KR20120045441A - Method for preparing pyromellitic acid - Google Patents

Abstract

PURPOSE: A manufacturing method of pyromellitic acid is provided to manufacture pyromellitic acid with high yield, and to easily separation refining product after reaction. CONSTITUTION: A manufacturing method of pyromellitic acid comprises: (i) a step of primary liquid phase-oxidizing durene by supplying oxygen-containing gas under the presence of an oxidization catalyst component comprising a cobalt compound and bromine compound using acetic acid solvent as a reaction medium; and (ii) a step of secondary liquid phase-oxidization by adding a manganese compound into the product of the step (i). The step (ii) is conducted at temperature higher than step (i). The amount of the cobalt compound is 0.01-1.5 weight% on the basis of acetic acid.

Description

Method for preparing pyromellitic acid {Method for Preparing Pyromellitic Acid}

The present invention prepares pyromellitic acid (Pyromellitic Acid; 1,2,4,5-tetracarboxylic acid) by oxidizing Durene (Durene; 1,2,4,5-tetramethyl benzene) to a gas containing molecular oxygen. It is about how to. More specifically, the present invention relates to a method for producing pyromellitic acid by oxidizing the starting material of durene in a two-step reaction in which the temperature is varied in the liquid phase.

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

As a commercial production method of pyromellitic acid, the liquid phase oxidation of durene is widely known. At this time, the durene used as a starting material is usually present in the C10 fraction in the catalytic reforming oil or pyrolysis oil, and is available in purified form through distillation. The liquid phase oxidation method is a method of oxidizing using acetic acid solvent in the presence of a heavy metal catalyst as in Scheme 1 below.

Scheme 1

Recently, pyromel is obtained by using acetic acid solvent as a reaction medium and oxidizing durene with a molecular oxygen-containing gas in the presence of a catalyst consisting of one or more metal compounds and one or two bromine compounds. Various methods of preparing lactic acid have been proposed, for example, continuous injection of bromine (Br) compounds or separation of reaction products to further oxidize.

In the case of sequentially injecting Br compounds in the reaction step (for example, US Pat. No. 4,755,622), the method of deactivating the catalyst and increasing the selectivity of pyromellitic acid, but not less than 70 mol% of pi It is known that no yield of lomellitic acid is obtained.

Meanwhile, in the case of a method of preparing pyromellitic acid by separating the products of the primary oxidation reaction (trimethylacetic acid, trimethylbenzyl alcohol and trimethylbenzaldehyde), and then further oxidation of trimethylacetic acid and / or trimethylbenzaldehyde (For example, Japanese Patent Application Laid-Open No. 2005-145954), although it is known that the selectivity and yield can be improved, the process operation is difficult, and the yield of pyromellitic acid still remains at a maximum of 80 mol%.

Therefore, there is a need for a method capable of producing pyromellitic acid with higher yields.

In an embodiment of the present invention to provide a method for producing pyromellitic acid in a higher yield compared to the prior art.

According to an embodiment of the invention,

a) first liquid phase oxidation of the durene 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 as a reaction medium;

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

Including;

Step b) is provided a method of preparing pyromellitic acid carried out at a higher temperature than step a).

According to one embodiment, the cobalt compound may be used in about 0.01 to 1.5% by weight based on the acetic acid solvent, wherein the weight ratio of bromine ions (Br ⁻ ) in the bromine compound to the cobalt metal in the cobalt compound is about 0.5 And a 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 and manganese metals may range from about 0.3 to about 14.

The method for producing pyromellitic acid according to an embodiment of the present invention uses acetic acid solvent as a reaction medium, and the liquid phase oxidation reaction is composed of two stages at different temperatures, and the oxidation catalyst component at each stage is in a specific form. By applying it is possible to achieve higher yields compared to the methods known in the art.

Embodiments provided according to the present invention can all be achieved by the following description. It is to be understood that the following description describes preferred embodiments of the invention, and the invention is not necessarily limited thereto.

According to an embodiment of the present invention, the starting material durene is converted to pyromellitic acid by liquid phase oxidation by using acetic acid solvent as a reaction medium and supplying gas containing molecular oxygen. 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 the overall oxidation catalyst component. In the above embodiment, the liquid phase oxidation step is configured in two steps to improve the yield, but the temperature in the first step and the second step is set differently. Preferably, the temperature of the second step may be set higher than that of the first step.

In addition, according to an embodiment of the present invention, the cobalt compound and the bromine compound are dissolved in the total amount of 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 second stage reaction step in the form of an aqueous solution. can do.

In the case of the cobalt compound and manganese compound, on the other hand, if it is a form that can be dissolved in the acetic acid solvent which is a reaction medium is not particularly limited, for example, organic acid salts such as acetates, propionates, naphthenates, octenates of these metals ; hydroxide; Halides of chloride or bromide; Inorganic acid salts, such as a borate, nitrate, and carbonate, etc. are mentioned. Preferably, acetate, phosphate, hydroxide, bromide, etc. can be illustrated, More preferably, acetate can be used.

In the case of a bromine compound, any substance (source) capable of generating bromine ions under reaction conditions may be used without particular limitation. Hydrogen bromide as the bromine source; Ammonium bromide; Alkali metal bromide such as sodium bromide, lithium bromide and potassium bromide; Inorganic bromide such as cobalt bromide, manganese bromide and iron bromide; And organic bromine compounds such as methane tetrabromide, tetrabromethane ethane, acetyl bromide and benzyl bromide. Preferably sodium bromide, cobalt bromide, manganese bromide, ammonium bromide and the like can be used, with sodium bromide being most preferred.

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

In the case of molecular oxygen-containing gases used as oxidants, the oxygen concentration in the gas may range from about 5 to 100%, more specifically about 10 to 50%, typically air is available. According to one embodiment, the molecular oxygen-containing gas can be supplied continuously from at least one inlet provided in the reaction medium. For example, when the oxidation reaction is carried out using a multi-stage reactor, it can be continuously supplied while controlling the supply amount through one or two or more intakes provided in each reactor. In addition, the reactor may be 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 acid oxidation step may be suitable, for example, about 2.5 to about 4 moles per mole of durene, more specifically It 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 durene are oxidized to suppress the catalyst deactivation or the side reaction, and in the second step, the conversion is not performed in the first step. The methyl group bound to the benzene ring is oxidized to the final conversion to the desired pyromellitic acid.

On the other hand, throughout 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 a reaction medium can maintain a liquid phase, but the present embodiment is not limited to a specific pressure range, For example, it may be set in the range of about 250 to 500 psig, more specifically about 300 to 450 psig.

In this case, in the case of the oxygen partial pressure of the reaction system, molecular oxygen introduced into the reactor such that the oxygen concentration in the off-gas discharged from the reactor is about 8% by volume or less, more specifically, about 1% to about 5% by volume. It may be desirable to adjust the amount of gas containing.

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

According to an embodiment according to the present invention, the second liquid phase reaction may be continuously performed after the first phase reaction to substantially complete the intended liquid phase oxidation reaction. In this case, either a batch multistage reaction method or a continuous flow multistage reaction method may be adopted. According to another embodiment, the first step may be performed in continuous mode and the second step may be performed in batch mode.

On the other hand, when the two-step liquid phase oxidation reaction is completed, the reaction product may optionally be subjected to purification treatment known in the art, for example, it may illustrate a filtration process or a distillation process. In some cases, the method may further include a further purification process of pyromellitic acid, for example, a method in which an aqueous solution in which the product is dissolved in water is cooled by crystallization under predetermined conditions, and then obtained by filtration, centrifugation, or the like. Can be illustrated.

 Through the process for preparing pyromellitic acid according to an embodiment of the present invention, the yield may achieve at least about 80 mol%, more specifically at least about 84 mol%, and may also facilitate separation and purification of the product after the reaction. .

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

First Stage Liquid Phase Oxidation

The first stage oxidation reaction uses acetic acid solvent as a reaction medium and a combination of cobalt and bromine compounds as catalyst components, which supplies a molecular oxygen-containing gas so that the oxidation reaction can occur in the liquid phase. At this time, the oxidation reaction may be performed using all of the cobalt compound, bromine compound and acetic acid solvent. According to a preferred embodiment, the oxidation reaction in the first step can proceed until the conversion rate of the starting material durene is at least about 90%, more specifically about 90 to 98%, which is the reaction yield Consideration has been made to increase and prevent catalyst deactivation.

In one embodiment, the acetic acid solvent, which is the reaction medium, may be preferably used in at least about 2 times, more specifically, about 4 to 15 times, the weight of the durene. Pure acetic acid may be used, or acetic acid in aqueous solution may be used. However, when using acetic acid in the form of an aqueous solution, too much water may affect the reaction rate and lower the yield. In view of this, it may be suitable to contain up to about 40% by weight of water. In addition, as water, ion-exchanged water or distilled water can be preferably used.

In an exemplary embodiment, the rate of oxidation reaction increases as the amount of the cobalt compound as a catalyst component increases, but when used too much, side reaction products other than the target pyromellitic acid increase, which is undesirable for purity and yield. It may not affect. In view of the above, it may be used in the range of about 0.01 to about 1.5 wt% based on the cobalt metal in the cobalt compound with respect to the acetic acid solvent.

On the other hand, the amount of the bromine compound can be adjusted so that the weight ratio (Br / Co) of the bromine ions to the cobalt metal in the cobalt compound is in the range of about 0.5 to about 15, preferably about 1 to 14. As the amount of bromine compound used increases, the activity tends to increase, but above a certain level, as a result of the incorporation of the bromine component into the target, the purity decreases, thereby increasing the purification cost and the catalyst cost, and decreasing the catalyst recovery efficiency. Can be. Therefore, it may be desirable to adjust the range described above.

In the first step, the liquid acid oxidation reaction may be set, for example, in the range of about 120 to about 200 ° C, preferably about 130 to about 180 ° C. Although the reaction rate tends to increase as the reaction temperature increases, when it is set at an excessively high temperature, an increase in side reactions such as a complete oxidation reaction and dealkylation of durene by pyrolysis occurs, resulting in a decrease in yield and deactivation of the catalyst. Considering that it can promote. The reaction temperature range is exemplary and the present invention is not necessarily limited thereto.

Second Stage Liquid Phase Oxidation

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

In this case, since the manganese compound is introduced in the form of an aqueous solution, the concentration of pyromellitic acid generated by the oxidation reaction may be diluted to prevent increase in yield and deactivation of pyromellitic acid. The aqueous solution of the manganese compound may be within about 30% by weight, specifically about 15 to about 30% by weight, based on the acetic acid solvent.

In an embodiment of the present invention, the amount of the manganese compound introduced in the second liquid oxidation step is a weight ratio of the manganese metal in the manganese compound to the cobalt metal in the cobalt compound used in the first liquid phase oxidation step (Mn). / Co) can be adjusted to range from about 0.1 to about 0.8, preferably from about 0.2 to about 0.6. Although the present invention is not necessarily limited thereto, when the amount of manganese compound used is set in the above-described range, the activity, selectivity of the entire catalyst component, and the recovery operation of the catalyst may be easy.

In addition, the atomic ratio (Br / (Co + Mn)) of bromine to cobalt metal and manganese metal throughout the two stage liquid phase oxidation process may range from about 0.3 to about 14. The reason is that when the amount of bromine compound is too small compared to the metal compound in the catalyst component, the intended activity may not be achieved, while in the case of too much bromine compound, the purity of the product and the increase in the cost of catalyst recovery may be caused. Can be considered. However, the above range is provided as an example, and embodiments of the present invention are not necessarily limited thereto.

The second stage liquid phase oxidation reaction can be carried out, for example, in the range of about 180 to about 250 ° C, preferably about 200 to about 240 ° C. This is to consider that if the reaction temperature is too low, it may be difficult to complete the oxidation to pyromellitic acid, while if too high, the yield may decrease due to an increase in the complete oxidation reaction. The reaction temperature range is exemplary 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 carried out in a different reaction temperature zone than the first liquid phase oxidation step, preferably at a higher temperature than the first oxidation step. In this case, the temperature of the second oxidation step may be set to about 20 to about 130 ℃, more specifically about 40 to about 110 ℃ higher than the first oxidation step.

Hereinafter, preferred examples are provided to aid in understanding the present invention, but the following examples are provided only for better understanding of the present invention, and the present invention is not limited thereto.

Example  One

In this example, a 1 gallon (3.785 liter) autoclave of titanium with reflux cooler, stirrer and air blow nozzle was used as reactor. 90.1 g of durene, 720 g of acetic acid, 2.85 g of cobalt acetate, and 1.23 g of sodium bromide were added to the reactor as a reactant, and then purged with helium gas, which is an inert gas, and the temperature was raised to 150 ° C. The pressure was maintained at 400 psig and the liquid phase oxidation reaction was initiated while slowly injecting compressed air into the autoclave.

After 100 minutes of the reaction, the injection of compressed air was stopped for a while, and 1.53 g of manganese acetate was dissolved in 140 g of water and heated to a temperature of 220 ° C., followed by oxidation while continuing to inject compressed air into the reactor. The concentration of oxygen in off-gas was analyzed using gas chromatography to stop the injection of compressed air and terminate the reaction when the oxygen concentration in the off-gas began to exceed 8% by volume.

When the reaction was completed, the reaction product was extracted to methyl ester the reaction product, and then the yield of pyromellitic acid was calculated using gas chromatography (HP product name: 5890). As a result, a yield of 88.1 mol% pyromellitic acid was obtained.

Example  2 to 6

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

Composition / Reaction Conditions unit Example 2 Example 3 Example 4 Example 5 Example 6 Duren 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 speed Nℓ / 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) First Stage Liquid Phase Oxidation

(2) Second Stage Liquid Phase Oxidation

The yield of pyromellitic acid according to Examples 2 to 6 is 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 similar manner as in Example 1. However, 700 g of acetic acid, 88.5 g of durene, 2.71 g of cobalt acetate, and 7.2 g of sodium bromide were added to the reactor and reacted at 150 ° C. for 100 minutes, followed by a second step of oxidation.

While raising the temperature of the second stage oxidation reaction to 220 ° C., 1.41 g of manganese acetate was dissolved and injected into 90 g of acetic acid, and then the second stage oxidation reaction was started. As a result, a pyromellitic acid yield of 82.3 mol% was obtained.

Comparative example  2

90.2 g of durene, 2.81 g of cobalt acetate, 1.48 g of manganese acetate, and 7.62 g of sodium bromide were added to a reactor used in Example 1, and reacted at a reaction temperature of 220 ° C. for 150 minutes. As a result, a yield of 72.2 mol% pyromellitic acid was obtained.

When pyromellitic acid was prepared according to Examples 1 to 6 from the above experimental results, all yields of 84 mol% or more were obtained. On the other hand, in Comparative Example 1 in which the second liquid phase oxidation reaction was performed in the form of dissolving a manganese compound in acetic acid, a yield of 80 mol% or more was obtained, but was lower than that of the example.

In addition, Comparative Example 2, which performed a single step oxidation reaction, showed a significantly lower yield than the Example.

All simple modifications and variations of the present invention fall within the scope of the present invention, and in particular, are not necessarily limited to the aspect in which the present invention is mentioned as being preferable or particularly advantageous. Specific scope of protection of the present invention will be apparent from the appended claims.

Claims (16)

a) first liquid phase oxidation of the durene 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 as a reaction medium;
b) secondary liquid phase oxidation by adding a manganese (Mn) compound in the form of an aqueous solution to the product of step a);
Including;
The step b) is a method for producing pyromellitic acid, characterized in that carried out at a higher temperature than step a). The method of claim 1, wherein the cobalt compound is used at 0.01 to 1.5 wt% based on the acetic acid solvent. The method for producing pyromellitic acid according to claim 1 or 2, wherein the weight ratio of bromine in the bromine compound to the cobalt metal in the cobalt compound is in the range of 0.5 to 15. The method of claim 1 or 2, wherein the weight ratio of the 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 method of claim 1, wherein the atomic ratio (Br / (Co + Mn)) of bromine to the cobalt metal and the manganese metal is in the range of 0.3 to 14. The method of claim 1, wherein the step a) and the step b) is carried out under a pressure of 250 to 500 psig. The method of claim 1, wherein step a) is performed at 120 to 200 ° C., and step b) is performed at 180 to 250 ° C. 8. The method of claim 7, wherein step b) is performed at a temperature of 20 to 130 ° C. higher than step a). The method of claim 1, wherein the cobalt compound is cobalt acetate. The method for producing pyromellitic acid according to claim 1, wherein the manganese compound is manganese acetate. The method for producing pyromellitic acid according to claim 1, wherein the bromine compound is sodium bromide or hydrogen bromide. The method of claim 1, wherein the liquid phase oxidation of step a) is carried out by supplying 2.5 to 4 moles of oxygen per mole of durene until the conversion of the durene is at least 90%. Manufacturing method. The method of claim 1, wherein the acetic acid solvent is used in the range of 4 to 15 times the weight of the durene by weight. The method of claim 1, wherein the acetic acid solvent is in the form of pure acetic acid or an aqueous solution containing up to 40% by weight of water. The method of claim 1, wherein the molecular oxygen-containing gas is air. The method of claim 1, wherein the aqueous solution of the manganese compound is added in an amount of 15 to 30% by weight based on the acetic acid solvent.