KR101144887B1 - Purification method for iso-phthalic acid - Google Patents

Abstract

The present invention relates to a process for purifying isophthalic acid comprising the step of extracting crude isophthalic acid in the presence of a solvent comprising water. According to the purification method of isophthalic acid, isophthalic acid having high purity and excellent commercial availability can be obtained, and the economical efficiency of the process can be improved by applying an inexpensive solvent and minimizing the loss of solvent in the purification process.

Isophthalic acid, purification, loss rate

Description

Purification method of isophthalic acid {PURIFICATION METHOD FOR ISO-PHTHALIC ACID}

The present invention relates to a method for purifying isophthalic acid, and more particularly, to obtain isophthalic acid having high purity and excellent commercial availability, and to applying economical solvents and minimizing the loss of solvents in the purification process. It relates to a method for purifying isophthalic acid that can be increased.

Benzenedicarboxylic acid is a useful compound used as a raw material for a wide range of products, and is mainly produced by oxidizing aromatic compounds such as dimethylbenzene (xylene) using a metal catalyst under high temperature and high pressure conditions. Examples of such benzenedicarboxylic acid include terephthalic acid produced by oxidizing paraxylene, isophthalic acid produced by oxidizing meta-xylene, and phthalic anhydride produced by oxidizing orthoxylene.

Among these, isophthalic acid is used as a raw material of polyester resin or PET resin, or as a waterproof coating or plastic additive. The isophthalic acid has excellent physical properties such as heat resistance, abrasion resistance, insulation and mechanical strength. Its use is expanding to various applications such as building materials or mechanical parts.

According to the known production method, isophthalic acid containing a large amount of impurities is obtained. In order to increase the purity of the isophthalic acid, a method of performing a hydrogenation reduction reaction under a transition metal catalyst is used. However, if the reduction reaction is applied, there is a problem in that the production cost of isophthalic acid is increased because excessive costs are required for the operation of raw materials, catalysts and processes.

Accordingly, in order to remove impurities of isophthalic acid without an expensive reduction process, a purification method using an organic solvent as an extraction solvent has been proposed. However, most of the organic solvents used as extraction solvents are expensive products, and the extraction process to which they are applied must be operated at high temperature, and more than 30% of them are lost due to evaporation or the like in the purification process of isophthalic acid. Requires input Accordingly, the purification method using the organic solvent also requires an excessive cost for the extraction solvent and the operation of the process to increase the production cost of isophthalic acid.

The present invention is to provide a method for purifying isophthalic acid which can obtain isophthalic acid having high purity and excellent commercial availability, and can improve the economics of the process by applying an inexpensive solvent and minimizing the loss of the solvent in the purification process. .

The present invention provides a process for purifying isophthalic acid comprising the step of extracting crude isophthalic acid in the presence of a solvent comprising water.

Hereinafter, a method for purifying isophthalic acid according to a specific embodiment of the present invention will be described in detail.

According to one embodiment of the invention, there can be provided a method for purifying isophthalic acid comprising the step of extracting crude isophthalic acid in the presence of a solvent comprising water.

The inventors have confirmed through experiments that extraction of crude isophthalic acid in the presence of a solvent containing water can not only purify isophthalic acid with high purity, but also minimize the loss of solvent in the purification process. The invention has been completed. Accordingly, the purified isophthalic acid in one embodiment of the invention is suitable for commercial use because it contains a low content of impurities, hardly occurs in the ester bond inhibition when used as a real product. In addition, applying the purification method of one embodiment of the invention, while using an inexpensive water-soluble solvent, the amount of solvent lost during the purification process is not necessary because additional input is not necessary, resulting in lower production cost of the isophthalic acid final product have.

The crude isophthalic acid refers to low purity isophthalic acid containing 0.1 wt% or more of impurities. Such impurities may include m-toluic acid, benzoic acid, 3-carboxybenzaldehyde or compounds thereof, and the like.

In one embodiment of the invention, the solvent mainly serves to dissolve the impurities contained in the crude isophthalic acid, in the extraction step impurities such as meta toluic acid, benzoic acid or 3-carboxybenzaldehyde contained in the isophthalic acid solvent And isophthalic acid remains in the solid phase. Accordingly, it is possible to obtain a high purity isophthalic acid from which impurities are removed through a separation and drying process that can be applied after the extraction step is completed.

On the other hand, in one embodiment of the invention, because the inexpensive water-soluble solvent is used, it is possible to lower the production cost of the isophthalic acid final product. In addition, conventionally known organic extraction solvents exhibit a high loss rate due to evaporation or the like during the purification process, whereas the solvent containing water has no substantial loss, and thus the process operation is possible without replenishing the extraction solvent. The production cost of the product can be lowered.

The ratio of the isophthalic acid and the solvent may be 1:20 to 1: 2, preferably 1:10 to 1: 5. If the ratio of the solvent to the isophthalic acid is too small, the impurities cannot be sufficiently dissolved, on the contrary, if the solvent is used in excess, the process operation and the cost for the solvent are more than necessary, which is not preferable in terms of economic efficiency of the process. not.

On the other hand, the solvent may further comprise a linear saturated carboxylic acid having 1 to 6 carbon atoms . Even when the solvent further includes linear saturated carboxylic acid having 1 to 6 carbon atoms, the loss of the solvent is very small in the purification process of isophthalic acid, and the extraction efficiency can be properly maintained.

Since an oxidation reaction solvent such as linear saturated carboxylic acid may be applied in the preparation step of the crude isophthalic acid, the crude isophthalic acid may contain a trace amount of the oxidation reaction solvent. Therefore, when the crude isophthalic acid containing the oxidation reaction solvent is purified using a solvent further comprising the linear saturated carboxylic acid having 1 to 6 carbon atoms, the oxidation reaction solvent may be contained in the crude isophthalic acid. Since no complicated drying step is required to remove, the production cost of the final product can be lowered and the continuous process of isophthalic acid production and purification can be efficiently constructed.

The linear saturated carboxylic acid having 1 to 6 carbon atoms (Carboxylic acid) includes formic acid, acetic acid, propionic acid, butyric acid, butyric acid (valeric acid), caproic acid (caproic acid) or mixtures thereof, among them Preference is given to using acetic acid.

The solvent is at least 50 wt%, preferably at least 90 wt% water; And a residual amount of linear saturated carboxylic acids having 1 to 6 carbon atoms. The higher the content of water in the solvent, the higher the extraction efficiency, and the lower the content of impurities contained in the final product isophthalic acid. When the content of water in the aqueous solution is less than 50 wt%, the amount of impurities to be extracted is small and the purity and commerciality of isophthalic acid is lowered.

On the other hand, the step of extracting the crude isophthalic acid may be made at 17 to 40 ℃, preferably 20 to 30 ℃. The higher the temperature in the extraction step can implement a high purification efficiency even with a small amount of solvent, but at too high a temperature it is not preferable because the solvent is evaporated to require the addition of additional solvent. In addition, when the temperature in the extraction step is too low, the linear saturated carboxylic acid in the solvent may be solidified, thereby reducing the purification efficiency of isophthalic acid. In particular, when acetic acid is included in the solvent, the solvent may solidify at a reaction temperature of less than 17 ° C, which is not preferable.

In addition, the step of extracting the crude isophthalic acid may be performed for 10 minutes to 1 hour. If the extraction time is too short, the solvent cannot dissolve the impurities sufficiently, and if it is too long, the residence time of the injected compounds in the process may be increased more than necessary to reduce the production yield of the final product.

In addition, extracting the crude isophthalic acid may include stirring the crude isophthalic acid on the solvent at a speed of 100 to 2000 rpm. When the stirring speed is too low, agitation does not occur properly between the solvent and isophthalic acid, and mass transfer between the impurity and the solvent does not occur properly, so that an effective purification cannot occur. Conversely, when the stirring speed is too high, the reaction temperature may be too high to cause evaporation of the solvent, and thus the solvent may be lost in excess.

On the other hand, in one embodiment of the invention, the ratio of the solvent lost in the step of extracting the crude isophthalic acid may be 1% or less, preferably 0.1% or less, even more preferably 0.01% or less. The amount of the solvent lost is less than 1%, the amount of the solvent separated by filtration at the completion of the purification process is very small compared to the amount of the solvent initially added in the extraction of crude isophthalic acid, the extraction step This means that no solvent is lost substantially. As shown in the experimental example described later, when applying a water or optionally a solvent containing the linear saturated carboxylic acid having 1 to 6 carbon atoms, the amount of the solvent lost due to evaporation or the like during the extraction process was found to be very small. Accordingly, in one embodiment of the invention, since it is not necessary to add an additional solvent to preserve the amount of solvent lost, the process can be simplified and the production cost of the isophthalic acid final product can be lowered.

Meanwhile, in one embodiment of the invention, m-toluic acid, benzoic acid or 3-carboxybenzaldehyde may be present in isophthalic acid after the extraction step at a concentration of 300 ppm or less, respectively. When the concentrations of m-toluic acid, benzoic acid and 3-carboxybenzaldehyde in isophthalic acid are each 300 ppm or less, ester binding inhibition does not appear when isophthalic acid is used as a real product, and thus high commerciality can be exhibited. As confirmed in the examples below, only a small amount of impurities are present in the isophthalic acid purified according to the method for purifying isophthalic acid according to one embodiment of the invention, and thus, the purified isophthalic acid has high purity and excellent commercial availability. Can be represented.

According to the present invention, isophthalic acid having purity and excellent commercial availability can be obtained, and a method for purifying isophthalic acid can be provided that can increase the economics of the process by applying an inexpensive solvent and minimizing the loss of the solvent in the purification process. have.

The invention is explained in more detail in the following examples. However, the following examples are merely to illustrate the invention, but the content of the present invention is not limited by the following examples.

< Example  1 to 3: Isophthalic acid  Tablet>

A crude isophthalic acid and a solvent were added to a 450 ml titanium reactor equipped with a stirrer at a volume ratio of 1: 9, and the reaction was performed for 30 minutes at atmospheric pressure under a reaction temperature of 23 ± 2 ° C. and a stirring speed of 500 rpm.

At this time, the concentration of the initial impurity contained in the crude isophthalic acid was 0.05 wt% of 3-carboxybenzaldehyde, 0.03 wt% of m- Toluic acid, and 0.13 wt% of benzoic acid. Table 1 shows.

After completion of the reaction, the reaction product was filtered and separated into a liquid phase and a solid phase. Then, the solid phase was dried in vacuo to obtain isophthalic acid of high purity.

Table 1 below describes the extraction rate of the total impurities in the purification process and the residual amount of impurities in isophthalic acid after extraction.

At this time, the residual amount of impurities after extraction was measured by high performance liquid chromatography (HPLC 1200 series, Agilent Technologies, Inc.), and the extraction rate of the total impurities was measured by calculating the ratio between the impurity concentration in crude isophthalic acid and the residual amount of impurities after extraction. .

[Table 1] Purification result of isophthalic acid

Solvent Composition (%) Total Impurity Extraction Rate (%) Residual amount of impurities after extraction (ppm) water Acetic acid m-tol BA 3-CBA Example 1 100 0 80.5 60 114 228 Example 2 95 5 75.0 78 189 249 Example 3 60 40 71.0 106 238 255

3-CBA (3-carboxybenzaldehyde), m-tol (m-toluic acid, m- Toluic acid), BA (benzoic acid)

It can be confirmed in Table 1 that the isophthalic acid purified in Examples 1 to 3 contained less than 300 ppm of m-toluic acid, benzoic acid and 3-carboxybenzaldehyde, respectively. Accordingly, the isophthalic acid obtained in the examples has low purity impurities and has high purity and good commercial availability.

And, as shown in Table 1, in Examples 1 to 3 it was confirmed that the high purity isophthalic acid can be prepared by removing about 70% or more of the initial impurities contained in the low-purity isophthalic acid.

< Experimental Example : Extraction solvent Loss rate  Compare>

In always Examples 1 to 3 and the comparative examples below, the loss ratio of the solvent was calculated by measuring the amount added at the beginning of the extraction reaction and the amount of solvent separated through filtration after the reaction.

In addition, the loss ratios of the solvents in Examples 1 to 3 and Comparative Examples measured above are shown in Table 2 below .

Comparative example

Example 1 and except that low-purity isophthalic acid and N-methyl pyrrolidone was added in a volume ratio of 1: 2, and the reaction was carried out at atmospheric pressure for 30 minutes at a reaction temperature of 23 ± 2 ° C. and a stirring speed of 500 rpm. In the same way, isophthalic acid was purified.

TABLE 2 Loss ratio of solvents in Examples 1 to 3 and Comparative Examples

Isophthalic acid loss rate (%) Example 1 0 Example 2 0 Example 3 0 Comparative example 24.9

As shown in Table 2, in the comparative example, while the loss rate of the solvent reached 25%, it was confirmed that the solvent loss rate was 1% or less as a result of purifying isophthalic acid in the above example. Accordingly, in the case of applying the purification method of the embodiment, since there is substantially no loss of solvent, high purity isophthalic acid can be obtained by a simple process without requiring a configuration or step for additionally adding a solvent depending on the loss of the solvent. You can get it.

Claims (14)

At least 50 wt% water; And in the presence of a solvent comprising a residual amount of said linear saturated carboxylic acid having 1 to 6 carbon atoms, extracting crude isophthalic acid comprising at least 0.1 wt% of at least one impurity selected from the group consisting of m-toluic acid, benzoic acid and 3-carboxybenzaldehyde, at 17-40 ° C., A method for purifying isophthalic acid, wherein the ratio of the solvent lost in the step of extracting the crude isophthalic acid is 1% or less. delete delete The method of claim 1, The isophthalic acid: the solvent is 1:20 to 1: 2 purification method of isophthalic acid. delete The method of claim 1, The carboxylic acid having 1 to 6 linear carbon atoms is a method for purifying isophthalic acid including at least one compound selected from the group consisting of formic acid, acetic acid, propionic acid, butyric acid, valeric acid, and caproic acid. . delete delete The method of claim 1, Extracting the crude isophthalic acid is a method for purifying isophthalic acid is performed for 10 minutes to 1 hour. The method of claim 1, Extracting the crude isophthalic acid comprises the step of stirring the crude isophthalic acid on the solvent at a rate of 100 to 2000rpm. delete The method of claim 1, After the extraction step, isophthalic acid purification method of m-toluic acid concentration is less than 300ppm in isophthalic acid. The method of claim 1, After the extraction step, the method for purifying isophthalic acid having a concentration of benzoic acid in isophthalic acid less than 300ppm. The method of claim 1, After the extraction step, a method for purifying isophthalic acid having a concentration of 3-carboxybenzaldehyde in isophthalic acid is 300 ppm or less.