A method for preparing a multi-channel co / cm ceramic catalytic membrane

Abstract

The application relates to a preparation method of a novel multi-channel Co / CM ceramic catalytic membrane, and belongs to the technical field of catalytic membrane preparation. The catalytic membrane takes a multi-channel ceramic membrane as a carrier, ZIF-67 is assembled layer by layer on the surface and in the hole of the ceramic membrane, and a one-step pyrolysis reduction method is adopted to prepare the catalytic membrane. The application has the advantages that nanoscale Co particles are loaded on the ceramic membrane to replace noble metals, the surface of the Co particles is wrapped by carbon and nitrogen, the loss of the Co particles in the reaction process is effectively inhibited, the obtained Co / CM ceramic membrane has excellent catalytic activity and stability, the problem of difficult separation of a traditional catalyst from products is solved, and the Co / CM ceramic membrane can be widely applied to a hydrogenation reaction process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic membrane catalysis, and relates to a preparation method of a multi-channel Co / CM ceramic catalytic membrane. BACKGROUND

[0002] Membrane separation and catalytic reaction can be coupled to form a catalytic membrane reactor, and a catalytic membrane is a core component of the catalytic membrane reactor. The special feature of the catalytic membrane is that the active component can be supported on the membrane material, the reactants and products can be separated by the membrane separation technology, and the catalytic reaction can be carried out at the same time, so that the advantages of realizing in-situ separation of materials and catalysts are achieved, thereby simplifying the process steps and saving energy. The research and development of the catalytic membrane mainly focuses on the aspects of membrane surface modification and preparation method. Patent (CN110841633B) reports a preparation method of a surface-modified catalytic membrane, that is, first, a ceramic membrane carrier is modified by titanium dioxide, then Pd(hfac)2 is deposited on the surface of the carrier by ALD, and then the precursor is reduced to Pd by Formalin (a formaldehyde solution with a concentration of 37% and containing 15% of methanol), thereby preparing the catalytic membrane, which improves the activity and stability of the catalytic membrane to a certain extent. However, noble metals are prone to loss during the reaction, and the cost is high, so it is difficult to be applied on a large scale. Therefore, in addition to these noble metal catalysts, non-noble metal catalysts such as Co are also used for catalytic reactions. In recent years, MOFs as a template material for preparing high-porosity carbon materials have attracted widespread attention. MOFs are a new type of ordered nanometer porous material assembled by metal ions and organic ligands, and have the characteristics of high specific surface area, ordered pore structure and adjustable pore size. It is also reported that MOFs can be directly carbonized (without adding a carbon source) to prepare MOFs-derived metal or metal oxide-carbon composite materials. Patent (CN113289666A) reports a preparation method of a catalytic membrane, in which ZIF-67 is in-situ grown on the surface of a ceramic membrane by an impregnation method, and then calcination is performed in an argon atmosphere, so that the reducing gas produced by pyrolysis of the imidazole skeleton reduces Co 2+ in-situ in ZIF-67 to Co 0Due to the carbonization of the organic ligand in the thermal decomposition process of the MOFs, the agglomeration of the metal nanoparticles is effectively avoided, and the pyrrole nitrogen is generated during the pyrolysis process, effectively improving the catalytic activity of the catalytic membrane. However, compared with the powder catalyst, the loading amount of the active component on the catalytic membrane is relatively low, which makes the catalytic efficiency per unit volume relatively low. Compared with the sheet membrane and the single-channel membrane, the multi-channel ceramic membrane has a more abundant pore structure, which can provide more loading sites for the active component per unit volume, thereby achieving the purpose of increasing the loading amount and significantly improving the catalytic efficiency per unit volume of the membrane. However, the combination of MOFs and ceramic membranes to prepare a catalytic membrane is still a challenge. The catalytic membrane prepared by the conventional method has a relatively small amount of active center components per unit volume, and the binding force between the active component and the membrane material is relatively weak, which leads to a relatively low catalytic activity of the catalytic membrane and easy deactivation during use, thereby hindering the large-scale industrial application of the catalytic membrane. SUMMARY

[0003] The present application is directed to the problems of low activity and poor stability of traditional catalytic membranes, and proposes a preparation method of a novel multi-channel Co / CM ceramic catalytic membrane.

[0004] In order to achieve the above purpose, the present application is realized by adopting the following technical scheme:

[0005] A preparation method of a novel multi-channel Co / CM ceramic catalytic membrane, the specific steps are as follows.

[0006] Step one: dissolve 2-methyl imidazole in methanol, stir until the solution is clear and transparent, and obtain solution A.

[0007] Step two: dissolve cobalt nitrate hexahydrate in methanol, stir until the solution is clear and transparent, and obtain solution B.

[0008] Step three: first fill the membrane channel with solution A, under the action of the peristaltic pump, force the solution A in the channel to flow through the membrane pores of the multi-channel ceramic membrane, and then flow out of the membrane tube. The pipeline is designed to enable the solution A to be recycled under the action of the peristaltic pump. After the forced flow of the solution A lasts for one hour, the solution A is discharged, and the solution B is replaced to repeat the above operation, and the solution A and the solution B are alternately introduced at least twice.

[0009] Step four: after the solution A and the solution B are discharged, force the methanol to flow through the surface and the membrane pores of the washing membrane tube, and after the washing is completed, the membrane tube is taken out and dried to obtain a multi-channel ZIF-67 / CM ceramic membrane.

[0010] Step five: calcine the ZIF-67 / CM ceramic membrane to obtain a multi-channel Co / CM ceramic catalytic membrane.

[0011] Step six: use an ethanol aqueous solution to force the flow through the membrane pores for a period of time to wash off the active component that is not firmly loaded, and obtain a multi-channel Co / CM ceramic catalytic membrane with stable performance.

[0012] As preferred, the concentration of 2-methylimidazole in the solution A prepared in step one is 0.32-0.64 mol / L.

[0013] As preferred, the concentration of cobalt nitrate hexahydrate in the solution B prepared in step two is 0.04-0.08 mol / L.

[0014] As preferred, the forced flow process in step three is kept in a water bath with a temperature of 25-45℃, and solution A is preferentially circulated through the solution alternately, the total time of the forced circulation of solution A and solution B is 4-6h, the material of the multi-channel ceramic membrane is alumina or zirconia, the number of channels is 7-61, and the pore size is 200-5000nm.

[0015] As preferred, the washing time in step four is 10-20min, the drying temperature is 50-70℃, and the drying time is 12-24h.

[0016] As preferred, the temperature of the calcination in step five is 450-770℃, the calcination atmosphere is argon, the heating rate is 2-10℃ / min, the target temperature is reached and kept for 4-6h.

[0017] As preferred, the flow rate of the forced flow washing in step six is 2.5L / h, the time is 45min, and the washing uses an ethanol aqueous solution with a volume ratio of deionized water to ethanol of 5:1.

[0018] The catalyst prepared in the present application is verified for catalytic performance by a reaction of selective hydrogenation of p-nitrophenol to p-aminophenol. In the reaction process, the catalytic membrane is fixed in a membrane module, after the temperature of the reaction system is controlled, an ethanol and deionized water mixed solvent is added, p-nitrophenol raw material is dissolved after being added, and NaBH4 is added as a reducing agent for reaction. During the reaction process, samples can be taken multiple times, the product composition is detected by high performance liquid chromatography (HPLC, Agilent 1200), after the reaction is completed, the liquid in the storage tank is discharged, deionized water is forced to flow through the membrane pores for 10-15min, the catalytic membrane is taken out and dried or oven dried for storage; or fresh raw material is added for continuous reaction.

[0019] The application takes a catalytic membrane of ZIF-67 and multi-channel ceramic membrane substrate as the research object, and prepares a novel Co / CM ceramic membrane through high-temperature one-step pyrolysis. It is proved that ZIF-67 retains a large amount of C and N atoms in the inert gas calcination process due to the absence of oxygen atoms, so that a nitrogen-rich catalytic membrane is obtained, which is beneficial to the transmission of electrons and can effectively inhibit the loss of active components, and excellent catalytic performance is shown in the reaction of p-nitrophenol hydrogenation to p-aminophenol. The application effectively prepares the metal-carbon-nitrogen composite material derived from ZIF-67 by adjusting the calcination temperature. It is found that Co 2+ will be reduced to Co by the reducing gas generated in the calcination process of ZIF-67 and serve as a catalytically active center. The application effectively prepares the metal-carbon-nitrogen composite material derived from ZIF-67 by adjusting the concentration of 2-methylimidazole and cobalt nitrate hexahydrate. It is found that the loading amount of Co is obviously improved with the increase of the concentration of raw materials. The carbonization of organic ligands in the thermal decomposition process of MOFs effectively avoids the agglomeration of metals, and pyrrole nitrogen is gradually generated in the pyrolysis process, which is beneficial to the conversion of reactants.

[0020] Compared with the prior art, the application has the advantages and positive effects that:

[0021] 1. The specific surface area of the multi-channel ceramic membrane is large, and more loading sites can be provided per unit volume, so that the loading amount of active components is increased, and the catalytic efficiency per unit volume is significantly improved.

[0022] 2. ZIF-67 can be orderly dispersed on the surface and in the pores of the ceramic membrane by using the layer-by-layer assembly method, so that the active components are uniformly distributed and the active centers are more after calcination.

[0023] 3. Forced flow not only can force a large amount of solution to flow into the membrane pores and improve the utilization rate of loadable sites inside the membrane pores, but also can remove active components with weak binding force to the ceramic membrane in the process of forced flow, further improving the stability of the catalytic membrane.

[0024] Therefore, the Co / CM ceramic catalytic membrane prepared by the application has high catalytic activity and high stability, realizes in-situ separation of the catalyst and the material, and is suitable for large-scale industrial popularization and application. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The device structure schematic diagram used for the preparation and catalytic performance test of the multi-channel Co / CM ceramic catalytic membrane in Example 1.

[0026] Figure 2 The schematic diagram of the membrane assembly and forced flow method.

[0027] Figure 3Catalytic performance test results of the multi-channel Co / CM ceramic catalytic membrane for different solutions in different orders.

[0028] Figure 4 XRD pattern of the multi-channel Co / CM ceramic catalytic membrane prepared in Example 1.

[0029] Figure 5 EDX pattern of the multi-channel Co / CM ceramic catalytic membrane in Example 1.

[0030] Figure 6 Stability test results of the catalytic membrane in Example 1.

[0031] The reference numerals are as follows: 1 constant temperature water bath, 2 peristaltic pump, 3 peristaltic pump, 4 storage tank jacket, 5 storage tank, 6 membrane reactor jacket, 7 membrane module, 8 pressure gauge, 9 material feeding pipe, 10 circulating water pipe, 11 normally closed exhaust valve, 12 sampling port, 13 discharge port. DETAILED DESCRIPTION

[0032] In order to enable a more clear understanding of the above-mentioned purposes, features and advantages of the present application, the present application will be further described below in conjunction with specific examples. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0033] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can be practiced in other manners different from those described herein, and therefore, the present application is not limited to the specific embodiments disclosed in the following description.

[0034] Example 1

[0035] In this and the following examples, the preparation of the catalytic membrane and the selective hydrogenation of p-nitrophenol to p-aminophenol are carried out using the device as shown in Figure 1 The preparation of the catalytic membrane and the subsequent reaction can also use other devices, this example only provides one of the devices that can realize the preparation of the catalytic membrane and the subsequent reaction process, and reserves the possibility of other devices that can implement the technical solutions of the present application, and does not limit the design of other devices. Figure 1A typical structure of the flow-through membrane reactor, the main components include constant temperature water bath 1, storage tank 5, membrane reactor and pipeline, the lower end of the storage tank 5 is connected with the discharge port 13 for discharging materials. The whole device includes two circulation, respectively, with constant temperature water bath 1 as the starting point of the water circulation, and the starting point of the material circulation of the storage tank. The outside of the membrane reactor and the storage tank 5 is provided with a jacket, the lower end of the jacket is connected with the inlet pipeline of the constant temperature water pipe, and the upper end of the jacket is connected with the outlet pipeline of the constant temperature water pipe. The constant temperature water bath 1 and the storage tank 5 are provided with a peristaltic pump 2, the constant temperature water flowing out of the constant temperature water bath 1 is pressurized by the peristaltic pump 2 and then flows into the storage tank jacket 4 and the membrane reactor jacket 6 in turn, and then flows out of the membrane reactor and then flows through the circulating water pipe 10 and returns to the constant temperature water bath 1, the temperature of the reaction system is controlled by setting the temperature of the water bath. The inside of the membrane reactor is provided with a membrane assembly 7 (custom-made), a multi-channel ceramic membrane tube is placed in the membrane assembly 7, the multi-channel ceramic membrane is fixed in the membrane assembly by sleeving rubber rings on both ends of the multi-channel ceramic membrane, and the flanges at the upper and lower ends are fixed on the membrane assembly by quick mounting clamps. The lower opening of the membrane assembly 7 is matched with the material feeding pipe 9 as the liquid inlet; the side of the membrane assembly is matched with the material outlet pipe as the discharge port, the top opening of the membrane assembly is matched with the exhaust pipeline as the pressure relief port; the peristaltic pump 3 is arranged on the material feeding pipe 9, the sampling port 12 is arranged on the material outlet pipe, the pressure gauge 8 is arranged on the exhaust pipeline, the normally closed exhaust valve 11 is arranged outside the pressure gauge, and the upper end of the membrane tube needs to be sealed, and the normally closed exhaust valve 11 can be closed.

[0036] The specific preparation process of the multi-channel Co / CM ceramic catalytic membrane is as follows.

[0037] (1) Preparation of ZIF-67 / CM membrane

[0038] A 200 mL 2-methylimidazole methanol solution (solution A) with a concentration of 0.48 M and a 200 mL cobalt nitrate hexahydrate methanol solution (solution B) with a concentration of 0.06 M were prepared, and the temperature of each solution was controlled at 30°C by a water bath. After the solid substances were completely dissolved, a multi-channel ceramic membrane (commercially available, alumina, 19 channels, pore size about 1000 nm, diameter 3 cm, length 8 cm) was filled into a membrane module, the 2-methylimidazole methanol solution was added to a storage tank 5 of the reactor, the temperature of a constant-temperature water bath 1 was continuously set at 30°C, a peristaltic pump 2 was turned on, after 5 minutes, a peristaltic pump 3 was turned on, the flow rate was adjusted to 3.5 L / h, and the solution was forced to flow through the membrane pores, which lasted for 1 h. After that, the solution A in the storage tank was poured out from a discharge port 13, and the solution B was replaced, which lasted for 1 h. One circulation was completed after the solution A and the solution B were passed through once. The whole preparation process was performed twice. After 4 h, the peristaltic pump 2 and the peristaltic pump 3 were turned off, the remaining solution in the reactor was discharged, a methanol solution was added to the storage tank, the peristaltic pump 3 was turned on, the flow rate was adjusted to 3.5 L / h, and the membrane tube was cleaned, which lasted for 15 min. Subsequently, the membrane tube was taken out and dried in an oven at 60°C for 18 h, and a sample was obtained, which was marked as ZIF-67 / CM-0.06.

[0039] (2) Preparation of Co / CM catalyst

[0040] The treated ZIF-67 / CM-0.06 was placed in a tube furnace, and calcination was performed at an initial temperature (room temperature) to 550°C, and the temperature was kept at the target temperature 550°C for 5 h, wherein the temperature rising rate was 5°C / min, the calcination atmosphere was argon, and natural cooling was performed to room temperature after the calcination was completed. A sample was obtained, which was marked as Co / CM-550-0.06.

[0041] The membrane pores of the multi-channel ceramic catalytic membrane were flushed to remove the active components that were not firmly loaded. The specific operation method was as follows: a sufficient amount of a mixed solution of deionized water and ethanol (the volume ratio of deionized water to ethanol was 5:1) was prepared and added to the storage tank of the flow-through membrane reactor, the peristaltic pump 2 was turned on, and the flow rate was adjusted to 2.5 L / h. During this process, the solution flowing out of the outlet of the membrane module was not returned to the storage tank, but directly flowed out from the sampling port. Figure 1 The whole process lasted for 45 min, and the stable multi-channel ceramic catalytic membrane was obtained after the flushing. Since the flushing liquid and the solvent of the reaction system were the same, the catalytic membrane after the flushing could be directly used for the catalytic reaction, or was air-dried and oven-dried for storage.

[0042] In order to characterize and verify the effect of the prepared multi-channel ceramic catalytic membrane, a plurality of catalytic membranes were prepared under the same conditions in this embodiment.

[0043] Figure 4The XRD pattern is shown in Figure 2. The diffraction peak centered at 26.4° is attributed to the (002) plane of graphitic carbon. The obvious derivative peaks appearing near 43.9°, 51.2°, and 75.6° are attributed to the (111), (200), and (220) crystal planes of metallic Co, respectively. This indicates that the Co element in ZIF-67 is reduced to zero-valent Co during the pyrolysis process and serves as a catalytic active center.

[0044] Figure 5 The distribution of Co, C, and N in the catalytic membrane prepared in Example 1 is shown. As can be seen from the figure, ZIF-67 pyrolyzes into metallic Co after calcination, and these three elements, Co, C, and N, are present and evenly distributed throughout all layers of the multichannel ceramic membrane. Therefore, the multichannel ceramic membrane provides more loading sites for Co, which is the basis for the catalytic membrane's efficient catalytic hydrogenation of p-nitrophenol to p-aminophenol and its ability to achieve a simple in-situ reduction process.

[0045] The catalytic membrane Co / CM-550-0.06 prepared in this example was used in an experiment to hydrogenate p-nitrophenol to p-aminophenol, and its catalytic performance was tested using a flow-through membrane reactor. First, a constant-temperature water bath was opened and set to 50°C. Once the temperature reached the set value, peristaltic pump 2 was turned on, allowing constant-temperature water to flow sequentially into the storage tank jacket and then the membrane reactor jacket. The reaction raw materials were then prepared: 1g of p-nitrophenol was dissolved in 240mL of a mixed solvent consisting of ethanol and deionized water (volume ratio of ethanol to deionized water = 1:5). Manual stirring was performed until the p-nitrophenol dissolved, and 0.4mL of the reaction solution was taken as the initial sample. Add 3.915g of NaBH₄ and stir manually for 5-10 minutes until the solids dissolve. Then, add the mixed reaction materials to the flow-through membrane reactor's reservoir. Turn on peristaltic pump 3 and adjust the flow rate to 3.5 L / h. Start the timer when the reaction liquid reaches the membrane module outlet. After the reaction liquid flows out of the membrane module, it circulates into the reservoir, sampling 0.4 mL of the reaction liquid every 5 minutes. After the reaction is complete, drain the reservoir and replace it with deionized water, forcing it through the membrane pores for 10-15 minutes. Remove the membrane tube and air-dry or oven-dry it for storage. Alternatively, add fresh raw materials and continue the reaction. High-performance liquid chromatography (HPLC, Agilent 1200) is used to determine product composition. The conversion and selectivity of the reaction are then calculated based on a standard curve.

[0046] Table 1 shows the turnover frequency (TOF) values ​​of Co / CM catalytic membrane and non-precious metal catalysts reported in recent literature. As can be seen from Table 1, under the condition of consuming a small amount of NaBH4, the Co / CM ceramic catalytic membrane obtained in Example still has a high TOF value (1.69×10 -2 s -1), which indicates that Co / CM catalytic membrane has excellent catalytic performance and good application prospect.

[0047] Table 1 Conversion frequency values (TOF) of Co / CM catalytic membrane and catalysts reported in literatures

[0048]

[0049] Note: The calculation method of TOF is the amount of reduction of p-nitrophenol per hour per mole of active component.

[0050] Example 2

[0051] (1) Preparation of ZIF-67 / CM membrane

[0052] A 2-methylimidazole methanol solution with a concentration of 0.32 M and a 200 mL cobalt nitrate hexahydrate methanol solution with a concentration of 0.04 M were prepared, and the two solutions were respectively placed in a water bath, and the water bath temperature was controlled at 30°C. After the solid material was completely dissolved, a multi-channel ceramic membrane (commercially available, zirconium oxide, 7 channels, pore size about 200 nm, diameter 3 cm, length 8 cm) was filled into a membrane module, and the 2-methylimidazole methanol solution was added to the storage tank of the reactor, and the temperature was controlled at 25°C by a constant temperature water bath device. The peristaltic pump was turned on, and the flow rate was adjusted to 2.5 L / h to force the solution to flow through the membrane pores. After 1 h, the solution in the reactor was replaced with solution B, and the solution was continuously introduced for 1 h. One cycle of solution A and solution B was introduced once, and the whole preparation process was carried out for 2 cycles. After 4 h, the remaining solution in the reactor was discharged, methanol solution was added to the storage tank, the peristaltic pump 3 was turned on, the flow rate was adjusted to 2.5 L / h, and the membrane tube was washed for 10 min. Subsequently, the membrane tube was taken out and dried in a 70°C oven for 12 h, and the obtained sample was labeled as ZIF-67 / CM-0.04.

[0053] (2) Preparation of Co / CM catalyst

[0054] The treated ZIF-67 / CM-0.04 was placed in a tube furnace, and the calcination temperature was set at 450°C, and the temperature was kept at the target temperature for 4 h, with a heating rate of 2°C / min, and the calcination atmosphere was argon. The obtained sample was labeled as Co / CM-450-0.04.

[0055] The catalytic membrane Co / CM was applied to the experiment of hydrogenation of p-nitrophenol to p-aminophenol, and the operation method was the same as that of Example 1. The conversion rate reached 84.7% and the selectivity was 100% after 20 min of reaction.

[0056] Example 3

[0057] (1) Preparation of ZIF-67 / CM membrane

[0058] In two 500 mL beakers, 2-methylimidazole methanol solution (solution A) with a concentration of 0.64 M, 200 mL, and cobalt nitrate hexahydrate methanol solution (solution B) with a concentration of 0.08 M, 200 mL, were prepared respectively, and were placed in water bath pots respectively, and the water bath temperature was controlled at 30 ℃, until the solid substances were completely dissolved. During this period, a multi-channel ceramic membrane (commercially available, alumina, 37 channels, pore size about 5000 nm, diameter 3 cm, length 8 cm) was filled into a membrane module, 2-methylimidazole methanol solution was added to the storage tank of the reactor, and the temperature was controlled at 45 ℃ by a constant temperature water bath device, the peristaltic pump was turned on, and the flow rate was adjusted to 4.5 L / h, forcing the solution to flow through the membrane pores, and after 1 h, the solution in the reactor was replaced with solution B, and the solution was continuously introduced for 1 h. One cycle of solution A and solution B was introduced once, and the whole preparation process was carried out for 2 cycles. After 4 h, the remaining solution in the reactor was discharged, methanol solution was added to clean the membrane tube, which lasted for 20 min, and then the membrane tube was taken out and dried in a 50 ℃ oven for 24 h, and the obtained sample was labeled as ZIF-67 / CM-0.10.

[0059] (2) Preparation of Co / CM catalyst

[0060] The treated ZIF-67@CM-0.10 was placed in a tube furnace, and was calcined from an initial temperature (room temperature) to 770 ℃, and was kept at the target temperature for 6 h, wherein the heating rate was 10 ℃ / min, and the calcination atmosphere was argon, and the obtained sample was labeled as Co / CM-770-0.10.

[0061] The catalytic membrane Co / CM was applied to the experiment of hydrogenation of p-nitrophenol to p-aminophenol, and the operation method was the same as in Example 1, and the conversion rate reached 92.3% and the selectivity was 100% after 20 min of reaction.

[0062] Example 4

[0063] (1) Preparation of ZIF-67 / CM membrane

[0064] In two 500 mL beakers, 2-methylimidazole methanol solution (solution A) with a concentration of 0.64 M, 200 mL, and cobalt nitrate hexahydrate methanol solution (solution B) with a concentration of 0.08 M, 200 mL, were prepared respectively, and were placed in water bath pots respectively, and the water bath temperature was controlled at 30°C until the solid substances were completely dissolved. During this period, a multi-channel ceramic membrane (commercially available, alumina, 61 channels, pore size about 1500 nm, diameter 3 cm, length 8 cm) was filled into a membrane module, 2-methylimidazole methanol solution was added into the storage tank of the reactor, the temperature was controlled at 30°C by a constant temperature water bath device, the peristaltic pump was turned on, and the flow rate was adjusted to 5.5 L / h to force the solution to flow through the membrane pores, and after 1 h, the solution in the reactor was replaced with solution B, and the solution was continuously introduced for 1 h. One cycle of solution A and solution B was introduced once, and the whole preparation process was carried out for 2 cycles. After 4 h, the remaining solution in the reactor was discharged, methanol solution was added to clean the membrane tube, and the cleaning was continued for 15 min, then the membrane tube was taken out and dried in an oven at 60°C for 12 h, and the obtained sample was labeled as ZIF-67 / CM-0.08.

[0065] (2) Preparation of Co / CM catalyst

[0066] The treated ZIF-67 / CM-0.08 was placed in a tube furnace, calcined from the initial temperature (room temperature) to 650°C, and kept at the target temperature for 5 h, wherein the heating rate was 5°C / min, and the calcination atmosphere was argon, and the obtained sample was labeled as Co / CM-650-0.08.

[0067] The catalytic membrane Co / CM was applied to the experiment of hydrogenation of p-nitrophenol to p-aminophenol, and the operation method was the same as in Example 1. The conversion rate reached 85% and the selectivity was 100% at 20 min.

[0068] Example 5

[0069] In this example, the Co / CM-550-0.06 prepared in Example 1 was used for testing the catalytic stability. Before testing the stability, the multi-channel ceramic catalytic membrane pores were flushed to remove the active components that were not firmly loaded by using the device shown in Figure 1 The specific operation method was as follows: a sufficient amount of deionized water and ethanol mixed solution (the volume ratio of deionized water to ethanol was 5:1) was prepared, and was added into the storage tank of the flow-through membrane reactor, the peristaltic pump 2 was turned on, and the flow rate was adjusted to 2.5 L / h. During this process, the solution flowing out of the outlet of the membrane module was not returned to the storage tank, but directly flowed out from the sampling port shown in Figure 1 The whole process was carried out for 45 min, and after the end, the multi-channel ceramic catalytic membrane could be directly used for the stability test (i.e. continuous catalytic process) of this example or air-dried, oven-dried and stored.

[0070] The specific method of stability test is: prepare enough 0.5 g / L p-nitrophenol solution, after the solid substance is completely dissolved, add sodium borohydride (the molar ratio of p-nitrophenol to sodium borohydride is 1:14.4), and stir until the solid is dissolved. Set the temperature of the constant temperature water bath to 50℃, when the temperature reaches the set value, open the peristaltic pump 2, so that the constant temperature water flows into the storage tank jacket and the membrane reactor jacket in turn. Add the reaction raw material to the storage tank of the flow-through membrane reactor, open the peristaltic pump 3, and adjust the flow rate to 3.5 L / h. During this process, the solution flowing out of the membrane module outlet is not returned to the storage tank, but directly flows out from the sampling port, and an additional receiving tank can be provided to store the reaction product. Take a sample every 25 min at the sampling port. During this process, when the solution in the storage tank is about to be consumed, fill the storage tank with the prepared solution, and continue for 5 h. As shown in Figure 1 , the conversion rate of the catalytic membrane to p-nitrophenol remains at 100% within 5 h, and there is no obvious deactivation. Figure 6

[0071] Comparative Example 1

[0072] (1) Preparation of ZIF-67 / CM membrane

[0073] In two 500 mL beakers, prepare 2-methylimidazole methanol solution (solution A) with a concentration of 0.48 M, 200 mL, and cobalt nitrate hexahydrate methanol solution (solution B) with a concentration of 0.06 M, 200 mL, respectively, and place them in a water bath, control the water bath temperature to 30℃, and wait until the solid substance is completely dissolved. During this period, fill the membrane module with a multi-channel ceramic membrane (commercially available, alumina, 19 channels, pore size about 1000 nm, diameter 3 cm, length 8 cm), add 2-methylimidazole methanol solution to the storage tank of the reactor, control the temperature at 30℃ by the constant temperature water bath device, open the peristaltic pump, and adjust the flow rate to 3.5 L / h to force the solution to flow through the membrane pores, continue for 1 h, then replace the solution in the reactor with solution B, and continue to pass for 1 h. One cycle of passing solution A and solution B is 1 h, and the whole preparation process is 2 cycles. After 4 h, discharge the remaining solution in the reactor, wash the membrane tube with methanol solution for 10 min, then take out the membrane tube and dry it in a 70℃ oven for 24 h, and the obtained sample is marked as ZIF-67 / CM-0.06.

[0074] (2) Preparation of Co / CM catalyst

[0075] Place the treated ZIF-67 / CM-0.06 in a tube furnace, calcine from the initial temperature (room temperature) to 350℃, and keep the temperature at the target temperature for 5 h, with a heating rate of 5℃ / min, and the calcination atmosphere is argon, and the obtained sample is marked as Co / CM-350-0.06. ​

[0076] The catalytic membrane Co / CM was applied to the experiment of hydrogenation of p-nitrophenol to p-aminophenol, and the operation method was the same as that in Example 1. The conversion rate was 53.1% and the selectivity was 100% at 20 min.

[0077] Comparative Example 2

[0078] (1) Preparation of ZIF-67 / CM membrane

[0079] In two 500 mL beakers, 2-methylimidazole methanol solution (solution A) with a concentration of 0.16 M and 200 mL, and cobalt nitrate hexahydrate methanol solution (solution B) with a concentration of 0.02 M and 200 mL were prepared, respectively, and were placed in a water bath, and the water bath temperature was controlled at 30°C. After the solid substances were completely dissolved, a multi-channel ceramic membrane (commercially available, alumina, 19 channels, pore size about 1000 nm, diameter 3 cm, length 8 cm) was filled into a membrane module, 2-methylimidazole methanol solution was added to the storage tank of the reactor, and the temperature was controlled at 30°C by a constant temperature water bath device. The peristaltic pump was turned on, and the flow rate was adjusted to 3.5 L / h to force the solution to flow through the membrane pores. After 1 h, the solution in the reactor was replaced with solution B, and the solution was continuously introduced for 1 h. One cycle of solution A and solution B was one cycle, and the whole preparation process was carried out for 2 cycles. After 4 h, the remaining solution in the reactor was discharged, and the membrane tube was washed with methanol solution for 10 min. Then the membrane tube was taken out and dried in a 70°C oven for 24 h. The obtained sample was labeled as ZIF-67 / CM-0.02.

[0080] (2) Preparation of Co / CM catalyst

[0081] The treated ZIF-67@CM-0.02 was placed in a tube furnace, and calcined from the initial temperature (room temperature) to 550°C at a heating rate of 5°C / min, and kept at the target temperature for 5 h. The calcination atmosphere was argon, and the obtained sample was labeled as Co / CM-550-0.02.

[0082] The catalytic membrane Co / CM was applied to the experiment of hydrogenation of p-nitrophenol to p-aminophenol, and the operation method was the same as that in Example 1. The conversion rate was 42.4% and the selectivity was 100% at 20 min.

[0083] The above is only a preferred embodiment of the present application, and is not intended to limit the present application in other forms. Any skilled person in the art can modify or change the above disclosed technical content to equivalent embodiments applied to other fields, but any simple modification, equivalent change and modification made to the above embodiments without departing from the technical solution content of the present application, according to the technical essence of the present application, still belongs to the protection scope of the technical solution of the present application.

Claims

1. A method for preparing a multi-channel Co@CM ceramic catalytic membrane, characterized in that, The steps are as follows: Step one: 2-methylimidazole is dissolved in methanol to obtain solution A; Step two: cobalt nitrate hexahydrate is dissolved in methanol to obtain solution B; Step three: one end of the multi-channel ceramic membrane tube is sealed, solution A is first filled into the channels of the ceramic membrane tube, and then pressure is provided to make solution A flow from the inside of the membrane channel to the outside of the membrane tube for forced circulation for more than 1 h, then solution B is switched to make solution B flow from the inside of the membrane channel to the outside of the membrane tube for forced circulation for more than 1 h, and the process is repeated, so that the number of times of alternating forced circulation of solution A and solution B is at least twice; Step four: methanol is forced to flow from the inside of the membrane channel to the outside of the membrane tube for washing, and then dried to obtain a multi-channel ZIF-67@CM ceramic membrane; Step five: the ZIF-67@CM ceramic membrane is calcined; Step six: the membrane pores are washed with an ethanol aqueous solution to obtain a stable multi-channel Co@CM ceramic catalytic membrane; In step one, the concentration of 2-methylimidazole in solution A is 0.32-0.64 mol / L; in step two, the concentration of cobalt nitrate hexahydrate in solution B is 0.04-0.08 mol / L; in step three, the pore size of the multi-channel ceramic membrane is 200-5000 nm; in step five, the calcination temperature is 450-770°C, the calcination atmosphere is argon, the heating rate is 2-10°C / min, and the temperature is kept at the calcination temperature for 4-6 h.

2. The method for preparing the multi-channel Co@CM ceramic catalytic membrane according to claim 1, characterized in that, In step three, the material of the multi-channel ceramic membrane is alumina or zirconia, the number of channels is 7-61, the temperature of solution A, solution B and the multi-channel ceramic membrane tube is kept at 25-45°C, the total time of alternating forced circulation of solution A and solution B is 4-6 h, and the flow rate of the alternating forced circulation of solution A and solution B is 2.5-5.5 L / h.

3. The method for preparing the multi-channel Co@CM ceramic catalytic membrane according to claim 1, characterized in that, In step four, the washing time is 10-20 min, the drying temperature is 50-70°C, and the drying time is 12-24 h.

4. The method of claim 1, wherein the multi-channel Co@CM ceramic catalytic membrane is prepared by the steps of: In step six, the flow rate of the forced flow washing is 2.5 L / h, the washing time is 45 min, and the washing is performed using an ethanol aqueous solution, and the volume ratio of deionized water to ethanol in the ethanol aqueous solution is 5:

1.

5. The application of the ceramic catalytic membrane prepared by the method of any one of claims 1-4 in the process of selectively hydrogenating p-nitrophenol to p-aminophenol.

6. A process for the selective hydrogenation of p-nitrophenol to p-aminophenol, characterized in that, The ceramic catalytic membrane prepared by the method of any one of claims 1-4 is used as a catalyst, and the ceramic catalytic membrane is immersed in a p-nitrophenol solution for batch or continuous reaction.

7. The process for the selective hydrogenation of p-nitrophenol to p-aminophenol according to claim 6, characterized in that, The recovered multi-channel Co@CM ceramic membrane is used to catalyze the batch or continuous reaction of a p-nitrophenol solution, and the recovery method is to wash the membrane pores with deionized water for 10-15 min, and then take out the ceramic membrane for air drying or oven drying.

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