KR101735110B1 - Method for Preparing Pyromellitic Acid - Google Patents

Abstract

A specific example of the present invention discloses a method for producing pyromellitic acid by oxidizing durene, which is a starting material, in a two-step reaction in a liquid phase with different temperatures.

Description

FIELD OF THE INVENTION The present invention relates to a method for preparing pyromellitic acid,

The present invention relates to a process for producing pyromellitic acid (1,2,4,5-tetracarboxylic acid) by oxidizing Durene (1,2,4,5-tetramethyl benzene) with a gas containing molecular oxygen . More specifically, the present invention relates to a method for producing pyromellitic acid by oxidizing durene, which is a starting material, in a two-step reaction at different temperatures in a liquid phase.

Pyromellitic acid is widely used as a raw material for a crosslinking agent for foam epoxy, a plasticizer, a polyimide for electronic materials, and a powder coating agent, and exhibits the characteristics of a light yellow crystalline powder in white. Typically, it is known to exhibit a melting point of about 276 DEG C (anhydrous), a density of about 1.79, and solubility in alcohol.

As a commercial production method of pyromellitic acid, the liquid phase oxidation method of duren is widely known. At this time, the duren used as the starting material is usually present in the C10 oil fraction in the contact reformed oil or pyrolysis oil, and is available in a purified form through distillation. The above-mentioned liquid phase oxidation method is a method in which an acetic acid solvent is oxidized in the presence of a heavy metal catalyst as shown in the following reaction formula (1).

[Reaction Scheme 1]

Recently, durene is oxidized with a molecular oxygen-containing gas in the presence of a catalyst comprising acetic acid as a reaction medium and one or more metal compounds and one or more bromine compounds, Various methods for producing lactic acid have been proposed. For example, there have been known methods in which a bromine (Br) compound is continuously injected or a reaction product is separated to perform an additional oxidation reaction.

In the case of a method of sequentially injecting Br compounds by the reaction step (for example, U.S. Patent No. 4,755,622), although it is a method for increasing the selectivity of pyromellitic acid and deactivation of the catalyst, It is known that the yield of rosemary acid can not be obtained.

On the other hand, in the case of separating the products of the first oxidation reaction (trimethyl acetic acid, trimethyl benzyl alcohol and trimethyl benzaldehyde) and then producing pyromellitic acid through additional oxidation reaction of double trimethyl acetic acid and / or trimethyl benzaldehyde (For example, Japanese Patent Laid-Open No. 2005-145954), it is known that it is possible to increase the selectivity and the yield, but the process operation is difficult and the yield of pyromellitic acid still remains at the maximum of 80 mol%.

Accordingly, a method for producing pyromellitic acid at a higher yield is required.

The present invention provides a method for producing pyromellitic acid at a higher yield than the prior art.

According to embodiments of the present invention,

a) subjecting duren to primary liquid phase oxidation by supplying a molecular oxygen-containing gas in the presence of an oxidation catalyst component comprising a cobalt (Co) compound and a bromine (Br) compound, using an acetic acid solvent as a reaction medium;

b) adding a manganese (Mn) compound to the product of step a) in the form of an aqueous solution to form a second liquid phase oxidation;

/ RTI >

The step b) provides a process for preparing pyromellitic acid which is carried out at a temperature higher than the step a).

According to one embodiment, the cobalt compound may be used in an amount of about 0.01 to 1.5 wt.%, Based on the acetic acid solvent, wherein the weight ratio of bromine ion (Br ^- ) to cobalt metal in the cobalt compound is about 0.5 To about 15, and the weight ratio of manganese metal in the manganese compound to cobalt metal in the cobalt compound may range from about 0.1 to about 0.8.

In addition, the atomic ratio (Br / (Co + Mn)) of bromine to cobalt metal and manganese metal may range from about 0.3 to about 14.

The method for producing pyromellitic acid according to an embodiment of the present invention is characterized in that acetic acid solvent is used as a reaction medium and the liquid phase oxidation reaction is carried out at two different temperatures, A high yield can be achieved as compared with a conventionally known method.

The embodiments provided in accordance with the present invention can be all achieved by the following description. It is to be understood that the following description is of a preferred embodiment of the present invention and that the present invention is not necessarily limited thereto.

According to the embodiment of the present invention, durene as a starting material is converted into pyromellitic acid by liquid-phase oxidation by supplying a gas containing molecular oxygen by using an acetic acid solvent as a reaction medium. At this time, a combination of a cobalt compound (cobalt source), a bromine compound (bromine source) and a manganese compound (manganese source) is adopted as an overall oxidation catalyst component. In the above embodiment, in order to improve the yield, the liquid phase oxidation step is constituted by two steps, and the temperatures in the first step and the second step are set differently. Preferably, the temperature of the second step can be set higher than that of the first step.

According to the embodiment of the present invention, the cobalt compound and the bromine compound are dissolved in an acetic acid solvent in the first stage reaction and introduced into the reaction system, while the manganese compound is introduced into the reaction system in the form of an aqueous solution in the second- can do.

The cobalt compound and the manganese compound are not particularly limited as long as they are soluble in acetic acid solvent as a reaction medium. Examples of the cobalt compound and manganese compound include organic acid salts such as acetate, propionate, naphthenate and octanoate ; hydroxide; Halides of chlorides or bromides; And inorganic acid salts such as borates, nitrates and carbonates. Preferable examples include nitrates, phosphates, hydroxides, bromides and the like, more preferably nitrates.

On the other hand, in the case of a bromine compound, a substance (source) capable of generating bromine ions under the reaction conditions can be used without particular limitation. Hydrogen bromide as the bromine source; Ammonium bromide; Alkali metal bromides such as sodium bromide, lithium bromide and potassium bromide; Inorganic bromides such as cobalt bromide, manganese bromide, and iron bromide; And organic bromine compounds such as tetrabromomethane, tetrabromethane, acetyl bromide, and benzyl bromide. Preferably, sodium bromide, cobalt bromide, manganese bromide, ammonium bromide and the like can be used, and sodium bromide is most preferable.

According to this specific example, the compounds exemplarily listed for each of the above-described cobalt compound, manganese compound and bromine compound may be used alone or in combination of two or more.

In the case of a molecular oxygen-containing gas used as an oxidizing agent, the oxygen concentration in the gas may range from about 5 to 100%, more particularly about 10 to 50%, typically air is available. According to one embodiment, the molecular oxygen-containing gas may be continuously supplied from at least one inlet port provided in the reaction medium. For example, when an oxidation reaction is carried out using a multi-stage reactor, it can be continuously supplied while controlling the supply amount through one or more inlet ports provided for each reactor. In addition, the reactor may be preferably in the form of a stirred reactor.

In this regard, the amount of oxygen supplied through the molecular oxygen-containing gas in the first liquid oxidation step may be, for example, from about 2.5 to about 4 moles per mole of duren, and more specifically, And may range from about 2.8 to 3.6 moles per mole. Accordingly, in the first step, only the 1 to 3 methyl groups bonded to the benzene ring of the duren are oxidized to suppress the deactivation of the catalyst or the side reaction, and in the second step, The methyl group bonded to the benzene ring is oxidized to be finally converted to the target pyromellitic acid.

On the other hand, during the first oxidation step and the second oxidation step, it may be preferable that the pressure is set so that the acetic acid solvent as the reaction medium can maintain the liquid phase, and this example is not limited to the specific pressure range, For example, in the range of about 250 to 500 psig, more specifically about 300 to 450 psig.

At this time, in the case of the oxygen partial pressure of the reaction system, the molecular oxygen introduced into the reactor such that the oxygen concentration in the off-gas discharged from the reactor is about 8 vol% or less, more specifically about 1 to about 5 vol% - < / RTI > containing gas.

According to a preferred embodiment, a reflux condenser may be optionally provided in the reactor to condense the solvent contained in the offgas (exhaust gas) and the water produced by the oxidation reaction, and recycle it to the reactor in whole or in part.

According to embodiments in accordance with the present invention, the first stage reaction followed by the second stage reaction may be carried out continuously to substantially complete the intended liquid phase oxidation reaction. At this time, either a batch multi-stage reaction system or a continuous multi-stage reaction system can be adopted. According to another embodiment, the first step may be performed in a continuous mode and the second step may be performed in a batch mode.

On the other hand, when the two-step liquid phase oxidation reaction is completed, the reaction product may be subjected to a purification treatment known in the art, for example, a filtration process or a distillation process may be exemplified. In some cases, it may further include a further refining step of pyromellitic acid, for example, a method in which an aqueous solution in which a product is dissolved in water is cooled under a predetermined condition to crystallize, followed by filtration and centrifugal separation Can be exemplified.

 The yield of the pyromellitic acid according to the embodiment of the present invention can be at least about 80 mol%, more specifically at least about 84 mol%, and the product can be easily separated and purified after the reaction .

The process conditions of the first liquid phase oxidation step and the second liquid phase oxidation step will be described in more detail below.

Phase 1 liquid phase oxidation

In the first stage oxidation reaction, an acetic acid solvent is used as a reaction medium, and a combination of a cobalt compound and a bromine compound is used as a catalyst component, a molecular oxygen-containing gas is supplied so that an oxidation reaction can take place in a liquid phase. At this time, the oxidation reaction may be performed using the entire amount of the cobalt compound, bromine compound and acetic acid solvent. According to a preferred embodiment, the oxidation reaction in the first stage can be carried out until the conversion of the starting durene is at least about 90%, more specifically about 90 to 98% And to prevent catalyst deactivation.

In one embodiment, it may be desirable to use acetic acid solvent as the reaction medium at least about twice the weight of duren, more specifically about 4 to 15 times, by weight. A pure acetic acid may be used, or an acetic acid in the form of an aqueous solution may be used. However, when acetic acid in the form of an aqueous solution is used, excessive use of water may affect the reaction rate and reduce the yield. Taking this into consideration, it may be appropriate to contain not more than about 40% by weight of water. As the water, ion-exchanged water or distilled water can be preferably used.

In an exemplary embodiment, the oxidation reaction rate increases as the amount of the cobalt compound used as the catalyst component increases. When the amount of the cobalt compound is excessively used, side reaction products other than the target pyromellitic acid are increased, It can have an unfavorable effect. In consideration of the above, the cobalt metal in the cobalt compound may be used in an amount of about 0.01 to about 1.5 wt% based on the acetic acid solvent.

On the other hand, the amount of the bromine compound to be used can be adjusted so that the weight ratio (Br / Co) of the bromine ion to the cobalt metal in the cobalt compound is about 0.5 to about 15, preferably about 1 to 14. [ The activity tends to increase as the amount of the bromine compound used increases. However, since the bromine component is incorporated into the object at a certain level or higher, the purification cost and the catalyst cost are increased because the purity is lowered. . Therefore, it may be desirable to adjust to the aforementioned range.

In the first step, the liquid phase oxidation reaction may be set at a temperature in the range of, for example, about 120 ° C to about 200 ° C, preferably about 130 ° C to about 180 ° C. However, when the reaction temperature is set to an excessively high temperature, an increase in side reaction such as complete oxidation reaction and a dealkylation reaction of duren due to pyrolysis may occur, thereby decreasing the yield and deactivation of the catalyst And that it can be facilitated. The reaction temperature range is illustrative and the present invention is not necessarily limited thereto.

Second stage liquid phase oxidation reaction

In the second-step reaction, a manganese compound as a catalyst component is introduced into the reaction system to convert the remaining methyl groups not converted in the first-step oxidation reaction to pyromellitic acid.

At this time, since the manganese compound is introduced in the form of an aqueous solution, the concentration of pyromellitic acid generated by the oxidation reaction proceeds, and the yield and inactivation of pyromellitic acid can be prevented. The aqueous solution of the manganese compound may be preferably about 30% by weight or less, more preferably about 15 to about 30% by weight based on the acetic acid solvent.

In the embodiment of the present invention, the amount of the manganese compound to be introduced in the second liquid phase oxidation step is set so that the weight ratio of manganese metal in the manganese compound to the cobalt metal in the cobalt compound used in the first liquid phase oxidation step / Co) is in the range of about 0.1 to about 0.8, preferably about 0.2 to about 0.6. The present invention is not necessarily limited to this, but when the amount of the manganese compound to be used is set within the above-mentioned range, the activity, selectivity, and catalyst recovery operation of the entire catalyst component can be facilitated.

Also, the atomic ratio (Br / (Co + Mn)) of bromine to cobalt metal and manganese metal throughout the two step liquid oxidation process may range from about 0.3 to about 14. The reason is that when the amount of the bromine compound is too small as compared with the amount of the metal compound in the catalyst component, the intended activity may not be attained, while in an excessive amount, the purity of the product due to the bromine compound is lowered and the catalyst recovery cost is increased . However, the scope of the present invention is not limited thereto.

The second stage liquid phase oxidation reaction can be carried out, for example, in the range of about 180 to about 250 캜, preferably about 200 to about 240 캜. It is considered that if the reaction temperature is too low, it may be difficult to complete the oxidation to pyromellitic acid, whereas when the reaction temperature is excessively high, the yield may be reduced due to an increase in complete oxidation reaction. The reaction temperature range is illustrative and the present invention is not necessarily limited thereto.

In an exemplary embodiment, the reaction temperature of the second liquid phase oxidation step may be performed at a reaction temperature zone different from the first liquid phase oxidation step, preferably at a higher temperature than the first oxidation step. At this time, it may be preferable that the temperature of the second oxidation step is set at about 20 to about 130 캜, more specifically about 40 to about 110 캜 higher than the first oxidation step.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the present invention is not limited thereto.

Example  One

In this example, a 1 gallon (3.785 liters) titanium autoclave equipped with a reflux condenser, a stirrer and an air blowing nozzle was used as the reactor. 90.1 g of durenne, 720 g of acetic acid, 2.85 g of cobalt acetate and 1.23 g of sodium bromide as a reactant were poured into the reactor, and the mixture was purged with helium gas, which is an inert gas, and heated to a temperature of 150 ° C. The pressure was maintained at 400 psig and the liquid phase oxidation reaction was initiated while the compressed air was slowly injected into the autoclave.

After 100 minutes of the reaction, the injection of compressed air was stopped briefly. After 1.53 g of manganese acetate was dissolved in 140 g of water, the temperature was raised to 220 캜, and the oxidation reaction was continued while injecting the compressed air into the reactor. The concentration of oxygen in the off-gas was analyzed by gas chromatography. When the oxygen concentration in the off-gas began to exceed 8 vol%, the injection of compressed air was stopped and the reaction was terminated.

Upon completion of the reaction, the reaction product was extracted, the reaction product was methyl-esterified, and the yield of pyromellitic acid was calculated by gas chromatography (product name: 5890, HP). As a result, a yield of pyromellitic acid of 88.1 mol% was obtained.

Example  2 to 6

Pyromellitic acid was prepared in the same manner as in Example 1 except that the composition of the reactants and the reaction conditions were changed as shown in Table 1 below.

Composition / reaction conditions unit Example 2 Example 3 Example 4 Example 5 Example 6 Durance g 90.3 90.2 90.3 90.4 90.2 Cobalt acetate g 4.87 3.65 2.43 1.22 4.87 Cobalt / acetic acid weight% 0.16 0.12 0.08 0.04 0.16 Manganese acetate (1) g 0 0 0 0 0 Manganese / cobalt Weight ratio 0 0 0 0 0 Manganese acetate (2) g 2.57 1.93 1.28 0.64 2.57 Manganese / cobalt Weight ratio 0.5 0.5 0.5 0.5 0.5 Sodium bromide g 13.39 10.04 6.68 3.34 6.7 Bromine / cobalt Weight ratio 9 9 9 9 4.5 Acetic acid g 720 720 720 720 720 Reactor pressure psig 400 400 400 400 400 Reaction temperature (1) ℃ 150 150 150 150 150 Reaction temperature (2) ℃ 220 220 220 220 220 Air injection rate N / min 2.5 2.5 2.5 2.5 2.5 Reaction time (1) min. 100 100 100 100 100 Reaction time (2) min. 80 80 80 80 80 Stirring speed rpm 500 500 500 500 500 water g 130 130 130 130 130

(1) Phase I liquid phase oxidation reaction

(2) Second stage liquid phase oxidation reaction

The yields of pyromellitic acid according to Examples 2 to 6 are shown in Table 2 below.

unit Example 2 Example 3 Example 4 Example 5 Example 6 Pyromellitic acid mole% 84.3 86.5 88.3 87.8 85.6 By-product mole% 15.7 13.5 11.7 12.2 14.4

Comparative Example  One

Pyromellitic acid was prepared in a manner similar to that in Example 1. However, 700 g of acetic acid, 88.5 g of duren, 2.71 g of cobalt acetate, and 7.2 g of sodium bromide were charged into the reactor and reacted at 150 캜 for 100 minutes, followed by a second stage oxidation reaction.

While raising the temperature of the second step oxidation reaction to 220 캜, 1.41 g of manganese acetate was dissolved in 90 g of acetic acid and injected, and the second stage oxidation reaction was initiated. As a result, a pyromellitic acid yield of 82.3 mol% was obtained.

Comparative Example  2

90.2 g of durenne, 2.81 g of cobalt acetate, 1.48 g of manganese acetate and 7.62 g of sodium bromide were fed into the reactor used in Example 1, and reacted at a reaction temperature of 220 占 폚 for 150 minutes. As a result, a pyromellitic acid yield of 72.2 mol% was obtained.

From the above-mentioned experimental results, when pyromellitic acid was produced according to Examples 1 to 6, all the yields of 84 mol% or more were obtained. On the other hand, in the case of Comparative Example 1 in which the manganese compound was dissolved in acetic acid and the second liquid phase oxidation reaction was performed, a yield of 80 mol% or more was obtained, but it was lower than in the Examples.

In addition, in the case of Comparative Example 2 in which the single stage oxidation reaction was performed, the yield was remarkably lower than in the Examples.

All such modifications and variations are intended to be included within the scope of the present invention, and are not necessarily to be construed as preferred or particularly advantageous aspects of the invention. The specific scope of protection of the present invention will be clarified by the appended claims.

Claims (16)

a) subjecting duren to primary liquid phase oxidation by supplying a molecular oxygen-containing gas in the presence of an oxidation catalyst component comprising a cobalt (Co) compound and a bromine (Br) compound, using an acetic acid solvent as a reaction medium;
b) adding a manganese (Mn) compound to the product of step a) in the form of an aqueous solution to form a second liquid phase oxidation,
Wherein said step b) is carried out at a temperature higher than said step a)
Wherein the total amount of the cobalt (Co) compound and the bromine (Br) compound is introduced in step a). 2. The method according to claim 1, wherein the cobalt compound is used in an amount of 0.01 to 1.5% by weight based on the acetic acid solvent. The process for producing pyromellitic acid according to claim 1 or 2, wherein the weight ratio of bromine in the bromine compound to cobalt metal in the cobalt compound is in the range of 0.5 to 15. The process for producing pyromellite according to claim 1 or 2, wherein the weight ratio of manganese metal in the manganese compound to the cobalt metal in the cobalt compound is in the range of 0.1 to 0.8. The process for producing pyromellite according to claim 1, wherein the atomic ratio (Br / (Co + Mn)) of bromine to cobalt metal and manganese metal is in the range of 0.3 to 14. 2. The process of claim 1, wherein step a) and step b) are carried out under a pressure of 250-500 psig. The process according to claim 1, wherein the step a) is carried out at 120 to 200 ° C, and the step b) is carried out at 180 to 250 ° C. The process according to claim 7, wherein step b) is carried out at a temperature 20 to 130 캜 higher than that of step a). The process for producing pyromellite according to claim 1, wherein the cobalt compound is cobalt acetate. The process for producing pyromellite according to claim 1, wherein the manganese compound is manganese acetate. The process for producing pyromellitic acid according to claim 1, wherein the bromine compound is sodium bromide or hydrogen bromide. 2. The process of claim 1, wherein the liquid phase oxidation reaction of step a) is carried out by supplying 2.5 to 4 moles of oxygen per mole of duren until the duren conversion is at least 90%. Gt; The method according to claim 1, wherein the acetic acid solvent is used in a range of 4 to 15 times the weight of durene. The method of claim 1, wherein the acetic acid solvent is in the form of an aqueous solution containing pure acetic acid or up to 40% by weight of water. The process for producing pyromellitic acid according to claim 1, wherein the molecular oxygen-containing gas is air. The method according to claim 1, wherein the aqueous solution of the manganese compound is added in an amount of 15 to 30 wt% based on the acetic acid solvent.