Method for preparing 1, 4-cyclohexanedicarboxylic acid by hydrogenation of terephthalic acid

Abstract

The invention relates to a method for preparing 1, 4-cyclohexanedicarboxylic acid by hydrogenation of terephthalic acid, which comprises the following steps: in the presence of a catalyst, contacting terephthalic acid with hydrogen for hydrogenation reaction, the catalyst comprises a modified beta molecular sieve, active metal loaded on the modified beta molecular sieve and a coating layer coated on the surface of the modified beta molecular sieve, the silica-alumina ratio of the modified beta molecular sieve is 50-200, and the active metal comprises noble metal and VIII-family non-noble metal. According to the method disclosed by the invention, the dosage of noble metal can be reduced, and the conversion rate of terephthalic acid and the selectivity of 1, 4-cyclohexanedicarboxylic acid are effectively and greatly improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of terephthalic acid hydrogenation, and in particular, to a method for preparing 1,4-cyclohexanedicarboxylic acid by hydrogenating terephthalic acid. Background Art

[0002] 1,4-cyclohexanedimethanol (CHDM) is an important organic chemical raw material and a common monomer for developing new polyester products. It is generally used to manufacture polyester fibers, polyester for films, polyester for bottles, polyester for sheets, unsaturated polyester resins, polyester glazes, and to produce lubricating oils and hydraulic fluids. At present, the main process for industrial production of CHDM is to use dimethyl terephthalate as raw material, first hydrogenate the benzene ring to produce dimethyl 1,4-cyclohexanedicarboxylate, and then further hydrogenate 1,4-cyclohexanedicarboxylate to prepare CHDM. In 1959, Eastman Chemical Company in the United States achieved industrial production using dimethyl terephthalate (DMT) as raw material. After 2000, Japan and South Korea also achieved industrial production. South Korea's SK Company used the technology of Japan's Shin Rika Co., Ltd. to build a 10,000-ton production unit. The first stage used Ru / Al2O3 catalyst, and the second stage used copper chromite catalyst for hydrogenation.

[0003] In comparison, the cost of terephthalic acid (PTA) is lower than that of dimethyl terephthalate raw materials, and the raw material source is more abundant, so it has become a new trend in research in recent years. The preparation of CHDM by hydrogenation of terephthalic acid (PTA) mostly adopts a two-step process. First, the PTA benzene skeleton is hydrogenated to produce CHDA under the action of a catalyst, and the generated CHDA is further hydrogenated to produce CHDM under the action of a catalyst. The reaction of hydrogenating PTA to produce CHDA generally uses Pd / C as a catalyst, and the CHDA yield is higher than 95%. The CHDA hydrogenation reaction to produce CHDM has higher requirements for catalysts.

[0004] In 1959, U.S. Patent No. 2888484 proposed the use of palladium-based catalysts to hydrogenate terephthalic acid to produce CHDA. In its example, 5 wt% Pd / C was used as a catalyst, the reaction temperature was 195°C, the reaction pressure was greater than 34 MPa, and after 2 hours of reaction, the conversion rate of terephthalic acid reached 100%, and the yield of 1,4-cyclohexanedicarboxylic acid also reached 98.5%, achieving good results. However, the reaction pressure was too high, making it difficult to implement.

[0005] US Patent No. 6291706 uses Pd / C catalyst to hydrogenate terephthalic acid (PTA) to produce CHDA. The catalyst is placed in a basket of an autoclave. A 5% aqueous solution of PTA is continuously stirred at 200°C and 4.5MPa for 45 minutes, and then the catalyst is contacted with the catalyst for reaction for 3 hours. The conversion rate reaches 66.5%, and the reaction liquid after removing the solvent water contains 98.5% of the product CHDA. Japanese Patent No. JP2002020346 uses PTA / H2O as raw material in an autoclave reactor, uses Pd-Ba / C catalyst, reacts at 170°C and 5.0MPa for 1 hour, and the CHDA yield reaches 96.4%. Other patents also propose to use relatively low-priced Ru as an active component, and Ru / C on an activated carbon carrier is used for the reaction. For example, US Patent Nos. 3027398 and 4654064 report the reaction; however, the activity and selectivity of the Ru / C catalyst used in the reaction are poor.

[0006] In the current prior art, when terephthalic acid is hydrogenated to produce 1,4-cyclohexanedicarboxylic acid, the amount of precious metal used in the catalyst is still relatively high, and the loaded active metal is prone to pulverization, shedding and loss. Summary of the invention

[0007] The purpose of the present disclosure is to provide a method for preparing 1,4-cyclohexanedicarboxylic acid by hydrogenating terephthalic acid. The catalyst used in the method includes a modified β molecular sieve, an active metal loaded on the modified β molecular sieve, and a coating layer coated on the surface of the modified β molecular sieve. When the catalyst is used in the terephthalic acid hydrogenation reaction, it can not only reduce the amount of precious metal used, but also improve the conversion rate of terephthalic acid and the selectivity of 1,4-cyclohexanedicarboxylic acid.

[0008] In order to achieve the above-mentioned object, the present disclosure provides a method for preparing 1,4-cyclohexanedicarboxylic acid by hydrogenating terephthalic acid, the method comprising: contacting terephthalic acid with hydrogen in the presence of a catalyst to carry out a hydrogenation reaction; the catalyst comprises a modified β molecular sieve, an active metal loaded on the modified β molecular sieve and a coating layer coated on the surface of the modified β molecular sieve, the silicon-aluminum ratio of the modified β molecular sieve is 50 to 200, and the active metal comprises a noble metal and a Group VIII non-noble metal.

[0009] Optionally, the temperature of the hydrogenation reaction is 150-250°C, preferably 160-210°C; the time is 1-10h, preferably 4-8h; the hydrogen pressure is 2-10MPa, preferably 3-6MPa; the weight ratio of the catalyst to terephthalic acid is 1:(2-30), preferably 1:(5-15); the hydrogenation reaction is carried out in a solvent, and the solvent includes water.

[0010] Optionally, the coating layer has a thickness of 1 to 20 nm, preferably 2 to 5 nm; the coating layer is a mesh membrane layer with a porous structure, and the average pore size of the mesh membrane layer is 1 to 20 nm, preferably 1 to 10 nm; the coating layer includes a silicon dioxide membrane layer.

[0011] Optionally, the noble metal is selected from one or more of Pd, Pt, Ru and Rh, preferably Pd; the Group VIII non-noble metal is selected from one or more of Fe, Mn and Ni; preferably, the Group VIII non-noble metal includes Fe and Mn, and the weight ratio of Fe to Mn is 1:(0.2~5), preferably 1:(0.5~2).

[0012] Optionally, based on the total weight of the modified β molecular sieve, the content of the noble metal calculated as metal element is 0.5-3% by weight, preferably 1-2% by weight; the content of the VIII group non-noble metal calculated as metal element is 0.1-5% by weight, preferably 0.8-3% by weight; the content of the coating layer calculated as SiO2 is 0.5-30% by weight, preferably 2-15% by weight; the weight ratio of the noble metal to the VIII group non-noble metal is 1:(0.1-10), preferably 1:(0.2-2).

[0013] Optionally, the method further comprises preparing the catalyst by the following steps:

[0014] (1) hydrothermally treating the β molecular sieve to obtain a modified β molecular sieve;

[0015] (2) contacting the modified β molecular sieve with a first impregnation solution containing an active metal source, performing a first impregnation treatment, and then drying to obtain a modified β molecular sieve loaded with an active metal;

[0016] (3) contacting the modified β molecular sieve loaded with active metal with a silicon source solution, performing a second impregnation treatment, and then calcining and reducing to obtain the catalyst;

[0017] Wherein, the active metal source includes a noble metal source and a Group VIII non-noble metal source.

[0018] Optionally, in step (1), the temperature of the hydrothermal treatment is 200 to 650° C., preferably 300 to 600° C.; and the time is 1 to 10 hours, preferably 1.5 to 3 hours.

[0019] Optionally, in step (2), the weight ratio of the modified β molecular sieve to the noble metal source calculated as metal element is 1:(0.005-0.05), preferably 1:(0.01-0.025); the weight ratio of the modified β molecular sieve to the Group VIII non-noble metal source calculated as metal element is 1:(0.002-0.05), preferably 1:(0.005-0.02); the temperature of the first impregnation treatment is 5-80°C, preferably 5- 50℃; time is 1 to 24h, preferably 3 to 8h; the drying temperature is 100 to 150℃, preferably 105 to 120℃; time is 1 to 10h, preferably 3 to 6h; the precious metal source is selected from one or more of tetraammonium platinum dichloride, chloroplatinic acid, palladium chloride, tetraammonium platinum acetate, dinitrosodiammonium platinum, platinum nitrate, ruthenium nitrate and rhodium nitrate, and the Group VIII non-precious metal source is selected from one or more of iron nitrate, manganese nitrate and nickel nitrate.

[0020] Optionally, in step (3), the weight ratio of the modified β molecular sieve to the silicon source solution is 1:(0.05-1), preferably 1:(0.1-0.5); the temperature of the second impregnation treatment is 5-80°C, preferably 5-50°C; the time is 1-15h, preferably 1-6h; the temperature of the roasting is 300-650°C, preferably 450-600°C; the time is 1-15h, preferably 2-6h; the reduction is carried out in the presence of a reducing gas, the reducing gas is selected from one or more of hydrogen, carbon monoxide, hydrogen sulfide and nitrogen-containing hydrogen, preferably hydrogen; the reduction temperature is 100-300°C, preferably 150-230°C; the heating rate is 0.1-3°C / min, preferably 0.3-1°C / min; the time is 1-10h, preferably 3-6h; the pressure is 0.2-5MPa, preferably 0.5-1.5MPa.

[0021] Optionally, in step (3), the silicon source solution is selected from one or more of silica sol, silica gel, silicon dioxide dispersion, water glass, sodium metasilicate solution and silicate solution, preferably silica sol.

[0022] Through the above technical scheme, the present disclosure provides a method for preparing 1,4-cyclohexanedicarboxylic acid by hydrogenating terephthalic acid, wherein the catalyst used in the method includes a modified β molecular sieve, an active metal loaded on the modified β molecular sieve, and a coating layer coated on the carrier modified β molecular sieve, wherein the active metal includes a noble metal and a VIII group non-noble metal, and the noble metal and the VIII group non-noble metal have a synergistic effect, which can effectively improve the catalytic activity of the catalyst; the coating layer not only plays a role in fixing the active metal, but also prevents the active metal from being pulverized, falling off and lost during the hydrogenation reaction; at the same time, the stability of the molecular sieve is effectively improved, so that it is not easy to collapse in a water-containing system, which is conducive to extending the service life of the catalyst. When the catalyst is used for the hydrogenation reaction of terephthalic acid, it can not only reduce the amount of noble metal, but also greatly improve the conversion rate of terephthalic acid and the selectivity of 1,4-cyclohexanedicarboxylic acid.

[0023] Other features and advantages of the present disclosure will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0024] The specific embodiments of the present disclosure are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure, and are not used to limit the present disclosure.

[0025] The present disclosure provides a method for preparing 1,4-cyclohexanedicarboxylic acid by hydrogenating terephthalic acid, the method comprising: contacting terephthalic acid with hydrogen in the presence of a catalyst to carry out a hydrogenation reaction; the catalyst comprises a modified β molecular sieve, an active metal loaded on the modified β molecular sieve and a coating layer coated on the surface of the modified β molecular sieve, the silicon-aluminum ratio of the modified β molecular sieve is 50-200, and the active metal comprises a noble metal and a Group VIII non-noble metal.

[0026] The present disclosure provides a method for preparing 1,4-cyclohexanedicarboxylic acid by hydrogenating terephthalic acid. The catalyst used in the method includes a modified beta molecular sieve, an active metal loaded on the modified beta molecular sieve, and a coating layer coated on the surface of the modified beta molecular sieve, wherein the active metal includes a noble metal and a VIII group non-noble metal, and the noble metal and the VIII group non-noble metal have a synergistic effect, which can effectively improve the catalytic activity of the catalyst; the coating layer not only plays a role in fixing the noble metal elements, but also avoids the active metal from being pulverized, falling off and lost during the hydrogenation reaction; at the same time, the stability of the molecular sieve is effectively improved, so that it is not easy to collapse in a water-containing system, which is conducive to extending the service life of the catalyst. When the catalyst is used for the hydrogenation reaction of terephthalic acid, it can not only reduce the amount of noble metals, but also greatly improve the conversion rate of terephthalic acid and the selectivity of 1,4-cyclohexanedicarboxylic acid.

[0027] In one embodiment of the present disclosure, the temperature of the hydrogenation reaction is 150-250°C, preferably 160-210°C; the time is 1-10h, preferably 4-8h; the hydrogen pressure is 2-10MPa, preferably 3-6MPa; the weight ratio of the catalyst to terephthalic acid is 1:(2-30), preferably 1:(5-15); the hydrogenation reaction is carried out in a solvent, and the solvent includes water.

[0028] In one embodiment of the present disclosure, the coating layer has a thickness of 1 to 20 nm, preferably 2 to 5 nm; the coating layer is a mesh film layer with a porous structure, and the average pore size of the mesh film layer is 1 to 20 nm, preferably 1 to 10 nm; the coating layer includes a silicon dioxide film layer. In the above embodiment, the preferred silicon dioxide film layer is used, which is beneficial for the silicon hydroxyl groups of the coating layer to form Si-O-Si bonds with the silicon element of the modified β molecular sieve, further preventing the migration, shedding and loss of active metals, and preventing the molecular sieve from collapse due to dealumination in an aqueous system. In addition, the coating layer is a mesh film layer with a porous structure, which facilitates the contact between terephthalic acid and the active metal through the mesh holes, thereby improving the catalytic effect of the catalyst.

[0029] In one embodiment of the present disclosure, the noble metal is selected from one or more of Pd, Pt, Ru and Rh, preferably Pd; the VIII group non-noble metal is selected from one or more of Fe, Mn and Ni; in a preferred embodiment, the VIII group non-noble metal includes Fe and Mn, and the weight ratio of Fe to Mn is 1:(0.2-5), preferably 1:(0.5-2). In the above embodiment, when the VIII group non-noble metal includes both Fe and Mn, it is beneficial to play a synergistic role at a lower noble metal loading, thereby further improving the conversion rate of terephthalic acid and the selectivity of 1,4-cyclohexanedicarboxylic acid.

[0030] In one embodiment of the present disclosure, based on the total weight of the modified β molecular sieve, the content of the noble metal calculated as the metal element is 0.5-3% by weight, preferably 1-2% by weight; the content of the VIII group non-noble metal calculated as the metal element is 0.1-5% by weight, preferably 0.8-3% by weight; the content of the coating layer calculated as SiO2 is 0.5-30% by weight, preferably 2-15% by weight; the weight ratio of the noble metal to the VIII group non-noble metal is 1:(0.1-10), preferably 1:(0.2-2).

[0031] In one embodiment of the present disclosure, the method further comprises preparing the catalyst by the following steps:

[0032] (1) hydrothermally treating the β molecular sieve to obtain a modified β molecular sieve;

[0033] (2) contacting the modified β molecular sieve with a first impregnation solution containing an active metal source, performing a first impregnation treatment, and then drying to obtain a modified β molecular sieve loaded with an active metal;

[0034] (3) contacting the modified β molecular sieve loaded with active metal with a silicon source solution, performing a second impregnation treatment, and then calcining and reducing to obtain the catalyst;

[0035] Wherein, the active metal source includes a noble metal source and a Group VIII non-noble metal source.

[0036] In one embodiment of the present disclosure, in step (1), the temperature of the hydrothermal treatment is 200 to 650° C., preferably 300 to 600° C.; and the time is 1 to 10 hours, preferably 1.5 to 3 hours.

[0037] In one embodiment, based on the total pore volume of the β molecular sieve, the micropore volume of the β molecular sieve in the pore size range of 0.35 to 2 nm is 90 to 98%, and the mesopore volume in the pore size range of 2 to 10 nm is 2 to 10%. The modified β molecular sieve obtained after hydrothermal treatment has a reduced content of micropores in the pore size range of 0.35 to 2 nm, for example, a reduction of 0.1 to 1%; and an increased content of mesopores in the pore size range of 2 to 10 nm, for example, an increase of 0.1 to 1%. In the above embodiment, by selecting the preferred hydrothermal treatment, the pore size of the β molecular sieve can be adjusted, the micropore content can be appropriately reduced, the mesopore content can be appropriately increased, and the internal diffusion resistance inside the β molecular sieve can be reduced, thereby improving the conversion rate of terephthalic acid and the selectivity of 1,4-cyclohexanedicarboxylic acid.

[0038] In one embodiment of the present disclosure, in step (2), the weight ratio of the modified β molecular sieve to the noble metal source calculated as metal element is 1: (0.005-0.05), preferably 1: (0.01-0.025); the weight ratio of the modified β molecular sieve to the Group VIII non-noble metal source calculated as metal element is 1: (0.002-0.05), preferably 1: (0.005-0.02); the temperature of the first impregnation treatment is 5-80°C, preferably The temperature of the drying process is 5 to 50 ° C; the time is 1 to 24 hours, preferably 3 to 8 hours; the drying temperature is 100 to 150 ° C, preferably 105 to 120 ° C; the time is 1 to 10 hours, preferably 3 to 6 hours; the precious metal source is selected from one or more of tetraammonium platinum dichloride, chloroplatinic acid, palladium chloride, tetraammonium platinum acetate, dinitrosodiammonium platinum, platinum nitrate, ruthenium nitrate and rhodium nitrate, and the Group VIII non-precious metal source is selected from one or more of iron nitrate, manganese nitrate and nickel nitrate.

[0039] In one embodiment of the present disclosure, in step (3), the weight ratio of the modified β molecular sieve to the silicon source solution is 1:(0.05-1), preferably 1:(0.1-0.5); the temperature of the second impregnation treatment is 5-80°C, preferably 5-50°C; the time is 1-15h, preferably 1-6h; the temperature of the calcination is 300-650°C, preferably 450-600°C; the time is 1-15h, preferably 2-6h; the reduction is carried out in the presence of a reducing gas, the reducing gas is selected from one or more of hydrogen, carbon monoxide, hydrogen sulfide and nitrogen-containing hydrogen, preferably hydrogen; the reduction temperature is 100-300°C, preferably 150-230°C; the heating rate is 0.1-3°C / min, preferably 0.3-1°C / min; the time is 1-10h, preferably 3-6h; the pressure is 0.2-5MPa, preferably 0.5-1.5MPa. The content of hydrogen in the hydrogen-containing nitrogen may be 10 to 99%.

[0040] In one embodiment, in step (3), the silicon source solution is selected from one or more of silica sol, silica gel, silicon dioxide dispersion, water glass, sodium metasilicate solution and silicate solution, preferably silica sol, and the mass fraction of the silica sol is 10-35%, preferably 20-30%.

[0041] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited thereby.

[0042] In the following examples, unless otherwise specified, the raw materials used are commercially available products.

[0043] In the following examples, the specific testing methods are as follows:

[0044] The chemical composition of the molecular sieve and the catalyst was determined using a 3013 X-ray fluorescence spectrometer from Rigaku Corporation, Japan, and the silicon-aluminum ratio of the molecular sieve was calculated. The target was a tungsten target, the excitation voltage was 40 kV, and the excitation current was 50 mA.

[0045] The total pore volume, micropore volume and mesopore volume of the molecular sieve were calculated using the BET method;

[0046] The thickness of the coating layer was tested by transmission electron microscopy, and the instrument model was FEI Tecnai G-20;

[0047] The test method for electrochemical cycle performance is the blue electric test system, and the instrument model is CT3001A.

[0048] Preparation Example 1

[0049] (1) hydrothermally treating the β molecular sieve at 380° C. for 3 h to obtain a modified β molecular sieve;

[0050] The silicon-aluminum ratio of the beta molecular sieve is 50. Based on the total pore volume of the beta molecular sieve, the volume of micropores in the pore size range of 0.35 to 2 nm is 98%, and the volume of mesopores in the pore size range of 2 to 10 nm is 2.0%. The silicon-aluminum ratio of the modified beta molecular sieve is 51, the volume of micropores in the pore size range of 0.35 to 2 nm is 97.8%, i.e., a decrease of 0.2%, and the volume of mesopores in the pore size range of 2 to 10 nm is 2.2%, i.e., an increase of 0.2%.

[0051] (2) Add 2.00 g of modified β molecular sieve, 4 g of palladium chloride solution with a mass fraction of 0.5% in terms of Pd (precious metal source, wherein the content of palladium is 0.02 g), 0.144 g of ferric nitrate nonahydrate, and 10 g of water to a small beaker, stir and stand overnight at 25° C. (i.e., the temperature of the first impregnation treatment is 25° C., the time is 12 h, the weight ratio of the modified β molecular sieve to the precious metal source in terms of Pd is 1:0.01, and the weight ratio of the modified β molecular sieve to the Group VIII non-precious metal source in terms of Fe is 1:0.01, and then dry at 105° C. for 6 h to obtain a modified β molecular sieve loaded with Pd-Fe;

[0052] (3) 2 g of the modified β molecular sieve loaded with Pd-Fe was mixed with 0.6 g of silica sol (the mass fraction of SiO2 was 25%) (the weight ratio of the modified β molecular sieve to the silica sol was 1:0.3, that is, the weight ratio of the modified β molecular sieve to SiO2 was 1:0.075), and a second impregnation treatment was performed at a temperature of 30°C for 2.5 h, followed by calcination at 550°C for 4.0 h and reduction under hydrogen atmosphere for 6.0 h at a reduction temperature of 200°C, a heating rate of 0.5°C / min, and a pressure of 1.0 MPa to obtain catalyst 1, denoted as C1, whose composition is shown in Table 1.

[0053] Preparation Example 2

[0054] The same as Preparation Example 1, the only difference is that in step (2), the palladium chloride solution with a mass fraction of 0.5% calculated as Pd is adjusted from 4 g to 6 g (precious metal source, wherein the palladium content is 0.03 g), the weight ratio of the modified β molecular sieve to the precious metal source calculated as Pd is 1:0.015, and finally catalyst 2 is obtained, denoted as C2, and its composition is shown in Table 1.

[0055] Preparation Example 3

[0056] The same as Preparation Example 1, the only difference is that in step (2), the mass fraction of 0.5% palladium chloride solution calculated as Pd is adjusted from 4g to 8g (precious metal source, wherein the palladium content is 0.04g), the weight ratio of modified β molecular sieve to the precious metal source calculated as Pd is 1:0.02, and finally catalyst 3 is obtained, denoted as C3, and its composition is shown in Table 1.

[0057] Preparation Example 4

[0058] The same as Preparation Example 1, the only difference is that in step (2), 0.144 g of ferric nitrate nonahydrate is replaced by 0.0456 g of manganese nitrate tetrahydrate, and the weight ratio of the modified β molecular sieve to the Group VIII non-precious metal source calculated as Mn is 1:0.005, and finally catalyst 4 is obtained, denoted as C4, and its composition is shown in Table 1.

[0059] Preparation Example 5

[0060] The same as Preparation Example 4, the only difference is that in step (2), the mass fraction of 0.5% palladium chloride solution calculated as Pd is adjusted from 4g to 6g (precious metal source, wherein the palladium content is 0.03g), the weight ratio of modified β molecular sieve to the precious metal source calculated as Pd is 1:0.015, and finally catalyst 5 is obtained, denoted as C5, and its composition is shown in Table 1.

[0061] Preparation Example 6

[0062] The same as Preparation Example 4, the only difference is that in step (2), the mass fraction of 0.5% palladium chloride solution calculated as Pd is adjusted from 4g to 8g (precious metal source, wherein the palladium content is 0.04g), the weight ratio of modified β molecular sieve to the precious metal source calculated as Pd is 1:0.02, and finally catalyst 6 is obtained, denoted as C6, and its composition is shown in Table 1.

[0063] Preparation Example 7

[0064] The same as Preparation Example 1, the only difference is that in step (2), 0.0456 g of manganese nitrate tetrahydrate is added to the small beaker, the weight ratio of the modified β molecular sieve to the Group VIII non-precious metal source calculated as Fe and Mn is 1:0.015, and finally catalyst 7 is obtained, denoted as C7, and its composition is shown in Table 1.

[0065] Preparation Example 8

[0066] The same as Preparation Example 7, the only difference is that in step (2), the palladium chloride solution with a mass fraction of 0.5% calculated as Pd is adjusted from 4 g to 6 g (precious metal source, wherein the palladium content is 0.03 g), the weight ratio of the modified β molecular sieve to the precious metal source calculated as Pd is 1:0.015, and finally catalyst 8 is obtained, denoted as C8, and its composition is shown in Table 1.

[0067] Preparation Example 9

[0068] The same as Preparation Example 7, the only difference is that in step (2), the palladium chloride solution with a mass fraction of 0.5% calculated as Pd is adjusted from 4 g to 8 g (precious metal source, wherein the palladium content is 0.04 g), the weight ratio of the modified β molecular sieve to the precious metal source calculated as Pd is 1:0.02, and finally catalyst 9 is obtained, denoted as C9, and its composition is shown in Table 1.

[0069] Preparation Example 10

[0070] The same as Preparation Example 1, the only difference is that: in step (3), the silica sol is replaced by an equal weight of cyclohexane containing tetraethyl orthosilicate (the mass fraction based on SiO2 is 20%), the weight ratio of the modified β molecular sieve to tetraethyl orthosilicate is 1:0.3, that is, the weight ratio of the modified β molecular sieve to SiO2 is 1:0.06), the calcination temperature is 600°C, and finally a catalyst 10 is obtained, denoted as C10, whose composition is shown in Table 1.

[0071] Preparation Comparative Example 1

[0072] The same as Preparation Example 1, the only difference is that in step (2), no ferric nitrate nonahydrate is added to the small beaker, and finally a Pd-loaded modified β molecular sieve and a comparative catalyst 1 are obtained, which are denoted as D1 and have a composition shown in Table 1.

[0073] Preparation Comparative Example 2

[0074] The same as Preparation Example 2, the only difference is that in step (2), no ferric nitrate nonahydrate is added to the small beaker, and finally a Pd-loaded modified β molecular sieve and a comparative catalyst 2 are obtained, which are denoted as D2 and have a composition shown in Table 1.

[0075] Preparation Comparative Example 3

[0076] The same as Preparation Example 3, the only difference is that in step (2), no ferric nitrate nonahydrate is added to the small beaker, and finally a Pd-loaded modified β molecular sieve and a comparative catalyst 3 are obtained, which are denoted as D3 and have a composition shown in Table 1.

[0077] Preparation Comparative Example 4

[0078] The same as Preparation Example 1, the only difference is that in step (3), the modified β molecular sieve loaded with Pd-Fe is not subjected to the second impregnation treatment, but is directly calcined and reduced, and finally a comparative catalyst 4 is obtained, denoted as D4, whose composition is shown in Table 1.

[0079] Preparation Comparative Example 5

[0080] The same as Preparation Example 1, the only difference is that in step (1), the β molecular sieve with a silicon-aluminum ratio of 50 is replaced by the same amount of β molecular sieve with a silicon-aluminum ratio of 25, and the silicon-aluminum ratio of the obtained modified β molecular sieve is 25.2. Finally, comparative catalyst 5 is obtained, denoted as D5, and its composition is shown in Table 1.

[0081] Preparation Comparative Example 6

[0082] The same as Preparation Example 1, the only difference is that in step (1), the β molecular sieve with a silicon-aluminum ratio of 50 is replaced by the same amount of mordenite molecular sieve with a silicon-aluminum ratio of 50 (the pore structure is basically the same as the β molecular sieve), and the silicon-aluminum ratio of the modified mordenite molecular sieve is 50.6. Finally, comparative catalyst 6 is obtained, denoted as D6, and its composition is shown in Table 1.

[0083] Table 1

[0084]

[0085]

[0086] Example 1

[0087] 0.20g of the catalyst C1 prepared in Example 1 was placed in two 80mL reactors, 1.0g of terephthalic acid (PTA, the weight ratio of catalyst C1 to terephthalic acid was 1:5) and 20g of water were added to the two reactors, stirring was started and the temperature was raised to 180°C. The initial hydrogen pressure of the reactor was controlled at 4.0MPa. When the temperature and pressure reached the requirements, hydrogenation reaction was carried out. After 6.0h of reaction, the first reactor was taken out, the temperature of the first reactor was lowered to room temperature, and the reaction product was taken out; after 24h of reaction, the second reactor was taken out, the temperature of the second reactor was lowered to room temperature, and the reaction product was taken out; the two reaction products were placed in an oven at 105°C to dry the water, and the solid reaction product was obtained and dissolved in dimethyl sulfoxide (DMSO). The 1,4-cyclohexanedicarboxylic acid (CHDA) content in the supernatant was analyzed by gas chromatography. The reaction results are shown in Table 2. The PTA conversion rate and CHDA selectivity were calculated according to the following formulas (1) to (2):

[0088]

[0089]

[0090] Embodiments 2 to 10

[0091] The hydrogenation reaction was carried out using the method and reaction conditions of Example 1, except that the catalysts C2 to C10 prepared in Preparation Examples 2 to 10 were used to catalyze the hydrogenation reaction. The reaction results are shown in Table 2.

[0092] Comparative Examples 1 to 6

[0093] The hydrogenation reaction was carried out according to the method and reaction conditions of Example 1, except that the comparative catalysts D1 to D6 prepared in Comparative Preparation Examples 1 to 6 were used to catalyze the hydrogenation reaction. The reaction results are shown in Table 2.

[0094] Table 2

[0095]

[0096]

[0097] It can be seen from the results of the above examples and comparative examples that the method disclosed in the present invention can effectively improve the conversion rate of terephthalic acid and the selectivity of 1,4-cyclohexanedicarboxylic acid.

[0098] Among them, by comparing the data of Example 1 with that of Comparative Example 1, it can be seen that when the catalyst of Example 1 contains a Group VIII non-precious metal, the catalytic performance of the catalyst is better, and the terephthalic acid conversion rate and 1,4-cyclohexanedicarboxylic acid selectivity are higher.

[0099] By comparing the data of Example 1 with those of Comparative Example 4, it can be seen that when the modified β molecular sieve of Example 1 has a coating layer on its surface, the catalytic activity of the catalyst is higher, and after 24 hours of hydrogenation reaction, the conversion rate of terephthalic acid and the selectivity of 1,4-cyclohexanedicarboxylic acid do not decrease significantly; while the modified β molecular sieve of Comparative Example 4 does not have a coating layer on its surface, and after 24 hours of hydrogenation reaction, the conversion rate of terephthalic acid and the selectivity of 1,4-cyclohexanedicarboxylic acid of the prepared catalyst both show a significant decrease. This is because the precious metal elements on the surface of the modified β molecular sieve are pulverized, fallen off and lost during the reaction, and the molecular sieve undergoes structural collapse after a long period of reaction, resulting in a decrease in the catalytic performance of the catalyst and a shortened service life.

[0100] By comparing the data of Example 1 with those of Comparative Example 5, it can be seen that when Example 1 uses a modified β molecular sieve with a silicon-aluminum ratio greater than 50 as a carrier, the prepared catalyst has excellent catalytic performance, and the catalytic performance of the catalyst does not decrease significantly after a long period of hydrogenation reaction in an aqueous system; while Comparative Example 5 uses a modified β molecular sieve with a silicon-aluminum ratio less than 50 as a carrier, and the selectivity of the prepared catalyst for 1,4-cyclohexanedicarboxylic acid is low.

[0101] Comparison of the data of Example 1 and Comparative Example 6 shows that when Example 1 uses modified β molecular sieve as a carrier, the prepared catalyst has excellent catalytic performance, while when Comparative Example 6 uses modified mordenite molecular sieve as a carrier, the terephthalic acid conversion rate of the prepared catalyst is too low.

[0102] The preferred embodiments of the present disclosure are described in detail above; however, the present disclosure is not limited to the specific details in the above embodiments. Within the technical concept of the present disclosure, a variety of simple modifications can be made to the technical solution of the present disclosure, and these simple modifications all fall within the protection scope of the present disclosure.

[0103] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0104] In addition, various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A method for preparing 1,4-cyclohexanedicarboxylic acid by hydrogenating terephthalic acid, characterized in that: The method comprises: contacting terephthalic acid with hydrogen in the presence of a catalyst to perform a hydrogenation reaction; The catalyst comprises a modified beta molecular sieve, an active metal loaded on the modified beta molecular sieve and a coating layer coated on the surface of the modified beta molecular sieve, the silicon-aluminum ratio of the modified beta molecular sieve is 50-200, and the active metal comprises a noble metal and a Group VIII non-noble metal.

2. The method according to claim 1, characterized in that The temperature of the hydrogenation reaction is 150-250°C, preferably 160-210°C; the time is 1-10h, preferably 4-8h; the hydrogen pressure is 2-10MPa, preferably 3-6MPa; the weight ratio of the catalyst to terephthalic acid is 1:(2-30), preferably 1:(5-15); The hydrogenation reaction is carried out in a solvent, and the solvent includes water.

3. The method according to claim 1, characterized in that The coating layer has a thickness of 1 to 20 nm, preferably 2 to 5 nm; the coating layer is a mesh film layer with a porous structure, and the average pore size of the mesh film layer is 1 to 20 nm, preferably 1 to 10 nm; the coating layer includes a silicon dioxide film layer.

4. The method according to claim 1, characterized in that: The noble metal is selected from one or more of Pd, Pt, Ru and Rh, preferably Pd; the Group VIII non-noble metal is selected from one or more of Fe, Mn and Ni; Preferably, the Group VIII non-noble metals include Fe and Mn, and the weight ratio of Fe to Mn is 1:(0.2-5), preferably 1:(0.5-2).

5. The method according to claim 1, characterized in that Based on the total weight of the modified β molecular sieve, the content of the noble metal calculated as metal element is 0.5-3% by weight, preferably 1-2% by weight; the content of the VIII group non-noble metal calculated as metal element is 0.1-5% by weight, preferably 0.8-3% by weight; the content of the coating layer calculated as SiO2 is 0.5-30% by weight, preferably 2-15% by weight; The weight ratio of the noble metal to the Group VIII non-noble metal is 1:(0.1-10), preferably 1:(0.2-2).

6. The method according to claim 1, characterized in that The method further comprises preparing the catalyst by the following steps: (1) hydrothermally treating the β molecular sieve to obtain a modified β molecular sieve; (2) contacting the modified β molecular sieve with a first impregnation solution containing an active metal source, performing a first impregnation treatment, and then drying to obtain a modified β molecular sieve loaded with an active metal; (3) contacting the modified β molecular sieve loaded with active metal with a silicon source solution, performing a second impregnation treatment, and then calcining and reducing to obtain the catalyst; Wherein, the active metal source includes a noble metal source and a Group VIII non-noble metal source.

7. The method according to claim 6, characterized in that In step (1), the temperature of the hydrothermal treatment is 200 to 650° C., preferably 300 to 600° C.; the time is 1 to 10 hours, preferably 1.5 to 3 hours.

8. The method according to claim 6, characterized in that In step (2), the weight ratio of the modified β molecular sieve to the noble metal source calculated as metal element is 1:(0.005-0.05), preferably 1:(0.01-0.025); the weight ratio of the modified β molecular sieve to the VIII group non-noble metal source calculated as metal element is 1:(0.002-0.05), preferably 1:(0.005-0.02); the temperature of the first impregnation treatment is 5-80°C, preferably 5-50°C; the time is 1-24h, preferably 3-8h; the temperature of the drying is 100-150°C, preferably 105-120°C; the time is 1-10h, preferably 3-6h; The noble metal source is selected from one or more of tetraammonium platinum dichloride, chloroplatinic acid, palladium chloride, tetraammonium platinum acetate, dinitrosodiammonium platinum, platinum nitrate, ruthenium nitrate and rhodium nitrate, and the Group VIII non-noble metal source is selected from one or more of iron nitrate, manganese nitrate and nickel nitrate.

9. The method according to claim 6, characterized in that In step (3), the weight ratio of the modified β molecular sieve to the silicon source solution is 1:(0.05-1), preferably 1:(0.1-0.5); The temperature of the second immersion treatment is 5 to 80° C., preferably 5 to 50° C.; the time is 1 to 15 hours, preferably 1 to 6 hours; The calcination temperature is 300-650°C, preferably 450-600°C; the calcination time is 1-15h, preferably 2-6h; The reduction is carried out in the presence of a reducing gas, wherein the reducing gas is selected from one or more of hydrogen, carbon monoxide, hydrogen sulfide and nitrogen-containing hydrogen, preferably hydrogen; the reduction temperature is 100-300°C, preferably 150-230°C; the heating rate is 0.1-3°C / min, preferably 0.3-1°C / min; the time is 1-10h, preferably 3-6h; and the pressure is 0.2-5MPa, preferably 0.5-1.5MPa.

10. The method according to claim 6, characterized in that In step (3), the silicon source solution is selected from one or more of silica sol, silica gel, silicon dioxide dispersion, water glass, sodium metasilicate solution and silicate solution, preferably silica sol.

Images