A kind of synthetic method of modified aluminum oxide

Abstract

The invention relates to the technical field of aluminum oxide modification, and specifically discloses a method for synthesizing modified aluminum oxide, which comprises the following steps: S1, dissolving a surfactant and a rare earth modifier 1 in a sodium aluminate aqueous solution to obtain a solution 1; S2, making the solution 1 flow in parallel with an aluminum sulfate aqueous solution to prepare a pseudo-boehmite slurry, stirring the pseudo-boehmite slurry, adding an organic solvent and then dripping a silane substance and continuing to stir, and finally adding lanthanum nitrate to react, filtering, washing, and drying after the reaction to obtain modified pseudo-boehmite powder; S3, calcining the modified pseudo-boehmite powder to obtain modified aluminum oxide; the synthetic method of the invention has simple steps and a short process flow, and can significantly shorten the preparation time while effectively improving the thermal stability of aluminum oxide.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum oxide modification, and more specifically, to a method for synthesizing modified aluminum oxide. Background Art

[0002] Activated alumina catalyst carrier has excellent properties such as high temperature resistance and oxidation resistance, and is widely used as a carrier for automobile exhaust catalysts, petroleum refining catalysts, hydrogenation and hydrodesulfurization catalysts, etc. Among them, the most commonly used catalyst carrier γ-Al 2 O 3 It has the advantages of large specific surface area, good pore structure, low price and easy availability, and is particularly suitable for use as a catalyst carrier for automobile exhaust purification.

[0003] In the prior art, activated alumina for automobile exhaust purification is mainly obtained by high-temperature calcination using pseudo-boehmite as a precursor. This method has significant deficiencies in improving the thermal stability of alumina. In a specific high-temperature environment (especially a high-temperature water vapor environment), activated 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 actual needs. Specifically, in applications such as automobile exhaust treatment and catalytic combustion, the operating temperature of activated alumina can be as high as 1000°C or above. At this time, γ-Al 2 O 3 It will transform into non-porous α-Al 2 O 3 , resulting in a significant reduction in specific surface area and pore volume, thereby losing catalytic activity and adsorption capacity.

[0004] In order to improve the thermal stability of activated alumina so that it can still maintain a high specific surface area and pore volume after high-temperature application, research in recent years has mainly focused on improving the preparation methods of alumina, such as sol-gel method, gel method, impregnation method and microemulsion method. Although the above methods can improve the performance of alumina to a certain extent, they usually have defects such as long preparation time and complicated 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 the current method of rare earth hydrothermal doping is mainly used to modify the activated alumina precursor (pseudo-boehmite). However, rare earth elements and pseudo-boehmite are prone to agglomeration during the hydrothermal doping process, and it is difficult to achieve uniform dispersion on a microscopic scale, resulting in the final prepared activated alumina carrier. The thermal stability is still low under high temperature conditions and fails to meet the requirements of automobile exhaust purification carriers. Based on the above statement, the present invention provides a method for synthesizing modified alumina. Summary of the invention

[0005] In order to solve the problems that rare earth elements and pseudo-boehmite are prone to agglomeration during the hydrothermal doping process, it is difficult to achieve uniform dispersion on a microscopic scale, resulting in the final prepared activated alumina carrier having low thermal stability under high temperature conditions, the present invention provides a method for synthesizing modified alumina.

[0006] The present invention provides a method for synthesizing modified alumina, which adopts the following technical scheme:

[0007] A method for synthesizing modified alumina comprises the following steps:

[0008] S1, dissolving a surfactant and a rare earth modifier 1 in a sodium aluminate aqueous solution to obtain a solution 1;

[0009] S2, the solution 1 and the aluminum sulfate aqueous solution are flowed in parallel to prepare a pseudo-boehmite slurry, the pseudo-boehmite slurry is stirred, the silane substance is added dropwise after the organic solvent is added, and the stirring is continued, and finally lanthanum nitrate is added to react, and after the reaction is completed, the reaction is filtered, washed, and dried to obtain a modified pseudo-boehmite powder;

[0010] S3. The modified pseudo-boehmite powder is calcined to obtain modified alumina.

[0011] Preferably, the surfactant in step S1 is at least one of polyethyleneimine, polyvinyl pyrrolidone and polyacrylamide.

[0012] Preferably, the surfactant in step S1 is polyvinyl pyrrolidone.

[0013] Preferably, the rare earth modifier 1 in step S1 is at least one of zirconium nitrate, cerium nitrate, neodymium nitrate, praseodymium nitrate and samarium nitrate.

[0014] Preferably, the rare earth modifier 1 in step S1 is cerium nitrate.

[0015] Preferably, the concentration of the sodium aluminate aqueous solution in step S1 is 80-200 g / L.

[0016] Preferably, in step S1, the mass ratio of the surfactant, the rare earth modifier 1, and the sodium aluminate aqueous solution is (0.02-0.05): (0.005-0.023): 1.

[0017] Preferably, the concentration of the aluminum sulfate aqueous solution in step S2 is 70 to 130 g / L in terms of aluminum oxide.

[0018] Preferably, the organic solvent in step S2 is at least one of ethanol, ethylene glycol, n-butanol, isopropanol and tert-butanol.

[0019] Preferably, the organic solvent in step S2 is ethylene glycol.

[0020] Preferably, the silane substance in step S2 is at least one of trifluoropropyltri(dimethylsiloxy)silane, 3,3,3-trifluoropropyltrimethoxysilane and allylmethyldimethoxysilane.

[0021] Preferably, the silane substance in step S2 is trifluoropropyltri(dimethylsiloxy)silane.

[0022] Preferably, in step S2, the mass ratio of the organic solvent, the silane substance, the lanthanum nitrate and the pseudo-boehmite slurry is (0.2-0.4): (0.04-0.12): (0.01-0.04): 1.

[0023] Preferably, the specific steps of step S2 are as follows:

[0024] Solution 1 and an aqueous solution of aluminum sulfate are fed in parallel for neutralization reaction, and the pH value of the solution is controlled to be 7-9 to prepare a pseudo-boehmite slurry, which is stirred for 30-60 minutes. After adding an organic solvent, a silane substance is added dropwise and stirring is continued for 5-20 minutes. Finally, lanthanum nitrate is added for reaction, and the reaction temperature is controlled to be 65-95°C. The stirring reaction is carried out for 60-180 minutes. After the doping reaction is completed, the slurry is subjected to solid-liquid separation by a vacuum filtration pump, washed with deionized water or by adding a certain amount of ammonium carbonate to deionized water, and filtered to reduce the impurity content in the slurry. The washed and filtered solid is dried in a blast drying oven at 120°C for 4 hours to obtain a modified pseudo-boehmite powder.

[0025] Preferably, in step S3, the calcination temperature is 500-800° C., and the calcination time is 3-5 hours.

[0026] In summary, the present invention has the following beneficial effects:

[0027] The present invention performs a modification treatment on the pseudo-boehmite during the synthesis process, and does not need to be modified after the pseudo-boehmite powder is synthesized, nor does it need to be modified after calcining into alumina. The synthesis steps are simple and the process flow is short. While effectively improving the thermal stability of alumina, the preparation time can be significantly shortened.

[0028] The present invention introduces a rare earth modifier 1 to combine with aluminum to form a heat-resistant skeleton to prevent the skeleton from collapsing; the rare earth modifier 1 and a surfactant are added to sodium aluminate and then flowed in parallel with aluminum sulfate, so that the rare earth elements can be evenly dispersed without agglomeration; lanthanum nitrate + trivalent La can be incorporated into Al 2 O 3 It plays a stabilizing role in the structure and further improves thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1It is the XRD diagram of the product in Example 1 of the present invention, wherein the abscissa is the diffraction angle and the ordinate is the absorbance.

[0030] Figure 2 This is a SEM image of the product in Example 1 of the present invention.

[0031] Figure 3 This is the XRD diagram of the product in Example 2 of the present invention, wherein the abscissa is the diffraction angle and the ordinate is the absorbance.

[0032] Figure 4 This is the SEM image of the product in Example 2 of the present invention.

[0033] Figure 5 This is the XRD diagram of the product in Example 3 of the present invention, wherein the abscissa is the diffraction angle and the ordinate is the absorbance.

[0034] Figure 6 This is the SEM image of the product in Example 3 of the present invention.

[0035] Figure 7 It is the XRD diagram of the product in Comparative Example 1 of the present invention, wherein the abscissa is the diffraction angle and the ordinate is the absorbance.

[0036] Figure 8 It is the SEM picture of the product in Comparative Example 1 of the present invention.

[0037] Fig. 9 It is the XRD diagram of the product in Comparative Example 2 of the present invention, wherein the abscissa is the diffraction angle and the ordinate is the absorbance.

[0038] Fig.10 This is the SEM image of the product in Comparative Example 2 of the present invention.

[0039] Fig.11 It is the XRD diagram of the product in Comparative Example 3 of the present invention, wherein the abscissa is the diffraction angle and the ordinate is the absorbance.

[0040] Fig.12 This is the SEM image of the product in Comparative Example 3 of the present invention.

[0041] Fig.13 This is the XRD diagram of the product in Comparative Example 4 of the present invention, wherein the abscissa is the diffraction angle and the ordinate is the absorbance.

[0042] Fig.14 This is the SEM image of the product in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0043] The present invention is further described in detail below with reference to the embodiments.

[0044] Unless otherwise specified, the materials, reagents, etc. used in the present invention can be obtained from commercial sources.

[0045] Example 1-3 provides a method for synthesizing modified alumina.

[0046] Example 1

[0047] A method for synthesizing modified alumina specifically comprises the following steps:

[0048] S1. At room temperature, weigh 2.6 g of polyvinyl pyrrolidone and 1.04 g of cerium nitrate, and dissolve them in 130 g of sodium aluminate aqueous solution to prepare solution 1; wherein the concentration of the sodium aluminate aqueous solution is 180 g / L.

[0049] S2. Weigh 48 g of aluminum sulfate and dissolve it in 80 g of water to prepare an aluminum sulfate aqueous solution; control the reaction temperature to 85°C, feed solution 1 and the aluminum sulfate aqueous solution in parallel for neutralization reaction, control the solution pH to 8, prepare pseudo-boehmite slurry, stir for 60 minutes, add 40 g of ethylene glycol, slowly dropwise add 7.36 g of trifluoropropyl tris(dimethylsiloxy)silane, stir for 5 minutes, add 2.76 g of lanthanum nitrate and stir for 120 minutes, after the doping reaction is completed, the slurry is subjected to solid-liquid separation by a vacuum filtration pump, washed with deionized water, and filtered to reduce the impurity content in the slurry, and the solid after washing and filtration is dried in a blast drying oven at 120°C for 4 hours to obtain modified pseudo-boehmite powder.

[0050] S3. The modified pseudo-boehmite powder is calcined at 500° C. for 5 hours to obtain modified alumina powder with high thermal stability.

[0051] Example 2

[0052] A method for synthesizing modified alumina specifically comprises the following steps:

[0053] S1. At room temperature, weigh 2.6 g of polyvinyl pyrrolidone and 1.04 g of cerium nitrate, and dissolve them in 130 g of sodium aluminate aqueous solution to prepare solution 1; wherein the concentration of the sodium aluminate aqueous solution is 180 g / L.

[0054] S2. Weigh 48 g of aluminum sulfate and dissolve it in 80 g of water to prepare an aluminum sulfate aqueous solution; control the reaction temperature to 95°C, feed solution 1 and the aluminum sulfate aqueous solution in parallel for neutralization reaction, control the solution pH to 8, prepare pseudo-boehmite slurry, stir for 60 minutes, add 40 g of ethylene glycol, slowly dropwise add 7.36 g of trifluoropropyl tris(dimethylsiloxy)silane, stir for 5 minutes, add 2.76 g of lanthanum nitrate and stir for 120 minutes, after the doping reaction is completed, the slurry is subjected to solid-liquid separation by a vacuum filtration pump, washed with deionized water, and filtered to reduce the impurity content in the slurry, and the solid after washing and filtration is dried in a blast drying oven at 120°C for 4 hours to obtain modified pseudo-boehmite powder.

[0055] S3. The modified pseudo-boehmite powder is calcined at 500° C. for 5 hours to obtain modified alumina powder with high thermal stability.

[0056] Example 3

[0057] A method for synthesizing modified alumina specifically comprises the following steps:

[0058] S1. At room temperature, weigh 2.6 g of polyvinyl pyrrolidone and 1.17 g of cerium nitrate, and dissolve them in 130 g of sodium aluminate aqueous solution to prepare solution 1; wherein the concentration of the sodium aluminate aqueous solution is 180 g / L.

[0059] S2. Weigh 48 g of aluminum sulfate and dissolve it in 80 g of water to prepare an aluminum sulfate aqueous solution; control the reaction temperature to 95°C, feed solution 1 and the aluminum sulfate aqueous solution in parallel for neutralization reaction, control the solution pH to 8, prepare pseudo-boehmite slurry, stir for 60 minutes, add 40 g of ethylene glycol, slowly drop 7.36 g of trifluoropropyl tris(dimethylsiloxy)silane, stir for 5 minutes, add 2.59 g of lanthanum nitrate and stir for 120 minutes. After the doping reaction is completed, the slurry is subjected to solid-liquid separation by a vacuum filtration pump, washed with deionized water, and filtered to reduce the impurity content in the slurry. The washed and filtered solid is dried in a blast drying oven at 120°C for 4 hours to obtain modified pseudo-boehmite powder.

[0060] S3. The modified pseudo-boehmite powder is calcined at 500° C. for 5 hours to obtain modified alumina powder with high thermal stability.

[0061] In order to verify the comprehensive performance of the modified alumina prepared in Examples 1-3 of the present invention, the applicant set up Comparative Examples 1-5, which are as follows:

[0062] Comparative Example 1

[0063] A method for synthesizing modified alumina specifically comprises the following steps:

[0064] S1. At room temperature, weigh 2.6 g of polyvinyl pyrrolidone and dissolve it in 130 g of sodium aluminate aqueous solution to prepare solution 1; wherein the concentration of the sodium aluminate aqueous solution is 180 g / L.

[0065] S2. Weigh 48 g of aluminum sulfate and dissolve it in 80 g of water to prepare an aluminum sulfate aqueous solution; control the reaction temperature to 85°C, feed solution 1 and the aluminum sulfate aqueous solution in parallel for neutralization reaction, control the solution pH to 8, prepare pseudo-boehmite slurry, stir for 60 minutes, add 40 g of ethylene glycol, slowly drop 7.36 g of trifluoropropyl tris(dimethylsiloxy)silane, stir for 5 minutes, add 1.04 g of cerium nitrate and 2.76 g of lanthanum nitrate, stir and react for 120 minutes, after the doping reaction is completed, the slurry is subjected to solid-liquid separation by a vacuum filtration pump, washed with deionized water, and filtered to reduce the impurity content in the slurry, and the solid after washing and filtration is dried in a blast drying oven at 120°C for 4 hours to obtain modified pseudo-boehmite powder.

[0066] S3. The modified pseudo-boehmite powder is calcined at 500° C. for 5 hours to obtain modified alumina powder with high thermal stability.

[0067] Comparative Example 2

[0068] A method for synthesizing modified alumina specifically comprises the following steps:

[0069] S1. At room temperature, weigh 2.6 g of polyvinyl pyrrolidone and 1.04 g of cerium nitrate, and dissolve them in 130 g of sodium aluminate aqueous solution to prepare solution 1; wherein the concentration of the sodium aluminate aqueous solution is 180 g / L.

[0070] S2. Weigh 48 g of aluminum sulfate and dissolve it in 80 g of water to prepare an aqueous solution of aluminum sulfate; control the reaction temperature to 85 ° C, feed solution 1 and the aqueous solution of aluminum sulfate in parallel for neutralization reaction, control the solution pH = 8, prepare pseudo-boehmite slurry, stir for 60 minutes, add 40 g of ethylene glycol, stir for 5 minutes, add 2.76 g of lanthanum nitrate and stir for 120 minutes. After the doping reaction is completed, the slurry is subjected to solid-liquid separation by a vacuum filtration pump, washed with deionized water, and filtered to reduce the impurity content in the slurry. The solid after washing and filtration is dried in a blast drying oven and dried at 120 ° C for 4 hours to obtain modified pseudo-boehmite powder.

[0071] S3. The modified pseudo-boehmite powder is calcined at 500° C. for 5 hours to obtain modified alumina powder with high thermal stability.

[0072] Comparative Example 3

[0073] A method for synthesizing modified alumina specifically comprises the following steps:

[0074] S1. At room temperature, weigh 2.6 g of polyvinyl pyrrolidone and 1.04 g of cerium nitrate, and dissolve them in 130 g of sodium aluminate aqueous solution to prepare solution 1; wherein the concentration of the sodium aluminate aqueous solution is 180 g / L.

[0075] S2. Weigh 48 g of aluminum sulfate and dissolve it in 80 g of water to prepare an aluminum sulfate aqueous solution; control the reaction temperature to 85°C, feed solution 1 and the aluminum sulfate aqueous solution in parallel for neutralization reaction, control the solution pH to 8, prepare pseudo-boehmite slurry, stir for 60 minutes, add 40 g of ethylene glycol, slowly drop 7.36 g of trifluoropropyl tris(dimethylsiloxy)silane, stir and react for 120 minutes, after the doping reaction is completed, the slurry is subjected to solid-liquid separation by a vacuum filtration pump, washed with deionized water, and filtered to reduce the impurity content in the slurry, and the solid after washing and filtration is dried in a blast drying oven at 120°C for 4 hours to obtain modified pseudo-boehmite powder.

[0076] S3. The modified pseudo-boehmite powder is calcined at 500° C. for 5 hours to obtain modified alumina powder with high thermal stability.

[0077] Comparative Example 4

[0078] A method for synthesizing modified alumina specifically comprises the following steps:

[0079] S1. At room temperature, weigh 2.6 g of polyvinyl pyrrolidone and dissolve it in 130 g of sodium aluminate aqueous solution to prepare solution 1; wherein the concentration of the sodium aluminate aqueous solution is 180 g / L.

[0080] S2. Weigh 48 g of aluminum sulfate and dissolve it in 80 g of water to prepare an aluminum sulfate aqueous solution; control the reaction temperature to 85°C, feed solution 1 and the aluminum sulfate aqueous solution in parallel for neutralization reaction, control the solution pH to 8, prepare pseudo-boehmite slurry, stir for 60 minutes, add 40 g of ethylene glycol, slowly drop 7.36 g of trifluoropropyl tris(dimethylsiloxy)silane, stir and react for 120 minutes, after the doping reaction is completed, the slurry is subjected to solid-liquid separation by a vacuum filtration pump, washed with deionized water, and filtered to reduce the impurity content in the slurry, and the solid after washing and filtration is dried in a blast drying oven at 120°C for 4 hours to obtain modified pseudo-boehmite powder.

[0081] S3. The modified pseudo-boehmite powder is calcined at 500° C. for 5 hours to obtain modified alumina powder with high thermal stability.

[0082] Comparative Example 5

[0083] A method for synthesizing modified alumina specifically comprises the following steps:

[0084] S1. At room temperature, weigh 2.6 g of polyvinyl pyrrolidone, 1.04 g of cerium nitrate, and 2.76 g of lanthanum nitrate and dissolve them in 130 g of sodium aluminate aqueous solution to prepare solution 1; wherein the concentration of the sodium aluminate aqueous solution is 180 g / L.

[0085] S2. Weigh 48 g of aluminum sulfate and dissolve it in 80 g of water to prepare an aluminum sulfate aqueous solution; control the reaction temperature to 85°C, feed solution 1 and the aluminum sulfate aqueous solution in parallel for neutralization reaction, control the solution pH to 8, prepare pseudo-boehmite slurry, stir for 60 minutes, add 40 g of ethylene glycol, slowly drop 7.36 g of trifluoropropyl tris(dimethylsiloxy)silane, stir and react for 120 minutes, after the doping reaction is completed, the slurry is subjected to solid-liquid separation by a vacuum filtration pump, washed with deionized water, and filtered to reduce the impurity content in the slurry, and the solid after washing and filtration is dried in a blast drying oven at 120°C for 4 hours to obtain modified pseudo-boehmite powder.

[0086] S3. The modified pseudo-boehmite powder is calcined at 500° C. for 5 hours to obtain modified alumina powder with high thermal stability.

[0087] Performance Testing

[0088] The comprehensive properties of the modified alumina powders prepared in Examples 1-3 of the present invention and Comparative Examples 1-5 were tested respectively, as follows:

[0089] The specific surface area and pore volume of the modified alumina powder were tested by the BET method before and after high temperature aging at 1200°C for 4 hours. The results are shown in Table 1.

[0090] Table 1:

[0091]

[0092] From the data shown in Table 1 above, it can be seen that the comprehensive performance of the modified alumina prepared in Examples 1-3 is significantly better than that of Comparative Examples 1-5, with high specific surface area and pore volume, obvious advantages in thermal stability, and broad market prospects.

[0093] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A method for synthesizing modified alumina, characterized in that: The following steps are involved: S1, dissolving a surfactant and a rare earth modifier 1 in a sodium aluminate aqueous solution to obtain a solution 1; S2, the solution 1 and the aluminum sulfate aqueous solution are flowed in parallel to prepare a pseudo-boehmite slurry, the pseudo-boehmite slurry is stirred, the silane substance is added dropwise after the organic solvent is added, and the stirring is continued, and finally lanthanum nitrate is added to react, and after the reaction is completed, the reaction is filtered, washed, and dried to obtain a modified pseudo-boehmite powder; S3, calcining the modified pseudo-boehmite powder to obtain modified alumina; The surfactant in step S1 is at least one of polyethyleneimine, polyvinyl pyrrolidone, and polyacrylamide; In step S1, the rare earth modifier 1 is at least one of zirconium nitrate, cerium nitrate, neodymium nitrate, praseodymium nitrate and samarium nitrate; The silane substance in step S2 is at least one of trifluoropropyl tris(dimethylsiloxy)silane, 3,3,3-trifluoropropyltrimethoxysilane and allylmethyldimethoxysilane.

2. The method for synthesizing modified alumina according to claim 1, characterized in that: The concentration of the sodium aluminate aqueous solution in step S1 is 80-200 g / L.

3. The method for synthesizing modified alumina according to claim 1, characterized in that: In the step S1, the mass ratio of the surfactant, the rare earth modifier 1, and the sodium aluminate aqueous solution is (0.02-0.05): (0.005-0.023):

1.

4. The method for synthesizing modified alumina according to claim 1, characterized in that: The concentration of the aluminum sulfate aqueous solution in step S2 is 70 to 130 g / L in terms of aluminum oxide.

5. The method for synthesizing modified alumina according to claim 1, characterized in that: The organic solvent in step S2 is at least one of ethanol, ethylene glycol, n-butanol, isopropanol and tert-butanol.

6. The method for synthesizing modified alumina according to claim 1, characterized in that: In the step S2, the mass ratio of the organic solvent, the silane substance, the lanthanum nitrate and the pseudo-boehmite slurry is (0.2-0.4): (0.04-0.12): (0.01-0.04):

1.

7. The method for synthesizing modified alumina according to claim 1, characterized in that: In step S3, the calcination temperature is 500-800° C. and the calcination time is 3-5 hours.

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