,94242 4,5
Example 10107052515950,493.04 from26005,0
Comparative example 8117057513950,492,43270020
Comparative example 979579515951,002,01250027

Table 11
The reaction temperature of 185°C
ExampleThe content of catalystThe relationships of the elements in the compositionTerephthalic acid
No.From (common./million)Mn(part./million) Br (part./million)Mn/Co (-)Br/Mn (-)4-KBA frequent./million)Ash part./million)
Example 11162032533100,2010,225505,0
Example 12132065045300,496,9725504,5
Example 13132065039300,496,0525005,0
Example 14132064533400,495,1824505,0
Comparative example 1016207953620 0,494,55261028
Comparative example 111080108036701,003,40257036

As you can see from the results, at each temperature the ash content increases sharply when the ratio Br/Mn in the catalyst is reduced. It was found that the ratio Br/Mn, which is limiting (basic example 4, example 8, example 10, example 14), essentially present at each reaction temperature.

Accordingly, we can say that the ratio of Mn/Co in the composition of the catalytically active metal (Mn, Co) also preferably has a downward trend (Mn/Co=1,5→0,2) by decreasing the reaction temperature, which is associated with the constraint relations Br/Mn.

Further, it was also found that they almost match the value for the relationship Br/Mn=2,5→2.2 on day 7→8 day, and the ash content of terephthalic acid was increased in the base example 1 (reaction temperature of 193°C), as the ratio Br/Mn as a limit in the examples (example 8: the minimum ratio of Br/Mn=1,82 at 195°C; case 10: the minimum ratio of Br/Mn3,04 at 190°C).

Next on the schedule was applied minimum ratio Br/Mn at each reaction temperature, as shown in Fig.6; there is a correlation between the reaction temperature and the utmost respect Br/Mn, which is described by the following equation:

where t is the reaction temperature, °C (temperature range from 185 to 200°C).

In addition, in examples (including basic and comparative examples) content bromine (Br/(Co+Mn)) depending on the amount of catalytically active metal (Co+Mn) is presented in the form of the curve of figure 7. From Fig.7 we can see that the relationship between the amount of catalytically active metal (Co+Mn) and the ratio of Br/(Co+Mn) is different for each of the temperatures of the reaction, accordingly differs effect of increasing the number of bromine. At the reaction temperature of 185°C, which requires the largest number of bromine, the effect of increasing the amount of bromine in the form of the ratio of Br/(Co+Mn) seem like much, but it does not manifest itself, even if the ratio of Br/(Co+Mn) is increased to about 1.7 or more. Accordingly, the oxidation reaction at 185°C suggest that the ratio of Br/(Co+Mn), equal to 1.7, is the maximum of the received number (bromine content in Br/(Co+Mn)=1.7 or less is sufficient at the reaction temperature of 185°C. or higher).

Accordingly, p and each of the reaction temperature in this reaction, it is preferable to apply such amount of bromine, which would have been sufficient for the ratio Br/Mn was not less than the value calculated by the equation described above, and the preparation you need to live with the high number of bromine to the ratio of Br/(Co+Mn) was 1.7 or less.

Example 15

In accordance with the scheme of obtaining pure terephthalic acid, is shown in figure 1, receipt of crude terephthalic acid and purified terephthalic acid was carried out in a continuous mode using as source material para-xylene by the method described in the basic example 1.

After the filing of the reaction solvent solution of the metal-containing catalyst (Co, Mn) and Hydrobromic acid to provide the content of the catalyst is presented in tabl, carried out the oxidation reaction at a temperature of 193±1°C.

Table 12
ExampleThe content in the catalystThe ratio of components
No.From (common./million)Mn (part./million)Br (part./million)Mn/Co (-)Br/Mn (-)
When is EP 15 920±10450±101370±150,493.04 from

As a result, for terephthalic acid obtained at the stage of obtaining the crude terephthalic acid, the content of 4-KBA amounted to approximately 2500 ppm million, and the oxidized amount of acetic acid (the basic unit of acetic acid) was approximately 42 kg/T. Next, purified terephthalic acid obtained at the stage of obtaining purified terephthalic acid, contained a pair of Truelove acid number of 120 ppm million or less, and the pressure in the layer of catalyst for hydrogenation purification 13 remained at the level of about 70 kg/cm2(Rel.), work installed without a glitch lasted for about 1 year with no signs of pressure drops, the pressure difference (differential pressure) was 1 kg/cm2or less.

Brief description of drawings

1 shows a diagram of the stages of obtaining the crude terephthalic acid with the use of para-xylene as a starting material and stages of obtaining purified terephthalic acid by dissolving crude terephthalic acid in water with subsequent hydrogenation treatment.

Figure 2 shows the amount of solvent, acetic acid is lost as a result, the ATA reaction liquid-phase oxidation (the basic unit of acetic acid) 4-KBA (4-carboxybenzene), contained in the terephthalic acid obtained by liquid-phase oxidation of the original para-xylene with air in the presence of a catalyst with acetic acid as solvent (oxidized amount of acetic acid (the basic unit of acetic acid) is the number of acetic acid lost during oxidation, relative to the amount of terephthalic acid (kg/t terephthalic acid)).

Figure 3 shows the number of Co+Mn catalyst for the preparation of terephthalic acid with a content of 4-KBA (4-carboxymethylthio)of 2000 and 3500 ppm million at each of the temperatures of the reaction liquid-phase oxidation of the source material, para-xylene with air in the presence of a catalyst using, as a solvent of acetic acid (symbol ◦ denoted by the curve corresponding to the content of 4-KBA 3500 frequent./million; • marked curve corresponding to the content of 4-KBA 2000 ppm million); the reaction temperature is shown by an index (x) and are shown as values (the reaction temperature is 185). The formula that determines the relationship between the reaction temperature (reaction temperature -185) (x) upon receipt of terephthalic acid with 4-KBA 3500 frequent./million and the concentration of metal in the obtained catalyst (number+ number (Mn) (y), shown in the drawing. Each is th the catalyst prepared at a ratio of Br/(Co+Mn)=1,7.

Figure 4 shows the change in the concentration of the components of the oxidation catalyst (Co, Mn, Br) in the feed solvent prepared in continuous receipt of terephthalic acid under liquid-phase oxidation of para-xylene with air (with an interval of 6 h) (contents 4-KBA in terephthalic acid in the course of the reaction ranged from 1800 to 3300 ppm million).

Figure 5 shows the pressure difference (differential pressure), resulting in a layer of catalytic hydrogenation in the implementation of hydrogenation purification after continuous receipt of terephthalic acid in the liquid phase oxidation of para-xylene in air (similar to figure 4) with the subsequent implementation of the hydrogenation purification after preparation of an aqueous solution of terephthalic acid. The drawing also shows the ash content of terephthalic acid fed to the reactor for hydrogenation treatment.

Figure 6 shows the ratio of Br/Mn (indicated by the symbol ○) in the examples for the preparation of catalyst (Co, Mn, Br) obtain terephthalic acid with 4-KBA, amounting to about 2500 ppm million (ranging from 2300 to 2800 ppm million), and for each temperature liquid-phase air oxidation of para-xylene as a starting material, and selected examples to a sharp increase in ash content (reference example 4, example 8, example 10, example 14) (rez is ltate ratio Br/Mn (y) is correlated with reaction temperature (reaction temperature -185) (x), the equation of correlation shown in the drawing. Accordingly, the area ratio Br/Mn under the curve in the drawing, each of the reaction temperatures can be defined as an area of high ash content.

7 shows the ratio of Br/(Co+Mn) and the number of Co+Mn obtained for catalytic composition (Co, Mn, Br) upon receipt of terephthalic acid with 4-KBA, amounting to about 2500 ppm million (from 2330 to 2720 part./million), liquid-phase air oxidation of para-xylene as a starting material depending on the temperature.

The method of obtaining the crude terephthalic acid for use on stage hydrogenation purification through liquid-phase oxidation of oxygen-containing gas in the oxidation reactor equipped with a mixer, using as source material para-xylene in the solvent is acetic acid, in the presence of a metal-containing catalyst comprising cobalt (Co), manganese (Mn) and bromine (Br) as an oxidation promoter, characterized in that the temperature of the oxidation reaction is adjusted so that it is in the range from 185 to 197°C., the average residence time in the reactor the mixture to liquid-phase oxidation is from 0.7 to 1.5 h, the water content in the reaction solvent is adjusted so that it ranged from 8 to 15 wt.%, and the catalyst composition in plants is the PR regulate the interval of contents specific depending on the reaction temperature so that it includes:
(1) a catalytically active metal (Co+Mn) in an amount of from 2650 frequent./million or less in number equal to or more than the value defined by the following ratio:
,
in which (Co+Mn) is the content of (Co+Mn) in part./million,
t is the reaction temperature (°C) (temperature range from 185 to 200°C),
(2) the mass ratio of Mn/Co regulate in the range from 0.2 to 1.5, preferably from 0.2 to 1;
(3) the content of Br is 1.7 or less, if its present value of Br/(Co+Mn) in the form of mass relations, and in number equal to or more than the value represented by the equation:
,
in which Br/Mn represents the mass ratio of Br/Mn (wt./wt.), a t is the reaction temperature (°C) (temperature range from 185 to 200°C), and obtaining the crude terephthalic acid is performed with the content of 4-carboxybenzene in the amount of from 2000 to 3500 ppm million as an intermediate reaction product of liquid-phase oxidation.



 

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FIELD: chemistry.

SUBSTANCE: invention relates to an improved method of producing a composition of aromatic dicarboxylic acid, involving (a) oxidation of a multiphase reaction medium in a primary oxidation reactor to obtain a first suspension; (b) further oxidation of at least a portion of said first suspension in a secondary oxidation reactor which is of the bubble column type, wherein the method further involves feeding an aromatic compound into said primary oxidation reactor, where at least about 80 wt % of said aromatic compound fed into said primary oxidation reactor is oxidised therein, wherein head gases are moved from the top of the secondary oxidation reactor into the primary oxidation reactor. Disclosed are an optimised process and equipment for more efficient and cheaper liquid-phase oxidation. Such liquid-phase oxidation is carried out in a bubble column type reactor which ensures a highly efficient reaction at relatively low temperatures. When the oxidised compound is para-xylene and the oxidation reaction product is crude terephthalic acid (TPA), such a product, TPA, can e purified and extracted using cheaper methods than when TPA is obtained using the conventional high-temperature oxidation process.

EFFECT: improved method of producing a composition of aromatic dicarboxylic acid.

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

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EFFECT: ensuring stable operation of a fluidised bed drier.

8 cl, 5 dwg, 1 tbl, 3 ex

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 an improved continuous method of producing terephthalic acid, involving (a) feeding para-xylene into an oxidation reactor; (b) oxidation of at least a portion of said para-xylene in the liquid phase of a multi-phase reaction medium contained in said oxidation reactor until crude terephthalic acid is obtained, where said oxidation results in production of carbon dioxide, carbon monoxide and/or methyl acetate; and maintaining, during said oxidation, the molar ratio of obtained carbon oxides to said para-xylene in the range from 0.02:1 to 0.24:1. The invention also relates to a continuous method of producing terephthalic acid, involving (a) feeding para-xylene into an oxidation reactor; (b) oxidation of at least a portion of said para-xylene in the liquid phase of a multi-phase reaction medium, contained in said oxidation reactor, until crude terephthalic acid is obtained; and (c) maintaining, during said oxidation, molar ratio of persistence of said para-xylene in the range from 99.0 to 99.7%.

EFFECT: more efficient and cheaper liquid-phase oxidation of an oxidisable compound.

33 cl, 35 dwg, 7 tbl, 4 ex

FIELD: process engineering.

SUBSTANCE: invention relates to processing waste gases in production of aromatic dicarboxylic acid by liquid phase oxidation of aromatic dialkyl hydrocarbon, an initial substance, using acetic acid as a solvent, in the presence of metallic catalyst containing, as a promoter, cobalt, manganese and bromine at reactor temperature of 185 to 205°C and using oxygen-containing gas, that comprises the following stages: oxidation reaction waste gas is cooled down and separated. After condensation, waste gas condensing components are separated at high pressure. Obtained waste gas is subjected to wet cleaning at 40°C or lower temperature in high-pressure absorption columns by rinsing fluid into two stages to reduce concentration of components contained therein. Said waste gas at 12.0-16.0 kg/cm2(surplus) is forced through two-stage pressure turbines after heating of said gas fed to turbine first and second stage by steam at pressure of approx. 5 kg/cm2 (surplus) to 140°C - 150°C. Note here that two-stage turbines are used with second stage-to-first stage power ratio varying from 1 to 1.4 to obtain heat- and waste-gas-generated power in compliance with the formula below: (T2/T1)γ=(P2/P1)(γ-1), where γ = Cp/Cv = 1.4, T1, P1 are temperature and pressure at inlet side, T2, P2 are those at outlet side, γ is relation between specific heat capacity at constant pressure Cp to specific heat capacity at constant volume Cv.

EFFECT: efficient process and system.

6 cl, 9 tbl, 3 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: terephthalic acid production method involves a step A) for oxidising paraxylene to terephthalic acid with air in the presence of a liquid reaction phase kept at temperature between 180°C and 230°C, where the liquid reaction phase contains paraxylene, acetic acid, water and a catalyst composition, where amount of water is 5-12% of the weight of acetic acid, the mass ratio of acetic acid to paraxylene is not less than 30:1 and must be such that 15-50% of reacted terephthalic acid is present in solid form at oxidation temperature and the catalyst composition contains cobalt, manganese and bromine combined with at least one element selected from a group consisting of zirconium and hafnium, where atomic ratio Co:Mn:Br is in the range 1:0.2-1.0:1.1-2.7, and atomic ratio of cobalt to elements selected from a group consisting of zirconium and hafnium is equal to 1:0.03:0.3, where total mass of Co and Mn is equal to 100-500 mg per 1 kg of the liquid reaction phase; and B) extraction of terephthalic acid through crystallisation at temperature between 150°C and 80°C.

EFFECT: method gives terephthalic high purity without a secondary purification step currently used in practice.

3 cl, 19 ex, 3 tbl

FIELD: chemistry.

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

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

22 cl, 3 tbl, 1 dwg, 3 ex

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 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 an improved method of drying aromatic carboxylic acid, involving drying of aromatic carboxylic acid precipitate using a fluidised bed drier, where the precipitate is fed into the drier at a rate of 50 kg/h or higher, and a drying gas at temperature 80-160°C is fed into the drier with reduced speed of 0.3-1 m/s, so that content of liquid in the precipitate is equal to or less than 14 wt %; as well as to an improved method of obtaining dry aromatic carboxylic acid, involving continuous drying of aromatic carboxylic acid precipitate using a fluidised bed drier to obtain ready aromatic carboxylic acid, where the precipitate is fed into the drier at a rate of 50 kg/h or higher, and drying gas at temperature 80-160°C is fed into the drier at reduced speed of 0.3-1 m/s so that content of liquid in the precipitate is equal to or less than 14 wt %. The aim of the invention is to develop a method of drying aromatic carboxylic acid and a method of drying aromatic carboxylic acid, each method solving problems associated with use of a fluidised bed drier, such as clogging by crystals or aromatic carboxylic acid crystals sticking in the drier, and low efficiency of the drier.

EFFECT: ensuring stable operation of a fluidised bed drier.

8 cl, 5 dwg, 1 tbl, 3 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of increasing utilisation factor of silver during adsorption and removal of decyl iodide from acetic acid which contains decyl iodide as an impurity, by passing acetic acid through a packed layer of a cation-exchange resin at temperature 50°C or lower, where the cation-exchange resin is a macroporous-type polystyrene resin with average particle size ranging from 0.3 to 0.6 mm and average pore size from 15 to 28 nm, and where the resin has sulpho groups, and silver occupies 40-60% of the active sites of sulpho groups.

EFFECT: high utilisation factor of silver during adsorption and removal of decyl iodide from acetic acid.

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 an improved continuous method of producing terephthalic acid, involving (a) feeding para-xylene into an oxidation reactor; (b) oxidation of at least a portion of said para-xylene in the liquid phase of a multi-phase reaction medium contained in said oxidation reactor until crude terephthalic acid is obtained, where said oxidation results in production of carbon dioxide, carbon monoxide and/or methyl acetate; and maintaining, during said oxidation, the molar ratio of obtained carbon oxides to said para-xylene in the range from 0.02:1 to 0.24:1. The invention also relates to a continuous method of producing terephthalic acid, involving (a) feeding para-xylene into an oxidation reactor; (b) oxidation of at least a portion of said para-xylene in the liquid phase of a multi-phase reaction medium, contained in said oxidation reactor, until crude terephthalic acid is obtained; and (c) maintaining, during said oxidation, molar ratio of persistence of said para-xylene in the range from 99.0 to 99.7%.

EFFECT: more efficient and cheaper liquid-phase oxidation of an oxidisable compound.

33 cl, 35 dwg, 7 tbl, 4 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing isophthalic acid and other by-products - terephthalic and benzoic acid, based on oxidation of a mixture of xylene isomers and monoalkylbenzenes contained therein with an oxygen-containing gas in the medium of acetic acid in the presence of a catalyst which contains heavy metal salts and halides at high temperature and pressure to a defined degree of conversion of said isomer mixtures to isophthalic acid and by-products, followed by purification and separation of isophthalic acid and by-products via re-crystallisation in a solvent, wherein said oxidation process is carried out in two steps with increasing concentration of the Co-Mn catalyst on the steps, promoted by halides in form of HBr in equimolar ratio to metals in the range of 800-1200 ppm at temperature 150-200°C and discrete stepwise reduction of pressure in the range of 1.8-1.2 MPa with pressure drop gradient between steps of 0.2-0.6 MPa; purification and separation of the mixture of isophthalic and by-product benzene-carboxylic acids is carried out in two steps by extracting impurities via re-crystallisation in acetic acid at temperature 140-230°C at the first step followed by extraction of the purified binary system of isophthalic and terephthalic acid and separation thereof at the second step via dissolution in water at temperature 220-230°C and stepwise selective crystallisation and extraction of terephthalic acid at temperature 180-195°C, and isophthalic acid at temperature 60-100°C.

EFFECT: improved quality of isophthalic acid and by-products and high efficiency of the synthesis process.

10 cl, 12 ex, 3 tbl

FIELD: chemistry.

SUBSTANCE: method of extracting acrylic acid from a liquid phase uses acrylic acid as the main component and desired product and methacrolein as the by-product, where the liquid phase used is obtained via at least one fuzzy separation from a gaseous mixture of products of gas-phase partial oxidation on a heterogeneous catalyst of at least one tri-carbon precursor of acrylic acid, where the liquid phase is crystallised with enriched acrylic acid in the formed crystallised product and methacrolein in the residual liquid phase.

EFFECT: method enables efficient separation of methacrolein from acrylic acid.

14 cl, 1 ex, 1 tbl

FIELD: chemistry.

SUBSTANCE: content of acrylic aid or methacrylic acid in the liquid per total weight of liquid II is at least 10 wt %, where, along with methacrylic acid and/or acrylic acid, said liquid also contains acrolien and/or methacrolein, as well as acetone in total amount of not more than 5 wt % per total content of acrylic acid and/or methacrylic acid in liquid II, provided that liquid II was produced without adding acrolen or methacrolein in form of a pure substance of another liquid I containing acrylic acid and/or methacrylic acid, wherein liquid II, in which the weight ratio of acrolien to acetone contained therein is not equal to 3.5, liquid II is fed into the fractionation column provided that it contains at least 10 wt % acetone which inhibits polymerisation of acrylic and/or methacrylic acid, in terms of acrolein and methacrolein contained in liquid II.

EFFECT: less susceptibility of acrylic acid or methacrylic acid to polymerisation during fractional separation of liquid II.

8 cl, 3 tbl, 3 ex

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing a solid sodium diformate composition, having forming acid content of at least 35% of the total weight of the sodium diformate composition, in which aqueous solution (E) is prepared at high temperature, said solution containing sodium formate and formic acid in molar ratio HCOOH:HCOONa higher than 1.5:1, and having molar ratio HCOOH:H2O of at least 1.1:1, said aqueous solution (E) is crystallised to obtain a solid phase and a mother solution, and the solid phase is separated from the mother solution, where (i) the mother solution is completely or partially fed into a distillation apparatus; (ii) the mother solution in the distillation apparatus is mixed with a sodium-containing base to obtain a mixture (B) which contains sodium formate and formic acid; (iii) the mixture (B) obtained at step (ii) is mixed with formic acid to obtain aqueous solution (E); or the mixture (B) obtained at step (ii) is removed from the distillation apparatus and taken for crystallisation, or, at the crystallisation step, mixed with formic acid to obtain an aqueous solution; and (iv) excess water is primarily removed by tapping from the distillation apparatus; the invention also relates to use of the solid sodium formate composition obtained using the disclosed method as an animal feed additive, particularly feed for non-ruminants, especially pigs and/or birds.

EFFECT: improved properties of the composition.

29 cl, 3 dwg, 1 tbl, 4 ex

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 producing a composition of aromatic dicarboxylic acid, involving (a) oxidation of a multiphase reaction medium in a primary oxidation reactor to obtain a first suspension; (b) further oxidation of at least a portion of said first suspension in a secondary oxidation reactor which is of the bubble column type, wherein the method further involves feeding an aromatic compound into said primary oxidation reactor, where at least about 80 wt % of said aromatic compound fed into said primary oxidation reactor is oxidised therein, wherein head gases are moved from the top of the secondary oxidation reactor into the primary oxidation reactor. Disclosed are an optimised process and equipment for more efficient and cheaper liquid-phase oxidation. Such liquid-phase oxidation is carried out in a bubble column type reactor which ensures a highly efficient reaction at relatively low temperatures. When the oxidised compound is para-xylene and the oxidation reaction product is crude terephthalic acid (TPA), such a product, TPA, can e purified and extracted using cheaper methods than when TPA is obtained using the conventional high-temperature oxidation process.

EFFECT: improved method of producing a composition of aromatic dicarboxylic acid.

30 cl, 4 tbl, 31 dwg

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