Nickel-based magnesium-aluminum aerogel catalyst and preparation method thereof
Through the steps of sealing and supercritical drying in magnesium-aluminum aerogel, a nickel-based magnesium-aluminum aerogel catalyst was prepared, which solved the problems of its instability at high temperatures and difficulty in adjusting lipophilicity, achieved better catalytic performance and stability, and was suitable for fuel catalytic reforming.
Patent Information
- Application Number
- CN202411867117.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-18
- Publication Date
- 2025-03-25
AI Technical Summary
The existing magnesium-aluminum aerogel catalysts are unstable at high temperatures and are difficult to adjust their lipophilicity, resulting in limited application in the field of fuel catalytic reforming.
The nickel-based magnesium-aluminum aerogel catalyst with a smaller average pore size and a larger specific surface area was prepared by adding n-hexane and ethanol to the magnesium-aluminum aerogel to the magnesium-aluminum aerogel to stabilize its structure, and by supercritical drying and heat treatment steps, a nickel-based magnesium-aluminum aerogel catalyst with a smaller average pore size and a larger specific surface area.
It improves the structural stability and lipophilicity of magnesium-aluminum aerogel, so that it exhibits better catalytic performance at high temperatures and can be stably dissolved in fuel oil, and is suitable for schema homogeneous catalytic reforming.
Smart Images
Figure CN119680550A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of nickel-based magnesium-aluminum aerogel catalyst preparation, and in particular to a nickel-based magnesium-aluminum aerogel catalyst and a preparation method thereof. Background Art
[0002] The special environment inside aircraft engines places requirements and challenges on the way catalysts are used in them. Hydrocarbon fuels flow fast and have a short residence time in the engine, so it is best to use homogeneous catalysis. Nitro compounds, triethylaluminum and other compounds that are soluble in hydrocarbon fuels have been used for catalytic cracking, but these compounds have disadvantages such as easy explosion, difficult storage and high cost. Therefore, researchers proposed to improve the distribution of functional groups on the surface of the catalyst to make it oil-soluble nanoparticles, and then add it to the fuel as an additive for pseudo-homogeneous catalytic reforming. Due to the small particle size of the pseudo-homogeneous catalyst, its specific surface area is relatively large, and its shape is relatively irregular. Such physical properties make it easy for a large number of positive and negative charges to accumulate on its surface, thereby enhancing the surface van der Waals attraction. Therefore, pseudo-homogeneous catalysts are prone to aggregation during the reaction.
[0003] Aerogel has a wide range of applications in the fields of catalyst carriers, high-temperature insulation, etc. due to its unique nanoporous three-dimensional network structure, high temperature resistance, large specific surface area, small porosity, and low density. Almost all oxides with catalytic properties can be made into aerogels, which provides the possibility for the application of aerogels in the field of catalysis. Aerogels have excellent structural properties, are easy to modify, and are resistant to high temperatures, giving them better catalytic properties. In addition, a large number of studies have shown that nanoparticles such as aerogels exhibit good fluidity by self-aggregating to a suitable size. Therefore, aerogels can be used as quasi-homogeneous catalyst carriers for catalytic reactions. However, at present, there are still some difficulties in this application, such as the structural instability of magnesium-aluminum aerogels after long-term storage, poor thermal stability at high temperatures, and difficulty in adjusting lipophilicity. Summary of the invention
[0004] The purpose of the present invention is to provide a nickel-based magnesium-aluminum aerogel catalyst and a preparation method thereof, so as to realize that the pseudo-homogeneous nickel-based magnesium-aluminum aerogel can be applied to the field of fuel catalytic reforming and improve the catalytic effect.
[0005] In order to achieve the above object, the present invention provides the following technical solution: a method for preparing a nickel-based magnesium-aluminum aerogel catalyst, the specific steps are as follows:
[0006] Step 1: dissolve aluminum nitrate nonahydrate and magnesium nitrate hexahydrate in anhydrous ethanol solution, and stir at room temperature (not higher than 40° C.) for 0.5-1 h until completely dissolved;
[0007] Step 2: Continue stirring the solution obtained in step 1, and quickly add propylene oxide during this process. When the solution begins to gel, stop stirring until the solution is completely gelled;
[0008] Step 3: Add n-hexane to the gel obtained in step 2, and seal it at 20-40°C, replacing the n-hexane every 12 hours for a total of 2 times;
[0009] Step 4: Add anhydrous ethanol to the gel obtained in step 3, and seal it at 20-40° C. Replace the anhydrous ethanol every 12 hours for a total of 3-4 times;
[0010] Step 5: supercritically drying the aged gel obtained in step 4 to obtain a magnesium aluminum aerogel precursor;
[0011] Step 6: placing the magnesium aluminum aerogel precursor obtained in step 5 into a muffle furnace for calcination to obtain magnesium aluminum aerogel;
[0012] Step 7: Grind the magnesium aluminum aerogel obtained in step 6 into powder and sieve it, take a certain amount of magnesium aluminum aerogel to measure the saturated water absorption rate, and calculate the amount of deionized water;
[0013] Step 8: dissolving nickel nitrate hexahydrate in the deionized water in step 7 to obtain a precursor solution;
[0014] Step nine: quickly pour the magnesium aluminum aerogel obtained in step six into the precursor solution obtained in step eight, and continue stirring for 0.5-1.5 hours until the precursor solution is completely and evenly immersed in the magnesium aluminum aerogel;
[0015] Step 10: Dry the catalyst obtained in step 9 in a 50°C water bath, increase the temperature by 10°C every hour until dry, and then dry it again in an oven at 100-110°C for 12 hours;
[0016] Step 11: Place the catalyst obtained in step 10 into a muffle furnace for calcination to obtain the final nickel-based magnesium-aluminum aerogel catalyst.
[0017] Preferably, in step 1, the amounts of aluminum nitrate nonahydrate and magnesium nitrate hexahydrate used satisfy a Mg / Al molar ratio of 0.5.
[0018] Preferably, in step 2, the molar ratio of propylene oxide to the total amount of magnesium and aluminum in the magnesium-aluminum aerogel is 2.5:1.
[0019] Preferably, the supercritical drying in step five uses a CO2 dryer, the temperature during replacement is 0°C, the replacement degassing rate is 0.5-1.5L / min, the replacement time is 5-8h, the reaction temperature of supercritical drying is 35°C, the pressure in the kettle is 8-10MPa, the degassing rate is 20-50ml / min, and the drying time is 1-3h.
[0020] Preferably, the heat treatment atmosphere in step six is nitrogen, the temperature is 650-800° C., the heating rate is 10° C. / min, and the heat treatment is performed for 5-6 hours.
[0021] Preferably, the sieve used in step seven is 400 mesh or larger, and the amount of magnesium aluminum aerogel used in step nine includes the magnesium aluminum aerogel used to measure the saturated water absorption rate in step seven.
[0022] Preferably, the criterion for judging dryness in step 10 is that the catalyst does not stick to the cup wall and the catalyst can flow when poured.
[0023] Preferably, the heat treatment atmosphere in step eleven is a mixture of hydrogen and nitrogen, the temperature is 650-800° C., the heating rate is 10° C. / min, and the heat treatment is performed for 1-3 hours.
[0024] The present invention also includes a nickel-based magnesium-aluminum aerogel catalyst prepared by the above method.
[0025] The present invention also includes the application of the nickel-based magnesium-aluminum aerogel catalyst in the field of fuel catalytic reforming, wherein the application is as a catalyst for pseudo-homogeneous catalytic reforming of fuel.
[0026] In the above technical solution, the technical effects and advantages provided by the present invention are:
[0027] 1. The present invention stabilizes the structure of magnesium-aluminum aerogel by sealing with n-hexane and ethanol, so that the stabilized magnesium-aluminum aerogel has a smaller average pore size and a larger specific surface area and pore volume. After aging at 850°C, the specific surface area is 157m 2 / g, the average pore size is 4.94nm, and the pore volume is 0.46mL / g, which is also convenient for demolding of magnesium-aluminum aerogel;
[0028] 2. The method of the present invention does not require a separate modification operation. The prepared nickel-based magnesium-aluminum aerogel catalyst has extremely strong lipophilicity and a contact angle of 0 with the fuel, which provides the possibility of realizing pseudo-homogeneous catalytic reforming of the fuel. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 This is a flow chart of a method for preparing a nickel-based magnesium-aluminum aerogel catalyst in an embodiment of the present invention;
[0030] Figure 2 Schematic diagram of the contact angles of the nickel-based magnesium-aluminum aerogel with fuel (a) and water (b) in the lipophilicity test in the embodiment of the present invention;
[0031] Figure 3 This is a schematic diagram of the nickel-based magnesium aluminum aerogel in an embodiment of the present invention being stably dispersed in n-decane after being left to stand for 2 months. DETAILED DESCRIPTION
[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.
[0033] The present invention provides a nickel-based magnesium-aluminum aerogel catalyst used in the field of fuel catalytic reforming. The preparation method of the nickel-based magnesium-aluminum aerogel catalyst is as follows: Figure 1 As shown, the steps include:
[0034] Solution preparation: dissolve aluminum nitrate nonahydrate and magnesium nitrate hexahydrate in anhydrous ethanol solution, the amount of aluminum nitrate nonahydrate and magnesium nitrate hexahydrate used satisfying the Mg / Al molar ratio of 0.5, and stir at room temperature for 1 hour until completely dissolved.
[0035] Sol preparation: Propylene oxide was added during the stirring of the solution, and the molar ratio of propylene oxide to the total amount of magnesium and aluminum in the magnesium-aluminum aerogel was 2.5:1. When the solution began to gel, stirring was stopped until the solution was completely gelled.
[0036] Gel regulation and aging: Add n-hexane to obtain gel, and seal it at 30°C. Replace the n-hexane every 12 hours, for a total of 2 changes. Then add anhydrous ethanol to the gel obtained in step 3, and seal it at 30°C. Replace the anhydrous ethanol every 12 hours, for a total of 3 changes, to obtain aged gel.
[0037] Supercritical drying treatment: Use a CO2 dryer to perform supercritical drying on the aged gel. The temperature during replacement is 0°C, the replacement degassing rate is 1L / min, the replacement time is 6h, the supercritical drying reaction temperature is 35°C, the pressure in the kettle is 10MPa, the degassing rate is 40ml / min, and the drying time is 3h to obtain a magnesium aluminum aerogel precursor.
[0038] Heat treatment: The magnesium aluminum aerogel precursor is placed in a muffle furnace for calcination. The heat treatment atmosphere is nitrogen, the temperature is 650-800°C, the heating rate is 10°C / min, and the heat treatment is 5-6h.
[0039] Ni is loaded by the initial wet impregnation method: the heat-treated magnesium-aluminum aerogel is ground into powder and sieved with a sieve of 400 mesh or above, and then nickel nitrate hexahydrate is dissolved in deionized water to obtain a precursor solution, and then the powdered magnesium-aluminum aerogel is quickly poured into the precursor solution and stirred for 1 hour until the precursor solution is completely and evenly immersed in the magnesium-aluminum aerogel. The catalyst is then placed in a 50°C water bath to dry, and the temperature is increased by 10°C every 1 hour until it is basically dry. The criterion for basic dryness is that the catalyst does not stick to the cup wall, and the catalyst can flow when poured, and then it is placed in an oven at 100°C and dried again for 12 hours.
[0040] Heat treatment: The catalyst is placed in a muffle furnace for calcination. The heat treatment atmosphere is a mixture of hydrogen and nitrogen. The temperature is 650-800°C, the heating rate is 10°C / min, and the heat treatment is performed for 1-3h to obtain the final nickel-based magnesium-aluminum aerogel catalyst.
[0041] The nickel-based magnesium-aluminum aerogel prepared in this embodiment was aged at high temperature (850°C) and had a specific surface area of 157 m 2 / g, average pore diameter 4.94nm, pore volume 0.46mL / g, and stable structure, with lipophilicity (such as Figure 2 As shown), dissolved in fuel oil and left to stand for more than 2 months, no sedimentation occurs (as shown Figure 3 This provides the possibility for realizing pseudo-homogeneous catalytic reforming of fuels.
[0042] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.
Claims
1. A method for preparing a nickel-based magnesium-aluminum aerogel catalyst, characterized in that: The specific steps are as follows: Step 1: dissolving aluminum nitrate nonahydrate and magnesium nitrate hexahydrate in an anhydrous ethanol solution to prepare a solution; Step 2: adding propylene oxide to the solution obtained in step 1 to prepare a gel; Step 3: adding n-hexane to the gel obtained in step 2 and sealing; Step 4: adding anhydrous ethanol to the gel obtained in step 3 and sealing the gel to obtain an aged gel; Step 5: supercritically drying the aged gel obtained in step 4 to obtain a magnesium aluminum aerogel precursor; Step 6: heat treating the magnesium aluminum aerogel obtained in step 5; Step 7: Grind the magnesium aluminum aerogel obtained in step 6 into powder; Step 8: dissolving nickel nitrate hexahydrate in deionized water to obtain a precursor solution; Step nine: pouring the powdered magnesium aluminum aerogel obtained in step seven into the precursor solution obtained in step eight, so that the precursor solution is completely and evenly immersed in the magnesium aluminum aerogel; Step 10: drying the catalyst obtained in step 9; Step 11: heat-treating the catalyst obtained in step 10 to obtain the final nickel-based magnesium-aluminum aerogel catalyst.
2. The method for preparing a nickel-based magnesium-aluminum aerogel catalyst according to claim 1, characterized in that: In step 1, the amounts of aluminum nitrate nonahydrate and magnesium nitrate hexahydrate are such that the Mg / Al molar ratio is 0.
5.
3. The method for preparing a nickel-based magnesium-aluminum aerogel catalyst according to claim 1, characterized in that: In step 2, the molar ratio of propylene oxide to the total amount of magnesium and aluminum in the magnesium-aluminum aerogel is 2.5:
1. When the solution begins to gel, stirring is stopped until the solution is completely gelled; In step 3, the sealing temperature is 20-40°C, and the n-hexane is replaced every 12 hours, for a total of 2 times; In step 4, the sealing temperature is 20-40°C, and the anhydrous ethanol is replaced every 12 hours, for a total of 3-4 times.
4. The method for preparing a nickel-based magnesium-aluminum aerogel catalyst according to claim 1, characterized in that: The supercritical drying in step 5 uses a CO2 dryer, the temperature during displacement is 0°C, the displacement degassing rate is 0.5-1.5L / min, the displacement time is 5-8h, the reaction temperature of supercritical drying is 35°C, the pressure in the kettle is 8-10MPa, the degassing rate is 20-50ml / min, and the drying time is 1-3h.
5. The method for preparing a nickel-based magnesium-aluminum aerogel catalyst according to claim 1, characterized in that: The heat treatment in step six is performed in a muffle furnace with a nitrogen atmosphere, a temperature of 650-800° C., a heating rate of 10° C. / min, and a heat treatment period of 5-6 hours.
6. The method for preparing a nickel-based magnesium-aluminum aerogel catalyst according to claim 1, characterized in that: In step 7, the powdered magnesium aluminum aerogel is sieved using a sieve with a mesh size of 400 or more.
7. The method for preparing a nickel-based magnesium-aluminum aerogel catalyst according to claim 1, characterized in that: The drying method of step 10 is as follows: the catalyst obtained in step 9 is placed in a 50°C water bath for drying, the temperature is increased by 10°C every 1h until it is basically dry, and then placed in an oven at 100-110°C for drying again for 12h; The basic dryness criterion is that the catalyst does not stick to the cup wall and can flow when poured.
8. The method for preparing a nickel-based magnesium-aluminum aerogel catalyst according to claim 1, characterized in that: The heat treatment in step eleven is calcination in a muffle furnace, the atmosphere is a mixture of hydrogen and nitrogen, the temperature is 650-800° C., the heating rate is 10° C. / min, and the heat treatment is 1-3 hours.
9. A nickel-based magnesium-aluminum aerogel catalyst, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.
10. An application of the nickel-based magnesium-aluminum aerogel catalyst according to claim 9 in the field of fuel catalytic reforming, characterized in that: The application is as a catalyst for pseudo-homogeneous catalytic reforming of fuels.