KR100543526B1 - Method for synthesizing terephthalic acid using high temperature and pressure water - Google Patents

Abstract

The present invention uses an excess of high temperature and high pressure water in a temperature range of 240 to 400 ℃ and a pressure range of 220 to 300 bar as a reaction medium, does not use any catalyst, and uses hydrogen peroxide or oxygen as an oxidizing agent. The present invention relates to a method for synthesizing terephthalic acid by oxidizing (para-xylene), which is less toxic to the human body than the conventional terephthalic acid synthesis method, and the corrosion rate of the device is reduced, resulting in safer and more economical production of terephthalic acid. It provides a terephthalic acid synthesis method that can be.

Description

Synthesis method of terephthalic acid using high temperature and high pressure water {METHOD FOR SYNTHESIZING TEREPHTHALIC ACID USING HIGH TEMPERATURE AND PRESSURE WATER}

Figure 1 schematically shows a batch reaction device.

2 schematically shows a continuous reactor.

*** Description of the main parts of the drawing ***

A1: Pump A2: Preheater

A3: safety rupture plate A4: reactor

A5: Sampling Loop A6: Sampling Machine

A7: pressure regulating valve A8: primary reservoir

A9: cooler A10: secondary reservoir

A11: paraxylene reservoir

The present invention relates to a method for producing terephthalic acid by partially oxidizing paraxylene (raw material) using oxygen or hydrogen peroxide without using a catalyst in high temperature and high pressure water having high solubility of organic matter and oxygen.

Terephthalic acid is a widely used material as a raw material for polyester fibers and polyethylene terephthalate. The conventional method for producing terephthalic acid is mainly prepared by oxidizing paraxylene as a raw material using a catalyst of cobalt, molybdenum, manganese, bromine under acetic acid medium. However, acetic acid and bromine-based materials used as reaction medium of the conventional synthesis method are toxic to humans, cobalt or molybdenum catalysts are expensive and bromine-based catalysts increase the corrosion rate of the device. There is a problem that the economic feasibility of the process is poor due to the factor. In addition, as a bromine component commonly used as a catalyst for the synthesis method, at least one or more of compounds such as bromic acid, manganese bromide, cobalt bromide, sodium bromide, potassium bromide, ammonium bromide, and tetrabromethane are used. Some bromine compounds have relatively low catalytic activity, so it is difficult to achieve the intended effect when the bromine precursor is incorrectly selected. In the case of bromic acid, it is cheap and efficient, but has a strong corrosiveness. The application of a single precursor has the disadvantage of corrosive process equipment and dangerous handling.

In the conventional method for synthesizing terephthalic acid, oxidation is carried out by advancing the reaction at a temperature of 150 ° C. to 220 ° C. while supplying paraxylene and air under an acetic acid medium containing approximately 30% water.

As a method proposed for preparing a conventional terephthalic acid, Japanese Patent Application Laid-Open No. 131,303 uses paraxylene containing 3 to 35% by weight of paratolualdehyde as a raw material, and uses a lower aliphatic monocarboxylic acid as a solvent. Liquid phase oxidation using molecular oxygen-containing gas at a temperature of 120 ° C to 240 ° C in the presence of a catalyst containing 50 to 1000 ppm by weight of manganese atoms, 50 to 2000 ppm by weight of cobalt atoms, and 100 to 4000 ppm by weight of bromine atoms. A method of making is disclosed.

In addition, Japanese Patent Application Laid-Open No. 247,925 discloses a method for producing terephthalic acid by solid-liquid separation and drying of terephthalic acid obtained by the liquid acid oxidation of paraxylene, but as described above, acetic acid, propionic acid, n-butyric acid, and iso Aliphatic carboxylic acids such as butyric acid, n-gilic acid, trimethyl acetate, caproic acid, or mixtures thereof with water, catalysts with cobalt 10 to 10.000 ppm with respect to solvents, manganese compounds with atomic ratio of cobalt 0.001 ~ 10, bromine compound is presented as 0.1 ~ 10, the oxidation reaction temperature is 150 ℃ ~ 270 ℃.

U.S. Patent No. 6,307,099 discloses paraxylene using oxygen molecules in a reaction medium containing lower C ₂ to C ₆ aliphatic monocarboxylic acids and acetic acid in the presence of a heavy metal catalyst system in which a promoter such as bromine is dissolved in the preparation of terephthalic acid. Liquid phase oxidation is described.

Because these existing processes have problems such as the formation of undesired oxidation by-products due to low reaction temperatures, the use of reaction media and reaction catalysts that are toxic to humans, and the corrosion of the device by bromine catalysts, ultimately, It is causing economic deterioration.

On the other hand, high temperature and high pressure water (supercritical water and subcritical water) has a high dissolving power for gases such as organic matter and oxygen, so that raw materials involved in the reaction can be maintained in a uniform phase. The physical properties can be arbitrarily adjusted appropriately, and there is an advantage in that organic matters such as a solvent and a raw material and a product can be separated relatively simply after the reaction. Since the reaction in the homogeneous phase does not have mass transfer resistance between the phases, it is possible to greatly improve the reaction rate in which the mass transfer rate is the dominant stage, and the heat of reaction is removed by the rapid movement of the reactants to suppress side reactions. Therefore, high temperature and high pressure water oxidation techniques are known to be useful for the complete oxidation of hardly decomposable materials.

Since the method according to the present invention uses water such as high temperature and high pressure water as a reaction medium, it is possible to produce terephthalic acid more effectively, has no toxicity to the human body, does not use expensive catalysts, and uses bromine catalysts. This does not have the advantage of reducing the corrosion rate of the device.

As described above, the present invention uses an excess of high temperature and high pressure water in a temperature range of 240 to 400 ℃ and a pressure range of 220 to 300 bar as a reaction medium and oxidizes paraxylene without using any catalyst to produce terephthalic acid. It is an object of the present invention to provide a method for synthesizing terephthalic acid, which is less toxic to the human body than the conventional terephthalic acid synthesis method, the corrosion rate of the device is reduced, and more economically and safely.

The present invention uses a high temperature and high pressure water in a temperature range of 240 to 400 ℃ and a pressure range of 220 to 300 bar as a reaction medium, does not use a catalyst, using hydrogen peroxide or oxygen as an oxidizing agent (para-xylene) The present invention relates to a method for synthesizing terephthalic acid by partial oxidation reaction. That is, the terephthalic acid synthesis method of the present invention, unlike the conventional terephthalic acid production process, using a high temperature and high pressure water as a reaction medium, and using a hydrogen peroxide or oxygen as an oxidizing agent to oxidize paraxylene.

This will be described in more detail as follows.

In the present invention, in order to oxidize paraxylene without using a catalyst, an excessively high temperature and high pressure water in a temperature range of 240 to 400 ° C. and a pressure range of 220 to 300 bar is used as a reaction medium. The critical point of water is 374 ° C., 221 bar. The high temperature high pressure water at the temperature and pressure above the critical point of the water is called supercritical water, and the high temperature high pressure water at the temperature and pressure below the critical point of the water is called the subcritical water. In the process of the present invention, the reaction is preferably carried out at a temperature of 240 to 400 ° C. and a pressure of 220 to 300 bar. In addition, hydrogen peroxide or oxygen is used as the oxidizing agent supplied to the reaction system, and the amount of the peroxide used is preferably in the range of 1 to 30 moles, more preferably 4 to 15 moles in the case of hydrogen peroxide, per mole of paraxylene. It is preferably in the range of 1 to 15 moles. Condition ranges such as temperature, pressure, and oxidant injection amount were determined through experiments varying them.

The present invention is also effective in both batch and continuous processes.

First, the batch process of FIG. 1 according to the present invention is described as follows:

After placing a certain amount of paraxylene contained in the paraxylene storage tank A11 into the reactor A4, pressurizing it with a pump A1, raising the desired temperature with a preheater A2, and then heating the high temperature and high pressure water as a reaction medium in the reactor A4. Put a certain amount. The reactor A4 is heated with a heating jacket installed outside the reactor A4 to raise the reactor temperature to a desired temperature. Then, pressurize with pump A1 and raise to desired temperature with preheater A2, add a certain amount of hydrogen peroxide or oxygen as oxidant into reactor A4, and then add water with pump A1 until the desired pressure is reached. Supply. The sample is taken through the sampling loop A5 every time a certain time passes while the mixer attached to the reactor A4 is operated. The collected sample is moved to a sampler A6 and separated into a gas and a liquid, and then the amount and composition of each sample are analyzed. At this time, when the oxidation reaction proceeds rapidly and the pressure of the reactor A4 rises sharply, the safety rupture plate A3 installed for safety ruptures.

Next, the continuous process of FIG. 2 according to the present invention is described as follows:

Into the reactor (A4), a high temperature, high pressure water, which is a reaction medium, is heated to a constant temperature by an external heating jacket, and the stirrer is operated. Water, hydrogen peroxide and paraxylene already mixed in a constant composition are pressurized by the pump A1, heated up to a desired temperature by the preheater A2, and then injected into the reactor A4 at a constant flow rate. At this time, when the oxidation reaction rate is rapidly increased and the pressure of the reactor A4 rises rapidly, the safety rupture plate A3 installed for safety ruptures. After moving the fluid through the reactor to the primary storage tank (A8), in order to prevent clogging of the device by precipitation of terephthalic acid solid at room temperature in the reaction product, methanol, hydroxide supplied as a solvent from the pump (A1) Mix with aqueous sodium solution, ammonia water and the like. Lower the temperature of the fluid using a cooler (A9), depressurize to atmospheric pressure using a pressure control valve (A7), move to a sampler (A6) to separate the gas and liquid, and then analyze the amount and composition of the sample, respectively. do.

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

<Example 1>

Terephthalic acid was prepared by reacting paraxylene with hydrogen peroxide using an excess of high temperature and high pressure water as a reaction medium in a reactor (volume 1391 ml) of a batch device as shown in FIG. 1. First, 5.0 g of para-xylene, 52.5 g of hydrogen peroxide and 1000 g of water are added thereto, and heated using a heating jacket to maintain the reaction temperature at 240 ° C. with a temperature controller. Kept constant.

The partial oxidation of paraxylene was mostly terminated within 20 minutes after the start of the reaction, but the reaction time was set to 120 minutes to induce sufficient reaction between the reactants.

When the sample is taken after the desired reaction time has elapsed, an oxidation reaction of the reaction product may occur. Therefore, it is necessary to cool it as soon as possible. In order to suppress unnecessary reaction thereafter, a separate sampler A6 is installed. , The reactants were moved to the sampler A6 by the pressure of the reactor itself. At this time, since the sampler A6 may be ruptured due to the high pressure of the reactor, a sampling loop A5 having high pressure valves connected to the sampler A6 was installed. In order to reduce the occurrence of unnecessary reactions after partial oxidation and the risk of sampler rupture, the pressure and temperature of the reactor in the sampling loop were lowered to ambient and near room temperature.

Liquid and gaseous samples obtained after sampling were analyzed in the same manner as in Table 1.

Analytical Substance Analyzer Analysis item Liquid Liquid Chromatography Terephthalic Acid and Organic Impurities * weather Vapor phase chromatography Carbon monoxide, carbon dioxide

Organic impurities: Organic impurities that can be produced during the oxidation of paraxylene, such as paratolualdehyde, para-toluic acid, 4-carboxybenzaldehyde, and the like.

The selectivity of the resulting terephthalic acid (amount of terephthalic acid produced (g) / amount of total product (g) x 100) was found to be 24.9%.

<Example 2>

Except that the reaction temperature was 300 ℃, in the same manner as in Example 1 without using a catalyst, paraxylene was partially oxidized batchwise to prepare terephthalic acid. The selectivity of the resulting terephthalic acid was 29.0%.

<Example 3>

Terephthalic acid was prepared by partially oxidizing paraxylene batchwise without using a catalyst in the same manner as in Example 1, except that the reaction temperature was 350 ° C. The selectivity of the resulting terephthalic acid was found to be 1.9%.

<Example 4>

Except that the reaction temperature was 374 ℃, in the same manner as in Example 1 without using a catalyst, paraxylene was partially oxidized batchwise to prepare terephthalic acid. The selectivity of the resulting terephthalic acid was 1.2%.

<Example 5>

Terephthalic acid was prepared by partially oxidizing paraxylene batchwise without using a catalyst in the same manner as in Example 1, except that the reaction temperature was 400 ° C. The selectivity of the resulting terephthalic acid was 4.6%.

Table 2 shows the conditions and results of the partial oxidation reaction of paraxylene using a batch device performed as in Examples 1 to 5.

Classification (unit) Example 1 Example 2 Example 3 Example 4 Example 5 Reaction temperature (℃) 240 300 350 374 400 Reaction pressure (bar) 220 220 220 220 220 Oxidizer input (molar ratio) 10.5 10.5 10.5 10.5 10.5 Terephthalic Acid (Selectivity,%) 24.9 29 1.9 1.2 4.6

Molar ratio = hydrogen peroxide mole / paraxylene mole

<Example 6>

Terephthalic acid was continuously prepared by oxidizing paraxylene with hydrogen peroxide in a medium of high temperature and high pressure water using the continuous reactor of FIG. 2. The reactor was heated to a heating jacket and maintained at 300 ° C., and the reaction pressure was adjusted to 220 bar through a pressure control valve installed at the rear of the cooler.

In this experiment, paraxylene was introduced into the reactor at a flow rate of 0.16 g / min, an aqueous solution of 2.55 wt.% Hydrogen peroxide as an oxidant was introduced into the reactor at a constant flow rate of 15.7 g / min by a pump, and the added paraxylene and hydrogen peroxide solutions were The gaseous state was passed through the preheater to be fed to the reactor. At this time, hydrogen peroxide was used so that the molar ratio "hydrogen peroxide (mole) / paraxylene (mole)" with respect to para xylene became 10.5. In addition, a reaction product containing terephthalic acid produced as a result of the reaction is transferred to a primary storage tank, and a solvent (methanol, sodium hydroxide or ammonia water) is introduced at the inlet of the cooler in order to prevent the blockage of the outlet pipe due to precipitation of the solid product thereafter. The solid product was dissolved in the liquid phase, and then discharged to the sampler through the pressure control valve.

The selectivity of the resulting terephthalic acid was 39.1%.

<Example 7>

Terephthalic acid was prepared by partially oxidizing paraxylene without using a catalyst in the same manner as in Example 6 except that the temperature was 400 ° C. The selectivity of the resulting terephthalic acid was 4.2%.

Table 3 shows the conditions and results of the continuous paraxylene partial oxidation reaction carried out in Examples 6 and 7 above.

Classification (unit) Example 6 Example 7 Reaction temperature (℃) 300 400 Reaction pressure (bar) 220 220 Oxidizer input (molar ratio) 10.5 10.5 Terephthalic acid (selectivity,%) 39.1 4.2

Molar ratio = hydrogen peroxide (mole) / paraxylene (mole)

Selectivity = amount of terephthalic acid produced (g) / total amount of product produced (g) × 100 (%)

Thus, oxidizing paraxylene under the condition of high temperature and high pressure water does not require a catalyst and can synthesize terephthalic acid even under mild conditions where no solvent such as acetic acid is used.

When preparing terephthalic acid by the method according to the invention, by using an excess of high temperature and high pressure water in the temperature range of 240 to 400 ℃ and the pressure range of 220 to 300 bar as a reaction medium without using a catalyst, Compared with the synthesis method under and acetic acid medium, problems such as the corrosion of the device due to the catalyst and the risk of exposure to toxic substances are eliminated, and the terephthalic acid can be produced more economically.

Claims (8)

In the method for producing terephthalic acid by oxidizing paraxylene, without using a catalyst, using an excess of high temperature and high pressure water in the temperature range of 240 to 400 ℃ and pressure range of 220 to 300 bar as a reaction medium, and as an oxidizing agent A method for synthesizing terephthalic acid, using hydrogen peroxide or oxygen, and reacting it with paraxylene to partially oxidize it. delete delete The method for synthesizing terephthalic acid according to claim 1, wherein 1 to 30 mol of hydrogen peroxide is used with respect to 1 mol of paraxylene as the oxidizing agent. The method for synthesizing terephthalic acid according to claim 1, wherein 1 to 15 moles of oxygen per 1 mole of paraxylene is used as the oxidizing agent. delete delete delete

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