METHOD FOR PRODUCING 1,4-CYCLOHEXANE DICARBOXYLIC ACID

Abstract

This invention relates to a method for preparing 1,4-cyclohexane dicarboxylic acid (CHDA). More specifically, this invention relates to a method for preparing 1,4-cyclohexane dicarboxylic acid having a high rate of trans isomers, without an isomerization reaction step.

Claims

1. A method for preparing 1,4-cyclohexane dicarboxylic acid comprising steps of: supplying a reaction solution comprising terephthalic acid, a hydrogenation catalyst, and water to a reactor equipped with a stirrer; supplying hydrogen gas to the reactor in which the reaction solution has been introduced; and stirring the stirrer of the reactor to conduct a hydrogenation reaction, thus preparing 1,4-cyclohexane dicarboxylic acid (CHDA), wherein the terephthalic acid is included in the content of 5 to 25 wt %, based on the total amount of terephthalic acid and water.

2. The method for preparing 1,4-cyclohexane dicarboxylic acid according to claim 1, wherein the terephthalic acid is included in the content of 12 to 22 wt %, based on the total amount of terephthalic acid and water.

3. The method for preparing 1,4-cyclohexane dicarboxylic acid according to claim 1, wherein the step of conducting a hydrogenation reaction is conducted at a temperature of 230 to 300° C.

4. The method for preparing 1, 4-cyclohexane dicarboxylic acid according to claim 1, wherein the hydrogen gas is supplied at a pressure of 50 to 220 bar.

5. The method for preparing 1, 4-cyclohexane dicarboxylic acid according to claim 1, wherein the hydrogenation catalyst comprises one or more metals selected from the group consisting of palladium (Pd), rhodium (Rh), ruthenium (Ru), and platinum (Pt).

6. The method for preparing 1,4-cyclohexane dicarboxylic acid according to claim 1, wherein the stirring is conducted such that the surface area per unit volume of hydrogen gas bubbles becomes 15 m.sup.2/m.sup.3 or more.

7. The method for preparing 1,4-cyclohexane dicarboxylic acid according to claim 1, wherein the 1,4-cyclohexane dicarboxylic acid comprises 60 wt % or more of trans isomers.

8. A composition comprising 1,4-cyclohexane dicarboxylic acid prepared by the method of claim 1.

Description

EXAMPLE

Example 1

[0078] A reactor equipped with a gas-induced type stirrer was prepared.

[0079] In the reactor, 286 g of terephthalic acid (TPA), 92 g of hydrogenation catalyst Pd/C (comprising 5 wt % of Pd, based on the carrier carbon), and 2,100 g of solvent distilled water were introduced as reactants, and the inner atmosphere of the reactor was replaced with nitrogen, and then, the temperature of the mixed solution was raised to 250° C. while stirring at 50 rpm.

[0080] After the temperature of the mixed solution reached 250° C., in order to dissolve TPA, it was stirred for 30 minutes while maintaining the temperature. And then, the stirring speed was increased, and while supplying hydrogen in the reaction solution such that the internal pressure of the reactor is maintained at 120 bar, and surface area per unit volume of hydrogen gas is maintained at 300 to 500 m.sup.2/m.sup.3, a hydrogen reaction was conducted for 1 hour.

Example 2

[0081] The same procedure as the step 1 of Example 1 was conducted, except that 378 g of terephthalic acid (TPA) was used in Example 1.

Example 3

[0082] The same procedure as the step 1 of Example 1 was conducted, except that 492 g of terephthalic acid (TPA) was used in Example 1.

Example 4

[0083] The same procedure as the step 1 of Example 1 was conducted, except that 592 g of terephthalic acid (TPA) was used in Example 1.

Comparative Example 1

[0084] As a reactor, a batch reactor capable of withstanding at 300° C., 150 bar was prepared. Into the batch reactor, 1.5 g of terephthalic acid (TPA), lg of 5 wt % hydrogenation catalyst Pd/C, and 250 g of distilled water solvent were introduced as reactants, and the inner atmosphere of the reactor was replaced with nitrogen, and then, the temperature of the mixed solution was raised to 250° C. while stirring at 50 rpm.

[0085] After the temperature of the mixed solution reached 250° C., in order to dissolve TPA, it was stirred for 30 minutes while maintaining the temperature. And then, hydrogen was filled to the hydrogen pressure of 120 bar in the reactor, and the stirring speed was increased to 800 rpm, and a hydrogenation reaction was conducted for 1 hour while stirring.

Comparative Example 2

[0086] It was attempted to conduct a hydrogenation reaction using 800 g of terephthalic acid (TPA) in Example 1, but terephthalic acid was not dissolved in the reaction solution and remained as solid, and thus, a hydrogenation reaction was not properly progressed, and the inner wall and stirrer of the reactor were stained, and thus, the reaction was not properly progressed.

[0087] For Examples and Comparative Examples, CHDA yield, conversion, and selectivity were calculated as follows, and shown in the following Table 1.

Conversion=mole number of reacted TPA/mole number of supplied TPA

Selectivity=mole number of produced CHDA/mole number of reacted TPA

Yield=conversion×selectivity

[0088] And, trans CHDA content in the product was analyzed with gas chromatography (GC, column: HP-5, detector: FID).

TABLE-US-00001 TABLE 1 Trans CHDA content in TPA product TPA CHDA CHDA content* CHDA conversion selectivity yield (wt %) (wt %) (%) (%) (%) Example 1 12 66 99.9 94.5 94.4 Example 2 18 67 99.9 94.4 94.3 Example 3 19 69 99.9 95 94.9 Example 4 22 76 99.9 95 94.9 Comparative 0.6 38 99.9 97 96.9 Example 1 *TPA content means the content (wt %), based on the total amount of terephthalic acid and water.

[0089] Referring to Table 1, it was confirmed that in the case of Examples 1 to 4 comprising a certain concentration of terephthalic acid, in the hydrogenation reaction product CHDA, trans CHDA content was higher than 66 wt %, and thus, very high content of trans isomers were produced

[0090] However, in the case of Comparative Example 1 comprising 0.6 wt % of terephthalic acid, in the product CHDA, only 38 wt % of trans CHDA was included, and thus, sufficient trans isomers could not be produced.