Method and system for modifying MOFs catalyst through hydrodynamic cavitation etching
The surface modification of the MOFs catalyst through hydraulic cavitation etching technology solves the problems of its stability and microporous structure limitation application, and achieves the effect of improving catalytic performance and environmental protection and efficiency.
Patent Information
- Application Number
- CN202510013255.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-06
- Publication Date
- 2025-04-29
AI Technical Summary
The application of existing MOFs catalysts in the fields of mass/thermal/charge carrier diffusion is limited by their stability and micropore structure, and there is a lack of effective surface modification methods.
Hydrocatalyst etching technology is used to perform surface etching on the MOFs catalyst, and the surface morphology of the catalyst is changed by utilizing the local high temperature and shock wave generated by cavitation to improve its active site.
The etching efficiency and catalytic performance of the catalyst are improved, and the method does not require the addition of chemical reagents, which is environmentally friendly and efficient.
Smart Images
Figure CN119897163A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of catalyst etching preparation, and in particular to the field of a method for preparing a modified catalyst. Background Art
[0002] Metal-organic frameworks (MOFs), also known as porous coordination polymers, have been extensively studied and applied in a variety of applications since their discovery in the mid-1990s. MOFs have had a lasting impact in various fields due to their attractive properties such as tunable composition, high porosity, well-defined pores, structural diversity, and rich functionality. However, most MOFs are microporous, and their inherent microscale chemical and physical environments greatly limit the widespread application of MOFs in different fields, especially when mass / heat / charge carrier diffusion is involved, and the poor stability of some MOFs has an adverse effect on the performance. Therefore, tailoring MOFs with desired structures and properties is necessary to overcome these inherent limitations of MOFs.
[0003] Etching is considered to be an effective method to customize MOFs with different pore structures and rich functions. Local etching in the MOF framework can change the surface morphology of MOFs and create defects, thereby exposing more active sites.
[0004] The phenomenon of hydrodynamic cavitation can be defined as the formation, growth, and collapse of cavities caused by pressure changes under constant pressure. In recent years, the energy generated by cavitation has been used in many different fields, such as water treatment, biotechnology, and chemical engineering. However, no one has yet applied hydrodynamic cavitation to the modification of MOFs catalysts. The application of cavitation is attributed to the energy released at the moment of cavitation bubble collapse, as well as the shock wave, which are natural physical etching conditions. Therefore, the use of hydrodynamic cavitation to etch the surface of MOFs provides a new method and idea for the modification and preparation of MOFs. Summary of the invention
[0005] Therefore, the present invention aims to solve the problem of physical etching on the surface of MOFs catalysts. The present invention provides a method for modifying MOFs catalysts by hydraulic cavitation etching. The modified catalyst is prepared by physical etching, which can improve the etching efficiency and does not pollute the environment.
[0006] A method for hydrodynamic cavitation etching modified MOFs catalyst, the method comprising: The MOFs catalyst is put into a solvent to obtain a mixed liquid, the hydraulic cavitation etching system is started, and the mixed liquid is passed into the cavitation generator. The catalyst is etched by utilizing the local high temperature generated by the hydraulic cavitation and the shock wave generated by the collapse of the cavitation bubbles. At the same time, the inlet pressure and the cavitation time are adjusted to control the etching effect. After the etching is completed, the catalyst is collected by centrifugation.
[0007] Furthermore, the solvent is a mixture of one or more of water, ethanol, methanol and acetone.
[0008] Furthermore, the volume of the solvent is 4-10 L to obtain a maximum number of passes based on the pump capacity.
[0009] Furthermore, the catalyst is a nano-powder MOFs catalyst; the MOFs catalyst is MIL-53 (Fe) or MIL-101 (Cr).
[0010] Furthermore, the concentration of the MOFs catalyst is 0-5 g / L.
[0011] Furthermore, the cavitation etching time is 0-5h.
[0012] Furthermore, the pressure of the fluid before entering the cavitation generator is 1-6 bar, and the flow rate is 200-800 L / H.
[0013] Furthermore, the hydraulic cavitation etching is a cyclic processing method.
[0014] Furthermore, the photocatalytic etching effect is specifically operated as follows: 10 mg of MOFs powder is suspended in 100 mL of 10 mg L-1 MB aqueous solution and mixed evenly by magnetic stirring. Then, the reaction mixture is kept in the dark for 30 minutes to establish adsorption / desorption equilibrium. After 30 minutes, the mixture is taken out under visible light, and then H2O2 of known concentration is added. Visible light is generated by a 500 W halogen tungsten lamp through a UV cutoff filter (420 nm). 4 ml of solution is taken at 0 min, 5 min, 15 min, 30 min, 45 min, 60 min, 90 min, and 120 min time points and then filtered for absorbance measurement.
[0015] The present invention also aims to provide a hydraulic cavitation etching system, using the method of hydraulic cavitation etching modified MOFs catalyst, the hydraulic cavitation etching system includes a water tank, a cavitation generator, and a booster pump, the water tank is connected to the cavitation generator through a main line, the booster pump is connected between the water tank and the cavitation generator; a branch line is also provided between the booster pump and the water tank, and a valve is provided on the branch line.
[0016] Preferably, the cavitation generator is one of venturi cavitation generator, orifice cavitation generator, eddy current diode, positive and negative pressure rotation cavitation generator and the like.
[0017] The technical solution adopted by the present invention can achieve the following effects:
[0018] 1. Etching method: The aqueous solution containing the catalyst is passed through a cavitation generator such as a venturi tube, orifice plate, eddy current diode, positive and negative pressure rotation, etc. by using a centrifugal pump, and the shock wave generated by cavitation and local high temperature are used to etch the surface morphology of the catalyst. Since the shock wave and high temperature of cavitation occur in a local range, the morphological changes of the catalyst are mostly presented in the form of local pits, which improves the catalytic performance of the catalyst.
[0019] 2. Due to the violent generation of cavitation, this etching method has higher etching efficiency compared with other etching methods.
[0020] 3. Since the etching is physical etching, there is no need to add chemical reagents and it will not cause pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Figure 1 This is a system flow chart of the etching method disclosed in an embodiment of the present invention.
[0022] Figure 2 This is the preparation process flow of MOFs catalysts.
[0023] Figure 3 This is a process flow chart of the cavitation etching method disclosed in an embodiment of the present invention.
[0024] Figure 4 It is an electron microscope image of the catalyst in the comparative example of the present invention.
[0025] Figure 5 This is an electron microscope image of the catalyst in Example 4 of the present invention.
[0026] Figure 6 MB degradation diagram of the etching catalysts of comparative examples and embodiments 1-5 of the present invention.
[0027] Figure 7 MB degradation diagram of the etching catalysts of comparative examples and embodiments 6-9 of the present invention.
[0028] The description of the accompanying drawings is as follows: it includes a water tank 1, a catalyst 2, a valve 3, a boost pump 4, a main line 5, a branch line 6, a valve 7, a flow meter 8, a pressure gauge 9, a cavitation generator 10, and a pressure gauge 11. DETAILED DESCRIPTION
[0029] like Figure 1 The system flow of the method for hydrodynamic cavitation etching MOFs catalyst of the present invention is as follows: a water tank 1 containing a solvent is connected to a cavitation generator 10 via a main line 5, a booster pump 4 is connected between the water tank 1 and the cavitation generator 10, a pressure gauge 9 and a pressure gauge 11 are respectively provided before and after the cavitation generator 10, a valve 3 is provided between the water tank 1 and the booster pump 4, a branch line 6 is also provided between the booster pump 4 and the water tank 1, and a valve 7 is provided on the branch line 6.
[0030] The following is an explanation of the method of hydraulic cavitation etching of MOFs catalysts based on experimental data, taking MIL-53(Fe) as the MOFs catalyst and water as the solvent as an example.
[0031] 1. Experimental test and etching effect verification:
[0032] Comparative Example Blank Control MIL-53 (Fe):
[0033] like Figure 2 , Preparation of catalyst: Figure 2 A mixture of FeCl3·6H2O (1.35 g, 5 mmol), terephthalic acid (TPA) (0.83 g, 5 mmol) and N,N-dimethylformamide (DMF) (25 mL) was first ultrasonicated for 10 minutes to completely dissolve it. The solution was then transferred to a 100 mL reactor and heated in an oven at 150°C for 15 h. The sample was collected by centrifugation, washed with methanol and distilled water in turn, and dried at 60°C. After being fully ground, MIL-53(Fe) was obtained.
[0034] 10 mg of MOFs powder was suspended in 100 mL of 10 mg L-1 MB aqueous solution by magnetic stirring. Then, the reaction mixture was kept in the dark for 30 min to establish adsorption / desorption equilibrium. After 30 minutes, the mixture was taken out under visible light, and then 50ul H2O2 was added. A 500 W halogen tungsten lamp was used for visible light. After the start of light, 3 ml of solution was taken into a test tube at 0 min, 5 min, 15 min, 30 min, 45 min, 60 min, 90 min, and 120 min, and the absorbance of the solution was tested using a spectrophotometer.
[0035] Example 1 P3-T1-MIL-53 (Fe):
[0036] like Figure 1 , Figure 3 , Cavitation etching process: 1.5 g of the catalyst prepared in the comparative example was put into 5 L of water and stirred evenly, valve 3 was fully opened, and then the centrifugal pump was turned on to pass the solution into the venturi tube for cavitation etching. When the equipment was started, valve 7 should be kept fully open, and valve 7 was gradually closed after the equipment was running stably. When the positive pressure was maintained at 3 bar, valve 7 was stopped. After the catalyst was cavitated for 1 hour, the equipment was turned off, the solution was allowed to stand for a period of time, and the lower layer of solution was centrifuged to collect the sample and dried at 60°C.
[0037] Photocatalytic verification of etching effect:
[0038] 10 mg of modified MOFs powder was suspended in 100 mL of 10 mg L-1 MB aqueous solution by magnetic stirring. Then, the reaction mixture was kept in the dark for 30 min to establish adsorption / desorption equilibrium. After 30 minutes, the mixture was taken out under visible light, and then 50 ulH2O2 was added. A 500 W halogen tungsten lamp was used for visible light. After the light was turned on, 3 ml of solution was taken into a test tube at 0 min, 5 min, 15 min, 30 min, 45 min, 60 min, 90 min, and 120 min, and the absorbance of the solution was tested using a spectrophotometer.
[0039] The remaining embodiments were tested with reference to embodiment 1, and the technical parameters and results are shown in Table 1 below.
[0040] Table 1 Technical parameters and results of various examples
[0041] Example Pressure (MPa) Etching time MB degradation rate Comparative Example 52% 1 3 1 60％ 2 4 1 72％ 3 5 1 85％ 4 6 1 93％ 5 7 1 83％ 6 3 2 63% 7 4 2 88% 8 5 2 76% 9 6 2 64%
[0042] 2. Characterization analysis
[0043] (1) SEM analysis
[0044] Figure 4 , Figure 5 They are SEM images of the catalysts in the comparative example and embodiment 4, Figure 4 It can be observed that the MIL-53(Fe) sample without cavitation etching presents a regular octahedral structure as a whole, and its surface morphology is smooth and uniform. Figure 5 It can be observed that after cavitation etching for 1 h at a pressure of 6 bar, the MIL-53(Fe) catalyst becomes a spindle-shaped catalyst as a whole, with a large number of grooves evenly distributed longitudinally on the surface. The appearance of the grooves not only greatly increases the specific surface area of the catalyst, but also enables the active sites inside the catalyst to participate in the catalytic reaction.
[0045] (2) Analysis of cavitation etching effect
[0046] Figure 6 The MB degradation effect diagram of the comparative example and Examples 1-5 is shown in FIG. Figure 7 The following are the MB degradation effect diagrams of comparative examples and examples 6-9. The ordinate is the ratio of the MB absorbance to the initial value at different times, and the abscissa is the catalytic degradation time. The active sites on the catalyst promote the decomposition of H2O2 into hydroxyl radicals under light conditions. The hydroxyl radicals have strong oxidizing properties and will destroy the molecular structure of MB. In addition, the absorbance and concentration of MB are linearly related, so the change in the absorbance is used to represent the change in the MB concentration. Figure 6It can be seen that when the cavitation time is 1 h, the greater the pressure, the faster the MB degradation. When the cavitation time is 1 h and the pressure is 6 bar, the degradation value is the largest; but when the pressure is greater than 6 bar, the catalyst degradation effect gradually deteriorates. Figure 7 When the time is extended to 2 h, the performance of the catalyst etched at 3-4 bar pressure is slightly improved. At 5-6 bar, its degradation effect is worse than that of the catalyst etched at the same pressure for 1 h. From the above phenomenon, it can be seen that pressure and cavitation time have a great influence on the catalytic performance of the catalyst. At present, the catalyst etched at 6 bar pressure for 1 h has the best effect. Extending the time and pressure will cause excessive etching, that is, excessive cavitation, and the high shear force generated will cause the active sites on the catalyst to be cut and peeled off. On the contrary, reducing the cavitation time and pressure will prevent the active sites inside the catalyst from being exposed due to insufficient cavitation intensity.
[0047] The above are only specific embodiments of the present invention, but the technical features of the present invention are not limited thereto. Any simple changes, equivalent replacements or modifications made based on the present invention to solve basically the same technical problems and achieve basically the same technical effects are all included in the protection scope of the present invention.
Claims
1. A method for modifying MOFs catalyst by hydrodynamic cavitation etching, characterized in that: The method comprises: The MOFs catalyst is put into a solvent to obtain a mixed liquid, the hydraulic cavitation etching system is started, and the mixed liquid is passed into the cavitation generator. The catalyst is etched by utilizing the local high temperature generated by the hydraulic cavitation and the shock wave generated by the collapse of the cavitation bubbles. At the same time, the inlet pressure and the cavitation time are adjusted to control the etching effect. After the etching is completed, the catalyst is collected by centrifugation.
2. A method for hydrodynamic cavitation etching modified MOFs catalyst according to claim 1, characterized in that: The solvent is a mixture of one or more of water, ethanol, methanol and acetone.
3. A method for modifying MOFs catalyst by hydrodynamic cavitation etching according to claim 1, characterized in that: The volume of solvent was 4-10 L to obtain the maximum number of passes based on the pump capacity.
4. A method for hydrodynamic cavitation etching modified MOFs catalyst according to claim 1, characterized in that: The catalyst is a nano powder MOFs catalyst.
5. The method of modifying MOFs catalyst by hydrodynamic cavitation etching according to claim 1, characterized in that: The concentration of the MOFs catalyst is 0-5 g / L.
6. A method for modifying MOFs catalyst by hydrodynamic cavitation etching according to claim 1, characterized in that: The cavitation etching time is 0-5h.
7. A method for modifying MOFs catalyst by hydrodynamic cavitation etching according to claim 1, characterized in that: The pressure of the fluid before entering the cavitation generator is 1-6 bar, and the flow rate is 200-800 L / H.
8. A method for modifying MOFs catalyst by hydrodynamic cavitation etching according to claim 1, characterized in that: The hydraulic cavitation etching is a cyclic processing method.
9. A hydraulic cavitation etching system, using a method for modifying MOFs catalyst by hydraulic cavitation etching according to any one of claims 1 to 8, characterized in that: The hydraulic cavitation etching system comprises a water tank, a cavitation generator and a booster pump. The water tank is connected to the cavitation generator through a main line, and the booster pump is connected between the water tank and the cavitation generator. A branch line is also provided between the booster pump and the water tank, and a valve is provided on the branch line.
10. A hydraulic cavitation etching system according to claim 9, characterized in that: The cavitation generator is one of venturi cavitation generator, orifice plate cavitation generator, eddy current diode, positive and negative pressure rotation cavitation generator and the like.