KR100508684B1 - The preparation method of aromatic carboxylic acids - Google Patents

Abstract

The present invention relates to a method for producing an aromatic carboxylic acid, and more particularly, to prepare an aromatic carboxylic acid corresponding to a reactant by oxidizing an alkylaromatic compound with an oxygen-containing gas while using acetic acid as a solvent in the presence of a cobalt / manganese / bromine catalyst. In addition, by adding a certain amount of carbonic ammonium bromide salts such as tetrapropyl ammonium bromide (TPA-Br) and carbon dioxide to the reaction system, not only the conventional cobalt / manganese / bromine catalyst-based reaction activity is significantly improved, but also by-products are produced. The present invention relates to a method for producing an improved aromatic carboxylic acid capable of maximizing the yield of a product having a carboxyl group corresponding to the number of alkyl groups in a reactant, that is, a desired product.

Description

The preparation method of aromatic carboxylic acids

The present invention relates to a method for producing an aromatic carboxylic acid, and more particularly, to prepare an aromatic carboxylic acid corresponding to a reactant by oxidizing an alkylaromatic compound with an oxygen-containing gas while using acetic acid as a solvent in the presence of a cobalt / manganese / bromine catalyst. In addition, by adding a certain amount of carbon dioxide and alkylammonium bromide salts such as tetrapropylammonium bromide (TPA-Br) and carbon dioxide to the reaction system, not only the reaction activity of the conventional cobalt / manganese / bromine catalyst system is improved but also the production of by-products is generated. The present invention relates to a method for producing an improved aromatic carboxylic acid which can be reduced to maximize the yield of a product having a carboxyl group corresponding to the number of alkyl groups in a reactant, that is, a desired product.

The first process using liquid phase instead of gas phase in preparing aromatic carboxylic acid is reaction temperature of about 100 ~ 320 ℃, pressure to maintain saturated fatty acid used as solvent, and catalyst of various valent metals dissolved in liquid phase of saturated fatty acid. Known to be possible by action [US Pat. No. 2,245,528]. According to the patent, the reaction activity was the highest in cobalt among the catalyst metals, and was promoted by the addition of ketone or aldehyde compound. However, they were only effective at converting benzene monocarboxylic acids, benzoic acid, toluic acid and dimethyl benzoic acid, in which only one alkyl group from mono-, di- and tri-methylbenzenes was converted to carboxyl groups.

Subsequent studies have since found successful catalyst systems for the production of aromatic carboxylic acids with carboxyl groups corresponding to the number of alkyl groups by the liquid phase oxidation of alkylaromatic compounds at high temperatures and pressures. Such catalyst systems are a catalyst system composed of bromine and a transition metal, and among them, a cobalt / manganese / bromine catalyst system is known as the most active catalyst system in the oxidation reaction of paraxylene for the production of terephthalic acid (US Pat. No. 2,833,816). . Furthermore, on the basis of the cobalt / manganese / bromine catalyst system, oxidation of di- or tri-methylbenzene, such as paraxylene, methaxylene, or pseudocumene (1,2,4-trimethylbenzene), to the corresponding benzene di- or Methods for preparing tri-carboxylic acids have been developed and widely applied commercially (US Pat. Nos. 5,041,633, 5,081,290). The aromatic carboxylic acids thus prepared are mainly used as raw materials for preparing materials such as polyester fibers and films after proper purification.

Prior arts based on cobalt / manganese / bromine catalyst systems in the production of aromatic carboxylic acids still require improvements in terms of increased side reactions, cost of catalysts, ease of operation and precipitation of catalysts. Furthermore, shortening the reaction time for the production of aromatic carboxylic acids can greatly increase productivity and cost competitiveness, and for this purpose, efforts have been made to develop an efficient catalyst system having improved reaction activity or to improve other processes. Coming. However, there are no other catalyst systems that are superior to the cobalt / manganese / bromine catalyst system as the basic catalyst system, and a method of improving the reaction activity by adding other materials based on the cobalt / manganese / bromine catalyst system has been steadily established. Is being studied.

Looking at the reaction technology using carbon dioxide for the liquid phase oxidation of alkylaromatic compounds, carbon dioxide is a process stability that can cause problems such as oxygen explosion when using pure oxygen or a gas containing excess oxygen as the oxidant In most cases, it is known that it was added for the purpose of improving the reaction efficiency, and in this case, the reaction efficiency was not affected (US Pat. No. 5,693,856, European Patent 0785183A2). Recently, there have been attempts to utilize carbon dioxide to improve the reaction efficiency in the production of aromatic carboxylic acid, which is added to the cobalt / manganese / bromine based catalyst system [Korean Patent Publication 2000-67444] 1 of alkali metals and alkaline earth metals It is a method of adding species and carbon dioxide at the same time [Korean Patent Publication 2000-41507]. However, there is still a need to develop additives that can enhance the effect of carbon dioxide in order to further improve the reaction efficiency.

Thus, in the present invention, when preparing aromatic carboxylic acid by liquid phase oxidation of alkylaromatics based on cobalt / manganese / bromine catalyst system, addition of carbon dioxide and alkylammonium bromide salts, such as ammonium bromide bromide, may reduce side reactions. In addition, the present invention was found to be able to significantly improve the reaction efficiency by shortening the reaction time.

Therefore, an object of the present invention is to improve the oxygen oxidation reaction by cobalt / manganese / bromine catalyst used in the conventional industrial process by using both carbon dioxide and alkylammonium bromide salt in an oxidation reaction system with much higher activity and improved selectivity.

The present invention provides an aromatic carboxylic acid to which an alkylammonium bromide salt and carbon dioxide are added in the production of an aromatic carboxylic acid by oxidizing an alkylaromatic compound and a partial oxidation intermediate thereof with an oxygen-containing gas in a liquid phase reaction system using acetic acid as a solvent under a cobalt / manganese / bromine catalyst. Characterized in that the manufacturing method.

The present invention will be described in more detail as follows.

The present invention oxidizes an alkylaromatic compound to an oxygen-containing gas in a liquid phase reaction system using acetic acid as a solvent in the presence of a cobalt / manganese / bromine catalyst. The reaction rate and the conversion of the reactor material are drastically increased, and as the production of intermediates due to partial oxidation is reduced, the selectivity of the desired product is increased, and a method for producing aromatic carboxylic acid in high yield is provided.

Hereinafter, the method for preparing an aromatic carboxylic acid by liquid phase oxidation of an alkylaromatic compound according to the present invention will be described in more detail according to the additive components and reaction conditions. The additive components include alkylaromatic compounds and oxygen-containing gases as reactants, cobalt / manganese / bromine catalyst systems as base catalysts, and alkylammonium bromide salts and carbon dioxide as reactive active materials.

As the reactant, an alkylaromatic compound uses a compound in which at least one alkyl group is substituted with an aromatic compound. As such an example, toluene, ortho-xylene, meta-xylene, m-xylene, p-xylene, 1,3,4-trimethylbenzene, 1, 3,5-trimethylbenzene (mesitylene), 2,3,5,6-tetramethylbenzene (durene), methylnaphthalene, dimethylnaphthalene and 4,4'-dimethylbiphenyl (4,4 ' alkylaromatics such as -dimethylbiphenyl) and partial oxidation oxidation intermediates thereof. These alkylaromatic compounds are converted by the present invention to the corresponding aromatic carboxylic acids, respectively. That is, in order of the alkylaromatic compounds, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid and trimesic acid, respectively. , Pyromellitic acid, carboxynaphthalic acid, 2,6-dicarboxynaphthalic acid, and 4,4'-dicarboxybiphenyl (4,4'- dicarboxybiphenylic acid).

In addition, the atomic weight ratio of manganese / cobalt in the cobalt / manganese / bromine catalyst is preferably 0.1 to 5, more preferably 0.5 to 3. The preferred atomic weight ratio of bromine / (manganese + cobalt) is 0.1 to 5, more preferably 0.5 to 2. The content of cobalt is suitably 50 to 10000 ppm of the weight of the reactants, more preferably 100 to 1000 ppm. As bromine source, any bromine compound such as HBr, Br ₂ , tetrabromoethane and benzyl bromide can be used. Manganese and cobalt sources include acetate, carbonate, acetate tetrahydrate and bromide, which have solubility in the solvent used. Any compound may be used. In addition, the alkylammonium bromide salt added as a reactive active material is tetramethyl ammonium bromide, tetraethyl ammonium bromide, tetrapropyl ammonium bromide (TPA-Br) or tetrabutyl ammonium bromide bromide. ) May be used alone or in combination, the weight ratio of the alkylammonium bromide salt / manganese is preferably 0.04 to 5, more preferably 0.1 to 1. If the amount of the alkylammonium bromide salt is out of the above range and the amount is insufficient, the effect of the addition does not appear, and if excessive, the excess amount is not preferable because it leads to an increase in cost.

As the reactive gas used in the present invention, oxygen or a mixed gas of an inert gas such as oxygen and nitrogen may be used. The concentration of oxygen (O ₂ ) is 2 to 75% (v / v) in the total gas introduced. In addition, carbon dioxide gas is added to promote reaction efficiency, and the amount of carbon dioxide may be 1 to 90% (v / v), preferably 10 to 85% (v / v) of the total gas introduced. If the input amount of carbon dioxide is less than 1% (v / v) it is not possible to obtain the expected addition effect, and if it exceeds 90% (v / v), the concentration of oxygen is lowered, there is a problem that the oxidation reaction is not smooth. I can't. The carbon dioxide is periodically or continuously added to the gas phase or the liquid phase in the reactor, when added to the gas phase is mixed with the unused reaction gas, or recycled by mixing with the reaction waste remaining oxygen and carbon dioxide.

The method for producing an aromatic carboxylic acid of the present invention can be carried out in a batch or continuous process. The reaction temperature is in the range of 100 to 255 ° C, more preferably 170 to 210 ° C. At this time, when the reaction temperature is too low, the reaction is slow and not practical. If the reaction temperature is too high, side reactions are severely generated, which is uneconomical. The pressure of the reaction should use the alkylaromatic compound, the oxidized intermediate thereof, and the pressure at which a part of the solvent can be maintained in the liquid phase. The gauge pressure is 1 to 35 atm, more preferably 8 to 30 atm. It is done.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited thereto.

In the following Examples 1 and 3, the yields and reaction activities of the desired product (terephthalic acid) and the partial oxidation intermediate (paratoluic acid) were compared in the preparation of terephthalic acid by oxidation of paraxylene.

Example 1

A 150 ml titanium pressure reactor was charged with paraxylene, acetic acid and catalysts. In this case, the total amount of the reactants was 30.42 g, and the composition ratio of paraxylene and acetic acid was 17:83. The composition of the cobalt / manganese / bromine catalyst was set to 899 ppm cobalt, 1170 ppm manganese and 2990 ppm bromine based on the reactant weight. Cobalt acetate tetrahydrate was used as the cobalt source, and tetrapropyl ammonium bromide (TPA-Br) was used as the bromine source, and manganese acetate tetrahydrate was used as the manganese source. The mixture contained in the reactor was heated to 170 ° C. in a nitrogen atmosphere while stirring. Thereafter, each gas was added so that the concentration of nitrogen was 50% and the carbon dioxide concentration was 33.3%, and then oxygen was instantaneously added so that the oxygen concentration was 16.7% to start the reaction. The total reaction pressure was 12 atm as the gauge pressure, and the amount of oxygen consumed was measured and the oxygen was continuously injected as much as the consumed amount. The reaction was terminated by cooling after 180 minutes of reaction, the obtained oxide was solid-liquid separated and the solid was analyzed with the mother liquor after drying to calculate the yield of the products. As a result of the reaction, the reaction conditions, oxygen consumption, and the yield of terephthalic acid and paratoluic acid are shown in Table 1, and the yield of terephthalic acid is improved by about 40% compared to the case where carbon dioxide and TPA-Br are not added (Comparative Example 3). I could see. In addition, the comparison with the case of adding only carbon dioxide (Comparative Example 1) showed that the addition of TPA-Br greatly increased the selectivity to the desired product, terephthalic acid, although the degree of reaction activity was similar.

Comparative Example 1

Preparation was carried out in the same manner as in Example 1, but cobalt bromide was added instead of cobalt acetate and the reaction proceeded without addition of TPA-Br. Table 1 shows the reaction conditions, oxygen consumption, and yield of terephthalic acid and paratoluic acid.The reaction activity is increased by 17% compared to the case where carbon dioxide and TPA-Br are not added (Comparative Example 3), and the desired product is terephthalic acid. It was found that the yield in the furnace was greatly improved.

Comparative Example 2

Prepared in the same manner as in Example 1, but proceeded without the addition of carbon dioxide. Table 1 shows the reaction conditions, oxygen consumption, and yield of terephthalic acid and paratoluic acid. The reaction activity and yield were similar compared to the case where carbon dioxide and TPA-Br were not added (Comparative Example 3). . Therefore, it can be seen that the addition of TPA-Br is effective only in the presence of the addition of carbon dioxide.

Comparative Example 3

Prepared in the same manner as in Example 1, but proceeded without the addition of carbon dioxide and TPA-Br. That is, the composition of the reactor was such that the nitrogen concentration was 83.3% and the oxygen concentration was 16.7%. Table 1 shows the reaction conditions, the oxygen consumption and the yield of terephthalic acid and paratoluic acid. The reaction activity and the yield of the desired product, terephthalic acid, were significantly lower.

Paraxylene Oxidation Results division Reaction temperature (℃) Response time (minutes) CO ₂ concentration (%) Br source Oxygen consumption (mmol) * Yield (mole%) Terephthalic acid Paratoluic acid Example One 170 180 33.3 TPA-Br 97.6 57.1 30.3 Comparative example One 170 180 33.3 CoBr ₂ 97.4 34.8 36.9 2 170 180 0 TPA-Br 83.5 17.9 48.0 3 170 180 0 CoBr ₂ 83.4 17.7 47.9 * Theoretical oxygen equivalent: 145.8mmol

In Examples 2 and Comparative Examples 4 to 6 below, the time required to consume the same amount of oxygen in the preparation of terephthalic acid by paraxylene oxidation was compared.

Example 2

The reaction was carried out in the same manner as in Example 1, but the reaction temperature was 190 ℃ and the reaction pressure was carried out at 20 atm by the gauge pressure. The composition of the reactor was 25% oxygen, 30% carbon dioxide, and 45% nitrogen. The reaction was terminated when 85% of the theoretical oxygen equivalent was consumed. It took 54 minutes to complete the reaction, and it was found that the reaction time was reduced by 2 times compared to the case where carbon dioxide and TPA-Br were not added (Comparative Example 6). In addition, the results of observing the amount of oxygen consumed by reaction time also showed that the rate of oxygen consumption increased greatly from the beginning of the reaction. A high yield of terephthalic acid, the desired product, was also observed. In other words, it was found that the addition of carbon dioxide and TPA-Br is effective in enhancing the reaction activity and improving the yield to the desired product by reducing side reactions as compared with the case where no carbon dioxide and TPA-Br were added.

Comparative Example 4

Prepared in the same manner as in Example 2, but proceeded without the addition of TPA-Br. A reaction time of 84 minutes was required for the oxygen consumption of 85% of the theoretical oxygen equivalent. Compared to the case in which carbon dioxide and TPA-Br were not added (Comparative Example 6), the reaction time was greatly reduced and the oxygen consumption rate was also greatly increased. In addition, the yield to terephthalic acid, which is the desired product, was also increased.

Comparative Example 5

Prepared in the same manner as in Example 2, but proceeded without the addition of carbon dioxide. A reaction time of 110 minutes was required for the oxygen consumption of 85% of the theoretical oxygen equivalent. There was no difference compared to the case where carbon dioxide and TPA-Br were not added (Comparative Example 6). Therefore, it was confirmed that the addition of TPA-Br was effective only in the presence of carbon dioxide.

Comparative Example 6

Prepared in the same manner as in Example 2, but proceeded without the addition of carbon dioxide and TPA-Br. At this time, the composition of the reactor was 25% oxygen and 75% nitrogen. A reaction time of 110 minutes was required for the oxygen consumption of 85% of the theoretical oxygen equivalent. The yield to terephthalic acid, the desired product, was also found to be lowest.

Results of Oxidation of Paraxylene at the Same Oxygen Consumption division Reaction temperature (℃) Response time (minutes) * CO ₂ concentration (%) Br source Oxygen consumption by reaction time (mmol) ** Yield (mole%) 15 minutes 30 minutes 45 minutes Terephthalic acid Paratoluic acid Example 2 190 54 30.0 TPA-Br 37.9 80.8 109.3 87.3 0.9 Comparative example 4 190 84 30.0 CoBr ₂ 35.1 68.1 91.1 85.4 0.0 5 190 110 0 TPA-Br 20.6 53.5 77.6 82.9 3.9 6 190 110 0 CoBr ₂ 20.5 53.3 77.4 82.7 3.8  * 85% of the theoretical oxygen equivalent time (85% of the theoretical oxygen equivalent ends the reaction) ** Theoretical oxygen equivalent: 145.8mmol

In the following Examples 3 and Comparative Examples 7 to 9, the yield and reaction activity of the product were compared in the preparation of isophthalic acid by metha xylene oxidation.

Example 3

Prepared in the same manner as in Example 2, but using metha xylene as a reaction, the reaction time was 60 minutes. The reaction for 60 minutes consumed 98.9 mmol of oxygen. The reaction activity was increased by about 4% compared to the case where carbon dioxide and TPA-Br were not added (Comparative Example 9), and the yield to isophthalic acid, the desired product, was increased. It can be seen that.

Comparative Example 7

Prepared in the same manner as in Example 3, but proceeded without the addition of TPA-Br. After 60 minutes of reaction, 95.7 mmol of oxygen was consumed, and it was found that the reaction activity and the yield to isophthalic acid, which is a desired product, were increased as compared with the case where carbon dioxide and TPA-Br were not added (Comparative Example 9).

Comparative Example 8

Prepared in the same manner as in Example 3, but proceeded without the addition of carbon dioxide. In the reaction for 60 minutes, 95.1 mmol of oxygen was consumed, and there was almost no difference in reaction activity and yield to isophthalic acid as a desired product, compared with the case where carbon dioxide and TPA-Br were not added (Comparative Example 9).

Comparative Example 9

The same method as in Example 3 was prepared, but the reaction was performed without adding carbon dioxide and TPA-Br. At this time, the composition of the reactant was 25% oxygen and 75% nitrogen. The reaction for 60 minutes consumed 95.0 mmol of oxygen, with the lowest oxygen consumption and yield to the desired product, isophthalic acid.

Result of oxidation of metha xylene division Reaction temperature (℃) Response time (minutes) CO ₂ concentration (%) Br source Oxygen consumption (mmol) * Yield (mole%) Isophthalic acid Metatoluic acid Example 3 190 60 30.0 TPA-Br 99.0 54.9 21.4 Comparative example 11 190 60 30.0 CoBr ₂ 95.7 53.0 17.2 12 190 60 0 TPA-Br 95.1 50.6 10.3 13 190 60 0 CoBr ₂ 95.0 50.4 10.4 * Theoretical oxygen equivalent: 145.8mmol

As described above, the method for producing an aromatic carboxylic acid by liquid phase oxidation of an alkylaromatic compound according to the present invention is carried out by oxidation of the alkylaromatic compound in a liquid phase using acetic acid as a solvent in the presence of a cobalt / manganese / bromine catalyst to the number of alkyl groups. In the preparation of the aromatic carboxylic acid having the corresponding carboxyl group, an alkylammonium bromide salt such as tetrapropyl ammonium bromide and carbon dioxide are simultaneously added to the reaction system to not only dramatically improve the reaction activity, but also to reduce the production of by-products to improve the yield of the desired product. It is possible to maximize the elimination of partial oxidation intermediates, there is an effect that suggests the possibility of directly producing a high-purity product without undergoing a purification process, which is an essential process for producing a high-purity aromatic carboxylic acid.

Claims (9)

In the liquid phase reaction system using acetic acid as a solvent under a cobalt / manganese / bromine catalyst, an aromatic aromatic acid is prepared by oxidizing an alkylaromatic compound and a partial oxidation intermediate thereof with an oxygen (O ₂ ) -containing gas. In the liquid phase reaction system, an oxidation reaction is carried out by containing an alkylammonium bromide salt having a weight ratio of 1 to 90% (v / v) of carbon dioxide (CO ₂ ) and an alkylammonium bromide salt / manganese in a range of 0.04 to 5%. A method for producing an aromatic carboxylic acid, characterized in that to increase the selectivity of the aromatic carboxylic acid compound having a number of carboxyl groups corresponding to the number of alkyl groups of the alkylaromatic compound used as a reactant. delete According to claim 1, wherein the alkyl ammonium bromide salt is tetramethyl ammonium bromide, tetraethyl ammonium bromide, tetrapropyl ammonium bromide and tetrabutyl ammonium bromide A method for producing an aromatic carboxylic acid, characterized by using one or two or more selected from among them. The method of claim 1, wherein the concentration of oxygen (O ₂ ) is 2 to 75% (v / v) in the total gas introduced. delete The method of claim 1, wherein the alkylaromatic compound is toluene, ortho-xylene (o-xylene), meta-xylene (m-xylene), para-xylene (p-xylene), 1,3,4-trimethyl Benzene (pseudocumene), 1,3,5-trimethylbenzene (mesitylene), 2,3,5,6-tetramethylbenzene (durene), methylnaphthalene, 2,6-dimethylnaphthalene and 4, 4'-dimethylbiphenyl (4,4'-dimethylbiphenyl) method of producing an aromatic carboxylic acid, characterized in that selected from. According to claim 1, wherein the aromatic carboxylic acid is benzoic acid (benzoic acid), phthalic acid (phthalic acid), isophthalic acid (isophthalic acid), terephthalic acid (terephthalic acid), trimellitic acid (trimellitic acid), trimesic acid (trimesic acid) , Pyromellitic acid, carboxynaphthalic acid, 2,6-dicarboxynaphthalic acid and 4,4'-dicarboxybiphenyl acid (4,4'- dicarboxybiphenylic acid) method of producing an aromatic carboxylic acid, characterized in that selected. The method of claim 1, wherein the carbon dioxide is introduced into the gas phase or liquid phase in the reactor periodically or continuously. The method of claim 8, wherein when the carbon dioxide is added to the gas phase, the mixture is mixed with an unused reaction gas or recycled by mixing with a reaction waste in which oxygen and carbon dioxide remain.