Preparation method of high-purity 1, 4-cyclohexanedicarboxylic acid

Abstract

The present invention relates to the field of organic synthesis, and discloses a high purity 1, 4-cyclohexanedicarboxylic acid preparation method, which comprises: in a main reactor, mixing terephthalic acid, a heterogeneous hydrogenation catalyst and a reaction solvent, and carrying out a hydrogenation reaction in an H2-containing atmosphere, an effluent of the main reactor enters a rear reactor and is subjected to a hydrogenation reaction in an H2-containing atmosphere; and separating a gas phase from the effluent of the post-reactor, carrying out solid-liquid separation on the residual solid-phase suspension, and carrying out cooling crystallization and solid-liquid separation on the separated liquid phase to obtain the solid phase 1, 4-cyclohexanedicarboxylic acid. According to the preparation method disclosed by the invention, hydrogenation reaction and post-hydrogenation reaction are combined, and the product is refined in a specific step-by-step separation mode, so that the finally prepared 1, 4-cyclohexanedicarboxylic acid has relatively high purity.

Description

Technical Field

[0001] The invention relates to the field of organic synthesis, and in particular to a method for preparing high-purity 1,4-cyclohexanedicarboxylic acid. Background Art

[0002] 1,4-cyclohexanedicarboxylic acid (CHDA for short) is an aliphatic dibasic acid with a symmetrical structure. As an important chemical intermediate, CHDA can enhance the corrosion resistance, aging resistance, impact resistance, thermal stability, flexibility and transparency of polyester materials when used to synthesize polyester materials. It has good application prospects in the production of polyester fibers, engineering plastics and coatings, and can be used in the fields of automobiles, transportation, industrial maintenance, aerospace, buildings, equipment and instruments, and ordinary metals and gel coatings.

[0003] The process of preparing 1,4-cyclohexanedicarboxylic acid by hydrogenation reaction using terephthalic acid (PTA) as raw material is simple and widely used at present, but the purity of the product produced by this process is difficult to reach high standards. This is because it is not easy to separate the unreacted raw material terephthalic acid from 1,4-cyclohexanedicarboxylic acid; and in addition to the target product 1,4-cyclohexanedicarboxylic acid, a certain amount of by-products such as benzoic acid, p-toluic acid, p-tolualdehyde, etc. are produced in the hydrogenation reaction of terephthalic acid. If these by-products cannot be fully separated, they will significantly affect the quality of 1,4-cyclohexanedicarboxylic acid products, which is not conducive to its application in high-end polyester manufacturing. Summary of the invention

[0004] In order to solve the technical problem of low product purity in the process of preparing 1,4-cyclohexanedicarboxylic acid by hydrogenation of terephthalic acid, the present invention provides a method for preparing high-purity 1,4-cyclohexanedicarboxylic acid. In the preparation method of the present invention, a hydrogenation reaction-post-hydrogenation reaction is combined, and the product is refined by a specific step-by-step separation method, so that the finally prepared 1,4-cyclohexanedicarboxylic acid has a higher purity.

[0005] The specific technical scheme of the present invention is: A method for preparing high-purity 1,4-cyclohexanedicarboxylic acid, comprising the following steps: S1: In the main reactor, terephthalic acid, a heterogeneous hydrogenation catalyst and a reaction solvent are mixed and hydrogenated in an atmosphere containing H2; S2: The effluent from the main reactor enters the post-reactor and undergoes a hydrogenation reaction in an atmosphere containing H2; S3: separating the gas phase from the effluent of the post-reactor, performing solid-liquid separation on the remaining solid phase suspension, cooling and crystallizing the separated liquid phase and performing solid-liquid separation, and obtaining the solid phase as 1,4-cyclohexanedicarboxylic acid.

[0006] The present invention is concerned that the product CHDA is not easy to separate from the raw material PTA, which easily leads to poor purity of the final product. To this end, the present invention adopts a process of hydrogenation reaction-post-hydrogenation reaction combination. After the hydrogenation reaction is completed in the main reactor, the hydrogenation reaction is carried out again in the post-reactor, which can improve the conversion rate of PTA, reduce the difficulty of separation, and improve the purity of the product CHDA.

[0007] In addition, after the hydrogenation reaction and the post-hydrogenation reaction are completed, the product is refined by a specific step-by-step separation method (step S3), which can better separate the by-products other than the target product CHDA, thereby further improving the purity of the product.

[0008] In addition, the entire hydrogenation reaction-post-hydrogenation reaction-product refining process of the present invention can be carried out continuously, and has the advantages of simple operation and high production efficiency.

[0009] Preferably, in step S2, the terephthalic acid content in the effluent of the main reactor is not higher than 1 wt%.

[0010] Preferably, in step S1, the conditions of the hydrogenation reaction are: hydrogen pressure 0.5-10 MPa, reaction temperature 100-250° C., mass ratio of terephthalic acid to reaction solvent 1:1.5-19, mass ratio of terephthalic acid to heterogeneous hydrogenation catalyst 1-50:1, and the volume space velocity of passing the mixture of terephthalic acid, heterogeneous hydrogenation catalyst and reaction solvent into the main reactor is 2-5 h -1 .

[0011] Preferably, in step S2, the conditions for the hydrogenation reaction are: hydrogen pressure 0.5-5 MPa, reaction temperature 100-200°C, and the volume space velocity of the effluent from the main reactor into the rear reactor is 5-20 h -1 .

[0012] Preferably, in step S1, the heterogeneous hydrogenation catalyst is a supported catalyst, wherein the active components thereof include one or more of palladium, platinum, rhodium, ruthenium, rhenium, iridium and tungsten.

[0013] Preferably, in step S1, the heterogeneous hydrogenation catalyst comprises: a composite composed of fullerene and activated carbon in a mass ratio of 1:4 to 49, and metal ruthenium, metal tungsten, metal nickel and phosphorus element supported on the composite; in the heterogeneous hydrogenation catalyst, the metal ruthenium content is not less than 0.3wt%, the mass ratio between metal ruthenium and metal tungsten is 1:2 to 30, the total content of phosphorus element and metal nickel is 6 to 20wt%, and the mass ratio between phosphorus element and metal nickel is 1:1 to 5.

[0014] 1,4-cyclohexanedicarboxylic acid has two isomers, cis and trans. Trans-CHDA is a white scaly columnar crystal, while cis-CHDA is a white leaf crystal. Trans-CHDA has a higher melting point than cis-CHDA, and polyester prepared from trans-CHDA has better performance. At present, in order to achieve a higher trans-CHDA selectivity in the PTA hydrogenation reaction, the catalyst needs to contain more Pd and Pt. When the Pd and Pt content in the catalyst is reduced, the trans-CHDA selectivity will drop significantly. However, the prices of these two precious metals are high, which will lead to excessively high catalyst costs.

[0015] The present invention, through the special design of the heterogeneous hydrogenation catalyst component, can achieve a higher trans product selectivity in the reaction of PTA hydrogenation to CHDA without using the expensive precious metals Pd and Pt. Specifically: The coordination between tungsten and ruthenium: The added metal tungsten forms a composite compound with metal ruthenium, which can regulate the size of ruthenium, inhibit the growth of ruthenium particles, and make the utilization rate of metal active components higher, thereby improving the selectivity of trans-1,4-cyclohexanedicarboxylic acid.

[0016] By increasing the content of metallic ruthenium, the catalytic activity and reaction selectivity can be improved. When the content of metallic ruthenium is 0.3wt% or more, the PTA hydrogenation reaction can achieve a higher trans-1,4-CHDA selectivity.

[0017] In addition, the content of tungsten metal relative to ruthenium metal (the mass ratio between the two) will affect the interaction effect between the two. When the mass ratio between ruthenium metal and tungsten metal is controlled in the range of 1:2 to 30, a higher selectivity for trans-1,4-CHDA can be achieved. When the content of tungsten metal relative to ruthenium metal is too small, it is difficult to use tungsten metal to effectively inhibit the growth of ruthenium particles, resulting in a low selectivity for trans products; when the content of tungsten metal relative to ruthenium metal is too large, tungsten will cause excessive coverage of ruthenium sites, which will also result in a low selectivity for trans products.

[0018] The role of metallic nickel and phosphorus: The present invention finds that, on the basis of using metal tungsten and metal ruthenium as the main active components, when metal nickel or phosphorus is used alone as an auxiliary agent, the selectivity of the trans product will be significantly reduced. However, when the two auxiliary agents, metal nickel and phosphorus, are matched in a certain ratio (mass ratio of 1:1 to 5), the two can change the electronic structure and acid sites on the catalyst surface through a synergistic effect, thereby improving the selectivity of trans-1,4-cyclohexanedicarboxylic acid.

[0019] Functions of fullerene / activated carbon composites: In the catalyst system of the present invention, compared with the use of fullerene or activated carbon alone, the use of a composite of the two as a carrier can further improve the selectivity of the trans product in the process of catalyzing the hydrogenation of PTA to prepare CHDA. The reason is that: under a certain ratio (mass ratio of 1:4 to 49), the synergistic effect between fullerene and activated carbon can provide a stable carrier with a suitable composite pore structure, thereby improving the selectivity of the trans product.

[0020] Furthermore, in the heterogeneous hydrogenation catalyst, the mass ratio of fullerene to activated carbon is 1:9-19, the content of metallic ruthenium is 0.3-2wt%, the mass ratio of metallic ruthenium to metallic tungsten is 1:5-10, and the mass ratio of phosphorus to metallic nickel is 1:1-5.

[0021] When the content or ratio of each component in the heterogeneous hydrogenation catalyst is controlled within the above range, the selectivity of the trans product can be further improved.

[0022] Furthermore, the phosphorus element exists in the heterogeneous hydrogenation catalyst in the form of phosphoric acid.

[0023] Furthermore, the preparation step of the heterogeneous hydrogenation catalyst comprises: 1) Dispersing fullerene and activated carbon in a dispersion medium, reacting at 80-100° C. for 1-4 hours, separating a solid product, and obtaining a carrier; 2) The ruthenium source, tungsten source, phosphorus source and nickel source are dissolved in a solvent, added to a carrier, fully impregnated and then dried, and then the ruthenium source, tungsten source and nickel source are reduced to metallic ruthenium, metallic tungsten and metallic nickel to obtain a heterogeneous hydrogenation catalyst.

[0024] Preferably, in step S3, the temperature of the cooling crystallization is 5-50°C.

[0025] Preferably, in step S3, the gas phase separated from the effluent of the post-reactor is returned to the main reactor and / or the post-reactor.

[0026] Preferably, in step S3, after solid-liquid separation is performed on the remaining solid phase suspension, the separated solid phase is returned to the main reactor and / or the post-reactor.

[0027] Preferably, in step S3, after cooling crystallization and solid-liquid separation, the separated liquid phase is returned to the main reactor.

[0028] Compared with the prior art, the present invention has the following advantages: (1) In the preparation method of the present invention, a hydrogenation reaction-post-hydrogenation reaction is combined, and the product is refined by a specific step-by-step separation method, so that the finally obtained 1,4-cyclohexanedicarboxylic acid has a higher purity, and the whole process can be carried out continuously, the operation is simple, and the production efficiency is high; (2) In the heterogeneous hydrogenation catalyst used in the present invention, by using a composite of fullerene and activated carbon as a carrier, loading metal ruthenium, metal tungsten, metal nickel and phosphorus on it, and controlling the content or ratio of each component in the catalyst, the reaction of hydrogenating PTA to prepare CHDA can achieve a higher trans product selectivity without using expensive precious metals Pd and Pt. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with the embodiments.

[0030] Overall embodiment A method for preparing high-purity 1,4-cyclohexanedicarboxylic acid, comprising the following steps: S1: In the main reactor, terephthalic acid, a heterogeneous hydrogenation catalyst and a reaction solvent are mixed and hydrogenated in an atmosphere containing H2; S2: The effluent from the main reactor enters the post-reactor and undergoes a hydrogenation reaction in an atmosphere containing H2; S3: separating the gas phase from the effluent of the post-reactor, performing solid-liquid separation on the remaining solid phase suspension, cooling and crystallizing the separated liquid phase and performing solid-liquid separation, and obtaining the solid phase as 1,4-cyclohexanedicarboxylic acid.

[0031] In some specific embodiments, in step S1, the conditions of the hydrogenation reaction are: hydrogen pressure 0.5-10 MPa, reaction temperature 100-250°C, mass ratio of terephthalic acid to reaction solvent 1:1.5-19, mass ratio of terephthalic acid to heterogeneous hydrogenation catalyst 1-50:1, and the volume space velocity of the mixture of terephthalic acid, heterogeneous hydrogenation catalyst and reaction solvent into the main reactor is 2-5 h -1 .

[0032] In some specific embodiments, in step S2, the terephthalic acid content in the effluent of the main reactor is not higher than 1 wt%.

[0033] In some specific embodiments, in step S2, the conditions of the hydrogenation reaction are: hydrogen pressure 0.5-5 MPa, reaction temperature 100-200°C, and the volume space velocity of the effluent from the main reactor into the rear reactor is 5-20h -1 .

[0034] In some specific embodiments, in step S1, the heterogeneous hydrogenation catalyst is a supported catalyst, wherein the active component includes one or more of palladium, platinum, rhodium, ruthenium, rhenium, iridium and tungsten.

[0035] In some specific embodiments, in step S1, the heterogeneous hydrogenation catalyst comprises: a composite composed of fullerene and activated carbon in a mass ratio of 1:4 to 49, and metal ruthenium, metal tungsten, metal nickel and phosphorus element supported on the composite; in the heterogeneous hydrogenation catalyst, the metal ruthenium content is not less than 0.3wt%, the mass ratio between metal ruthenium and metal tungsten is 1:2 to 30, the total content of phosphorus element and metal nickel is 6 to 20wt%, and the mass ratio between phosphorus element and metal nickel is 1:1 to 5. In this specific embodiment: Optionally or preferably, the phosphorus element is present in the heterogeneous hydrogenation catalyst in the form of phosphoric acid.

[0036] Optionally or preferably, the preparation step of the heterogeneous hydrogenation catalyst comprises: 1) Dispersing fullerene and activated carbon in a dispersion medium, reacting at 80-100° C. for 1-4 hours, separating a solid product, and obtaining a carrier; 2) The ruthenium source, tungsten source, phosphorus source and nickel source are dissolved in a solvent, added to a carrier, fully impregnated and then dried, and then the ruthenium source, tungsten source and nickel source are reduced to metallic ruthenium, metallic tungsten and metallic nickel to obtain a heterogeneous hydrogenation catalyst.

[0037] In some specific embodiments, in step S3, the temperature of the cooling crystallization is 5-50°C.

[0038] In some specific embodiments, in step S3, the gas phase separated from the effluent of the post-reactor is returned to the main reactor and / or the post-reactor; after solid-liquid separation of the remaining solid suspension, the separated solid phase is returned to the main reactor and / or the post-reactor; after cooling crystallization and solid-liquid separation, the separated liquid phase is returned to the main reactor. Specific embodiments The present invention is described below by specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be thought of by those skilled in the art are included in the present invention, and the attached claims and any equivalents thereof are the protection scope of the present invention.

[0040] In the following examples and comparative examples, the meanings of the abbreviations are as follows: PTA: terephthalic acid; CHDA: 1,4-cyclohexanedicarboxylic acid; CFU: Fullerene; AC: activated carbon; DMO: dimethyl oxalate.

[0041] Example 1 A method for preparing high-purity 1,4-cyclohexanedicarboxylic acid, comprising the following steps: S1: Preparation of heterogeneous hydrogenation catalyst (Ru@CFU) According to the Ru element loading (content) in the catalyst of 0.5wt%, the corresponding mass of ruthenium trichloride was weighed and dissolved in pure water to obtain an impregnation solution. The obtained impregnation solution was mixed with CFU, impregnated for 24 hours, and then dried in a vacuum drying oven at 100°C for 12 hours to obtain a catalyst precursor. The catalyst precursor was reduced with a 10vol% hydrogen-nitrogen mixed gas at 250°C for 2 hours to obtain a Ru@CFU catalyst.

[0042] S2: Preparation of raw material mixture Terephthalic acid and water are fully mixed to obtain a terephthalic acid solution with a concentration of 10 wt%. The Ru@CFU catalyst prepared in step S1 is fully reduced by hydrogen at 250°C, and then added to the terephthalic acid solution and fully stirred to obtain a raw material mixture, wherein the mass ratio of terephthalic acid to Ru@CFU catalyst is 5:1.

[0043] S3: Hydrogenation reaction After the main reactor and the post-reactor were replaced with hydrogen three times, the temperatures were raised to 200°C and 170°C, respectively, and the hydrogen pressures were adjusted to 5.0 MPa and 2.0 MPa, respectively. The raw material mixture prepared in step S2 was heated to 2.0 h / min at a volume space velocity of 2.0 h / min. -1 The effluent from the main reactor (referred to as "effluent A") has a composition as shown in Table 1. Effluent A is discharged at a volume space velocity of 6.0 h -1 The rate of entering the post-reactor is , and the composition of the effluent from the post-reactor (recorded as "effluent B") is shown in Table 1.

[0044] S4: Product separation and purification The effluent B is passed into the separator, the separated gas phase (containing hydrogen) and the supplemented fresh hydrogen are compressed by the compressor and then passed into the main reactor, the remaining solid suspension enters the centrifuge for liquid-solid separation, the separated solid phase (containing Ru@CFU catalyst) is washed and returned to the main reactor, the remaining liquid phase enters the crystallization reactor, cooled to 10°C, and solid-liquid separation is performed, and the obtained solid phase is the CHDA product, the composition of which is shown in Table 2. The remaining liquid in the crystallization reactor is mixed with PTA and supplementary water and then passed into the main reactor.

[0045] Example 2 A method for preparing high-purity 1,4-cyclohexanedicarboxylic acid, comprising the following steps: S1: Preparation of heterogeneous hydrogenation catalyst (Ru-W@CFU) According to the Ru element loading (content) of 0.5wt% and the W element loading (content) of 5wt% in the catalyst, the corresponding mass of ruthenium trichloride and ammonium tungstate were weighed and dissolved in pure water to obtain an impregnation solution. The obtained impregnation solution was mixed with CFU, impregnated for 24h, and then dried in a vacuum drying oven at 100℃ for 12h to obtain a catalyst precursor. The catalyst precursor was reduced with 10vol% hydrogen and nitrogen mixed gas at 250℃ for 2h to obtain a Ru-W@CFU catalyst.

[0046] S2: Preparation of raw material mixture Terephthalic acid and water are fully mixed to obtain a terephthalic acid solution with a concentration of 20 wt%. The Ru-W@CFU catalyst prepared in step S1 is fully reduced by hydrogen at 250°C, and then added to the terephthalic acid solution and fully stirred to obtain a raw material mixture, wherein the mass ratio of terephthalic acid to Ru-W@CFU catalyst is 10:1.

[0047] S3: Hydrogenation reaction After the main reactor and the post-reactor were replaced with hydrogen three times, the temperatures were raised to 180°C and 150°C, respectively, and the hydrogen pressures were adjusted to 3.0 MPa and 1.0 MPa, respectively. The raw material mixture prepared in step S2 was heated to 4.0 h / min at a volume space velocity of 1.0 h / min. -1 The effluent from the main reactor (referred to as "effluent A") has a composition as shown in Table 1. Effluent A is injected into the main reactor at a volume space velocity of 20.0 h -1 The rate of entering the post-reactor is , and the composition of the effluent from the post-reactor (recorded as "effluent B") is shown in Table 1.

[0048] S4: Product separation and purification The effluent B is passed into the separator, the separated gas phase (containing hydrogen) and the supplemented fresh hydrogen are compressed by the compressor and then passed into the main reactor, the remaining solid suspension enters the centrifuge for liquid-solid separation, the separated solid phase (containing Ru-W@CFU catalyst) is washed and returned to the main reactor, the remaining liquid phase enters the crystallization reactor, cooled to 20°C, and solid-liquid separation is performed, and the obtained solid phase is the CHDA product, the composition of which is shown in Table 2. The remaining liquid in the crystallization reactor is mixed with PTA and supplementary water and then passed into the main reactor.

[0049] Example 3 A method for preparing high-purity 1,4-cyclohexanedicarboxylic acid, comprising the following steps: S1: Preparation of heterogeneous hydrogenation catalyst (Ru-W / Ni-P@CFU-AC) Weigh CFU and AC in a mass ratio of 5:95, mix them with 20 times the mass of DMO and 20 times the mass of pure water, respectively, stir vigorously for 30 minutes, then mix the two dispersions obtained under stirring, and then transfer them to a hydrothermal kettle, react at 95°C for 3 hours, cool and centrifuge to obtain a solid, then wash it with anhydrous ethanol and pure water for 3 times respectively, filter, and place it in an oven at 100°C to dry for 12 hours to obtain a CFU-AC composite carrier for standby use.

[0050] According to the Ru element loading (content) of 0.5wt%, the W element loading (content) of 5wt%, the P element loading (content) of 1wt%, and the Ni element loading (content) of 5wt%, the corresponding mass of ruthenium trichloride, ammonium tungstate, phosphoric acid and nickel acetate were weighed respectively and dissolved in pure water to obtain an impregnation solution. The obtained impregnation solution was mixed with the CFU-AC composite carrier, impregnated for 24h, and then dried in a vacuum drying oven at 100°C for 12h to obtain a catalyst precursor. The catalyst precursor was reduced with a 10vol% hydrogen-nitrogen mixed gas at 250°C for 2h to obtain a Ru-W / P-Ni@CFU-AC catalyst.

[0051] S2: Preparation of raw material mixture Terephthalic acid and water are fully mixed to obtain a terephthalic acid solution with a concentration of 20 wt%. The Ru-W / Ni-P@CFU-AC catalyst prepared in step S1 is fully reduced by hydrogen at 250°C, and then added to the terephthalic acid solution and fully stirred to obtain a raw material mixture, wherein the mass ratio of terephthalic acid to Ru-W@CFU catalyst is 15:1.

[0052] S3: Hydrogenation reaction After the main reactor and the post-reactor were replaced with hydrogen three times, the temperatures were raised to 160°C and 120°C, respectively, and the hydrogen pressures were adjusted to 2.5 MPa and 0.5 MPa, respectively. The raw material mixture prepared in step S2 was heated to 400 °C at a volume space velocity of 5.0 h -1 The effluent from the main reactor (referred to as "effluent A") has a composition as shown in Table 1. Effluent A is injected into the main reactor at a volume space velocity of 10.0 h -1 The rate of entering the post-reactor is , and the composition of the effluent from the post-reactor (recorded as "effluent B") is shown in Table 1.

[0053] S4: Product separation and purification The effluent B is passed into the separator, the separated gas phase (containing hydrogen) and the supplemented fresh hydrogen are compressed by the compressor and then passed into the main reactor, the remaining solid suspension enters the centrifuge for liquid-solid separation, the separated solid phase (containing Ru-W / Ni-P@CFU-AC catalyst) is washed and returned to the main reactor, the remaining liquid phase enters the crystallization reactor, cooled to 20°C, and solid-liquid separation is performed, and the obtained solid phase is the CHDA product, the composition of which is shown in Table 2. The remaining liquid in the crystallization reactor is mixed with PTA and supplementary water and then passed into the main reactor.

[0054] Example 4 A method for preparing high-purity 1,4-cyclohexanedicarboxylic acid, comprising the following steps: S1: Preparation of heterogeneous hydrogenation catalyst (Ru-W / Ni-P@CFU-AC) Same as step S1 in Example 1.

[0055] S2: Preparation of raw material mixture Terephthalic acid and water are fully mixed to obtain a terephthalic acid solution with a concentration of 20 wt%. The Ru-W / Ni-P@CFU-AC catalyst prepared in step S1 is fully reduced by hydrogen at 250°C, and then added to the terephthalic acid solution and fully stirred to obtain a raw material mixture, wherein the mass ratio of terephthalic acid to Ru-W@CFU catalyst is 20:1.

[0056] S3: Hydrogenation reaction After the main reactor and the post reactor were replaced with hydrogen three times, the temperatures were raised to 150°C and 100°C, respectively, and the hydrogen pressures were adjusted to 1.5 MPa and 0.5 MPa, respectively. The raw material mixture prepared in step S2 was heated to 2.0 h / min at a volume space velocity of 2.0 h / min. -1 The effluent from the main reactor (referred to as "effluent A") has a composition as shown in Table 1. Effluent A is discharged at a volume space velocity of 5.0 h -1 The rate of entering the post-reactor is , and the composition of the effluent from the post-reactor (recorded as "effluent B") is shown in Table 1.

[0057] S4: Product separation and purification The effluent B is passed into the separator, the separated gas phase (containing hydrogen) and the supplemented fresh hydrogen are compressed by the compressor and then passed into the main reactor, the remaining solid suspension enters the centrifuge for liquid-solid separation, the separated solid phase (containing Ru-W / Ni-P@CFU-AC catalyst) is washed and returned to the main reactor, the remaining liquid phase enters the crystallization reactor, cooled to 5°C, and solid-liquid separation is performed, and the obtained solid phase is the CHDA product, the composition of which is shown in Table 2. The remaining liquid in the crystallization reactor is mixed with PTA and supplementary water and then passed into the main reactor.

[0058] Table 1 Composition of the effluent from the main reactor and post-reaction 1 “Other” refers to the components in the effluent other than water and catalyst; 2 "ND" means that the component was not detected (the "ND" in the following tables has the same meaning).

[0059] Table 2CHDA product composition Cis-CHDA / wt% Trans-CHDA / wt% PTA / wt% Others / wt% Example 1 68.2 31.3 0.2 0.3 Example 2 39.5 60.2 0.1 0.2 Example 3 13.7 86.1 ND 0.2 Example 4 6.7 93.2 ND 0.1 It can be seen from Table 1 and Table 2 that the method of the present invention can make the purity of CHDA product (the sum of the content of cis-CHDA and trans-CHDA in the product) reach 99.5% or more. In addition, the present invention adopts a combined method of hydrogenation reaction-post-hydrogenation reaction to make PTA conversion more thorough, which will help reduce the content of PTA in the product and improve the purity of the product.

[0060] Comparative Examples 1 to 3 and Examples 5 to 7: Effect of Carrier on Catalytic Performance In Comparative Examples 1 to 3 and Examples 5 to 7, 1,4-cyclohexanedicarboxylic acid was prepared according to the steps of Example 4, and the only difference from Example 4 was that in the process of preparing the heterogeneous catalyst in step S1, the carrier composition was changed according to Table 3. The compositions of the products obtained in Comparative Examples 1 to 3 and Examples 5 to 7 are shown in Table 4.

[0061] Table 3 Composition of heterogeneous catalysts 1 “0:100” means that the vector is composed entirely of AC and contains no CFU; 2 "100:0" means that the vector is composed entirely of CFU and does not contain AC.

[0062] Table 4 CHDA product composition It can be seen from Table 4 that in the heterogeneous hydrogenation catalyst used in the present invention, compared with using CFU or AC alone as a carrier, a composite of the two in a certain ratio (mass ratio 1:9-49) can achieve a higher trans-1,4-CHDA selectivity, and on this basis, when the mass ratio of CFU to AC is 1:4-49, the trans-1,4-CHDA selectivity can be further improved, and more preferably 1:9-19 (which can improve the trans product selectivity to a greater extent). The reason is presumed to be that the synergistic effect between fullerene and activated carbon can provide a stable carrier with a suitable composite pore structure, thereby improving the trans product selectivity.

[0063] Comparative Examples 4-6 and Examples 8-13: Effect of the Composition of the Main Active Component on Catalytic Performance In Comparative Examples 4-6 and Examples 8-13, 1,4-cyclohexanedicarboxylic acid was prepared according to the steps of Example 4, and the only difference from Example 4 was that in the process of preparing the heterogeneous catalyst in step S1, the content of Ru or W in the catalyst was changed according to Table 5. The compositions of the products obtained in Comparative Examples 4-6 and Examples 8-13 are shown in Table 6.

[0064] Table 5 Composition of heterogeneous catalysts Table 6 CHDA product composition From Table 6 we can see that: (1) In the heterogeneous hydrogenation catalyst used in the present invention, the selectivity of trans-1,4-CHDA can be increased by increasing the Ru content. When the Ru content is 0.3 wt % or more, the content of trans-1,4-CHDA in the product can reach more than 84%.

[0065] (2) In the heterogeneous hydrogenation catalyst used in the present invention, when the content of metal tungsten relative to metal ruthenium is too low or too high, the selectivity for trans-1,4-CHDA will be adversely affected; when the mass ratio of metal ruthenium to metal tungsten is 1:2 to 30, a higher selectivity for trans-1,4-CHDA can be achieved, and the further preferred mass ratio is 1:5 to 10. The reason is presumed to be that: when the content of metal tungsten relative to metal ruthenium is too low, the growth of ruthenium particles cannot be well suppressed by using metal tungsten; when the content of metal tungsten relative to metal ruthenium is too high, the metal tungsten will excessively cover the ruthenium sites in the catalyst.

[0066] Comparative Examples 7-12 and Examples 14-15: Effect of the composition of the additive on the catalytic performance In Comparative Examples 7 to 12 and Examples 14 to 15, 1,4-cyclohexanedicarboxylic acid was prepared according to the steps of Example 4, and the only difference from Example 4 was that in the process of preparing the heterogeneous catalyst in step S1, the content of P or Ni in the catalyst was changed according to Table 7. The compositions of the products obtained in Comparative Examples 7 to 12 and Examples 14 to 15 are shown in Table 8.

[0067] Table 7 Composition of heterogeneous catalyst Table 8 CHDA product composition Cis-CHDA / wt% Trans-CHDA / wt% PTA / wt% Others / wt% Comparative Example 7 21.6 78.3 ND 0.1 Comparative Example 8 57.6 42.1 ND 0.3 Comparative Example 9 50.1 49.5 0.1 0.3 Comparative Example 10 37.8 61.9 ND 0.3 Example 4 6.7 93.2 ND 0.1 Embodiment 14 5.0 94.9 ND 0.1 Embodiment 15 9.6 90.3 ND 0.1 Comparative Example 12 25.2 74.6 ND 0.2 It can be seen from Table 8 that in the heterogeneous hydrogenation catalyst used in the present invention, compared with no auxiliary agent (Comparative Example 7), when only one of the auxiliary agents P and Ni is loaded (Comparative Examples 8 and 9), the selectivity of trans-1,4-CHDA decreases, but when P and Ni are used in a certain ratio (mass ratio of 1:1 to 5) and loaded in the catalyst together (Examples 4, 14 to 15), the selectivity of trans-1,4-CHDA can be improved. It is speculated that the reason is that the added auxiliary metal nickel and non-metallic phosphorus can change the electronic structure and acid sites of the catalyst surface through synergistic effects at a certain ratio, thereby improving the selectivity of trans-1,4-cyclohexanedicarboxylic acid.

[0068] Unless otherwise defined, all technical terms and scientific terms used in the present invention have the same meanings as those commonly understood by ordinary technicians in the field to which the present disclosure belongs. Unless otherwise specified, the raw materials and equipment used in the present invention are conventional raw materials and equipment in the field and can be obtained from conventional commercial channels; unless otherwise specified, the methods used in the present invention are conventional methods in the field.

[0069] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing high-purity 1,4-cyclohexanedicarboxylic acid, characterized in that the steps include: S1: In the main reactor, terephthalic acid, a heterogeneous hydrogenation catalyst and a reaction solvent are mixed and hydrogenated in an atmosphere containing H2; S2: The effluent from the main reactor enters the post-reactor and undergoes a hydrogenation reaction in an atmosphere containing H2; S3: separating the gas phase from the effluent of the post-reactor, performing solid-liquid separation on the remaining solid phase suspension, cooling and crystallizing the separated liquid phase and performing solid-liquid separation, and obtaining the solid phase as 1,4-cyclohexanedicarboxylic acid.

2. The preparation method according to claim 1, characterized in that: In step S2, the terephthalic acid content in the effluent of the main reactor is not higher than 1 wt %.

3. The preparation method according to claim 1, characterized in that: In step S1, the conditions of the hydrogenation reaction are: hydrogen pressure 0.5~10MPa, reaction temperature 100~250°C, mass ratio of terephthalic acid to reaction solvent 1:1.5~19, mass ratio of terephthalic acid to heterogeneous hydrogenation catalyst 1~50:1, and the volume space velocity of the mixture of terephthalic acid, heterogeneous hydrogenation catalyst and reaction solvent into the main reactor is 2~5h -1 .

4. The preparation method according to claim 1, characterized in that: In step S2, the conditions of the hydrogenation reaction are: hydrogen pressure 0.5~5MPa, reaction temperature 100~200℃, and the volume space velocity of the effluent from the main reactor into the rear reactor is 5~20h -1 .

5. The preparation method according to claim 1, 3 or 4, characterized in that: In step S1, the heterogeneous hydrogenation catalyst is a supported catalyst, wherein the active components thereof include one or more of palladium, platinum, rhodium, ruthenium, rhenium, iridium and tungsten.

6. The preparation method according to claim 5, characterized in that: In step S1, the heterogeneous hydrogenation catalyst includes: a composite composed of fullerene and activated carbon in a mass ratio of 1:4-49, and metal ruthenium, metal tungsten, metal nickel and phosphorus element supported on the composite; in the heterogeneous hydrogenation catalyst, the metal ruthenium content is not less than 0.3wt%, the mass ratio between metal ruthenium and metal tungsten is 1:2-30, the total content of phosphorus element and metal nickel is 6-20wt%, and the mass ratio between phosphorus element and metal nickel is 1:1-5.

7. The preparation method according to claim 1, characterized in that: In step S3, the temperature of the cooling crystallization is 5-50°C.

8. The preparation method according to claim 1, characterized in that: In step S3, the gas phase separated from the effluent of the post-reactor is returned to the main reactor and / or the post-reactor.

9. The preparation method according to claim 1, characterized in that: In step S3, after the remaining solid phase suspension is subjected to solid-liquid separation, the separated solid phase is returned to the main reactor and / or the post-reactor.

10. The preparation method according to claim 1, characterized in that: In step S3, after cooling crystallization and solid-liquid separation, the separated liquid phase is returned to the main reactor.

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