JP2003128620A - Method for producing trans-1,4-cyclohexanedicarboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing colorless t-CHDA at a high isomerization ratio by simple operation. SOLUTION: The method for producing trans-1,4-cyclohexanedicarboxylic acid is characterized by obtaining the trans-1,4-cyclohexanedicarboxylic acid by isomerizing cis-1,4-cyclohexanedicarboxylic acid by heating it under an atmosphere of oxygen of 2 vol.% or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing trans-1,4-cyclohexanedicarboxylic acid (hereinafter referred to as "t-CHDA").

[0002]

2. Description of the Related Art 1,4-Cyclohexanedicarboxylic acid (hereinafter referred to as "CHDA"), especially t-CHDA
Is useful as a raw material for the production of resins and fibers having excellent heat resistance, weather resistance and physical strength. Known methods for producing CHDA include a method of directly hydrogenating terephthalic acid (hereinafter referred to as “TPA”), a method of hydrogenating a TPA alkali metal salt, and a method of hydrogenating a TPA ester. . However, the t-CHDA content in CHDA obtained by these methods is 20 to 40.
%, And a method for efficiently producing t-CHDA is desired.

For this reason, cis-1,4-cyclohexanedicarboxylic acid (hereinafter referred to as "c-CHDA") present together with t-CHDA in CHDA is isomerized to obtain t-.
Various methods for obtaining CHDA have been studied. Examples of the isomerization method include JP-B-39-27244, JP-A-49-81349, JP-A-49-82648, JP-A-58-24540, and JP-A-58-58.
The method described in JP-A-150539 is mentioned.

However, all of these methods have problems that the operation is complicated, the isomerization rate is low, and only colored t-CHDA is obtained.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides a simple operation with a high isomerization rate and uncolored t-CHDA.
It is an object to provide a manufacturing method of

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies on the above problems, and as a result, heated crude CHDA in an atmosphere of a gas having a specific oxygen concentration to convert c-CHDA to t-C.
The present invention has been achieved by knowing that the above problems can be solved by isomerizing HDA. That is, the gist of the present invention is to add cis-1,4-cyclohexanedicarboxylic acid to
A method for producing trans-1,4-cyclohexanedicarboxylic acid, which comprises heating in a gas atmosphere having an oxygen concentration of 2% by volume or less to isomerize into trans-1,4-cyclohexanedicarboxylic acid.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The contents of the present invention will be described in detail below. The crude CHDA used in the production method of the present invention includes:
Any one may be used as long as it contains c-CHDA. For example, TPA, TPA alkali metal salt or TPA
The thing obtained through the process of hydrogenating an ester is mentioned. Of these, crude C obtained by directly hydrogenating TPA
It is preferred to use HDA. Also, from crude CHDA
It is also possible to use c-CHDA after separating -CHDA.

The crude CHDA may contain a reaction solvent for hydrogenation reaction and the like, but the smaller the content, the more preferable. Therefore, it is preferable to use one having a residual solvent content of 25% by weight or less, preferably 15% by weight or less. In the present invention, the isomerization reaction is carried out in an atmosphere of gas having an oxygen concentration of 2% by volume or less. The main component of such gas is CHD
Any substance can be used as long as it does not react with A to change its quality or produce a decomposition product.
For example, carbon dioxide, nitrogen, argon, steam and the like can be mentioned, and if desired, they can be mixed and used.

When the isomerization reaction is carried out in an atmosphere of a gas having an oxygen concentration of more than 2% by volume, the obtained t-CHDA is colored, but if it is 2% by volume or less, the risk of coloring is small. In addition, even with t-CHDA which is not colored visually, when this is dissolved in an aqueous potassium hydroxide solution and the ultraviolet transmittance thereof is measured, the ultraviolet transmittance becomes larger as the oxygen concentration in the atmosphere of the isomerization reaction becomes lower, It shows that the quality is good. Therefore, the isomerization reaction is preferably carried out in an atmosphere having an oxygen concentration of 1% by volume or less, particularly 0.5% by volume or less. However, when the oxygen concentration is reduced to 2 ppm by volume, the ultraviolet ray transmittance is remarkably increased, so it is not necessary to further reduce the oxygen concentration.

In order to isomerize c-CHDA to t-CHDA, heating at 180 to 310 ° C is sufficient. 18
0-280 degreeC, especially 190-280 degreeC are preferable. The pressure during heating can be set arbitrarily, but is usually 0.01 to 1MP.
is a. The time required for heating depends on the temperature, the desired isomerization rate, and the like. From the viewpoint of production efficiency, the heating time may be set to be within 10 hours. Within 5 hours,
Particularly preferably within 1 hour.

The heating may be carried out in either a batch system or a continuous system, but it is preferred to carry out the heating in consideration of production efficiency. Examples of the gas flow type heater used for the reaction include a rotary kiln, a shaft type stirring type heater, a kneader type heater, and a fluidized firing furnace.

[0012]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. The component ratio in the crude CHDA and the product was determined by liquid chromatography. Also, 1 g of the reaction product was dissolved in 10 mL of 2N aqueous potassium hydroxide solution to obtain 10 m
The transmittance when measured at a wavelength of 400 nm using an m-square cell was expressed as T-400.

Example 1 10 g of crude CHDA containing 37% by weight of c-CHDA was charged into a four-necked flask equipped with a gas introduction tube, a cooling tube and a stirrer, depressurized with a vacuum pump, and then 2 ppm by volume of oxygen was added.
Nitrogen gas containing was introduced up to normal pressure. After repeating this operation of reduced pressure-normal pressure 5 times, it was confirmed with an oxygen meter that the oxygen concentration in the flask was 2 ppm by volume. Then, nitrogen gas containing 2 ppm by volume of oxygen was passed through the gas introduction tube into the flask at a rate of 1 liter / hour and stirred while stirring at 250
The temperature was raised to 0 ° C. and the temperature was maintained for 1 hour to carry out an isomerization reaction. After cooling to room temperature, the reaction product in the flask was analyzed by liquid chromatography. The results are shown in Table 1.

Example 2 Nitrogen gas containing 2 ppm by volume of oxygen of Example 1 was mixed with oxygen 8
Example 1 except that nitrogen gas containing 00 ppm by volume was used.
An isomerization reaction was carried out in the same manner as in. The results are shown in Table 1. Example 3 Nitrogen gas containing 2 ppm by volume of oxygen of Example 1 was mixed with oxygen 4
An isomerization reaction was carried out in the same manner as in Example except that nitrogen gas containing 000 ppm by volume was used. The results are shown in Table 1.

Example 4 Nitrogen gas containing 2 ppm by volume of oxygen of Example 1 was replaced with oxygen 8
The isomerization reaction was performed in the same manner as in Example 1 except that nitrogen gas containing 500 ppm by volume was used. The results are shown in Table 1. Example 5 An isomerization reaction was carried out in the same manner as in Example 1 except that the nitrogen gas containing 2 ppm by volume of oxygen of Example 1 was replaced with the nitrogen gas containing 1.9% by volume of oxygen. The results are shown in Table 1.

Comparative Example 1 An isomerization reaction was carried out in the same manner as in Example 1 except that the nitrogen gas containing 2 ppm by volume of oxygen of Example 1 was replaced with the nitrogen gas containing 2.5% by volume of oxygen. The results are shown in Table 1. Comparative Example 2 The isomerization reaction was carried out in the same manner as in Example 1 except that the nitrogen gas containing 2 ppm by volume of oxygen of Example 1 was changed to air (21% by volume of oxygen). The results are shown in Table 1.

[0017]

[Table 1]

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hiroyoshi Endo             1000 Kamoshida-cho, Aoba-ku, Yokohama-shi, Kanagawa             Within Mitsubishi Chemical Corporation F-term (reference) 4H006 AA02 AB46 AC27 BB60 BC10                       BC13 BS20

Claims (4)

[Claims] 1. A cis-1,4-cyclohexanedicarboxylic acid is heated in a gas atmosphere having an oxygen concentration of 2% by volume or less to isomerize into trans-1,4-cyclohexanedicarboxylic acid. Process for producing trans-1,4-cyclohexanedicarboxylic acid. 2. A trans-1, characterized in that a crude 1,4-cyclohexanedicarboxylic acid obtained by hydrogenating terephthalic acid in a liquid phase is heated in an atmosphere of a gas having an oxygen concentration of 2% by volume or less. , 4-Cyclohexanedicarboxylic acid production method. 3. The heating according to claim 1, wherein the heating is carried out in an atmosphere of a gas having an oxygen concentration of 2% by volume to 2% by volume.
The manufacturing method described. 4. The manufacturing method according to claim 1, wherein the heating is performed at 180 to 310 ° C.