Synthesis method for modified alumina
Modified alumina was prepared by co-current reaction of surfactants and rare earth modifiers, which solved the problem of rare earth element agglomeration during hydrothermal doping and achieved alumina carrier with high thermal stability and high specific surface area, suitable for automobile exhaust purification.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- TIANJIN PASSION ADVANCED MATERIAL TECH CO LTD
- Filing Date
- 2025-07-18
- Publication Date
- 2026-07-16
AI Technical Summary
In the existing technology, rare earth elements and pseudoboehmite are prone to agglomeration during the hydrothermal doping process, resulting in low thermal stability of the final prepared active alumina carrier under high temperature conditions, which cannot meet the requirements of the automotive exhaust purification carrier.
Modified boehmite powder was prepared by reacting surfactants, rare earth modifiers, and sodium aluminate aqueous solution in a co-current manner, combined with silanes and organic solvents. The powder was then calcined to form modified alumina, ensuring uniform dispersion of rare earth elements and forming a heat-resistant framework.
It significantly improves the thermal stability of alumina, shortens the preparation time, and maintains a high specific surface area and pore volume, making it suitable as a catalyst support for automotive exhaust purification.
Smart Images
Figure CN2025109309_16072026_PF_FP_ABST
Abstract
Description
A method for synthesizing modified alumina
[0001] Cross-reference to related applications
[0002] This application claims the benefit of Chinese application number 2025100396613, filed January 10, 2025. The application number 2025100396613 is hereby incorporated by reference in its entirety. TECHNICAL FIELD
[0003] The present application relates to the technical field of alumina modification, more specifically, it relates to a method for synthesizing modified alumina. BACKGROUND
[0004] Active alumina catalyst carriers have excellent properties such as high temperature resistance and oxidation resistance, and are widely used as carriers for automobile exhaust catalysts, petroleum refining catalysts, hydrogenation and hydrodesulfurization catalysts, etc. Among them, the most commonly used catalyst carrier γ-Al2O3 has the advantages of large specific surface area, good pore structure, and low cost and easy availability, and is particularly suitable for use as a catalyst carrier for automobile exhaust purification.
[0005] In the prior art, active alumina for automobile exhaust purification is mainly obtained by calcining boehmite as a precursor at high temperature. This method has significant shortcomings in improving the thermal stability of alumina. In a specific high temperature environment (especially a high temperature water vapor environment), active alumina will undergo sintering and phase transformation, resulting in a significant decrease in specific surface area and pore volume, and its high temperature stability and hydrothermal stability often cannot meet the actual demand. Specifically, in applications such as automobile exhaust treatment and catalytic combustion, the working temperature of active alumina can be as high as 1000°C or higher, at which time γ-Al2O3 will transform into non-porous α-Al2O3, resulting in a significant decrease in specific surface area and pore volume, thereby losing catalytic activity and adsorption capacity.
[0006] In order to improve the thermal stability of active alumina and enable it to maintain a high specific surface area and pore volume after high temperature application, recent research has mainly focused on improving the preparation method of alumina, such as sol-gel method, gel method, impregnation method, and microemulsion method, etc. Although the above methods can improve the performance of alumina to some extent, they usually have the defects of long preparation time and complex preparation process. At the same time, studies have shown that the introduction of alkaline earth and rare earth elements can significantly improve the thermal stability of alumina, so currently the method of hydrothermal doping of rare earth elements is mainly used to modify the active alumina precursor (boehmite). However, the rare earth elements tend to agglomerate during the hydrothermal doping process with boehmite, making it difficult to achieve uniform dispersion at the microscale, resulting in the active alumina carrier prepared finally still having low thermal stability under high temperature conditions, failing to meet the requirements of automobile exhaust purification carriers. Based on the above statements, the present application provides a method for synthesizing modified alumina. SUMMARY
[0007] In order to solve the problems that the existing rare earth elements and pseudo-boehmite are prone to agglomeration in the hydrothermal doping process, it is difficult to achieve uniform dispersion on the microscale, and the thermal stability of the finally prepared active alumina carrier under high temperature conditions is still low, the application provides a synthesis method of modified alumina.
[0008] The application provides a synthesis method of modified alumina.
[0009] The synthesis method of the modified alumina comprises the following steps:
[0010] S1, dissolving a surfactant and a rare earth modifier 1 in a sodium metaaluminate aqueous solution to obtain a solution 1;
[0011] S2, flowing the solution 1 and an aluminum sulfate aqueous solution to prepare a pseudo-boehmite slurry, stirring the pseudo-boehmite slurry, adding an organic solvent, then adding a silane substance to continue stirring, finally adding lanthanum nitrate to react, after the reaction is completed, filtering, washing, and drying to obtain a modified pseudo-boehmite powder;
[0012] S3, calcining the modified pseudo-boehmite powder to obtain modified alumina.
[0013] Preferably, the surfactant in the step S1 is at least one of polyethyleneimine, polyvinylpyrrolidone and polyacrylic amine.
[0014] Preferably, the surfactant in the step S1 is polyvinylpyrrolidone.
[0015] Preferably, the rare earth modifier 1 in the step S1 is at least one of zirconium nitrate, cerium nitrate, neodymium nitrate, praseodymium nitrate and samarium nitrate.
[0016] Preferably, the rare earth modifier 1 in the step S1 is cerium nitrate.
[0017] Preferably, the concentration of the sodium metaaluminate aqueous solution in the step S1 is 80-200 g / L.
[0018] Preferably, the mass ratio of the surfactant, the rare earth modifier 1 and the sodium metaaluminate aqueous solution in the step S1 is (0.02-0.05):(0.005-0.023):1.
[0019] Preferably, the concentration of the aluminum sulfate aqueous solution in the step S2 is 70-130 g / L in terms of alumina.
[0020] Preferably, the organic solvent in the step S2 is at least one of ethanol, ethylene glycol, n-butanol, isopropyl alcohol and tert-butyl alcohol.
[0021] Preferably, the organic solvent in step S2 is ethylene glycol.
[0022] Preferably, the silane substance in step S2 is at least one of trifluoropropyl tri(dimethylsiloxy)silane, 3,3,3-trifluoropropyltrimethoxysilane, and allylmethyldimethoxysilane.
[0023] Preferably, the silane substance in step S2 is trifluoropropyl tri(dimethylsiloxy)silane.
[0024] Preferably, the mass ratio of the organic solvent, the silane substance, the lanthanum nitrate, and the pseudoboehmite slurry in step S2 is (0.2-0.4):(0.04-0.12):(0.01-0.04):1.
[0025] Preferably, the specific steps of step S2 are as follows:
[0026] Solution 1 and an aqueous aluminum sulfate solution are fed in a parallel flow method to perform a neutralization reaction, the solution PH is controlled to be 7-9, a pseudoboehmite slurry is prepared, stirring is performed for 30-60 minutes, an organic solvent is added, a silane substance is added dropwise to continue stirring for 5-20 minutes, and finally lanthanum nitrate is added to perform a reaction, the reaction temperature is controlled to be 65-95 DEG C, stirring is performed for 60-180 minutes, after the doping reaction is completed, the slurry is subjected to solid-liquid separation through a vacuum filter pump, washing is performed using deionized water or by adding a certain amount of ammonium carbonate in the deionized water, the slurry is reduced in impurity content through the vacuum filtration, the solid after the washing and filtration is dried in a blast drying oven, and the modified pseudoboehmite powder is obtained after drying at 120 DEG C for 4 hours.
[0027] Preferably, the calcination temperature in step S3 is 500-800 DEG C, and the calcination time is 3-5 hours.
[0028] In summary, the present application has the following beneficial effects:
[0029] The present application modifies the pseudoboehmite in the process of synthesizing the pseudoboehmite, does not need to modify the synthesized pseudoboehmite powder or modify the synthesized pseudoboehmite after being calcined into alumina, has a simple synthesis step, a short process flow, can effectively improve the thermal stability of the alumina, and can significantly shorten the preparation time.
[0030] The rare earth modifier 1 is combined with aluminum to form a heat-resistant skeleton to prevent the skeleton from collapsing, the rare earth modifier 1 and the surfactant are added to the sodium metaaluminate to flow with the aluminum sulfate, the rare earth elements are uniformly dispersed and do not agglomerate, the lanthanum nitrate + 3-valence La can be fused into the Al2O3 structure and play a stabilizing role to further improve the thermal stability. BRIEF DESCRIPTION OF DRAWINGS
[0031] Figure 1 is the XRD pattern of the product in Example 1 of the present invention, where the horizontal axis is the diffraction angle and the vertical axis is the absorbance.
[0032] Figure 2 is an SEM image of the product in Example 1 of the present invention.
[0033] Figure 3 is the XRD pattern of the product in Example 2 of the present invention, where the horizontal axis is the diffraction angle and the vertical axis is the absorbance.
[0034] Figure 4 is an SEM image of the product in Example 2 of the present invention.
[0035] Figure 5 is the XRD pattern of the product in Example 3 of the present invention, where the horizontal axis is the diffraction angle and the vertical axis is the absorbance.
[0036] Figure 6 is a SEM image of the product in Example 3 of the present invention.
[0037] Figure 7 is the XRD pattern of the product in Comparative Example 1 of the present invention, where the horizontal axis is the diffraction angle and the vertical axis is the absorbance.
[0038] Figure 8 is a SEM image of the product in Comparative Example 1 of the present invention.
[0039] Figure 9 is the XRD pattern of the product in Comparative Example 2 of the present invention, where the horizontal axis is the diffraction angle and the vertical axis is the absorbance.
[0040] Figure 10 is a SEM image of the product in Comparative Example 2 of the present invention.
[0041] Figure 11 is the XRD pattern of the product in Comparative Example 3 of the present invention, where the horizontal axis is the diffraction angle and the vertical axis is the absorbance.
[0042] Figure 12 is a SEM image of the product in Comparative Example 3 of the present invention.
[0043] Figure 13 is the XRD pattern of the product in Comparative Example 4 of the present invention, where the horizontal axis is the diffraction angle and the vertical axis is the absorbance.
[0044] Figure 14 is a SEM image of the product in Comparative Example 4 of the present invention. Detailed Implementation
[0045] The present invention will be further described in detail below with reference to the embodiments.
[0046] Unless otherwise specified, all materials and reagents used in this invention are commercially available.
[0047] Examples 1-3 provide a method for synthesizing modified alumina.
[0048] Example 1
[0049] A method for synthesizing modified alumina specifically includes the following steps:
[0050] S1, at room temperature, take polyvinylpyrrolidone 2.6g, cerium nitrate 1.04g, dissolved in 130g sodium metaaluminate aqueous solution, prepared to obtain solution 1; wherein the concentration of sodium metaaluminate aqueous solution is 180g / L.
[0051] S2, take aluminum sulfate 48g, dissolved in 80g water, prepared to obtain aluminum sulfate aqueous solution; control the reaction temperature to be 85℃, solution 1 and aluminum sulfate aqueous solution are fed by using the method of parallel flow to carry out neutralization reaction, control the solution PH=8, prepare to obtain pseudo-boehmite slurry, after stirring for 60 minutes, add ethylene glycol 40g, slowly drop trifluoro propyl tri(dimethyl siloxane) silane 7.36g, stir for 5 minutes, add lanthanum nitrate 2.76g, stir for 120 minutes, after the doping reaction is finished, the slurry is subjected to solid-liquid separation by vacuum filtration pump, washed with deionized water, the impurity content in the slurry is reduced by filtration, the washed and filtered solid is dried in a blast drying oven, dried at 120℃ for 4 hours, to obtain modified pseudo-boehmite powder.
[0052] S3, after calcining the modified pseudo-boehmite powder at 500℃ for 5 hours, high-thermal-stability modified alumina powder is obtained.
[0053] Example 2
[0054] A synthesis method of modified alumina, specifically comprising the following steps:
[0055] S1, at room temperature, take polyvinylpyrrolidone 3.2g, cerium nitrate 1.04g, dissolved in 130g sodium meta aluminate aqueous solution, prepared to obtain solution 1; wherein the concentration of sodium meta aluminate aqueous solution is 180g / L.
[0056] S2, take aluminum sulfate 48g, dissolved in 80g water, to prepare aluminum sulfate aqueous solution; control the reaction temperature to be 95℃, solution 1 and aluminum sulfate aqueous solution are fed by using the method of parallel stream to carry out neutralization reaction, control the solution PH=8, prepare to obtain pseudo-bohemite slurry, after stirring for 60 minutes, add ethylene glycol 40g, slow drop trifluoro propyl tri(dimethyl siloxane) silane 7.36 g, stir for 5 minutes, add lanthanum nitrate 2.76g, stirring for 120 minutes, after the doping reaction is finished, the slurry is subjected to solid liquid separation by vacuum filtration pump, washed with deionized water, the impurity content in the pulp is reduced by filtration, the washed and filtered solid is dried in a blast drying oven, dried for 4 hours at 120℃, to obtain modified pseudo-boehmite powder.
[0057] S3, after calcining the modified pseudo-boehmite powder at 500℃for 5 hours, high-thermal-stability modified alumina powder is obtained.
[0058] Example 3
[0059] A synthesis method of modified alumina, specifically comprising the following steps:
[0060] S1, at room temperature, 2.6g of polyvinylpyrrolidone and 1.17g of cerium nitrate were weighed and dissolved in 130g of sodium metaaluminate aqueous solution to prepare solution 1; wherein the concentration of the sodium metaaluminate aqueous solution was 180g / L.
[0061] S2, 48g of aluminum sulfate was weighed and dissolved in 80g of water to prepare an aluminum sulfate aqueous solution; the reaction temperature was controlled at 95℃, solution 1 and the aluminum sulfate aqueous solution were fed by the parallel flow method for neutralization reaction, the solution PH was controlled at 8, a pseudo-boehmite slurry was prepared, 40g of ethylene glycol was added after stirring for 60 minutes, 7.36g of trifluoropropyl tris(dimethyl siloxane) silane was slowly added dropwise, stirring was performed for 5 minutes, 2.59g of lanthanum nitrate was added, and stirring reaction was performed for 120 minutes; after the doping reaction was completed, the slurry was subjected to solid-liquid separation by a vacuum filtration pump, washed with deionized water, and subjected to filtration to reduce the impurity content in the slurry; the washed and filtered solid was subjected to drying in a blast drying oven, and was dried at 120℃ for 4 hours to obtain modified pseudo-boehmite powder.
[0062] S3, the modified pseudo-boehmite powder was calcined at 500℃ for 5 hours to obtain high-thermal-stability modified alumina powder.
[0063] In order to verify the comprehensive performance of the modified alumina prepared in embodiments 1-3 of the application, the applicant set up comparative examples 1-5, as follows:
[0064] Comparative example 1
[0065] A synthesis method of modified alumina, specifically comprising the following steps:
[0066] S1, at room temperature, 2.6g of polyvinylpyrroline was weighed and dissolved in 130g of sodium metaaluminate aqueous solution to prepare solution1; wherein the concentration of the sodium metaaluminate aqueous solution was 180g / l.
[0067] S2, 48g of aluminum sulfate was weighed and dissolved in 80g of deionized water to prepare an aluminum sulfate aqueous solution; the reaction temperature was controlled at 85℃, solution 1 and the aluminum sulfate aqueous solution were fed by the parallel flow method to perform neutralization reaction, the solution PH was controlled at 8, a pseudo-boehmite sludge was prepared, 40g of ethylene glycol was added after stirring for 60 minutes; 7.36g of trifluoropropyl tris(dimethyl siloxane)silane was slowly added dropwise, stirring was performed for 5 minutes, 1.04g of cerium nitrate and 2.76g of lanthanum nitrate were added, and stirring reaction was performed for 120 minutes; after the doping reaction was completed, slurry was subjected to solid-liquid separation by a vacuum filtration pump, washed with deionised water, and subjected to filtration to reduce the impurity content in the slurry; the washed, filtered solid was subjected to drying in a blast drying oven, and was dried at 120℃for 4 hours to obtain modified pseudo-boehmite powder.
[0068] S3, calcining the modified pseudoboehmite powder at 500°C for 5 hours to obtain a modified alumina powder with high thermal stability.
[0069] Comparative Example 2
[0070] A synthesis method of a modified alumina, specifically comprising the following steps:
[0071] S1, at room temperature, polyvinylpyrrolidone 2.6g, cerium nitrate 1.04g, dissolved in 130g sodium metaaluminate aqueous solution, to obtain solution 1; wherein the concentration of sodium metaaluminate aqueous solution is 180g / L.
[0072] S2, take aluminum sulfate 48g, dissolved in 80g water, to prepare aluminum sulfate aqueous solution; control the reaction temperature to be 85°C, solution 1 and aluminum sulfate aqueous solution are fed by parallel flow method to carry out neutralization reaction, control the solution PH=8, to prepare pseudoboehmite slurry, after stirring for 60 minutes, add ethylene glycol 40g, slowly add trifluoropropyl tris(dimethylsiloxane) silane 7.36g, stirring reaction for 120 minutes, after the doping reaction is completed, the slurry is subjected to solid-liquid separation by vacuum filtration pump, washed with deionized water, and the impurity content in the slurry is reduced by filtration, the washed and filtered solid is dried in a blast drying oven, and dried at 120°C for 4 hours to obtain a modified pseudoboehmite powder.
[0073] S3, calcining the modified pseudoboehmite powder at 500°C for5 hours to obtain a modified alumina powder with high thermal stability.
[0074] Comparative Example 3
[0075] A synthesis method of a modified alumina, specifically comprising the following steps:
[0076] S1, at room temperature, polyvinylpyrrolidone 2g, cerium nitrate 1.04g, dissolved in 130g sodium meta aluminate aqueous solution, to obtain solution 1; wherein the concentration of sodium meta aluminate aqueous solution is 180g / L.
[0077] S2, take aluminum sulfate 48g, dissolved in 80g water, prepare aluminum sulfate aqueous solution; control the reaction temperature to be 85°C, solution 2 and aluminum sulfate aqueous solution are fed by parallel flow method to carry out neutralization reaction, and the solution PH=8 is controlled to prepare pseudoboehmite slurry, after stirring for 60 minutes, add ethylene 40g, slowly add trifluoropropyl tris(dimethylsiloxane)silane 7.36g, stirring reaction for 120 minutes, after the doping reaction is finished, the slurry is subjected to solid-liquid separation by vacuum filtration pump, washed with de-ionized water, and the impurity content in the slurry is reduced by filtration, the washed solid is dried in a blast drying oven, and dried at 120°C for 4 hours, to obtain a modified pseudoboehmite powder.
[0078] S3. After calcining the modified boehmite powder at 500℃ for 5 hours, a modified alumina powder with high thermal stability was obtained.
[0079] Comparative Example 4
[0080] A method for synthesizing modified alumina specifically includes the following steps:
[0081] S1. At room temperature, weigh 2.6g of polyvinylpyrrolidone and dissolve it in 130g of sodium aluminate aqueous solution to prepare solution 1; wherein the concentration of sodium aluminate aqueous solution is 180g / L.
[0082] S2. Weigh 48g of aluminum sulfate and dissolve it in 80g of water to prepare an aluminum sulfate aqueous solution. Control the reaction temperature at 85℃ and feed the solution 1 and the aluminum sulfate aqueous solution in a parallel flow to carry out a neutralization reaction. Control the pH of the solution to 8 to prepare a pseudoboehmite slurry. After stirring for 60 minutes, add 40g of ethylene glycol and slowly add 7.36g of trifluoropropyltris(dimethylsiloxane)silane. Stir the reaction for 120 minutes. After the doping reaction is completed, the slurry is separated into solid and liquid by a vacuum filtration pump. It is washed with deionized water and filtered to reduce the impurity content in the slurry. The washed and filtered solid is dried in a forced-air drying oven at 120℃ for 4 hours to obtain modified pseudoboehmite powder.
[0083] S3. After calcining the modified boehmite powder at 500℃ for 5 hours, a modified alumina powder with high thermal stability was obtained.
[0084] Comparative Example 5
[0085] A method for synthesizing modified alumina specifically includes the following steps:
[0086] S1. At room temperature, weigh 2.6g of polyvinylpyrrolidone, 1.04g of cerium nitrate, and 2.76g of lanthanum nitrate and dissolve them in 130g of sodium aluminate aqueous solution to prepare solution 1; wherein the concentration of sodium aluminate aqueous solution is 180g / L.
[0087] S2. Weigh 48g of aluminum sulfate and dissolve it in 80g of water to prepare an aluminum sulfate aqueous solution. Control the reaction temperature at 85℃ and feed the solution 1 and the aluminum sulfate aqueous solution in a parallel flow to carry out a neutralization reaction. Control the pH of the solution to 8 to prepare a pseudoboehmite slurry. After stirring for 60 minutes, add 40g of ethylene glycol and slowly add 7.36g of trifluoropropyltris(dimethylsiloxane)silane. Stir the reaction for 120 minutes. After the doping reaction is completed, the slurry is separated into solid and liquid by a vacuum filtration pump. It is washed with deionized water and filtered to reduce the impurity content in the slurry. The washed and filtered solid is dried in a forced-air drying oven at 120℃ for 4 hours to obtain modified pseudoboehmite powder.
[0088] S3, the modified pseudo-boehmite powder is calcined at 500°C for 5 hours to obtain the modified alumina powder with high thermal stability.
[0089] Performance detection
[0090] The comprehensive performance of the modified alumina powder prepared in the examples 1-3 and the comparative examples 1-5 of the present application is tested respectively, and the details are as follows:
[0091] The specific surface area and pore volume of the modified alumina powder before and after aging at 1200°C for 4h are tested by BET method, and the results are shown in Table 1.
[0092] Table 1:
[0093] As shown in the data in Table 1, the comprehensive performance of the modified alumina prepared in the examples 1-3 is obviously superior to that of the comparative examples 1-5, has high specific surface area and pore volume, and has obvious advantages in thermal stability, and has broad market prospect.
[0094] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application, and the person skilled in the art can make modifications to the embodiments without creative contribution according to the needs after reading the present specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.
Claims
1. A method for the synthesis of a modified alumina, characterized in that, The method comprises the following steps: S1, dissolving a surfactant and a rare earth modifier 1 in a sodium metaaluminate aqueous solution to obtain a solution 1; S2, preparing a pseudo-boehmite slurry by co-currently mixing the solution 1 and an aluminum sulfate aqueous solution, stirring the pseudo-boehmite slurry, adding an organic solvent, then adding a silane substance and continuing to stir, and finally adding lanthanum nitrate for reaction; after the reaction, filtering, washing, and drying to obtain a modified pseudo-boehmite powder; S3, obtaining a modified alumina by calcining the modified pseudo-boehmite powder.
2. The method of synthesizing modified alumina according to claim 1, wherein, The surfactant in the step S1 is at least one of polyethyleneimine, polyvinylpyrrolidone, and polyacrylic amine.
3. The method of claim 1, wherein the modified alumina is synthesized by the process comprising: The rare earth modifier 1 in the step S1 is at least one of zirconium nitrate, cerium nitrate, neodymium nitrate, praseodymium nitrate, and samarium nitrate.
4. The method of claim 1, wherein the modified alumina is synthesized by the process comprising: The concentration of the sodium metaaluminate aqueous solution in the step S1 is 80-200 g / L.
5. The method of claim 1, wherein the modified alumina is synthesized by the process comprising: The mass ratio of the surfactant, the rare earth modifier 1, and the sodium metaaluminate aqueous solution in the step S1 is (0.02-0.05):(0.005-0.023):
1.
6. The method of claim 1, wherein the modified alumina is synthesized by the process comprising: The concentration of the aluminum sulfate aqueous solution in the step S2 is 70-130 g / L in terms of alumina.
7. The method for synthesizing modified alumina according to claim 1, characterized in that, The organic solvent in the step S2 is at least one of ethanol, ethylene glycol, n-butanol, isopropyl alcohol, and tert-butyl alcohol.
8. The method of claim 1, wherein the modified alumina is synthesized by the process comprising: The silane substance in the step S2 is at least one of trifluoropropyltris(dimethylsiloxy)silane, 3,3,3-trifluoropropyltrimethoxysilane, and allylmethyldimethoxysilane.
9. The method of claim 1, wherein the modified alumina is synthesized by the process comprising: The mass ratio of the organic solvent, the silane substance, the lanthanum nitrate, and the pseudo-boehmite slurry in the step S2 is (0.2-0.4):(0.04-0.12):(0.01-0.04):
1.
10. The method of claim 1, wherein the modified alumina is synthesized by the process comprising: The calcination temperature in the step S3 is 500-800 ℃, and the calcination time is 3-5 hours.