Method for preparing 1, 4-cyclohexanedicarboxylic acid

Abstract

The invention provides a method for preparing 1, 4-cyclohexanedicarboxylic acid. The method comprises the following steps: (1) mixing terephthalic acid and water, and heating to 240 DEG C or above to obtain a terephthalic acid solution; (2) the terephthalic acid solution obtained in the step (1) reacts with hydrogen under the action of a catalyst to generate 1, 4-cyclohexanedicarboxylic acid, the catalyst comprises an activated carbon carrier and precious metal loaded on the carrier, and the carrier is coconut shell activated carbon. The method for preparing 1, 4-cyclohexanedicarboxylic acid has the advantages of high raw material conversion rate and high reaction selectivity.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and specifically relates to a method for preparing 1,4-cyclohexanedicarboxylic acid. Background Art

[0002] 1,4-cyclohexanedicarboxylic acid (CHDA) can be used as a modified monomer for the production of polyester due to its own symmetry and the "chair and bridge" motion of the cyclohexane ring. In addition, CHDA can also be an intermediate for the production of 1,4-cyclohexanedimethanol (CHDM), which is an important industrial raw material for polyester production and is mainly used in the production of polyester fibers, with broad application prospects.

[0003] At present, among the methods for preparing CHDA, the most promising method is to use terephthalic acid (TPA) as a raw material for hydrogenation catalytic reaction. For example, U.S. Patent No. 2888484 proposed the use of palladium catalysts to hydrogenate terephthalic acid to prepare CHDA, but the reaction pressure in this method is too high (greater than 34MPa), the energy consumption is large, and it is difficult to implement. In order to solve the problem of low solubility of terephthalic acid in water, resulting in low conversion rate, Japan Towa Chemical Industry Co., Ltd. applied for a U.S. patent for the preparation process of 1,4-cyclohexanedicarboxylic acid in 1993, using ethanol and water as solvents. Although the patent increases the feed concentration of terephthalic acid solution, due to the introduction of ethanol in the system, there are more by-products, and subsequent separation is difficult. In addition, when terephthalic acid is hydrogenated to prepare 1,4-cyclohexanedicarboxylic acid, terephthalic acid is prone to decarboxylation, resulting in reduced reaction selectivity.

[0004] Therefore, it is still necessary to select suitable catalysts and preparation processes to reduce the energy consumption and improve the product selectivity when preparing 1,4-cyclohexanedicarboxylic acid by hydrogenation of terephthalic acid. Summary of the invention

[0005] In order to solve one of the above problems existing in the prior art, the present invention provides a method for preparing 1,4-cyclohexanedicarboxylic acid. By selecting a suitable catalyst and optimizing the preparation process, the feed concentration of the terephthalic acid solution is increased, so that the conversion rate of terephthalic acid and the yield of 1,4-cyclohexanedicarboxylic acid are greatly improved, and the obtained product terephthalic acid has high selectivity.

[0006] To achieve the above object, the present invention adopts the following technical solution:

[0007] A method for preparing 1,4-cyclohexanedicarboxylic acid comprises the following steps:

[0008] (1) mixing terephthalic acid and water and heating the mixture to above 240° C. to obtain a terephthalic acid solution;

[0009] (2) reacting the terephthalic acid solution obtained in step (1) with hydrogen in the presence of a catalyst to generate 1,4-cyclohexanedicarboxylic acid, wherein the catalyst comprises an activated carbon carrier and a precious metal supported on the carrier, and the carrier is coconut shell activated carbon.

[0010] The present invention can greatly increase the content of terephthalic acid in the raw material liquid and the feed concentration by dissolving terephthalic acid at a high temperature above 240°C, thereby greatly improving the conversion rate and utilization rate of the raw material.

[0011] The present invention selects coconut shell activated carbon as a noble metal carrier to prepare the catalyst, thereby improving the catalytic activity of the noble metal catalyst in the reaction of preparing 1,4-cyclohexanedicarboxylic acid by hydrogenating terephthalic acid and the selectivity of the product 1,4-cyclohexanedicarboxylic acid.

[0012] In the coconut shell activated carbon of the present invention, the content of metal elements such as K, Na, Ca, Mg, Al, and Fe needs to be controlled within a suitable range. If the content is too high, the activity and reaction selectivity of the catalyst will be reduced. Preferably, the sum of the contents of K and Na does not exceed 500ppm, more preferably does not exceed 400ppm. Preferably, the sum of the contents of Ca, Mg, and Al does not exceed 500ppm, preferably does not exceed 300ppm, and more preferably does not exceed 200ppm. Preferably, the content of Fe does not exceed 200ppm, preferably does not exceed 100ppm.

[0013] In the coconut shell activated carbon of the present invention, the content of non-metallic element S also needs to be controlled within a certain range. If the sulfur content is too high, it may cause catalyst poisoning, thereby reducing or even losing activity. Preferably, the S content does not exceed 250ppm, preferably not more than 150ppm.

[0014] In some embodiments, the noble metal includes at least one of Pd, Ru and Rh, preferably Pd.

[0015] In some embodiments, the specific surface area of ​​the coconut shell activated carbon is not less than 900 m 2 / g, preferably not less than 1000m 2 / g, more preferably 1000-1300m 2 / g.

[0016] In some embodiments, the particle size of the coconut shell activated carbon is less than 10 mesh, preferably 4-8 mesh.

[0017] In the present invention, the preparation method of the catalyst is not particularly limited, and the noble metal can be loaded on the coconut shell activated carbon carrier using conventional methods in the art. As an example, the preparation of the catalyst includes the following steps:

[0018] The coconut shell activated carbon is immersed in a solution containing the ions of the precious metal, heated, reduced using a reducing agent such as hydrazine hydrate, and the reduced product is washed and dried to obtain a coconut shell activated carbon catalyst loaded with precious metals. Preferably, the precious metal is palladium. Preferably, the heating temperature is 70-90°C. Preferably, the solvent used for the washing is deionized water. Preferably, the drying temperature is 100-120°C.

[0019] In some embodiments, the reaction in step (2) is carried out in a hydrogenation reactor, preferably in a trickle bed reactor. The present invention does not specifically limit the model of the trickle bed reactor, and the technical effect of the present invention can be achieved by selecting a conventional trickle bed reactor in the art. In some preferred embodiments, the inlet temperature of the hydrogenation reactor is 245-255°C. In some preferred embodiments, the inlet temperature of the hydrogenation reactor is 248-252°C. In some more preferred embodiments, the inlet temperature of the hydrogenation reactor is 250°C.

[0020] In order to further improve the utilization rate and conversion rate of terephthalic acid, in step (1), terephthalic acid is mixed with water and heated to 245-255°C, preferably 248-252°C, more preferably 250°C. Further preferably, the obtained terephthalic acid solution is kept warm at the dissolution temperature.

[0021] In the present invention, by selecting a suitable dissolution temperature, the mass fraction of terephthalic acid in the terephthalic acid solution as the raw material liquid can reach 5-12%, such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12% or any value therebetween. In some embodiments, the mass fraction of terephthalic acid in the terephthalic acid solution is 8-12%. In some embodiments, the mass fraction of terephthalic acid in the terephthalic acid solution is 8-10%.

[0022] Furthermore, in order to improve the conversion rate of terephthalic acid while preventing the decarboxylation reaction of terephthalic acid, reduce the formation of by-products, and improve the yield of 1,4-cyclohexanedicarboxylic acid, the reaction temperature in step (2) is preferably controlled at 245-255°C, for example, it can be 245°C, 248°C, 250°C, 252°C, 255°C or any value therebetween, preferably 248-252°C, more preferably 250°C.

[0023] In some embodiments, the reaction pressure is 6-10 MPa, for example, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa or any value therebetween, preferably 8-10 MPa.

[0024] In some embodiments, the method further comprises the steps of crystallizing the reacted solution and separating the solid from the liquid. In some specific embodiments, the temperature of the cooling crystallization is 15-60°C, for example, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C or any value therebetween, preferably 25-45°C.

[0025] In some specific embodiments, the liquid phase obtained after solid-liquid separation is returned to step (1), mixed with the terephthalic acid and water, and heated to 245-255° C. to obtain a raw material liquid containing terephthalic acid. Preferably, the liquid phase obtained after solid-liquid separation is first diluted with water to a 1,4-cyclohexanedicarboxylic acid content of 0-8wt%, preferably 3-5wt%, and then returned to step (1).

[0026] In addition, the present invention also provides an apparatus for implementing the above method, which includes a terephthalic acid (TPA) dissolution system, a hydrogenation reactor, a gas-liquid (G / L) separator, a crude product receiving tank, a crystallization tank and a solid-liquid (S / L) separator connected in sequence.

[0027] In the above-mentioned device of the present invention, the terephthalic acid (TPA) dissolution system is used to mix and dissolve terephthalic acid and water to obtain a terephthalic acid solution; the hydrogenation reactor is equipped with a catalyst, which is used to make hydrogen and the terephthalic acid solution from the dissolution system react under the action of the catalyst; the gas-liquid (G / L) separator is used to separate the gas and liquid generated after the reaction in the hydrogenation reactor; the crude product receiving tank is used to receive the 1,4-cyclohexanedicarboxylic acid crude solution separated from the gas-liquid (G / L) separator; the crystallization tank is used to cool and crystallize the 1,4-cyclohexanedicarboxylic acid crude solution; the solid-liquid (S / L) separator is used to separate the solid phase and liquid phase after cooling and crystallization in the crystallization tank.

[0028] In some embodiments, one end of the solid-liquid separator is also directly connected to the terephthalic acid dissolution system.

[0029] In some embodiments, the terephthalic acid (TPA) dissolution system is further provided with a heating device to fully dissolve the terephthalic acid in water to obtain a terephthalic acid solution of a desired concentration.

[0030] In the present invention, one end of the solid-liquid separator can also be directly connected to the terephthalic acid dissolution system, so that the liquid phase separated in the solid-liquid (S / L) separator can enter the terephthalic acid dissolution system and be recycled as a reaction raw material.

[0031] In some embodiments, the hydrogenation reactor is a trickle bed reactor.

[0032] In some embodiments, the solid-liquid separator is also connected to a pure 1,4-cyclohexanedicarboxylic acid receiving tank.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention selects coconut shell activated carbon with developed pores, large specific surface area, good adsorption performance and easy recycling as a carrier, controls the content of metal and non-metal contained in the activated carbon, and loads a catalyst prepared by precious metals. The catalyst exhibits excellent catalytic activity and high product selectivity in the reaction of preparing 1,4-cyclohexanedicarboxylic acid by hydrogenation of terephthalic acid.

[0035] 2. The present invention dissolves the raw material terephthalic acid at a relatively high temperature to obtain a terephthalic acid raw material liquid with a relatively high concentration, and the feed concentration is high, and the raw material conversion rate and utilization rate are high.

[0036] 3. The present invention also controls the temperature of the terephthalic acid hydrogenation reaction, especially when it is kept within the same range as the dissolution temperature of terephthalic acid, while ensuring the maximum conversion rate of the raw materials, it can also prevent the occurrence of side reactions and improve the yield and purity of the product 1,4-cyclohexanedicarboxylic acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are used to provide further understanding of the present application and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present application, but do not constitute a limitation to the present application.

[0038] Figure 1 This is a process flow chart for preparing 1,4-cyclohexanedicarboxylic acid in Example 1.

[0039] The reference numerals are as follows:

[0040] 1. Terephthalic acid dissolution system, 2. Hydrogenation reactor, 3. Gas-liquid separator, 4. Crude product receiving tank, 5. Crystallization tank, 6. Solid-liquid separator. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments and drawings. The specific embodiments described herein are only used to explain the present invention and are not intended to constitute any limitation to the present invention.

[0042] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0043] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight, unless the weight basis does not conform to the common understanding of those skilled in the art.

[0044] In order to improve the utilization and conversion rate of terephthalic acid raw materials and improve the selectivity of 1,4-cyclohexanedicarboxylic acid in the reaction product, the reaction of terephthalic acid solution and hydrogen in the present invention is preferably carried out in a hydrogenation reactor, wherein the inlet temperature of the hydrogenation reactor is preferably 245-255°C.

[0045] The process flow of preparing 1,4-cyclohexanedicarboxylic acid by hydrogenation of terephthalic acid in Example 1 of the present invention is as follows: Figure 1 As shown. The reaction raw materials terephthalic acid and water are mixed and dissolved in the terephthalic acid (TPA) dissolution system to obtain a terephthalic acid solution of the required concentration. The terephthalic acid solution from the dissolution system reacts with the hydrogen introduced in a hydrogenation reactor equipped with a catalyst. The materials after the reaction (including gas and reaction liquid) enter the gas-liquid (G / L) separator for gas-liquid separation, the gas is emptied, and the liquid is collected in the 1,4-cyclohexanedicarboxylic acid crude product receiving tank. The crude product then enters the crystallization tank for cooling and crystallization. The crystallized material enters the solid-liquid (S / L) separator for solid-liquid separation. The solid phase is the product (pure 1,4-cyclohexanedicarboxylic acid), and the liquid phase can enter the terephthalic acid dissolution system and be recycled as a reaction raw material.

[0046] The hydrogenation reactor used herein below is a trickle bed reactor.

[0047] The coconut shell activated carbon, wood activated carbon and coal activated carbon used in the following examples are all provided by Nanjing Mulinsen Activated Carbon Co., Ltd. The specific surface area of ​​the coconut shell activated carbon used in Examples 1-3 and Examples 6-7 is 1078 m 2 / g, particle size 4-8 mesh, the sum of K and Na content in activated carbon is 386ppm, the sum of Ca, Mg and Al is 145ppm, Fe content is 50ppm, and S content is 169ppm.

[0048] Unless otherwise specified, the reagents and instruments used in the following examples of the present invention can be obtained through commercial channels.

[0049] Example 1

[0050] Preparation of Pd / C catalyst: Take 100g coconut shell activated carbon as a carrier and 50g chloropalladic acid solution containing 1.5g palladium as an impregnation liquid, impregnate 100g coconut shell activated carbon therein and stir continuously. After the chloropalladic acid solution is completely absorbed by the coconut shell activated carbon, age it at 80°C for 4h. After aging, add the reducing agent hydrazine hydrate for reduction. After the reduction, wash the catalyst with deionized water until no chloride ions are detected. Finally, dry the catalyst at 110°C for 2h. The Pd content of the catalyst is 1.5wt% as analyzed by ICP-AES.

[0051] Catalytic hydrogenation reaction of terephthalic acid: 10g of the above-mentioned Pd / C catalyst is loaded into a hydrogenation reactor, 100g of terephthalic acid and 900g of water are added to a raw material kettle, and then stirring is started and the temperature is raised to 250°C. After the terephthalic acid is completely dissolved, it is pumped into the hydrogenation reactor with a pump at a pumping rate of 100g / h. The reaction temperature is controlled to be 250°C, and the reaction is reacted with the introduced hydrogen at a reaction pressure of 8MPa. After the reaction is completed, the reaction product is introduced into a crystallizer and cooled to 25°C and maintained for 1h. The solid-liquid mixture in the crystallizer is subjected to solid-liquid separation to obtain a solid phase product and a liquid phase product, which are sampled and analyzed respectively. For convenience, the analysis results are listed in Table 1.

[0052] Example 2

[0053] The liquid product in Example 1 (weighing 885g) was returned to the raw material kettle and mixed with terephthalic acid (100g) and 15g of water was added as a raw material. Then, stirring was started and the temperature was raised to 250°C. After the terephthalic acid was completely dissolved, it was pumped into the hydrogenation reactor at a pumping rate of 100g / h. The reaction temperature was controlled to be 250°C and reacted with the introduced hydrogen. The reaction pressure was 8MPa. After the reaction was completed, the reaction product was introduced into a crystallization tank and cooled to 25°C and maintained for 1h. The solid-liquid mixture in the crystallization tank was subjected to solid-liquid separation to obtain a solid product and a liquid, which were sampled and analyzed separately. For convenience, the analysis results are listed in Table 1.

[0054] Example 3

[0055] Preparation of Pd / C catalyst: Take 100g coconut shell activated carbon as a carrier and 50g chloropalladic acid solution containing 1.5g palladium as an impregnation liquid, impregnate 100g coconut shell activated carbon therein and stir continuously. After the chloropalladic acid solution is completely absorbed by the coconut shell activated carbon, age it at 80°C for 4h. After aging, add the reducing agent hydrazine hydrate for reduction. After the reduction, wash the catalyst with deionized water until no chloride ions are detected. Finally, dry the catalyst at 110°C for 2h. The Pd content of the catalyst is 1.5wt% as analyzed by ICP-AES.

[0056] Hydrogenation of terephthalic acid: 10 g of the above-mentioned Pd / C catalyst was loaded into a hydrogenation reactor, 100 g of terephthalic acid and 900 g of water were added to a raw material kettle, and then stirring was started and the temperature was raised to 250° C. After the terephthalic acid was completely dissolved, it was pumped into the hydrogenation reactor with a pump rate of 100 g / h. The reaction temperature was controlled to be 250° C. and reacted with the introduced hydrogen gas at a reaction pressure of 8 MPa. After the reaction was completed, the reaction product was introduced into a crystallizer and cooled to 45° C. and maintained for 1 h. The solid-liquid mixture in the crystallizer was subjected to solid-liquid separation to obtain a solid phase product and a liquid phase product, which were sampled and analyzed respectively. For convenience, the analysis results are listed in Table 1.

[0057] Example 4

[0058] The only difference from Example 1 is that the sum of K and Na content in the coconut shell activated carbon used is 742 ppm, and the sum of Ca, Mg and Al is 517 ppm. The analysis results of the obtained solid phase product and liquid phase product are listed in Table 1.

[0059] Example 5

[0060] The only difference from Example 1 is that the sum of K and Na content in the coconut shell activated carbon used is 2205 ppm, and the sum of Ca, Mg and Al is 851 ppm. The analysis results of the obtained solid phase product and liquid phase product are listed in Table 1.

[0061] Example 6

[0062] The only difference from Example 1 is that the temperature of the hydrogenation catalytic reaction of terephthalic acid is different:

[0063] Preparation of Pd / C catalyst: Take 100g coconut shell activated carbon as a carrier and 50g chloropalladic acid solution containing 1.5g palladium as an impregnation liquid, impregnate 100g coconut shell activated carbon therein and stir continuously. After the chloropalladic acid solution is completely absorbed by the coconut shell activated carbon, age it at 80°C for 4h. After aging, add the reducing agent hydrazine hydrate for reduction. After the reduction, wash the catalyst with deionized water until no chloride ions are detected. Finally, dry the catalyst at 110°C for 2h. The Pd content of the catalyst is 1.5wt% as analyzed by ICP-AES.

[0064] 10g of the above-mentioned Pd / C catalyst was loaded into a hydrogenation reactor, 70g of terephthalic acid and 930g of water were added into a raw material kettle, and then stirring was started and the temperature was raised to 250°C. After the terephthalic acid was completely dissolved, it was pumped into the hydrogenation reactor with a pump rate of 100g / h. The reaction temperature was controlled to be 240°C, and reacted with the introduced hydrogen. The reaction pressure was 8MPa. After the reaction was completed, the reaction product was introduced into a crystallization tank and cooled to 25°C and maintained for 1h. The solid-liquid mixture in the crystallization tank was subjected to solid-liquid separation to obtain solid phase products and liquid phase products, which were sampled and analyzed respectively. For comparison convenience, the analysis results are listed in Table 1.

[0065] Example 7

[0066] The only difference from Example 1 is that the temperature of the hydrogenation catalytic reaction of terephthalic acid is different:

[0067] Preparation of Pd / C catalyst: Take 100g coconut shell activated carbon as a carrier and 50g chloropalladic acid solution containing 1.5g palladium as an impregnation liquid, impregnate 100g coconut shell activated carbon therein and stir continuously. After the chloropalladic acid solution is completely absorbed by the coconut shell activated carbon, age it at 80°C for 4h. After aging, add the reducing agent hydrazine hydrate for reduction. After the reduction, wash the catalyst with deionized water until no chloride ions are detected. Finally, dry the catalyst at 110°C for 2h. The Pd content of the catalyst is 1.5wt% as analyzed by ICP-AES.

[0068] 10 g of the above-mentioned Pd / C catalyst was loaded into a hydrogenation reactor, 100 g of terephthalic acid and 900 g of water were added into a raw material kettle, and then stirring was started and the temperature was raised to 250° C. After the terephthalic acid was completely dissolved, it was pumped into the hydrogenation reactor with a pump rate of 100 g / h. The reaction temperature was controlled to be 260° C. and reacted with the introduced hydrogen. The reaction pressure was 8 MPa. After the reaction was completed, the reaction product was introduced into a crystallization tank and cooled to 25° C. and maintained for 1 hour. The solid-liquid mixture in the crystallization tank was subjected to solid-liquid separation to obtain solid phase products and liquid phase products, which were sampled and analyzed respectively. For comparison convenience, the analysis results are listed in Table 1.

[0069] Comparative Example 1

[0070] The only difference from Example 1 is that the coconut shell activated carbon is replaced by wood activated carbon with a specific surface area of ​​900-1000m 2 The analysis results of the solid phase product and the liquid phase product are listed in Table 1.

[0071] Comparative Example 2

[0072] The only difference from Example 1 is that the coconut shell activated carbon is replaced by coal-based activated carbon with a specific surface area of ​​900-1000m 2The analysis results of the solid phase product and the liquid phase product are listed in Table 1.

[0073] Table 1

[0074]

[0075] As can be seen from Table 1, the present invention selects coconut shell activated carbon as a catalyst carrier, dissolves the raw material terephthalic acid at a relatively high temperature, and selects a suitable reaction temperature, thereby improving the raw material conversion rate and the selectivity of 1,4-cyclohexanedicarboxylic acid in the product, and the solid product yield is high.

[0076] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing 1,4-cyclohexanedicarboxylic acid, comprising the steps of: (1) mixing terephthalic acid and water and heating the mixture to above 240° C. to obtain a terephthalic acid solution; (2) reacting the terephthalic acid solution obtained in step (1) with hydrogen in the presence of a catalyst to produce 1,4-cyclohexanedicarboxylic acid, wherein: The catalyst comprises an activated carbon carrier and a noble metal loaded on the carrier, and the carrier is coconut shell activated carbon.

2. The method according to claim 1, characterized in that The noble metal comprises at least one of Pd, Ru and Rh, preferably Pd; and / or, in the catalyst, the loading amount of the noble metal is 0.5-3wt%, preferably 1-1.5wt%.

3. The method according to claim 1 or 2, characterized in that: The sum of the contents of K and Na in the coconut shell activated carbon does not exceed 500 ppm; and / or, In the coconut shell activated carbon, the sum of the contents of Ca, Mg and Al does not exceed 500 ppm, preferably does not exceed 300 ppm.

4. The method according to any one of claims 1 to 3, characterized in that: The specific surface area of ​​the coconut shell activated carbon is not less than 900m 2 / g, preferably 1000-1300m 2 / g; and / or, the particle size of the coconut shell activated carbon is less than 10 mesh, preferably 4-8 mesh.

5. The method according to any one of claims 1 to 4, characterized in that: In step (1), terephthalic acid is mixed with water and heated to 245-255° C., preferably 248-252° C., more preferably 250° C.; and / or, The mass fraction of terephthalic acid in the terephthalic acid solution is 5-12%.

6. The method according to any one of claims 1 to 5, characterized in that: In step (2), the reaction is carried out in a hydrogenation reactor, preferably in a trickle bed reactor; Preferably, the inlet temperature of the hydrogenation reactor is 245-255°C, preferably 248-252°C, more preferably 250°C.

7. The method according to any one of claims 1 to 6, characterized in that: In step (2), the reaction temperature is 245-255°C, preferably 248-252°C, more preferably 250°C; and / or the reaction pressure is 6-10 MPa, preferably 8-10 MPa.

8. The method according to any one of claims 1 to 7, characterized in that: The method further comprises: cooling the solution after the reaction, crystallizing it and performing solid-liquid separation to obtain a 1,4-cyclohexanedicarboxylic acid solid product; Preferably, the temperature of the temperature-drop crystallization is 15-60°C, preferably 25-45°C.

9. The method according to claim 8, characterized in that The method further comprises: returning the liquid phase obtained after solid-liquid separation to step (1), mixing it with the terephthalic acid and water, and heating it to 245-255° C. to obtain a raw material liquid containing terephthalic acid.

10. The method according to claim 9, characterized in that The liquid phase obtained after solid-liquid separation is diluted with water to a 1,4-cyclohexanedicarboxylic acid content of 0-8 wt%, preferably 3-5 wt%, and then returned to step (1).

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