A method for improving the activity of a multi-channel co / cm catalytic membrane

Abstract

This invention belongs to the field of catalytic membrane preparation technology, and relates to a method for improving the activity of multi-channel Co / CM catalytic membranes. The process involves forcibly circulating a sodium borohydride solution through the pores and walls of the multi-channel Co / CM catalytic membrane. This invention significantly improves the catalytic performance and stability of the multi-channel Co / CM catalytic membrane by subjecting it to forced circulation with sodium borohydride solution. The process is simple, low-cost, and highly effective, providing new possibilities for improving the performance and large-scale application of non-precious metal catalytic membranes. This treatment effectively enhances the adsorption capacity of the catalytic membrane to the reaction solution, thereby significantly improving the reaction efficiency of the catalytic membrane, and can be widely applied in hydrogenation processes.

Description

Technical Field

[0001] This invention belongs to the field of catalytic membrane preparation technology, and relates to a method for improving the activity of multi-channel Co / CM catalytic membranes. Background Technology

[0002] As the core component of a catalytic membrane reactor (CMR), the performance of the catalytic membrane directly affects the reactor's operating efficiency. The working principle of a catalytic membrane involves loading active components onto the membrane material, achieving the separation of reactants and products through the membrane's own separation action, while simultaneously acting as a catalyst. This simplifies process steps and saves energy. In recent years, researchers have focused on developing non-precious metal-based catalytic membranes to reduce costs and improve sustainability. Cobalt or nickel-based membranes have been successfully loaded into membrane channels, resulting in catalytic membranes with certain activity. However, compared to precious metal membranes, the catalytic efficiency of existing non-precious metal catalytic membranes is still not high enough, hindering their large-scale application. Summary of the Invention

[0003] This invention addresses the technical problem of insufficient catalytic efficiency of traditional non-precious metal catalytic membranes by proposing a method to improve the activity of multi-channel Co / CM catalytic membranes.

[0004] To achieve the above objectives, the present invention is implemented using the following technical solution: A method for improving the activity of a multichannel Co / CM catalytic membrane involves a process in which sodium borohydride solution is forced to circulate through the pores and walls of the multichannel Co / CM catalytic membrane.

[0005] Preferably, the multi-channel Co / CM catalytic membrane is prepared by the following steps: (1) The methanol solution of 2-methylimidazole and the methanol solution of cobalt nitrate hexahydrate were sequentially filled and forced to circulate through the membrane tube channels and walls of the multi-channel ceramic membrane, and then washed and dried to obtain the ZIF-67 / CM catalytic membrane.

[0006] (2) After calcining and reducing the ZIF-67 / CM catalytic membrane, it was immersed in ethanol to obtain a multi-channel Co / CM catalytic membrane.

[0007] Preferably, the sodium borohydride solution concentration is 25-80 g / L, and the forced circulation flow rate of the sodium borohydride solution is 0.8-2.5 cm. 3 / s, with a duration of no less than 30 minutes.

[0008] Preferably, the forced circulation process of the sodium borohydride solution is carried out under constant temperature conditions, with the constant temperature being 25-45℃.

[0009] As a preferred option, the processing procedure in step (1) is as follows: under water bath conditions, the methanol solution of 2-methylimidazole and the methanol solution of cobalt nitrate hexahydrate are forcibly circulated sequentially for at least 1 hour, and each is forcibly circulated twice alternately. Then, the methanol is forcibly circulated through the membrane tube channels and wall surfaces of the multi-channel ceramic membrane for washing. After washing, the membrane is dried.

[0010] This invention proposes the application of the multichannel Co / CM catalytic membrane prepared by the above method in catalytic hydrogenation reactions.

[0011] After forced circulation treatment with sodium borohydride solution on a multi-channel Co / CM catalytic membrane, the composition of oxygen-containing functional groups on the surface of the Co / CM catalytic membrane underwent a significant transformation. The original OC=O, C=O, and Co-O groups of the Co / CM catalytic membrane disappeared, while C-OH, BO, BO-Co, and Co-OH bonds appeared. This is because cobalt oxides (such as Co3O4 and CoO) were partially reduced to metallic Co by sodium borohydride, forming Co-B, a process that helps improve the catalytic efficiency of the membrane. Secondly, the C=O and OC=O functional groups on the carbon skeleton were reduced to C-OH, a transformation that significantly enhances the adsorption capacity of the catalytic membrane surface. Simultaneously, B bonds with O to form BO and BO-Co bonds, which improve the adsorption and activation capacity of the catalyst by adjusting the local electron density, ultimately enhancing the catalytic efficiency. The catalytic activity and stability of the catalytic membrane treated with forced circulation of sodium borohydride solution were significantly improved.

[0012] Compared with the prior art, the advantages and positive effects of the present invention are as follows: 1. This invention significantly improves the catalytic performance and stability of multi-channel Co / CM catalytic membranes by subjecting them to forced circulation of sodium borohydride solution. The process is simple, low-cost, and highly effective, providing new possibilities for improving the performance and large-scale application of non-precious metal catalytic membranes.

[0013] 2. This treatment process effectively improves the adsorption capacity of the catalytic membrane to the reaction solution and significantly enhances the reaction efficiency of the catalytic membrane, making it widely applicable to hydrogenation reaction processes. Attached Figure Description

[0014] Figure 1 For multi-channel Co / CM catalytic membrane ( Figure 1 a) and the multi-channel Co / CM catalytic membrane after forced flow treatment with sodium borohydride solution ( Figure 1 b) O• element XPS plot.

[0015] Figure 2 The results show the stability test of the multichannel Co / CM catalytic membrane after treatment with sodium borohydride solution. Detailed Implementation

[0016] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below with reference to specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0017] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification. Example 1

[0018] The forced circulation and catalytic reaction in this embodiment and the following embodiments can be performed using the equipment described in patent (CN117160510A), which will not be repeated here. Prepare 200 mL of a 0.48 M 2-methylimidazole methanol solution and 200 mL of a 0.06 M cobalt nitrate hexahydrate methanol solution, and place both solutions separately in a water bath. After the solid material is completely dissolved, fill the membrane module with a multi-channel ceramic membrane (commercially available, alumina, 19 channels, pore size approximately 1000 nm, diameter 3 cm, length 8 cm) and seal the top of the membrane tube. Force the 2-methylimidazole methanol solution through the membrane pores for 1 hour, then drain it. Then switch to the cobalt nitrate hexahydrate methanol solution, force it through the membrane pores, and continue for 1 hour before draining it again. During the forced circulation process, the solution and equipment temperature are controlled at 35°C. o C. The flow rate is 3.5 L / h, and the two solutions are alternately and forcibly circulated twice. Then, 200 mL of methanol is taken, and the temperature is controlled at 35°C. o At C, the membrane tube was cleaned by forced flow at a rate of 3.5 L / h for 15 min, and then the membrane tube was removed and dried in an oven at 70 °C for 4 h. The resulting sample was labeled ZIF-67 / CM.

[0019] The treated ZIF-67 / CM was placed in a tube furnace and calcined at a rate of 5°C / min to 550°C, and held at the target temperature of 550°C for 5 hours. The calcination atmosphere was argon. After calcination, the sample was allowed to cool naturally to room temperature. The resulting sample was labeled Co / CM, and its XPS spectrum is shown below. Figure 1 As shown in Figure a. The prepared multichannel Co / CM catalytic membrane was placed in a beaker, and 500 mL of ethanol was added to completely submerge it. It was then soaked at 35°C for 18 hours. After soaking, the multichannel Co / CM catalytic membrane was removed from the ethanol and placed in a forced circulation convection device. 10.4 g of sodium borohydride was dissolved in 200 mL of deionized water, and the solution was pumped at 1.2 cm⁻¹ using a peristaltic pump. 3The multi-channel Co / CM catalytic membrane was circulated and rinsed for 30 min at a rate of / s. The XPS results of the multi-channel Co / CM catalytic membrane after draining the sodium borohydride solution are shown below. Figure 1 b. This membrane can be directly used for the hydrogenation reaction of p-nitrophenol. Multiple catalytic membranes were prepared in batches under the same conditions in this embodiment for characterization and catalytic reaction. The reaction raw material preparation process is as follows: 2g of p-nitrophenol was added to a mixed solvent of 240mL ethanol and deionized water (ethanol to deionized water volume ratio = 1:5), and the mixture was manually stirred with a glass rod for 2min to dissolve the p-nitrophenol. 0.4mL of the reaction solution was taken as the initial sample; then 5.20g of sodium borohydride was added and stirring continued for 6min. The reaction temperature was controlled at 35℃ using a water bath. The above reaction solution was added to a forced circulation device; the reaction raw material was forced to flow through the bottom of the open membrane tube at a flow rate of 3.5L / h under the action of a peristaltic pump, flowing out through the side membrane pores of the catalytic membrane via the internal channels. When the reaction solution reached the membrane module outlet, timing began, and 0.4mL of the reaction solution was taken as a test sample every 3min. After the reaction was completed, the catalytic membrane was fixed in place, and fresh raw materials were added to continue the reaction. The composition of the product was determined by high performance liquid chromatography. The results showed that the conversion rate was 71.6% and the selectivity was 100% after 3 minutes of reaction.

[0020] from Figure 1 The results show that the oxygen on the surface of the original Co / CM catalytic membrane exists mainly in three forms: OC=O (23.52%), C=O (60.72%), and Co-O (15.76%). After treatment with sodium borohydride, the composition of oxygen-containing functional groups on the surface of the catalytic membrane underwent a significant transformation: the signals of OC=O, C=O, and Co-O completely disappeared, while new groups appeared, including C-OH (12.21%), BO (7.1%), BO-Co (36.19%), Co-OH (39.00%), and a small amount of Na KLL Auger peak (5.5%). This transformation can significantly improve the adsorption capacity of the catalytic membrane surface.

[0021] Stability verification: Add 0.2 g of p-nitrophenol to 1 L of ethanol-water mixture (ethanol to deionized water volume ratio = 1:5), stir for 2 min to dissolve the p-nitrophenol, and take 0.4 mL of the reaction solution as the initial sample; then add 0.52 g of sodium borohydride, and stir at 35 °C. o Under condition C, the reaction solution composed of p-nitrophenol and sodium borohydride is placed in a storage tank, and then... 3 A flow rate of / s was forced through the surface-treated Co / CM catalytic membrane under the pressure of a peristaltic pump and then directly discharged. Samples were taken every 1 hour for component analysis, and the reaction was continued for 12 hours. The product composition was analyzed by high-performance liquid chromatography, and the reaction conversion rate was calculated using a standard curve. The results are as follows: Figure 2 As shown. From Figure 2 As can be seen, the catalytic membrane prepared in this embodiment has good stability, and its catalytic performance did not change significantly during 12 hours of continuous use. Example 2

[0022] Unless otherwise specified, this embodiment and the following embodiments are consistent with Embodiment 1. 23.65 g of 2-methylimidazole was dissolved in 200 mL of methanol and stirred until the solution was clear and transparent, yielding solution A. 10.48 g of cobalt nitrate hexahydrate was dissolved in 200 mL of methanol and stirred until the solution was clear and transparent, yielding solution B. Solution A was first forced to flow through the membrane pores for 1 hour and then discharged. Then, solution B was switched to and similarly forced to flow through the membrane pores for 1 hour before being discharged. Throughout the above process, the temperature of both the solution and the equipment was controlled at 35°C. o C, with a flow rate of 3.5 L / h, the two solutions were circulated alternately in this manner twice each. Then, 200 mL of methanol was taken and circulated at 35 °C. o At temperature C, the membrane tube was forcibly flushed through the pores and sidewalls of the multi-channel ceramic membrane at a rate of 3.5 L / h for 15 min. After flushing, the membrane tube was removed and placed at 70 °C. o The sample was dried in a C oven for 4 hours, and then placed in a tube furnace and heated under an argon atmosphere at 5°C. o Heating rate increased to 550 °C / min o C, calcine for 5 hours, then allow to cool naturally to room temperature. Place the calcined sample in a beaker, add 500 mL of ethanol, and heat at 35°C. o Soak at C for 18 h. After soaking, the multi-channel Co / CM catalytic membrane was flushed for 30 min with 200 mL of a solution containing 10.4 g of sodium borohydride at a rate of 7.2 L / h. The sodium borohydride solution was then drained, thus obtaining the multi-channel Co / CM catalytic membrane. Testing showed that, under the same conditions as in Example 1, the conversion rate was 62.6% and the selectivity was 100% after 3 min of reaction. Example 3

[0023] The difference between this embodiment and Example 1 lies in the treatment time of the sodium borohydride solution, as follows: 200 mL of sodium borohydride solution with a concentration of 52 g / L was prepared and added to a forced convection circulation device. Driven by a peristaltic pump or other power device, the solution flowed in from the bottom of the open membrane tube at a flow rate of 3.5 L / h, forced through the channels inside the Co / CM catalytic membrane, and flowed out from the side membrane pores to perform surface treatment on the multi-channel Co / CM catalytic membrane for 60 min. The rest of the preparation process was the same as in Example 1.

[0024] The pretreated multichannel Co / CM catalytic membrane was used to catalyze the hydrogenation of p-nitrophenol to p-aminophenol, and the product composition was determined by high-performance liquid chromatography (HPLC). The results showed that the conversion rate was 60.7% and the selectivity was 100% after 3 min of reaction.

[0025] Comparative Example 1 The difference between this comparative example and Example 1 is that there is no need to subject the Co / CM catalytic membrane to forced circulation of sodium borohydride solution. The preserved Co / CM catalytic membrane is taken out and directly used in the hydrogenation of p-nitrophenol to p-aminophenol catalytic reaction under the same conditions as in Example 1. After 3 minutes of reaction, the conversion rate is 42.3% and the selectivity is 100%.

[0026] Comparative Example 2 The difference between this comparative example and Example 1 is that the surface treatment and reaction processes of the Co / CM catalytic membrane are combined. Specifically, the sodium borohydride required for both the surface treatment and reaction processes is dissolved together in a p-nitrophenol solution and added to a storage tank for the reaction. The stored Co / CM catalytic membrane is then removed and directly placed in a forced-flow reaction apparatus. The reaction raw material preparation process is as follows: 2g of p-nitrophenol is dissolved in a mixed solvent of 240mL ethanol and deionized water (ethanol to deionized water volume ratio = 1:5), and stirred thoroughly until the p-nitrophenol dissolves. 0.4mL of the reaction solution is taken as the initial sample; then 15.6g of sodium borohydride is added and stirred thoroughly for 3 minutes until the solid dissolves. The reaction temperature is controlled at 35°C using a super-constant temperature water bath. The above reaction solution is added to a forced-flow apparatus, and the p-nitrophenol hydrogenation to p-aminophenol catalytic reaction is carried out through a multi-channel Co / CM catalytic membrane at a flow rate of 3.5L / h under the action of a peristaltic pump or other power equipment. After 3 minutes of reaction, the conversion rate is 50.1%, and the selectivity is 100%.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for improving the activity of a multi-channel Co / CM catalytic membrane, characterized in that, The process involves forcibly circulating a sodium borohydride solution through the pores and walls of the multi-channel Co / CM catalytic membrane.

2. The method for improving the activity of a multi-channel Co / CM catalytic membrane according to claim 1, characterized in that, The multichannel Co / CM catalytic membrane was prepared by the following steps: (1) The methanol solution of 2-methylimidazole and the methanol solution of cobalt nitrate hexahydrate were sequentially filled and forced to circulate through the membrane tube channels and walls of the multi-channel ceramic membrane, and then washed and dried to obtain the ZIF-67 / CM catalytic membrane. (2) After calcining and reducing the ZIF-67 / CM catalytic membrane, it was immersed in ethanol to obtain a multi-channel Co / CM catalytic membrane.

3. The method for improving the activity of a multi-channel Co / CM catalytic membrane according to claim 2, characterized in that, The concentration of sodium borohydride solution is 25-80 g / L, and the flow rate of forced circulation flow of sodium borohydride solution is 0.8-2.5 cm / s, and the time is not less than 30 min. 3 / s, time not less than 30 min.

4. The method for improving the activity of a multi-channel Co / CM catalytic membrane according to claim 3, characterized in that, The forced circulation process of sodium borohydride solution is carried out under constant temperature conditions, with the constant temperature being 25-45℃.

5. The method for improving the activity of a multi-channel Co / CM catalytic membrane according to claim 2, characterized in that, The process of step (1) is as follows: Under water bath conditions, the methanol solution of 2-methylimidazole and the methanol solution of cobalt nitrate hexahydrate are forcibly circulated for at least 1 hour, and each is forcibly circulated twice alternately. Then, the methanol is forcibly circulated through the membrane tube channel and wall of the multi-channel ceramic membrane for washing. After washing, it is dried.

6. The application of the multi-channel Co / CM catalytic membrane prepared by any one of claims 1-5 in the catalytic hydrogenation reaction process.

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