Carbon nanotube catalyst for hydroquinone fixed bed hydrogenation reaction and preparation method thereof
By using a composite support supported Ni metal catalyst combined with carbon nanotubes and alumina, the problems of low strength and easy deformation of the existing catalyst are solved, and the efficiency and stability of the catalyst are achieved, and the production cost is reduced.
Patent Information
- Application Number
- CN202411689026.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-25
- Publication Date
- 2025-02-25
AI Technical Summary
The existing hydroquinone hydrogenation catalysts have problems such as low strength, easy deformation and easy blockage of the pores after a long reaction.
Carbon nanotubes are used as support, combined with alumina and Ni metal catalysts, and alumina/carbon nanotube composite support is prepared by ultrasonication, acidification reaction and calcination, and the Ni metal catalyst is reduced before use.
The strength and stability of the catalyst are improved, the use time of the catalyst is extended, the production efficiency is improved, and the production cost is reduced.
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Figure BDA0005150408710000081 
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Abstract
Description
Technical Field
[0001] The present invention relates to a catalyst containing carbon nanotubes for the selective hydrogenation of hydroquinone to 1,4-cyclohexanediol in the chemical industry and a preparation method thereof, and in particular to a carbon nanotube catalyst for the fixed-bed hydrogenation reaction of hydroquinone and a preparation method thereof. Background Art
[0002] 1,4-cyclohexanediol is an important chemical intermediate. Due to its unique cis-trans isomerism, it can be used to produce monomers for polyesters and polyethers, such as polytrimethylene terephthalate (PBT) and polyethylene terephthalate (PET). These polymers are widely used in the fields of plastics, fibers and films. In addition, 1,4-cyclohexanediol can also be used to manufacture optical lenses with high refractive index, high smoothness and low dispersion properties, which are in great demand in the fields of office equipment and home appliances. In the medical field, 1,4-cyclohexanediol can increase the targeting of drugs to the skin [1], so it can be used to synthesize certain antibiotics. In industrial production, 1,4-cyclohexanediol is an intermediate for some pesticides and dyes, and the demand is on the rise.
[0003] Most of the existing hydroquinone hydrogenation catalysts use TIO2 or Y-type molecular sieve as carriers, but the catalysts generally have problems such as low strength after long-term reaction, easy deformation and easy pore blockage. Summary of the invention
[0004] The purpose of the present invention is to provide an alumina supported catalyst for the selective hydrogenation of hydroquinone to 1,4-cyclohexanediol and a preparation method thereof, which can improve the catalyst strength, extend the service life of the catalyst, improve production efficiency, and thus reduce production costs in view of the shortcomings and limitations of the prior art.
[0005] In order to achieve the above-mentioned object, the present invention provides a method for preparing a carbon nanotube catalyst for a fixed-bed hydrogenation reaction of hydroquinone, wherein the method comprises: step 1, crushing the carbon nanotubes, and then uniformly dispersing them in an ethanol aqueous solution, ultrasonicating, adding a nitric acid solution, continuing ultrasonicating, and then filtering, and washing the obtained solid to neutrality, heating and drying; step 2, mixing the solid obtained in step 1 with γ-Al2O3, extruding and molding, and then loading active components; step 3, reducing the catalyst obtained in step 2 before use; step 4, using the catalyst obtained in step 3 to carry out a fixed-bed hydrogenation reaction of hydroquinone.
[0006] The above-mentioned method for preparing a carbon nanotube catalyst for fixed-bed hydrogenation reaction of hydroquinone, wherein, in the step 1, the carbon nanotubes are crushed and then uniformly dispersed in an ethanol aqueous solution with a volume concentration of 50%, ultrasonicated for 3 hours, and then a nitric acid solution with a molar concentration of 0.5 mol / L is added, and ultrasonicated for 1 hour, and then filtered, and the obtained solid is washed with deionized water and ethanol in turn until neutral, and then dried at a temperature of 80°C for 12 hours.
[0007] The above-mentioned method for preparing a carbon nanotube catalyst for fixed-bed hydrogenation reaction of hydroquinone, wherein in the step 2, the loaded active component is Ni, and the obtained catalyst is an alumina / carbon nanotube composite carrier loaded Ni metal catalyst.
[0008] The above-mentioned preparation method of the carbon nanotube catalyst for the fixed-bed hydrogenation reaction of hydroquinone, wherein the step 2 comprises: step 2.1, the treated carbon nanotubes obtained in step 1 are mixed evenly with γ-Al2O3, sesbania powder and citric acid, a dilute nitric acid solution is added dropwise, and after an acidification reaction, extrusion molding is performed; step 2.2, the molded product obtained in step 2.1 is heated and dried, and then roasted to prepare an alumina / carbon nanotube composite carrier; step 2.3, a compound containing Ni is dissolved in water, and then the alumina / carbon nanotube composite carrier is immersed in the obtained solution and stirred evenly; step 2.4, the mixed solution obtained in step 2.3 is dehydrated, and then roasted to obtain an alumina / carbon nanotube composite carrier loaded with Ni metal catalyst.
[0009] The above-mentioned preparation method of the carbon nanotube catalyst for the fixed-bed hydrogenation reaction of hydroquinone, wherein the step 2 comprises: step 2.1, the treated carbon nanotubes obtained in step 1 are mixed evenly with γ-Al2O3, sesbania powder and citric acid, and a dilute nitric acid solution with a mass concentration of 8% is added dropwise, and after acidification reaction, extrusion molding is performed; step 2.2, the molded product obtained in step 2.1 is heated to a temperature of 110°C for drying, and then calcined at a temperature of 550°C for 6h to prepare an alumina / carbon nanotube composite carrier with uniform particle size; step 2.3, Ni(NO3)2·6H2O is dissolved in deionized water, and then the alumina / carbon nanotube composite carrier is immersed in the obtained solution, stirred for 2h, and mixed evenly; step 2.4, the mixed solution obtained in step 2.3 is rotary evaporated at a temperature of 60°C to remove the liquid, and then calcined at a temperature of 550°C for 4h to obtain an alumina / carbon nanotube composite carrier loaded with Ni metal catalyst.
[0010] The above-mentioned preparation method of carbon nanotube catalyst for fixed-bed hydrogenation reaction of hydroquinone, wherein, in said step 3, the reduction conditions of the catalyst are pressure 0.1-3MPa, reduction temperature 100℃-400℃, reduction time 1-6h, the reduction gas used is a mixture of H2 and N2, and the volume concentration of hydrogen is 10%-100%.
[0011] The preparation method of the carbon nanotube catalyst for the fixed-bed hydrogenation reaction of hydroquinone, wherein, in the step 4, the reduced catalyst is used to carry out a fixed-bed selective hydrogenation reaction of hydroquinone to produce 1,4-cyclohexanediol in a fixed-bed reactor, the reaction temperature is 50°C-180°C, the reaction pressure is 1-4MPa, the mass concentration of hydroquinone is 1%-20%, the solvent is any one of ethanol, isopropanol, and n-butanol, the molar ratio of hydrogen to catechol is 10-200:1, and the weight hourly space velocity of hydroquinone is 0.05-1h -1 .
[0012] The present invention also provides a carbon nanotube catalyst prepared by the above method for fixed-bed hydrogenation reaction of hydroquinone.
[0013] The carbon nanotube catalyst for the fixed-bed hydrogenation reaction of hydroquinone mentioned above, wherein the amount of carbon nanotubes used in the catalyst is 5%-10% by mass.
[0014] The carbon nanotube catalyst for the fixed-bed hydrogenation reaction of hydroquinone mentioned above, wherein the Ni loading amount of the catalyst is 1%-10% by mass percentage.
[0015] The carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone provided by the present invention and the preparation method thereof have the following advantages:
[0016] The present invention provides a Ni-based catalyst supported by an alumina / carbon nanotube (CNTs) composite carrier, which has a large specific surface area, good formability and thermal stability, and good anti-carbon deposition and anti-coking properties, and can meet the strength requirements of hydroquinone selective hydrogenation to 1,4-cyclohexanediol under multiphase reaction conditions. At the same time, it can extend the service life of the catalyst, improve production efficiency, and thus reduce production costs. DETAILED DESCRIPTION
[0017] The specific embodiments of the present invention are further described below.
[0018] The present invention provides a method for preparing a carbon nanotube catalyst for a fixed-bed hydrogenation reaction of hydroquinone, which comprises the following steps: 1, crushing carbon nanotubes, then uniformly dispersing them in an ethanol aqueous solution, performing ultrasound, adding a nitric acid solution, continuing ultrasound, then filtering, washing the obtained solid to neutrality, and heating and drying; 2, mixing the solid obtained in step 1 with γ-Al2O3, extruding the mixture, and then loading active components; 3, reducing the catalyst obtained in step 2 before use; and 4, using the catalyst obtained in step 3 to perform a fixed-bed hydrogenation reaction of hydroquinone.
[0019] Preferably, step 1 is to crush the carbon nanotubes, and then evenly disperse them in an ethanol aqueous solution with a volume concentration of 50%, perform ultrasound for 3 hours, then add a nitric acid solution with a molar concentration of 0.5 mol / L, continue ultrasound for 1 hour, and then filter, and wash the obtained solid with deionized water and ethanol in turn until neutral, and then dry it at 80°C for 12 hours.
[0020] In step 2, the loaded active component is Ni, and the obtained catalyst is a Ni metal catalyst loaded on an alumina / carbon nanotube composite carrier.
[0021] Preferably, step 2 comprises: step 2.1, the treated carbon nanotubes obtained in step 1 are mixed evenly with γ-Al2O3, sesbania powder and citric acid, a dilute nitric acid solution is added dropwise, and after an acidification reaction, extrusion molding is performed; step 2.2, the molded product obtained in step 2.1 is heated and dried, and then roasted to prepare an alumina / carbon nanotube composite carrier; step 2.3, a Ni-containing compound is dissolved in water, and then the alumina / carbon nanotube composite carrier is immersed in the obtained solution and stirred evenly; step 2.4, the mixed solution obtained in step 2.3 is dehydrated, and then roasted to obtain an alumina / carbon nanotube composite carrier loaded with Ni metal catalyst.
[0022] More preferably, step 2 comprises: step 2.1, the treated carbon nanotubes obtained in step 1 are mixed evenly with γ-Al2O3, sesbania powder and citric acid, a dilute nitric acid solution with a mass concentration of 8% is added dropwise, and after acidification reaction, extrusion molding is performed; step 2.2, the molded product obtained in step 2.1 is heated to a temperature of 110°C for drying, and then calcined at a temperature of 550°C for 6h to prepare an alumina / carbon nanotube composite carrier with uniform particle size; step 2.3, Ni(NO3)2·6H2O is dissolved in deionized water, and then the alumina / carbon nanotube composite carrier is immersed in the obtained solution, stirred for 2h, and mixed evenly; step 2.4, the mixed solution obtained in step 2.3 is rotary evaporated at a temperature of 60°C to remove the liquid, and then calcined at a temperature of 550°C for 4h to obtain an alumina / carbon nanotube composite carrier loaded with Ni metal catalyst.
[0023] Preferably, in step 3, the reduction conditions of the catalyst are pressure 0.1-3MPa, reduction temperature 100°C-400°C, reduction time 1-6h, the reducing gas used is a mixture of H2 and N2, and the volume concentration of hydrogen is 10%-100%.
[0024] More preferably, the reduction conditions are a pressure of 0.5-1.0 MPa, a reduction temperature of 180° C.-200° C., a reduction time of 4-5 h, a reducing gas of a mixture of H 2 and N 2 , and a hydrogen volume concentration of 10%-20%.
[0025] Preferably, in step 4, the reduced catalyst is used in a fixed bed reactor to carry out a fixed bed selective hydrogenation reaction of hydroquinone to 1,4-cyclohexanediol, the reaction temperature is 50°C-180°C, the reaction pressure is 1-4MPa, the mass concentration of hydroquinone is 1%-20%, the solvent is any one of ethanol, isopropanol, and n-butanol, the molar ratio of hydrogen to hydroquinone is 10-200:1, and the weight hourly space velocity of hydroquinone is 0.05-1h -1 .
[0026] More preferably, the reaction is carried out in a fixed bed reactor, the material of the reactor is 316L stainless steel, and the reaction conditions are: reaction temperature 140°C-160°C, reaction pressure 2-3MPa, mass concentration of hydroquinone 1%-5%, solvent ethanol or isopropanol, molar ratio of hydrogen to hydroquinone is 50-75:1, and weight hourly space velocity of hydroquinone is 0.1-0.2h -1 .
[0027] The invention also provides a carbon nanotube catalyst prepared by the method and used for fixed-bed hydrogenation reaction of hydroquinone.
[0028] Preferably, the amount of carbon nanotubes used in the catalyst is 5%-10% by mass.
[0029] More preferably, the catalyst has a Ni loading of 1%-10% by mass.
[0030] The carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone and the preparation method thereof provided by the present invention are further described below in conjunction with the examples.
[0031] It should be noted that these embodiments are merely illustrative and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, conventional experimental conditions or conditions recommended in the manufacturer's instructions are used. Where the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially, and substitutes with the same or similar effects can be used for equivalent replacement.
[0032] Example 1
[0033] 20 g of carbon nanotubes (CNTs) were crushed and then evenly dispersed in 40 g of 50% ethanol aqueous solution, ultrasonicated for 3 h, and then 5 g of 0.5 mol / L nitric acid solution was added, ultrasonicated for 1 h, and then filtered. The obtained solid was washed with deionized water and ethanol in turn until neutral, and then dried at 80°C for 12 h.
[0034] Weigh 10g of treated CNTs, mix evenly with 190g of γ-Al2O3, 3.2g of sesbania powder, and 2.6g of citric acid, then weigh 0.58g of concentrated nitric acid with a mass concentration of 65%, dilute it to a dilute nitric acid with a mass concentration of 8%, and slowly add it to the mixture. After acidification reaction, squeeze it into a 1.5mm clover shape, dry it at 110°C, and then calcine it at 550°C for 6h to make a CNTs-Al2O3 composite carrier with uniform particle size.
[0035] Weigh 2.53 g of Ni(NO3)2·6H2O, dissolve it in 20 g of deionized water, then weigh 10 g of the composite carrier and immerse it in the resulting solution, stir for 2 h, rotary evaporate at 60°C until there is no liquid, and then calcine at 550°C for 4 h to prepare a catalyst with a Ni loading of 5%.
[0036] Example 2
[0037] 20 g of carbon nanotubes (CNTs) were crushed and then evenly dispersed in 40 g of 50% ethanol aqueous solution, ultrasonicated for 3 h, and then 5 g of 0.5 mol / L nitric acid solution was added, ultrasonicated for 1 h, and then filtered. The obtained solid was washed with deionized water and ethanol in turn until neutral, and then dried at 80°C for 12 h.
[0038] Weigh 20g of treated CNTs, mix them evenly with 180g of γ-Al2O3, 3.2g of sesbania powder, and 2.6g of citric acid, then weigh 0.58g of concentrated nitric acid with a mass concentration of 65%, dilute it to a dilute nitric acid with a mass concentration of 8%, and slowly add it to the mixture. After acidification reaction, squeeze it into a 1.5mm clover shape, dry it at 110°C, and then calcine it at 550°C for 6h to make a CNTs-Al2O3 composite carrier with uniform particle size.
[0039] Weigh 2.53 g of Ni(NO3)2·6H2O, dissolve it in 20 g of deionized water, then weigh 10 g of the composite carrier and immerse it in the resulting solution, stir for 2 h, rotary evaporate at 60°C until there is no liquid, and then calcine at 550°C for 4 h to prepare a catalyst with a Ni loading of 5%.
[0040] Example 3
[0041] 20 g of carbon nanotubes (CNTs) were crushed and then evenly dispersed in 40 g of 50% ethanol aqueous solution, ultrasonicated for 3 h, and then 5 g of 0.5 mol / L nitric acid solution was added, ultrasonicated for 1 h, and then filtered. The obtained solid was washed with deionized water and ethanol in turn until neutral, and then dried at 80°C for 12 h.
[0042] Weigh 10g of treated CNTs, mix evenly with 190g of γ-Al2O3, 3.2g of sesbania powder, and 2.6g of citric acid, then weigh 0.58g of concentrated nitric acid with a mass concentration of 65%, dilute it to a dilute nitric acid with a mass concentration of 8%, and slowly add it to the mixture. After acidification reaction, squeeze it into a 1.5mm clover shape, dry it at 110°C, and then calcine it at 550°C for 6h to make a CNTs-Al2O3 composite carrier with uniform particle size.
[0043] Weigh 5.06 g of Ni(NO3)2·6H2O, dissolve it in 20 g of deionized water, then weigh 10 g of the composite carrier and immerse it in the resulting solution, stir for 2 h, rotary evaporate at 60°C until there is no liquid, and then calcine at 550°C for 4 h to prepare a catalyst with a Ni loading of 10%.
[0044] Example 4
[0045] 20 g of carbon nanotubes (CNTs) were crushed and then evenly dispersed in 40 g of 50% ethanol aqueous solution, ultrasonicated for 3 h, and then 5 g of 0.5 mol / L nitric acid solution was added, ultrasonicated for 1 h, and then filtered. The obtained solid was washed with deionized water and ethanol in turn until neutral, and then dried at 80°C for 12 h.
[0046] Weigh 20g of treated CNTs, mix them evenly with 180g of γ-Al2O3, 3.2g of sesbania powder, and 2.6g of citric acid, then weigh 0.58g of concentrated nitric acid with a mass concentration of 65%, dilute it to a dilute nitric acid with a mass concentration of 8%, and slowly add it to the mixture. After acidification reaction, squeeze it into a 1.5mm clover shape, dry it at 110°C, and then calcine it at 550°C for 6h to make a CNTs-Al2O3 composite carrier with uniform particle size.
[0047] Weigh 5.06 g of Ni(NO3)2·6H2O, dissolve it in 20 g of deionized water, then weigh 10 g of the composite carrier and immerse it in the resulting solution, stir for 2 h, rotary evaporate at 60°C until there is no liquid, and then calcine at 550°C for 4 h to prepare a catalyst with a Ni loading of 10%.
[0048] Comparative Example 1
[0049] Weigh 200g of γ-Al2O3, 3.2g of sesbania powder and 2.6g of citric acid, mix them evenly, then weigh 0.58g of concentrated nitric acid with a mass concentration of 65%, dilute it to a dilute nitric acid with a mass concentration of 8%, and slowly add it to the mixture. After acidification reaction, squeeze it into a 1.5mm clover shape, dry it at 110°C, and then calcine it at 550°C for 6h to make an Al2O3 composite carrier with uniform particle size.
[0050] Weigh 2.53 g of Ni(NO3)2·6H2O, dissolve it in 20 g of deionized water, then weigh 10 g of the composite carrier and immerse it in the resulting solution, stir for 2 h, rotary evaporate at 60°C until there is no liquid, and then calcine at 550°C for 4 h to prepare a catalyst with a Ni loading of 5%.
[0051] Comparative Example 2
[0052] Weigh 200g of γ-Al2O3, 3.2g of sesbania powder and 2.6g of citric acid, mix them evenly, then weigh 0.58g of concentrated nitric acid with a mass concentration of 65%, dilute it to a dilute nitric acid with a mass concentration of 8%, and slowly add it to the mixture. After acidification reaction, squeeze it into a 1.5mm clover shape, dry it at 110°C, and then calcine it at 550°C for 6h to make an Al2O3 composite carrier with uniform particle size.
[0053] Weigh 5.06 g of Ni(NO3)2·6H2O, dissolve it in 20 g of deionized water, then weigh 10 g of the composite carrier and immerse it in the resulting solution, stir for 2 h, rotary evaporate at 60°C until there is no liquid, and then calcine at 550°C for 4 h to prepare a catalyst with a Ni loading of 10%.
[0054] The catalysts prepared by Examples 1 to 4 and Comparative Examples 1 to 2 were used in the fixed-bed hydrogenation reaction of hydroquinone.
[0055] The catalyst is reduced before use. The preferred reduction conditions are pressure 0.1-3MPa, reduction temperature 100°C-400°C, reduction time 1-6h, and the reduction gas used is a mixture of H2 and N2, with a hydrogen volume concentration of 10%-100%.
[0056] More preferably, the reduction conditions are a pressure of 0.5-1.0 MPa, a reduction temperature of 180° C.-200° C., a reduction time of 4-5 h, a reducing gas of a mixture of H 2 and N 2 , and a hydrogen volume concentration of 10%-20%.
[0057] Most preferably, the reduction conditions are: pressure 0.8 MPa, reduction temperature 190°C, heating rate 10°C / min, reduction time 4h, reduction gas is a mixture of H2 and N2, the volume concentration of hydrogen is 10%, and the gas space velocity GHSV = 2500h -1 .
[0058] Gas Hourly Space Velocity (GHSV), also known as volumetric space velocity, is a parameter that characterizes catalyst performance, especially in catalytic reactions. It is defined as the volume flowing through the catalyst surface area per unit time.
[0059] The reduced catalyst is used to carry out a fixed-bed selective hydrogenation reaction of hydroquinone to produce 1,4-cyclohexanediol in a fixed-bed reactor. The reactor is made of 316L stainless steel.
[0060] Preferably, the reaction temperature is 50°C-180°C, the reaction pressure is 1-4MPa, the mass concentration of hydroquinone is 1%-20%, the solvent is any one of ethanol, isopropanol, and n-butanol, the molar ratio of hydrogen to hydroquinone is 10-200:1, and the weight hourly space velocity of hydroquinone is 0.05-1h -1 .
[0061] More preferably, the reaction conditions are: reaction temperature 140°C-160°C, reaction pressure 2-3MPa, mass concentration of hydroquinone 1%-5%, solvent ethanol or isopropanol, molar ratio of hydrogen to hydroquinone 50-75:1, hydroquinone weight hourly space velocity 0.1-0.2h -1 .
[0062] More preferably, the catalyst loading is 5 ml, the reaction temperature is 150°C, the reaction pressure is 3 MPa, the mass concentration of hydroquinone is 1.95%, the solvent is ethanol, the molar ratio of H2 to hydroquinone is 75:1, and the weight hourly space velocity of hydroquinone is 0.1 h -1 .
[0063] The liquid product obtained by the reaction was analyzed by gas chromatography using an Agilent Poroshell 120 chiral chromatographic column and a FID detector, and the chromatogram was processed by an area percentage normalization method. After the catalyst was dried, the strength was tested using a Zwick Roell strength tester.
[0064] The results of the fixed bed hydrogenation reaction of hydroquinone are shown in Table 1 below.
[0065] Table 1. Results of the reaction of selective hydrogenation of hydroquinone to 1,4-cyclohexanediol using the catalysts of the examples and comparative examples.
[0066]
[0067]
[0068] The results show that the cutting strength of the CNTs-Al2O3 composite carrier is much higher than that of γ-Al2O3, and it decreases less after the reaction, indicating that the catalyst has good integrity and does not affect the activity of the catalyst.
[0069] The present invention provides a carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone and a preparation method thereof. The catalyst is an alumina / carbon nanotube carrier-loaded Ni-based catalyst for selective hydrogenation of hydroquinone to produce 1,4-cyclohexanediol, which is of great significance for improving catalyst strength, extending catalyst service life, improving production efficiency and thus reducing costs.
[0070] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.
Claims
1. A method for preparing a carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone, characterized in that: The method comprises: Step 1, crushing the carbon nanotubes, and then evenly dispersing them in an ethanol aqueous solution, ultrasonicating them, adding a nitric acid solution, and continuing ultrasonicating them, and then filtering them, and washing the obtained solid to neutrality, and heating and drying them; Step 2, mixing the solid obtained in step 1 with γ-Al2O3, extruding and molding, and then loading the active component; Step 3, reducing the catalyst obtained in step 2 before use; Step 4: Using the catalyst obtained in step 3, a fixed-bed hydrogenation reaction of hydroquinone is carried out.
2. The method for preparing a carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone according to claim 1, characterized in that: In the step 1, the carbon nanotubes are crushed and then evenly dispersed in an ethanol aqueous solution with a volume concentration of 50%, ultrasonicated for 3 hours, and then a nitric acid solution with a molar concentration of 0.5 mol / L is added, and ultrasonicated for 1 hour, and then filtered, and the obtained solid is washed with deionized water and ethanol in turn until neutral, and then dried at 80°C for 12 hours.
3. The method for preparing a carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone according to claim 1, characterized in that: In the step 2, the loaded active component is Ni, and the obtained catalyst is a Ni metal catalyst loaded on an alumina / carbon nanotube composite carrier.
4. The method for preparing a carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone according to claim 3, characterized in that: The step 2 comprises: Step 2.1: evenly mix the treated carbon nanotubes obtained in step 1 with γ-Al2O3, sesbania powder and citric acid, dropwise add dilute nitric acid solution, and after acidification reaction, extrude and shape; Step 2.2, heating and drying the molded product obtained in step 2.1, and then calcining it to prepare an alumina / carbon nanotube composite carrier; Step 2.3, dissolving the Ni-containing compound in water, and then immersing the alumina / carbon nanotube composite support in the obtained solution and stirring evenly; Step 2.4: remove moisture from the mixed solution obtained in step 2.3, and then calcine to obtain a catalyst in which Ni metal is loaded on an alumina / carbon nanotube composite carrier.
5. The method for preparing a carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone according to claim 4, characterized in that: The step 2 comprises: Step 2.1: The treated carbon nanotubes obtained in step 1 are uniformly mixed with γ-Al2O3, sesbania powder and citric acid, and a dilute nitric acid solution with a mass concentration of 8% is added dropwise, and after an acidification reaction, the mixture is extruded and formed; Step 2.2, heating the molded product obtained in step 2.1 to 110° C. for drying, and then calcining at 550° C. for 6 h to prepare an alumina / carbon nanotube composite carrier with uniform particle size; Step 2.3, dissolving Ni(NO3)2·6H2O in deionized water, and then immersing the alumina / carbon nanotube composite support in the resulting solution, stirring for 2 hours, and mixing evenly; Step 2.4: The mixed solution obtained in step 2.3 is subjected to rotary evaporation at 60° C. to remove the liquid, and then calcined at 550° C. for 4 h to obtain a catalyst with Ni metal loaded on an alumina / carbon nanotube composite carrier.
6. The method for preparing a carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone according to claim 1, characterized in that: In the step 3, the reduction conditions of the catalyst are as follows: pressure 0.1-3MPa, reduction temperature 100°C-400°C, reduction time 1-6h, and the reducing gas used is a mixture of H2 and N2, with a volume concentration of hydrogen of 10%-100%.
7. The method for preparing a carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone according to claim 1, characterized in that: In step 4, the reduced catalyst is used to carry out a fixed-bed selective hydrogenation reaction of hydroquinone to produce 1,4-cyclohexanediol in a fixed-bed reactor, the reaction temperature is 50°C-180°C, the reaction pressure is 1-4MPa, the mass concentration of hydroquinone is 1%-20%, the solvent is any one of ethanol, isopropanol, and n-butanol, the molar ratio of hydrogen to catechol is 10-200:1, and the weight hourly space velocity of hydroquinone is 0.05-1h -1 .
8. A carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone prepared by the method according to any one of claims 1 to 7.
9. The carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone according to claim 8, characterized in that: The catalyst contains 5% to 10% carbon nanotubes by mass.
10. The carbon nanotube catalyst for fixed-bed hydrogenation of hydroquinone according to claim 9, characterized in that: The catalyst has a Ni loading of 1%-10% by mass.