Method for preparing co@cm multichannel ceramic catalytic membrane for hydrogenation of p-nitrophenol

Abstract

The present invention belongs to the technical field of membrane catalysis. Disclosed is a method for preparing a Co@CM multichannel ceramic catalytic membrane for the hydrogenation of p-nitrophenol. In the catalytic membrane, a multichannel ceramic membrane is used as a matrix; in virtue of the good reduction and anchoring effects of dopamine, an active component, i.e., a cobalt salt, is loaded in situ both on the surface of the multichannel ceramic membrane and in the pore channels of the membrane by means of a forced circulation method; and the Co@CM multichannel ceramic catalytic membrane is constructed by further performing calcination and in-situ self-reduction. The present invention has the advantages that the multichannel ceramic membrane is loaded with nanoscale Co particles in place of noble metals, and the surfaces of the Co particles are coated with carbon and nitrogen, thereby effectively inhibiting the loss of the Co particles during the reaction process; in addition, an additional reducing agent does not need to be added during the reduction process of the metal Co; and the obtained Co@CM multichannel ceramic catalytic membrane has good catalytic activity and stability during the preparation of p-aminophenol by means of the hydrogenation of p-nitrophenol, and also overcomes the problem of difficulties in the subsequent separation of a traditional catalyst and a product.

Description

Preparation method of Co@CM multi-channel ceramic catalytic membrane for p-nitrophenol hydrogenation Technical Field

[0001] The invention belongs to the technical field of membrane catalysis and relates to a method for preparing a Co@CM multi-channel ceramic catalytic membrane for hydrogenation of p-nitrophenol. Background Art

[0002] Nitrophenol is a common persistent organic pollutant in the plasticizer, pesticide, dye, and pharmaceutical industries. Long-term exposure to wastewater containing p-nitrophenol can cause organ damage, blood disorders, and endocrine system dysfunction in humans and animals. p-Aminophenol, the main reduction product of p-nitrophenol, is an important chemical and pharmaceutical intermediate, primarily used in the synthesis of antipyretic and analgesic drugs, paracetamol, rubber additives, fuels, and petroleum additives. Therefore, reducing p-nitrophenol to p-aminophenol is of great significance in both industrial production and environmental protection. Existing p-nitrophenol hydrogenation catalysts include precious metal and non-precious metal catalysts. Precious metal catalysts are expensive and easily lost during the reaction, limiting their large-scale application. Non-precious metal catalysts, such as Ni and Co-based catalysts, have attracted widespread attention due to their low price. However, traditional catalysts are often powder catalysts, and their small particle size makes separation from the product more difficult.

[0003] Membrane catalysis technology is a technology that combines catalytic reaction and product separation. It loads catalytically active components on the membrane surface or in the pores to form a catalytic membrane with catalytic properties, thereby achieving in-situ separation between the reactants and the catalyst. Patent (ZL201010617062.9) reports a method for preparing a catalytic membrane, namely, first modifying the ceramic membrane carrier with amino groups, then immersing it in an ionic solution of the active component palladium, and then chemically reducing it to obtain a membrane catalyst, thereby improving the catalytic activity of the catalyst. However, due to the weak binding force between the precious metal and the membrane material, it is easily lost during the reaction process, resulting in poor stability of the catalytic membrane. At the same time, compared with powder catalysts, the content of active components per unit volume of the catalytic membrane is low, and the catalytic activity is low. Therefore, the weak binding force between the metal ions and the carrier and the low content of active components are key issues restricting its application.

[0004] Polydopamine (PDA) contains a large number of active groups, such as phenolic hydroxyl and amino groups, which can bind to metal ions through phenolic oxygen bonds, can adhere to the surfaces of different materials, and can also enhance the stability of secondary modifications. It has excellent reducibility and adhesion properties. The formation process of polydopamine is simple. It only requires immersing the material in a weakly alkaline Tris-HCl buffer solution of dopamine or other weakly alkaline aqueous solutions, and a polydopamine coating can be formed without the need for organic solvents. Therefore, dopamine can be used to functionalize the surface of membrane materials. For example, by coating dopamine on ceramic membranes, the properties of surface functional groups can be modified. In addition, by combining with other metal ions or metal oxides and undergoing a one-step carbonization, carbon-nitrogen-coated metal catalysts with good catalytic activity can be prepared. Therefore, using dopamine to modify the surface of ceramic membranes and loading cobalt salts is expected to provide more sites for cobalt loading and anchor the cobalt salts, thereby improving the binding force between cobalt and the membrane surface and preventing cobalt aggregation and loss. However, there are still many uncertainties regarding the binding mode of dopamine to the membrane surface, the loading mode of the cobalt source, and its performance in hydrogenation of p-nitrophenol.

[0005] Summary of the Invention

[0006] Aiming at the problem that traditional catalysts for hydrogenation reduction of p-nitrophenol to p-aminophenol mostly use precious metals, which are costly and difficult to recycle, the present invention proposes a method for preparing a Co@CM multi-channel ceramic catalytic membrane for p-nitrophenol hydrogenation.

[0007] In order to achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0008] The present invention is based on the carbonization of organic matter during the thermal decomposition of dopamine, which effectively avoids metal agglomeration. By adjusting various parameters in the preparation process, uniformly dispersed metal nanoparticles with small particle size are obtained. Based on the principle that the carbon-nitrogen-coated nanoparticles obtained by one-step carbonization can effectively inhibit the loss of active components during the reaction, dopamine is further applied to the catalytic membrane to synthesize a Co@CM multi-channel ceramic catalytic membrane rich in active sites, which is then applied to the reaction of hydrogenating p-nitrophenol to p-aminophenol.

[0009] A preparation method for a Co@CM multi-channel ceramic catalytic membrane for hydrogenation of p-nitrophenol, the specific steps are as follows.

[0010] Step 1: Dissolve tris(hydroxymethylaminomethane) (Tris) in deionized water to obtain solution I.

[0011] Step 2: Slowly add dilute hydrochloric acid dropwise to solution I and adjust the pH of the solution to obtain solution II.

[0012] Step 3: Add dopamine (DA) to solution II and stir to obtain solution III.

[0013] Step 4: Add solution III to the forced circulation convection equipment. Under the action of a peristaltic pump or other power equipment, solution III fills all channels of the ceramic membrane tube, and then is forced to flow through the ceramic membrane tube from the inside to the outside. Solution III continues to be forced to circulate and convect, so that the surface of the ceramic membrane tube and the inside of the pores are in situ loaded with dopamine.

[0014] Step 5: Take out the ceramic membrane from step 4 and dry it to obtain a dopamine-modified ceramic membrane.

[0015] Step 6: Dissolve cobalt nitrate hexahydrate in methanol to obtain solution IV.

[0016] Step 7: Add solution IV to the storage tank of the forced convection equipment and repeat the operation of step 4 to load cobalt ions in situ on the surface of the ceramic membrane tube and the inside of the pores.

[0017] Step 8: Take out the ceramic membrane from step 7 and dry it to obtain a ceramic membrane loaded with cobalt salt.

[0018] Step 9: Take out the ceramic membrane from step 8 and calcine and reduce it in a tubular furnace.

[0019] Step 10: Place the catalytic membrane obtained in step 9 into a forced circulation device, rinse it with a mixed solution of ethanol and water, and then dry it naturally to obtain a stable Co@CM multi-channel ceramic catalytic membrane.

[0020] Preferably, the concentration of tris(hydroxymethyl)aminomethane in solution I prepared in step 1 is 0.05-0.2 mol / L.

[0021] Preferably, the pH of solution II prepared in step 2 is 8.0-9.0.

[0022] Preferably, the concentration of dopamine in the solution III prepared in step 3 is 2.0-4.0 g / L.

[0023] Preferably, during the in-situ dopamine loading process in step 4, the flow rate of solution III is controlled to be 3-5 L / h by a forced circulation device, the water bath temperature is 20-40° C., and the modification loading time is 12-36 h.

[0024] Preferably, in step five and step eight, the drying temperature is 50-70° C. and the drying time is 12-36 h.

[0025] Preferably, the concentration of cobalt nitrate hexahydrate in solution IV prepared in step 6 is 0.05-0.5 mol / L.

[0026] Preferably, during the in-situ cobalt loading process in step seven, the flow rate of solution IV is controlled to be 3-5 L / h by a forced circulation device, the water bath temperature is 20-40° C., and the loading time is 12-36 h.

[0027] Preferably, the calcination temperature in step nine is 600-800° C., the calcination atmosphere is argon, the heating rate is 2-10° C. / min, and the temperature is maintained for 4-6 hours after reaching the calcination temperature.

[0028] Preferably, the flow rate of the forced circulation flushing of the ethanol-water mixed solution in step ten is 2-5 L / h, the time is at least 60 min, and the volume ratio of ethanol to water in the ethanol-water solution is 1:3.

[0029] The catalytic membrane prepared above is used in the hydrogenation of p-nitrophenol to p-aminophenol. The reaction is carried out in a flow-through membrane reactor, where the membrane tube is fixed during the reaction. The reaction mode is not limited and can be intermittent or continuous. The concentration of the reaction system and the reaction residence time can be adjusted according to actual needs. No catalyst separation is required during the entire catalytic reaction. After the catalytic reaction is completed, the membrane can be removed, cleaned, and dried for further use.

[0030] The present invention effectively prepares a dopamine-derived metal or metal oxide-carbon composite material by regulating the dopamine concentration, cobalt salt loading concentration and calcination temperature. The introduction of dopamine provides more loading sites, significantly increases the loading amount of Co, and improves the catalytic activity; significantly improves the binding force between cobalt and ceramic membrane, improves the stability of the catalytic membrane, and lays the foundation for industrial application. Studies have found that during the dopamine modification process, a tight polydopamine layer will be generated in situ on the surface of the multi-channel ceramic catalytic membrane and inside the pores. From the chemical structure of dopamine, it can be seen that it contains catechol hydroxyl and amino groups. With the help of the highly active functional groups phenolic hydroxyl and amino groups on the benzene ring, they can form a strong force with various materials through covalent or non-covalent bonds and can be combined with various metal ions through phenolic oxygen bonds, acting as a bridge for material functionalization and providing a platform for secondary modification of the material. In particular, the reduction carbonization during the thermal decomposition of dopamine effectively avoids the agglomeration of metals, and gradually produces CN materials during the thermal decomposition process, which is beneficial to the conversion of reactants. Studies have found that Co 2+ It will be reduced to Co by the reducing gas generated during the calcination of dopamine and serve as a catalytic active center. Therefore, no additional reducing agent is required during the experiment, and the in-situ self-polymerization and in-situ reduction process can be completed.

[0031] The study found that a key to improving the dopamine modification effect and improving the performance of the catalytic membrane lies in the drying operation after the dopamine modification step and the cobalt loading step. The drying operation can remove excess solvent to enhance the bonding strength between the ceramic membrane and the polydopamine layer, and is also beneficial to the loading of free cobalt ions, thereby enhancing the stability of the catalytically active substances on the ceramic membrane. In addition, the forced circulation method has a greater advantage over the traditional impregnation method. The forced circulation method uses external pressure to force the modified substances and catalytically active substances to pass through the surface and pores of the multi-channel ceramic membrane, which is more powerful and efficient than the traditional simple surface impregnation. The catalytic membrane prepared at a suitable calcination temperature is conducive to promoting the contact between the reaction substrate and the active component, shortening the mass transfer path, and thereby enhancing the reaction activity. The results show that when the calcination temperature is 600-800℃, the impregnation concentration of cobalt nitrate hexahydrate is 0.05-0.5mol / L, and the dopamine concentration is 2.0-4.0g / L, the obtained multi-channel catalytic membrane has excellent performance.

[0032] Compared with the prior art, the advantages and positive effects of the present invention are:

[0033] 1. The catalytic membrane prepared by the present invention is a multi-channel ceramic catalytic membrane, which is convenient for installation and fixation. At the same time, multiple channels can support and stabilize each other, have higher flux, better stability, higher specific surface area, and can provide more active sites.

[0034] 2. The present invention proposes a drying process after the dopamine modification and cobalt loading steps, which effectively enhances the dopamine modification effect and, in turn, the performance of the catalytic membrane. Drying removes excess solvent, strengthening the bonding between the ceramic membrane and the polydopamine layer. It also facilitates the loading of free cobalt ions and enhances the stability of the catalytically active species on the ceramic membrane.

[0035] 3. The Co@CM multi-channel ceramic catalytic membrane prepared by this invention exhibits excellent stability. It maintains good catalytic activity even after 300 minutes of continuous catalytic reaction. Furthermore, the recovered membrane after the extended reaction contains no difference in active component content compared to fresh catalyst, and the catalytic effect remains unchanged. Therefore, the catalytic membrane prepared by this invention overcomes the problems of traditional fine-particle precious metal catalysts, such as severe loss, difficult separation, and poor stability, and has great potential for industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is a schematic diagram of the forced circulation equipment used in Example 1.

[0037] FIG2 is an EDX image of the Co@CM multi-channel ceramic catalytic membrane in Example 1.

[0038] FIG3 is a reaction mechanism diagram of the Co@CM multi-channel ceramic catalytic membrane in Example 1.

[0039] FIG4 shows the stability test results of the Co@CM multi-channel ceramic catalytic membrane in Example 4.

[0040] FIG5 is a performance comparison diagram of the Co@CM multi-channel ceramic catalytic membrane in Example 1 and Comparative Example 4 when the membrane is dry or not.

[0041] The figures are marked as follows: 1 constant temperature water bath device, 2 external circulation peristaltic pump, 3 internal circulation peristaltic pump, 4 storage tank jacket, 5 storage tank, 6 membrane reactor jacket, 7 membrane assembly, 8 pressure detection gauge, 9 feed pipeline, 10 external circulation water outlet pipe, 11 normally closed exhaust valve, 12 sampling port. DETAILED DESCRIPTION

[0042] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below in conjunction with specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features therein can be combined with each other.

[0043] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0044] Example 1

[0045] This example provides a specific preparation process of a Co@CM multi-channel ceramic catalytic membrane.

[0046] The preparation and reaction of the catalytic membrane in this embodiment and the following embodiments are carried out using the following device. It should be noted that the preparation of the catalytic membrane and the subsequent reactions can also be carried out using other devices. This embodiment only provides one of the devices that can be realized to realize the preparation of the catalytic membrane and the subsequent reaction process, and retains the possibility of other devices that can implement the technical solution of the present invention. The design of other devices is not limited. Figure 1 is a complete set of devices that can realize the preparation and performance evaluation of the catalytic membrane in each embodiment. The entire device consists of several parts such as a temperature control system, a power system, a pressure detection system, a storage tank, a membrane reactor assembly, a sampling port, and a pipeline. The complete set of devices includes two sets of internal and external circulation systems, wherein the external circulation system is a constant temperature water circuit with a temperature control component as the core and a constant temperature water bath device 1 as the starting position; the internal circulation system is a material circulation with a storage tank 5 and a membrane reactor assembly 7 as the core and a storage tank 5 as the starting position. The internal and external circulation systems are separated by a hollow jacket structure at the position of the membrane assembly 7 and the storage tank 5, and the upper and lower ends of the jacket are respectively connected to the inlet and outlet of the constant temperature water circuit. The outer circulation peristaltic pump 2 and the inner circulation peristaltic pump 3 provide power for the whole set of devices, wherein the outer circulation peristaltic pump 2 pumps out the constant temperature water in the constant temperature water bath device 1, flows into the water inlet of the storage tank jacket 4, then flows into the water inlet of the membrane reactor jacket 6 from the water outlet of the storage tank jacket 4, and then flows out of the membrane reactor through the outer circulation outlet pipe 10 and returns to the constant temperature water bath device 1. The temperature of the reaction system is controlled by setting the temperature of the constant temperature water bath device 1. The inner circulation system is composed of a storage tank 5 and a membrane reactor as the core. The feed liquid takes the storage tank 5 as the starting point, is pressurized by the inner circulation peristaltic pump 3 and pumped into the membrane reactor, is forced to flow through the interior of the membrane reactor, and returns to the storage tank 5 from the membrane reactor outlet through the sampling port. The interior of the membrane reactor is fixed with a catalytic ceramic membrane tube through a membrane assembly 7. The upper and lower ends of the membrane assembly 7 are hollow cylindrical rings. The structure of the middle part can be cage-shaped, grid-shaped, fence-shaped, etc., to facilitate the outflow of materials. The upper and lower ends of the membrane assembly 7 are both open. The multi-channel ceramic membrane tube is inserted from the upper or lower opening of the membrane assembly 7. Rubber rings are put on both ends of the multi-channel ceramic membrane to fix it in the membrane assembly 7 and also play a sealing role. Flanges are set at the upper and lower ends and fixed to the membrane assembly 7 by quick-release clamps. The lower opening of the membrane assembly 7 is connected to the material feed pipeline 9 as a feed port; the side of the membrane assembly 7 is connected to the material outlet pipeline as a discharge port, and the top opening of the membrane assembly 7 is connected to the emptying pipeline as a pressure relief port; the sampling port 12 is provided on the material outlet pipe, and the pressure detection gauge 8 is provided on the upper end of the membrane reactor. A normally closed exhaust valve 11 is provided on the outside of the pressure detection gauge 8. When the membrane reactor as a whole needs to be sealed, the normally closed exhaust valve 11 can be closed.

[0047] The process of preparing a multi-channel ceramic membrane using the above device is as follows.

[0048] Prepare 300mL of a 0.1mol / L tris(hydroxymethylaminomethane) aqueous solution (Solution I). Then, slowly add 0.01mol / L dilute hydrochloric acid to Solution I to adjust the pH of the solution to 8.5. Then, add 0.9g of dopamine to a concentration of 3.0g / L. Then, fill the multichannel ceramic membrane into the membrane assembly. Pour the prepared dopamine Tris-HCl buffer solution into the equipment storage tank and adjust the flow rate to 4L / h to force the dopamine Tris-HCl solution to flow through the membrane pores. The modification process temperature is 30°C and the modification time is controlled to 16h. After the modification is completed, remove the membrane tube and place it in a 60°C oven to dry for 24h. The resulting sample is labeled DA@CM-3.0.

[0049] Prepare 300 mL of a 0.1 mol / L Co(NO₃)₂·6H₂O methanol solution. Reinstall the DA@CM-3.0 multichannel ceramic membrane into the membrane assembly. Add the prepared Co(NO₃)₂·6H₂O methanol solution to the storage tank. Adjust the flow rate to 4 L / h to force the Co(NO₃)₂·6H₂O methanol solution through the membrane pores. Maintain a temperature of 30°C for 16 hours. After modification, remove the membrane tube and dry it in a 60°C oven for 24 hours before use. The resulting sample is labeled Co@CM-3.0-0.1.

[0050] The prepared multi-channel ceramic membrane Co@CM-3.0-0.1 was placed in a crucible and placed in a tubular furnace for high-temperature calcination. The calcination conditions were as follows: in an argon (Ar) atmosphere, the temperature was raised from room temperature to the target temperature (700°C) at a rate of 5°C / min, and the target temperature was maintained for 5 hours. After that, the sample was naturally cooled to room temperature to obtain a black catalytic membrane. The obtained catalytic membrane was placed in a forced circulation device, and the flow rate of the ethanol-water mixed solution was controlled to 3L / h by adjusting the speed of the peristaltic pump. The ethanol-water mixed solution was rinsed for 60 minutes and then naturally dried to obtain a Co@CM multi-channel ceramic catalytic membrane, in which the volume ratio of ethanol and water was 1:3. The catalytic membrane was labeled Co@CM-3.0-0.1-700. In order to characterize the catalytic membrane and verify the catalytic performance, multiple catalytic membranes were prepared under the same conditions in this example.

[0051] The catalytic membrane Co@CM-3.0-0.1-700 was used in an experiment to hydrogenate p-nitrophenol to p-aminophenol. The reaction was carried out in a flow-through membrane reactor. First, a constant-temperature water bath was started, and peristaltic pump 2 was turned on at a speed of 30 r / min to operate the external circulation water system. A 30°C water bath was used to maintain a constant reaction temperature. After peristaltic pump 2 had run for 5 minutes, 1 g of p-nitrophenol was added to a mixed solvent of ethanol and deionized water (250 mL, ethanol:deionized water volume ratio = 1:11.5) to prepare a reaction solution. The solution was stirred for 10 minutes, and 0.4 mL of the solution was taken as an initial sample. 3.92 g of NaBH₄ was then added and stirred for 10 minutes. The reaction solution was then added to the flow-through membrane reactor's reservoir. Peristaltic pump 3 was turned on, and the reaction solution flow rate was controlled to 4 L / h. The internal circulation system was operated. When the reaction solution flowed back to the reservoir through the peristaltic pump, a timer was started, and 0.4 mL of the reaction solution was sampled every 10 minutes (for first-time users, the sampling interval can be shortened). After the reaction is completed, the reaction liquid is completely drained, and deionized water is added to the storage tank. The peristaltic pump 2 is turned on and the residual liquid on the catalytic membrane is washed by forced circulation for 20-30 minutes. After the flushing is completed, the catalytic membrane tube is taken out and dried and stored for the next reaction. There is no limit on the flushing flow rate, which can be the same as the flow rate during the preparation of the catalytic membrane and the catalytic reaction, such as 4L / h. High performance liquid chromatography (HPLC, Agilent1200) is used to detect the product composition. The conversion rate and selectivity of the reaction are then calculated based on the standard curve. Under the conditions of a molar ratio of p-nitrophenol to sodium borohydride of 1:9.6, a concentration of p-nitrophenol of 28.8mM, a reaction temperature of 30°C, and a material flow rate of 4L / h, the conversion rate is 100% and the selectivity is 100% after 20 minutes of reaction.

[0052] The device shown in Figure 1 can force the catalytically active component cobalt to pass through the pores and interior of the ceramic membrane, greatly increasing the cobalt loading compared to the traditional impregnation method. Cobalt, as a catalytic active site, can efficiently catalyze the hydrogenation of p-nitrophenol to p-aminophenol, realizing an effective in-situ reduction process.

[0053] Figure 2 is an EDX image of the Co@CM-3.0-0.1-700 multi-channel ceramic catalytic membrane prepared in this example. The distribution of Co, C, and N was detected in various regions of the Co@CM-3.0-0.1-700 multi-channel ceramic membrane, indicating that the Co@CN derived from Co@polydopamine has been successfully loaded into various parts of the multi-channel ceramic membrane through the forced circulation method with the help of the excellent reduction and anchoring effect of polydopamine, proving the successful preparation of the multi-channel Co@CM catalytic membrane.

[0054] Figure 3 illustrates the reaction mechanism of the Co@CM-3.0-0.1-700 catalytic membrane prepared in this example. In the initial stages of the reaction, p-nitrophenol and sodium borohydride are adsorbed onto the membrane. Subsequently, the BH bond breaks within the cobalt nanoparticles at the active sites, accelerating the transfer of active hydrogen and electrons from sodium borohydride to p-nitrophenol, thereby producing p-aminophenol. The content of the active component used to activate hydrogen significantly influences the reduction of p-nitrophenol; a higher cobalt content results in a relatively higher conversion rate. The excellent bioadhesive properties of polydopamine facilitate the uniform and stable dispersion of the cobalt nanoactive sites within the membrane, facilitating the diffusion and transport of reactants. Consequently, the Co@CM catalytic membrane exhibits excellent catalytic activity in the p-nitrophenol hydrogenation reaction. Furthermore, the Co@CM catalytic membrane exhibits excellent stability.

[0055] Example 2

[0056] This example provides a specific preparation process of the Co@CM ceramic catalytic membrane. Matters not specifically described in this example are consistent with those of Example 1.

[0057] Prepare 300mL of a 0.05mol / L tris(hydroxymethylaminomethane) aqueous solution (Solution I). Then, slowly add 0.01mol / L dilute hydrochloric acid to Solution I to adjust the pH of the solution to 8.0. Then, add 0.6g of dopamine to a concentration of 2.0g / L. Then, fill the multichannel ceramic membrane into the membrane assembly. Pour the prepared dopamine Tris-HCl buffer solution into the equipment storage tank and adjust the flow rate to 3L / h to force the dopamine Tris-HCl solution to flow through the membrane pores. The modification process temperature is 20°C and the modification time is controlled to 36h. After the modification is completed, remove the membrane tube and place it in a 50°C oven to dry for 34h. The resulting sample is labeled DA@CM-2.0.

[0058] Prepare 300 mL of a 0.05 mol / L Co(NO₃)₂·6H₂O methanol solution. Reinstall the DA@CM-2.0 multichannel ceramic membrane into the membrane assembly. Add the prepared Co(NO₃)₂·6H₂O methanol solution to the storage tank. Adjust the flow rate to 3 L / h to force the Co(NO₃)₂·6H₂O methanol solution through the membrane pores. Maintain a temperature of 20°C for 12 hours. After modification, remove the membrane tube and dry it in a 50°C oven for 36 hours before use. The resulting sample is labeled Co@CM-2.0-0.05.

[0059] The prepared multi-channel ceramic membrane Co@CM-2.0-0.05 was placed in a crucible and placed in a tube furnace for high-temperature calcination. The calcination conditions were argon (Ar) atmosphere, rising from room temperature to the target temperature (600°C) at a rate of 2°C / min, and the final target temperature was maintained for 6 hours. After that, the sample was naturally cooled to room temperature to obtain a black catalytic membrane. The obtained catalytic membrane was placed in a forced circulation device with a flow rate of 2L / h. It was rinsed with a mixed solution of ethanol and water in a ratio of 1:3 for 70 minutes and then naturally dried to obtain a Co@CM multi-channel ceramic catalytic membrane, marked as Co@CM-2.0-0.05-600.

[0060] The catalytic membrane Co@CM-2.0-0.05-600 was applied to the hydrogenation of p-nitrophenol to p-aminophenol. After 20 minutes of reaction, the conversion rate was 95.3% and the selectivity was 100%.

[0061] Example 3

[0062] This example provides a specific preparation process of the Co@CM ceramic catalytic membrane. Matters not specifically described in this example are consistent with those of Example 1.

[0063] Prepare 300mL of a 0.2mol / L tris(hydroxymethylaminomethane) aqueous solution (Solution I). Then, slowly add 0.01mol / L dilute hydrochloric acid to Solution I to adjust the pH of the solution to 9.0. Then, add 1.2g of dopamine to a concentration of 4.0g / L. Then, fill the multichannel ceramic membrane into the membrane assembly. Pour the prepared dopamine Tris-HCl buffer solution into the equipment storage tank and adjust the flow rate to 5L / h to force the dopamine Tris-HCl solution to flow through the membrane pores. The modification process temperature is 40°C and the modification time is controlled to 12h. After the modification is completed, remove the membrane tube and place it in a 70°C oven to dry for 12h. The resulting sample is labeled DA@CM-4.0.

[0064] Prepare 300 mL of a 0.5 mol / L Co(NO₃)₂·6H₂O methanol solution. Reinstall the DA@CM-4.0 multichannel ceramic membrane into the membrane assembly. Add the prepared Co(NO₃)₂·6H₂O methanol solution to the storage tank. Adjust the flow rate to 5 L / h to force the Co(NO₃)₂·6H₂O methanol solution through the membrane pores. Maintain a temperature of 40°C for 12 hours. After modification, remove the membrane tube and dry it in a 70°C oven for 12 hours before use. The resulting sample is labeled Co@CM-4.0-0.5.

[0065] The prepared multi-channel ceramic membrane Co@CM-4.0-0.5 was placed in a crucible and placed in a tube furnace for high-temperature calcination. The calcination conditions were as follows: in an argon (Ar) atmosphere, the temperature was raised from room temperature to the target temperature (800°C) at a rate of 10°C / min, and the final target temperature was maintained for 4 hours. After that, the sample was naturally cooled to room temperature to obtain a black catalytic membrane. The obtained catalytic membrane was placed in a forced circulation device with a flow rate of 5L / h. It was rinsed with a mixed solution of ethanol and water with a volume ratio of 1:3 for 60 minutes and then naturally dried to obtain a Co@CM multi-channel ceramic catalytic membrane, marked as Co@CM-4.0-0.5-800.

[0066] The catalytic membrane Co@CM-4.0-0.5-800 was used in the experiment of hydrogenating p-nitrophenol to p-aminophenol. After 20 minutes of reaction, the conversion rate was 94.8% and the selectivity was 100%.

[0067] Example 4

[0068] In this example, the Co@CM-3.0-0.1-700 prepared in Example 1 was used to test the catalytic stability.

[0069] First, start the constant temperature water bath 1 and peristaltic pump 2, setting its speed to 30 r / min and operating the external circulation water system. A 30°C water bath is used to maintain a constant reaction temperature. Then, 10g of p-nitrophenol is added to a mixed solvent consisting of ethanol and deionized water (2500mL, ethanol:deionized water volume ratio = 1:11.5) and stirred for 10 minutes. 0.4mL of the reaction solution is taken as an initial sample. 3.92g of NaBH4 is added and stirred for 10 minutes. Once the system temperature is constant, a portion of the reaction solution is added to the flow-through membrane reactor's storage tank 5, depending on the tank's capacity. Peristaltic pump 3 is turned on and set to a flow rate of 4L / h. The reaction solution flowing out of storage tank 5 is pressurized by peristaltic pump 3 and flows through feed pipe 9 into membrane module 7. In membrane module 7, it is forced to flow through the catalytic membrane and then out of the discharge port on the side of the reactor. The reacted liquid is discharged from the sampling port through the discharge pipe and does not return to storage tank 5. The storage tank is open. When the reaction raw materials in the storage tank are insufficient, fresh pre-prepared reaction solution is poured into the open storage tank to continue the reaction. When the reaction solution flows out of the sampling port, the timer starts, and 0.4mL of reaction solution is sampled every 10 minutes. After the reaction solution is completely consumed, peristaltic pumps 2 and 3 are turned off. Deionized water is then added to the storage tank, and peristaltic pump 2 is turned on to use forced circulation to wash the residual liquid on the catalytic membrane for 20-30 minutes. After rinsing, the catalytic membrane tube is removed and dried at 40-50°C for storage. Testing shows that the catalytic membrane still maintains high activity after 300 minutes of continuous reaction, with no obvious deactivation. The specific results are shown in Figure 4.

[0070] Comparative Example 1

[0071] Prepare 300mL of a 0.1mol / L tris(hydroxymethyl)aminomethane aqueous solution (Solution I). Then, slowly add 0.01mol / L dilute hydrochloric acid to Solution I to adjust the pH of the solution to 8.5. Then, add 0.15g of dopamine to a concentration of 0.5g / L. Then, fill the multichannel ceramic membrane into the membrane assembly. Pour the prepared dopamine Tris-HCl buffer solution into the equipment storage tank and adjust the flow rate to 4L / h to force the dopamine Tris-HCl solution to flow through the membrane pores. The modification process temperature is 30°C and the modification time is controlled to 16h. After the modification is completed, remove the membrane tube and place it in a 60°C oven to dry for 24h. The resulting sample is labeled DA@CM-0.5.

[0072] Prepare 300 mL of a 0.1 mol / L Co(NO₃)₂·6H₂O methanol solution. Reinstall the DA@CM-0.5 multichannel ceramic membrane into the membrane assembly. Add the prepared Co(NO₃)₂·6H₂O methanol solution to the storage tank. Adjust the flow rate to 4 L / h to force the Co(NO₃)₂·6H₂O methanol solution through the membrane pores. Maintain a temperature of 30°C for 16 hours. After modification, remove the membrane tube and dry it in a 60°C oven for 24 hours before use. The resulting sample is labeled Co@CM-0.5-0.1.

[0073] The prepared multi-channel ceramic membrane Co@CM-0.5-0.1 was placed in a crucible and placed in a tube furnace for high-temperature calcination. The calcination conditions were argon (Ar) atmosphere, rising from room temperature to the target temperature (700°C) at a rate of 5°C / min, and the final target temperature was maintained for 5 hours. After that, the sample was naturally cooled to room temperature to obtain a black catalytic membrane. The obtained catalytic membrane was placed in a forced circulation device with a flow rate of 3L / h. It was rinsed with a mixed solution of ethanol and water in a ratio of 1:3 for 60 minutes and then naturally dried to obtain a Co@CM multi-channel ceramic catalytic membrane, marked as Co@CM-0.5-0.1-700.

[0074] The catalytic membrane Co@CM-0.5-0.1-700 was used in the experiment of hydrogenating p-nitrophenol to p-aminophenol. After 20 minutes of reaction, the conversion rate was 42.0% and the selectivity was 100%.

[0075] Comparative Example 2

[0076] Prepare 300mL of a 0.1mol / L tris(hydroxymethylaminomethane) aqueous solution (Solution I). Then, slowly add 0.01mol / L dilute hydrochloric acid to Solution I to adjust the pH of the solution to 8.5. Then, add 0.9g of dopamine to a concentration of 3.0g / L. Then, fill the multichannel ceramic membrane into the membrane assembly. Pour the prepared dopamine Tris-HCl buffer solution into the equipment storage tank and adjust the flow rate to 4L / h to force the dopamine Tris-HCl solution to flow through the membrane pores. The modification process temperature is 30°C and the modification time is controlled to 16h. After the modification is completed, remove the membrane tube and place it in a 60°C oven to dry for 24h. The resulting sample is labeled DA@CM-3.0.

[0077] Prepare 300 mL of a 1.0 mol / L Co(NO₃)₂·6H₂O methanol solution. Reinstall the DA@CM-3.0 multichannel ceramic membrane into the membrane assembly. Add the prepared Co(NO₃)₂·6H₂O methanol solution to the storage tank. Adjust the flow rate to 4 L / h to force the Co(NO₃)₂·6H₂O methanol solution through the membrane pores. Maintain a temperature of 30°C for 16 hours. After modification, remove the membrane tube and dry it in a 60°C oven for 24 hours before use. The resulting sample is labeled Co@CM-3.0-1.0.

[0078] The prepared multi-channel ceramic membrane Co@CM-3.0-1.0 was placed in a crucible and placed in a tube furnace for high-temperature calcination. The calcination conditions were argon (Ar) atmosphere, rising from room temperature to the target temperature (700°C) at a rate of 5°C / min, and the final target temperature was maintained for 5 hours. After that, the sample was naturally cooled to room temperature to obtain a black catalytic membrane. The obtained catalytic membrane was placed in a forced circulation device with a flow rate of 3L / h. It was rinsed with a mixed solution of ethanol and water in a ratio of 1:3 for 60 minutes and then naturally dried to obtain a Co@CM multi-channel ceramic catalytic membrane, marked as Co@CM-3.0-1.0-700.

[0079] The catalytic membrane Co@CM-3.0-1.0-700 was used in the experiment of hydrogenating p-nitrophenol to p-aminophenol. After 20 minutes of reaction, the conversion rate was 56.3% and the selectivity was 100%.

[0080] Comparative Example 3

[0081] Prepare 300mL of a 0.1mol / L tris(hydroxymethylaminomethane) aqueous solution (Solution I). Then, slowly add 0.01mol / L dilute hydrochloric acid to Solution I to adjust the pH of the solution to 8.5. Then, add 0.9g of dopamine to a concentration of 3.0g / L. Then, fill the multichannel ceramic membrane into the membrane assembly. Pour the prepared dopamine Tris-HCl buffer solution into the equipment storage tank and adjust the flow rate to 4L / h to force the dopamine Tris-HCl solution to flow through the membrane pores. The modification process temperature is 30°C and the modification time is controlled to 16h. After the modification is completed, remove the membrane tube and place it in a 60°C oven to dry for 24h. The resulting sample is labeled DA@CM-3.0.

[0082] Prepare 300 mL of a 0.1 mol / L Co(NO₃)₂·6H₂O methanol solution. Reinstall the DA@CM-3.0 multichannel ceramic membrane into the membrane assembly. Add the prepared Co(NO₃)₂·6H₂O methanol solution to the storage tank. Adjust the flow rate to 4 L / h to force the Co(NO₃)₂·6H₂O methanol solution through the membrane pores. Maintain a temperature of 30°C for 16 hours. After modification, remove the membrane tube and dry it in a 60°C oven for 24 hours before use. The resulting sample is labeled Co@CM-3.0-0.1.

[0083] The prepared multi-channel ceramic membrane Co@CM-3.0-0.1 was placed in a crucible and placed in a tube furnace for high-temperature calcination. The calcination conditions were argon (Ar) atmosphere, rising from room temperature to the target temperature (1000°C) at a rate of 5°C / min, and the final target temperature was maintained for 5 hours. After that, the sample was naturally cooled to room temperature to obtain a black catalytic membrane. The obtained catalytic membrane was placed in a forced circulation device with a flow rate of 3L / h. It was rinsed with a mixed solution of ethanol and water in a ratio of 1:3 for 60 minutes and then naturally dried to obtain the Co@CM multi-channel ceramic catalytic membrane, marked as Co@CM-3.0-0.1-1000.

[0084] The catalytic membrane Co@CM-3.0-0.1-1000 was used in the experiment of hydrogenating p-nitrophenol to p-aminophenol. After 20 minutes of reaction, the conversion rate was 51.3% and the selectivity was 100%.

[0085] Comparative Example 4

[0086] This comparative example differs from Example 1 in that drying is not performed after modification of the dopamine Tris-HCl solution and the Co(NO3)2·6H2O methanol solution; the remaining steps are consistent with Example 1. The results, as shown in Figure 5, show that whether the catalytic membrane is dried after the key steps in the preparation process has a significant impact on its catalytic performance. The drying process removes excess solvent, strengthens the bonding between the ceramic membrane and the polydopamine layer, and facilitates the loading of free cobalt ions, enhancing the stability of the catalytically active substances on the ceramic membrane. The catalytic performance of the catalytic membrane prepared after drying is significantly improved.

[0087] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any person skilled in the art may utilize the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes for application in other fields. However, any simple modification, equivalent change, and modification of the above embodiments made in accordance with the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a Co@CM multi-channel ceramic catalytic membrane for hydrogenation of p-nitrophenol, characterized in that: The specific steps are as follows: Step 1: dissolving tris(hydroxymethyl)aminomethane in deionized water to obtain solution I; Step 2: slowly dropwise add dilute hydrochloric acid solution into solution I to adjust the pH to obtain solution II; Step 3: Add dopamine to solution II and mix well to obtain solution III; Step 4: In a forced circulation device, the solution III is forced to flow through the pores and walls of the multi-channel ceramic membrane tube to load dopamine in situ; Step 5: drying to obtain a dopamine-modified multi-channel ceramic membrane; Step 6: Dissolve cobalt nitrate hexahydrate in methanol to obtain solution IV. Step 7: Circulate solution IV and force it to flow through the pores and walls of the multi-channel ceramic membrane tube modified with dopamine to load the cobalt salt in situ; Step 8: drying to obtain a ceramic membrane loaded with cobalt salt; Step nine: calcining and reducing the ceramic membrane loaded with cobalt salt; Step 10: Use ethanol-water solution to forcefully flow through the pores and walls of the membrane tube, and then dry it naturally to obtain a Co@CM multi-channel ceramic catalytic membrane.

2. The method for preparing the Co@CM multi-channel ceramic catalytic membrane for p-nitrophenol hydrogenation according to claim 1, characterized in that: In step 1, the concentration of tris(hydroxymethyl)aminomethane in solution I is 0.05-0.2 mol / L; in step 3, the concentration of dopamine in solution III is 2.0-4.0 g / L; and in step 6, the concentration of cobalt nitrate hexahydrate in solution IV is 0.05-0.5 mol / L.

3. The method for preparing the Co@CM multi-channel ceramic catalytic membrane for p-nitrophenol hydrogenation according to claim 1, characterized in that: In step 2, the pH of solution II is 8.0-9.0, and the concentration of the dilute hydrochloric acid solution is 0.1 mol / L.

4. The method for preparing the Co@CM multi-channel ceramic catalytic membrane for p-nitrophenol hydrogenation according to claim 1, characterized in that: In step 4, the flow rate of solution III in forced circulation is 3-5 L / h, the forced circulation time is 12-36 h, and the temperature controlled by the forced circulation equipment is 20-40°C.

5. The method for preparing the Co@CM multi-channel ceramic catalytic membrane for p-nitrophenol hydrogenation according to claim 1, characterized in that: In step 5 and step 8, the drying temperature is 50-70° C. and the drying time is 12-36 hours.

6. The method for preparing the Co@CM multi-channel ceramic catalytic membrane for p-nitrophenol hydrogenation according to claim 1, characterized in that: In step 7, the flow rate of solution IV in the forced circulation is 3-5 L / h, the time of the forced circulation is 12-36 h, and the temperature controlled by the forced circulation equipment is 20-40°C.

7. The method for preparing the Co@CM multi-channel ceramic catalytic membrane for p-nitrophenol hydrogenation according to claim 1, characterized in that: In step nine, the calcination temperature is 600-800°C, the calcination atmosphere is argon, the heating rate is 2-10°C / min, and the calcination temperature is kept for 4-6 hours; in step ten, the flow rate of forced circulation and flushing of ethanol-water solution is 2-5L / h, the forced circulation and flushing time is at least 60 minutes, and the volume ratio of ethanol to water is 1:

3.

8. Use of the Co@CM multi-channel ceramic catalytic membrane prepared by the method of any one of claims 1 to 7 in hydrogenating p-nitrophenol to prepare p-aminophenol.

9. The use according to claim 8, characterized in that: The reaction process of hydrogenating p-nitrophenol to p-aminophenol is intermittent or continuous. During the reaction, the Co@CM multi-channel ceramic catalytic membrane is fixed, and the p-nitrophenol raw material passes through the pores of the Co@CM multi-channel ceramic catalytic membrane and flows out from the side wall of the Co@CM multi-channel ceramic catalytic membrane.

10. The use according to claim 9, characterized in that: The recycled Co@CM multi-channel ceramic catalytic membrane is used for catalysis. The recycling method is to circulate pure water through the pores and walls of the multi-channel ceramic membrane tube in a forced circulation device for more than 20 minutes and then dry it.

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