A method for preparing a silica-alumina composite sol with controllable particle size

Abstract

This invention discloses a method for preparing a silicon-aluminum composite sol with controllable particle size, relating to the field of silicon-aluminum composite sol preparation technology. The steps are as follows: (1) Dissolve and disperse aluminum alkoxide in an alcohol solvent under heating conditions to obtain an alcohol dispersion of aluminum alkoxide; (2) Add tetramethoxysilane to the alcohol dispersion of aluminum alkoxide and stir evenly to obtain a silicon-aluminum alkoxide mixture, controlling the molar ratio of silicon to aluminum in the silicon-aluminum alkoxide mixture to be 1:(2-2.5); (3) Prepare an aluminum nitrate solution and add it to the silicon-aluminum alkoxide mixture to make the molar ratio of silicon to aluminum in the solution 1:3. Then, carry out hydrolysis and aging reactions under stirring conditions to obtain a silicon-aluminum composite sol with controllable particle size. The method for preparing a silicon-aluminum composite sol with controllable particle size of this invention has a short reaction cycle time, is easy to operate, has a high hydrolysis conversion rate, and the particle size of the silicon-aluminum composite sol can be controlled.

Description

Technical Field

[0001] This invention relates to the field of silicon-aluminum composite sol preparation technology, and in particular to a method for preparing silicon-aluminum composite sol with controllable particle size. Background Technology

[0002] Aluminosilicates are a class of inorganic substances with the chemical formula xAl₂O₃·ySiO₂. Mullite is the most representative aluminosilicate material, characterized by uniform expansion, excellent thermal shock resistance, high softening point under load, low high-temperature creep, high hardness, and good chemical corrosion resistance, thus considered a high-quality high-temperature resistant material. Due to the extreme scarcity of natural mullite, high-performance mullite for industrial applications is primarily synthesized artificially. The sol-gel method is the most commonly used method for preparing mullite powder. Based on the uniformity of the aluminum and silicon components, it is mainly divided into two types: one involves first hydrolyzing the aluminum source to prepare an aluminum sol, which is then physically mixed with a silica sol. The resulting sol product shows aluminum and silicon mixed at the molecular level, called a two-phase aluminosilicate composite sol. The other involves simultaneously hydrolyzing the aluminum and silicon sources, resulting in a sol product where aluminum and silicon are mixed at the atomic level, called a single-phase aluminosilicate composite sol. The mullite formation temperature of the product obtained from single-phase silica-alumina composite sol is around 980℃, while the product obtained from dual-phase silica-alumina composite sol can form mullite at temperatures above 1250℃.

[0003] Existing methods for preparing silica-alumina composite sols include Chinese patent CN101717262B, which discloses a sol-gel-solventothermal method for preparing nano-mullite powder. First, tetraethyl orthosilicate is dissolved in an ethanol solution, then distilled water is added and the pH is adjusted to 2-4 with hydrochloric acid. The mixture is then magnetically stirred to obtain a mixed solution. Next, Al(NO3)3·9H2O is dissolved in distilled water to obtain an Al(NO3)3·9H2O solution. The Al(NO3)3·9H2O solution is added to the mixed solution and magnetically stirred until homogeneous. The pH is then adjusted to 4.5-5.5 with ammonia water, and the mixture is dried in an oven to form a dry gel. The dry gel is then placed in a hydrothermal reactor, and anhydrous ethanol is added. The mixture is then treated at 200℃ for 12-16 hours. The sample is then removed and dried in an oven. Finally, the dried sample is placed in an alumina crucible and heated in a muffle furnace to 1150-1200℃ for 2 hours to obtain nano-mullite powder. Chinese patent CN102602947A discloses a method for preparing mullite sol without using alcohol or water as solvents, comprising: dissolving a soluble aluminum salt in a solvent, adjusting the pH of the solution to 1-3 with acid, then adding an aluminum alkoxide, reacting for 10-40 minutes, adding a silicon ester, hydrolyzing at room temperature for 12-36 hours, and finally carrying out a polycondensation reaction at 75-85°C for 10-60 hours to obtain mullite sol. Chinese patent CN104692403B discloses a method for preparing single-phase mullite sol, which involves preparing fresh aluminum hydroxide precipitate, preparing an alumina suspension, introducing a silicon source into the alumina suspension, and dissolving the mixed suspension. The above-mentioned single-phase mullite sol preparation processes have drawbacks such as complex processes, long preparation cycles, uncontrollable sol particle size, and poor repeatability. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a silicon-aluminum composite sol with controllable particle size, which has a short reaction cycle time, is easy to operate, has a high hydrolysis conversion rate, and the particle size of the silicon-aluminum composite sol can be adjusted.

[0005] To achieve the above-mentioned technical objectives and related technical objectives, the present invention provides a method for preparing a silicon-aluminum composite sol with controllable particle size, the steps of which are as follows:

[0006] (1) Dissolve and disperse aluminum alkoxide in an alcohol solvent under heating conditions to obtain an alcohol dispersion of aluminum alkoxide;

[0007] (2) Cool the alcohol dispersion of the aluminum alkoxide to 20-25°C, then add tetramethoxysilane to the alcohol dispersion of the aluminum alkoxide, stir evenly to obtain a silicon-aluminum alkoxide mixture, and control the molar ratio of silicon to aluminum in the silicon-aluminum alkoxide mixture to be 1:(2-2.5).

[0008] (3) Prepare aluminum nitrate solution, add aluminum nitrate solution to the silicon-aluminum alkoxide mixture to make the molar ratio of silicon to aluminum in the solution 1:3, and control the temperature of the silicon-aluminum alkoxide mixture to 30-35℃, and then carry out hydrolysis reaction and aging reaction under stirring conditions to obtain silicon-aluminum composite sol with controllable particle size.

[0009] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the aluminum alkoxide is dissolved and dispersed in an alcohol solvent under water bath heating conditions.

[0010] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the water bath heating temperature is 80-85℃, the time is 1-2h, and the stirring speed is 80-100r / min.

[0011] In one example of a method for preparing a silicon-aluminum composite sol with controllable particle size according to the present invention, the aluminum alkoxide includes one or more of aluminum isopropoxide and aluminum sec-butoxide.

[0012] In one example of a method for preparing a silicon-aluminum composite sol with controllable particle size according to the present invention, the alcohol solvent includes one or more of isopropanol, ethanol, and butanol.

[0013] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the concentration of aluminum alkoxide in the alcohol dispersion of the aluminum alkoxide is 20-30%.

[0014] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the step of preparing aluminum nitrate solution includes: adding aluminum nitrate nonahydrate to deionized water at room temperature and stirring to dissolve it evenly, wherein the concentration of aluminum nitrate in the aluminum nitrate solution is 12-20%.

[0015] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the aluminum nitrate solution is added to the aluminum-silicon alkoxide mixture under stirring conditions, the stirring time is 1 to 1.5 h, and the stirring speed is 80 to 120 r / min.

[0016] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the reaction temperature of the hydrolysis reaction is 50-70℃, the reaction time is 3-6h, and the stirring speed is 80-120r / min.

[0017] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the reaction temperature of the aging reaction is 70-90℃, the reaction time is 2-4h, and the stirring speed is 80-120r / min.

[0018] This invention discloses a method for preparing a silicon-aluminum composite sol with controllable particle size. The particle size of the silicon-aluminum composite sol is controlled by adjusting the amount of aluminum nitrate added to a silicon-aluminum alkoxide mixture. Since aluminum ions in the aluminum nitrate solution participate in the hydrolysis reaction and combine with silicon to form Al-O-Si bonds, and the remaining nitrate ions combine with hydrogen ions, altering the pH of the system, this results in a difference in the hydrolysis rates of aluminum alkoxide and tetramethoxysilane. This difference in hydrolysis rates leads to different rates of Al-O-Si bond formation between Al and Si, resulting in controllable particle size of the final silicon-aluminum composite sol. This process does not require the introduction of other regulators, thus the synthesized silicon-aluminum composite sol has high purity. The tetramethoxysilane raw material is added in a single step, resulting in a high hydrolysis conversion rate, which is more convenient than the dropwise addition method used for other organosilanes. This invention features a short reaction cycle, convenient operation, high hydrolysis conversion rate, and controllable particle size of the silicon-aluminum composite sol with good reproducibility. Attached Figure Description

[0019] Figure 1 This is a TEM image of the silicon-aluminum composite sol prepared in Example 1 of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention.

[0020] Figure 2 This is a TEM image of the silicon-aluminum composite sol prepared in Example 3 of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention.

[0021] Figure 3 This is a TEM image of the silicon-aluminum composite sol prepared in Example 5 of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention. Detailed Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features can be combined with each other. It should also be understood that the terminology used in the embodiments of the present invention is for describing specific implementation schemes and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0023] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of the invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to the methods, devices, and materials in the embodiments of the present invention.

[0024] This invention provides a method for preparing a silicon-aluminum composite sol with controllable particle size, the steps of which are as follows:

[0025] (1) Dissolve and disperse aluminum alkoxide in an alcohol solvent under heating conditions to obtain an alcohol dispersion of aluminum alkoxide;

[0026] (2) Cool the alcohol dispersion of the aluminum alkoxide to 20-25°C, then add tetramethoxysilane to the alcohol dispersion of the aluminum alkoxide, stir evenly to obtain a silicon-aluminum alkoxide mixture, and control the molar ratio of silicon to aluminum in the silicon-aluminum alkoxide mixture to be 1:(2-2.5).

[0027] (3) Prepare aluminum nitrate solution, add aluminum nitrate solution to the silicon-aluminum alkoxide mixture to make the molar ratio of silicon to aluminum in the solution 1:3, and control the temperature of the silicon-aluminum alkoxide mixture to 30-35℃, and then carry out hydrolysis reaction and aging reaction under stirring conditions to obtain silicon-aluminum composite sol with controllable particle size.

[0028] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the aluminum alkoxide is dissolved and dispersed in an alcohol solvent under stirring under water bath heating conditions. The water bath heating temperature is 80-85℃, the time is 1-2 hours, and the stirring speed is 80-100 r / min.

[0029] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the aluminum alkoxide includes one or more of aluminum isopropoxide and aluminum sec-butoxide. The alcohol solvent includes one or more of isopropanol, ethanol, and butanol. The concentration of aluminum alkoxide in the alcohol dispersion of the aluminum alkoxide is 20-30%.

[0030] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the step of preparing aluminum nitrate solution includes: adding aluminum nitrate nonahydrate to deionized water at room temperature and stirring to dissolve it evenly, wherein the concentration of aluminum nitrate in the aluminum nitrate solution is 12-20%.

[0031] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the aluminum nitrate solution is added to the aluminum-silicon alkoxide mixture under stirring conditions, the stirring time is 1 to 1.5 h, and the stirring speed is 80 to 120 r / min.

[0032] In one example of the preparation method of a silicon-aluminum composite sol with controllable particle size according to the present invention, the hydrolysis reaction is carried out at a temperature of 50–70°C for 3–6 h and a stirring speed of 80–120 r / min. The aging reaction is carried out at a temperature of 70–90°C for 2–4 h and a stirring speed of 80–120 r / min.

[0033] To better illustrate the present invention, several embodiments will be listed below. It should be noted that the raw materials, reagents and equipment used in the embodiments can all be purchased from the market.

[0034] Example 1

[0035] A method for preparing a silica-alumina composite sol with controllable particle size, comprising the following steps:

[0036] (1) Under the heating condition of water bath at 80℃, aluminum isopropoxide was added to isopropanol and stirred to dissolve for 1 hour. The stirring speed was 80 r / min. After uniform dispersion, an alcohol dispersion of aluminum isopropoxide was obtained, wherein the concentration of aluminum isopropoxide was 21.8%.

[0037] (2) Cool the aluminum isopropoxide alcohol dispersion obtained in step (1) to 20°C, then add tetramethoxysilane to the aluminum isopropoxide alcohol dispersion obtained in step (1), stir and mix evenly to obtain a silicon-aluminum alkoxide mixture, and control the molar ratio of silicon to aluminum in the silicon-aluminum alkoxide mixture to be 1:2.

[0038] (3) Under normal temperature conditions, prepare an aluminum nitrate solution with a concentration of 20%, add aluminum nitrate solution to the silicon-aluminum alkoxide mixture obtained in step (2), so that the molar ratio of silicon to aluminum in the solution is 1:3, and control the temperature of the silicon-aluminum alkoxide mixture to 30℃, stir and mix for 1h, then heat the mixed solution to 50℃ for hydrolysis reaction, the reaction time is 6h, the stirring speed is 100r / min, then heat the solution to 75℃ for aging reaction, the reaction time is 3h, the stirring speed is 100r / min, and after the reaction, silicon-aluminum composite sol is obtained.

[0039] Example 2

[0040] A method for preparing a silica-alumina composite sol with controllable particle size, comprising the following steps:

[0041] (1) Under the heating condition of water bath at 80℃, aluminum isopropoxide was added to isopropanol and stirred to dissolve for 1 hour. The stirring speed was 100 r / min. After uniform dispersion, an alcohol dispersion of aluminum isopropoxide was obtained, wherein the concentration of aluminum isopropoxide was 27.6%.

[0042] (2) Cool the aluminum isopropoxide alcohol dispersion obtained in step (1) to 25°C, then add tetramethoxysilane to the aluminum isopropoxide alcohol dispersion obtained in step (1), stir and mix evenly to obtain a silicon-aluminum alkoxide mixture, and control the molar ratio of silicon to aluminum in the silicon-aluminum alkoxide mixture to be 1:2.5.

[0043] (3) Under normal temperature conditions, prepare an aluminum nitrate solution with a concentration of 16%, add aluminum nitrate solution to the silicon-aluminum alkoxide mixture obtained in step (2), so that the molar ratio of silicon to aluminum in the solution is 1:3, and control the temperature of the silicon-aluminum alkoxide mixture to 35℃, stir and mix for 1h, then heat the mixed solution to 60℃ for hydrolysis reaction, the reaction time is 4h, the stirring speed is 80r / min, then heat the solution to 80℃ for aging reaction, the reaction time is 2h, the stirring speed is 80r / min, and after the reaction, silicon-aluminum composite sol is obtained.

[0044] Example 3

[0045] A method for preparing a silica-alumina composite sol with controllable particle size, comprising the following steps:

[0046] (1) Under the heating condition of water bath at 85℃, aluminum isopropoxide was added to isopropanol and stirred to dissolve for 1.5h. The stirring speed was 80r / min. After uniform dispersion, an alcohol dispersion of aluminum isopropoxide was obtained, wherein the concentration of aluminum isopropoxide was 24.2%.

[0047] (2) Cool the aluminum isopropoxide alcohol dispersion obtained in step (1) to 20°C, then add tetramethoxysilane to the aluminum isopropoxide alcohol dispersion obtained in step (1), stir and mix evenly to obtain a silicon-aluminum alkoxide mixture, and control the molar ratio of silicon to aluminum in the silicon-aluminum alkoxide mixture to be 1:2.

[0048] (3) Under normal temperature conditions, prepare an aluminum nitrate solution with a concentration of 12%, add aluminum nitrate solution to the silicon-aluminum alkoxide mixture obtained in step (2), so that the molar ratio of silicon to aluminum in the solution is 1:3, and control the temperature of the silicon-aluminum alkoxide mixture to 30℃, stir and mix for 1h, then heat the mixed solution to 60℃ for hydrolysis reaction, the reaction time is 3.5h, the stirring speed is 100r / min, then heat the solution to 85℃ for aging reaction, the reaction time is 2h, the stirring speed is 100r / min, and after the reaction, silicon-aluminum composite sol is obtained.

[0049] Example 4

[0050] A method for preparing a silica-alumina composite sol with controllable particle size, comprising the following steps:

[0051] (1) Under the heating condition of water bath at 80℃, aluminum isopropoxide was added to isopropanol and stirred to dissolve for 1 hour. The stirring speed was 90 r / min. After uniform dispersion, an alcohol dispersion of aluminum isopropoxide was obtained, wherein the concentration of aluminum isopropoxide was 25.5%.

[0052] (2) Cool the aluminum isopropoxide alcohol dispersion obtained in step (1) to 25°C, then add tetramethoxysilane to the aluminum isopropoxide alcohol dispersion obtained in step (1), stir and mix evenly to obtain a silicon-aluminum alkoxide mixture, and control the molar ratio of silicon to aluminum in the silicon-aluminum alkoxide mixture to be 1:2.5.

[0053] (3) Under normal temperature conditions, prepare an aluminum nitrate solution with a concentration of 12%, add aluminum nitrate solution to the silicon-aluminum alkoxide mixture obtained in step (2), so that the molar ratio of silicon to aluminum in the solution is 1:3, and control the temperature of the silicon-aluminum alkoxide mixture to 35°C. Stir and mix for 1 hour, then heat the mixed solution to 65°C for hydrolysis reaction for 4 hours, with a stirring speed of 90 r / min. Then heat the solution to 75°C for aging reaction for 3 hours, with a stirring speed of 90 r / min. After the reaction, silicon-aluminum composite sol is obtained.

[0054] Example 5

[0055] A method for preparing a silica-alumina composite sol with controllable particle size, comprising the following steps:

[0056] (1) Under the heating condition of water bath at 80℃, aluminum isopropoxide was added to isopropanol and stirred to dissolve for 1 hour. The stirring speed was 80 r / min. After uniform dispersion, an alcohol dispersion of aluminum isopropoxide was obtained, wherein the concentration of aluminum isopropoxide was 25.5%.

[0057] (2) Cool the aluminum isopropoxide alcohol dispersion obtained in step (1) to 20°C, then add tetramethoxysilane to the aluminum isopropoxide alcohol dispersion obtained in step (1), stir and mix evenly to obtain a silicon-aluminum alkoxide mixture, and control the molar ratio of silicon to aluminum in the silicon-aluminum alkoxide mixture to be 1:2.

[0058] (3) Under normal temperature conditions, prepare an aluminum nitrate solution with a concentration of 13%, add aluminum nitrate solution to the silicon-aluminum alkoxide mixture obtained in step (2), so that the molar ratio of silicon to aluminum in the solution is 1:3, and control the temperature of the silicon-aluminum alkoxide mixture to 30℃, stir and mix for 1h, then heat the mixed solution to 70℃ for hydrolysis reaction, the reaction time is 3h, the stirring speed is 80r / min, then heat the solution to 90℃ for aging reaction, the reaction time is 2h, the stirring speed is 80r / min, and after the reaction, silicon-aluminum composite sol is obtained.

[0059] Example 6

[0060] A method for preparing a silica-alumina composite sol with controllable particle size, comprising the following steps:

[0061] (1) Under the heating condition of 80℃ water bath, aluminum isopropoxide was added to ethanol and stirred to dissolve for 2 hours. The stirring speed was 80r / min. After uniform dispersion, an alcohol dispersion of aluminum isopropoxide was obtained, wherein the concentration of aluminum isopropoxide was 20%.

[0062] (2) Cool the aluminum isopropoxide alcohol dispersion obtained in step (1) to 20°C, then add tetramethoxysilane to the aluminum isopropoxide alcohol dispersion obtained in step (1), stir and mix evenly to obtain a silicon-aluminum alkoxide mixture, and control the molar ratio of silicon to aluminum in the silicon-aluminum alkoxide mixture to be 1:2.

[0063] (3) Under normal temperature conditions, prepare an aluminum nitrate solution with a concentration of 18%, add aluminum nitrate solution to the silicon-aluminum alkoxide mixture obtained in step (2), so that the molar ratio of silicon to aluminum in the solution is 1:3, and control the temperature of the silicon-aluminum alkoxide mixture to 30℃, stir and mix for 1.5h, then heat the mixed solution to 50℃ for hydrolysis reaction, the reaction time is 6h, the stirring speed is 120r / min, then heat the solution to 70℃ for aging reaction, the reaction time is 4h, the stirring speed is 120r / min, and after the reaction, silicon-aluminum composite sol is obtained.

[0064] Example 7

[0065] A method for preparing a silica-alumina composite sol with controllable particle size, comprising the following steps:

[0066] (1) Under the heating condition of 85℃ water bath, aluminum sec-butoxide was added to butanol and stirred to dissolve for 1 hour. The stirring speed was 100r / min. After uniform dispersion, an alcohol dispersion of aluminum sec-butoxide was obtained, wherein the concentration of aluminum sec-butoxide was 30%.

[0067] (2) Cool the sec-butoxide aluminum alcohol dispersion obtained in step (1) to 20°C, then add tetramethoxysilane to the sec-butoxide aluminum alcohol dispersion obtained in step (1), stir and mix evenly to obtain a silicon-aluminum alkoxide mixture, and control the molar ratio of silicon to aluminum in the silicon-aluminum alkoxide mixture to be 1:2.5.

[0068] (3) Under normal temperature conditions, prepare an aluminum nitrate solution with a concentration of 14%, add aluminum nitrate solution to the silicon-aluminum alkoxide mixture obtained in step (2), so that the molar ratio of silicon to aluminum in the solution is 1:3, and control the temperature of the silicon-aluminum alkoxide mixture to 30℃, stir and mix for 1.5h, then heat the mixed solution to 70℃ for hydrolysis reaction, the reaction time is 3h, the stirring speed is 80r / min, then heat the solution to 90℃ for aging reaction, the reaction time is 2h, the stirring speed is 80r / min, and after the reaction, silicon-aluminum composite sol is obtained.

[0069] The silicon-aluminum composite sols prepared in Examples 1, 3, and 5 were observed using transmission electron microscopy, and the results are as follows: Figures 1 to 3 As shown. Figure 1 The particle size of the silicon-aluminum composite sol shown in the image is approximately 50 nm. Figure 2 The particle size of the silicon-aluminum composite sol shown in the image is approximately 20–30 nm. Figure 3 The particle size of the silicon-aluminum composite sol shown in the image is approximately 10–15 nm, composed of… Figures 1 to 3 It can be seen that different amounts of aluminum nitrate added to the system will lead to differences in the particle size of the silicon-aluminum composite sol.

[0070] In summary, this invention provides a method for preparing a silicon-aluminum composite sol with controllable particle size. By controlling the amount of aluminum nitrate added to the silicon-aluminum alkoxide mixture, the particle size of the silicon-aluminum composite sol can be regulated. Since aluminum ions in the aluminum nitrate solution participate in the hydrolysis reaction in the system, combining with silicon to form Al-O-Si bonds, and the remaining nitrate ions combine with hydrogen ions, changing the pH value of the system, this results in a difference in the hydrolysis rate between the aluminum alkoxide and tetramethoxysilane. This leads to different rates of Al-O-Si bond formation between Al and Si, resulting in controllable particle size of the final mullite sol. This process does not require the introduction of other regulators, thus the synthesized mullite sol has high purity. The tetramethoxysilane raw material is added in a single step, resulting in a high hydrolysis conversion rate, which is more convenient than the dropwise addition method of other organosilanes. This invention features a short reaction cycle, convenient operation, high hydrolysis conversion rate, and controllable particle size of the mullite sol with good reproducibility.

[0071] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing a silicon-aluminum composite sol with controllable particle size, characterized in that, The steps are as follows: (1) Dissolve and disperse aluminum alkoxide in an alcohol solvent under heating conditions to obtain an alcohol dispersion of aluminum alkoxide; (2) Cool the alcohol dispersion of the aluminum alkoxide to 20-25°C, then add tetramethoxysilane to the alcohol dispersion of the aluminum alkoxide, stir evenly to obtain a silicon-aluminum alkoxide mixture, and control the molar ratio of silicon to aluminum in the silicon-aluminum alkoxide mixture to be 1:(2-2.5). (3) Prepare aluminum nitrate solution, add aluminum nitrate solution to the silicon-aluminum alkoxide mixture to make the molar ratio of silicon to aluminum in the solution 1:3, and control the temperature of the silicon-aluminum alkoxide mixture to 30-35℃, and then carry out hydrolysis reaction and aging reaction under stirring conditions to obtain silicon-aluminum composite sol with controllable particle size.

2. The method for preparing a silicon-aluminum composite sol with controllable particle size as described in claim 1, characterized in that, The aluminum alkoxide is dissolved and dispersed in an alcohol solvent under water bath heating conditions.

3. The method for preparing a silicon-aluminum composite sol with controllable particle size as described in claim 2, characterized in that, The water bath heating temperature is 80-85℃, the time is 1-2 hours, and the stirring speed is 80-100 r / min.

4. The method for preparing a silicon-aluminum composite sol with controllable particle size as described in claim 1, characterized in that, The aluminum alkoxide includes one or more of aluminum isopropoxide and aluminum sec-butoxide.

5. The method for preparing a silicon-aluminum composite sol with controllable particle size as described in claim 1, characterized in that, The alcohol solvents include one or more of isopropanol, ethanol, and butanol.

6. The method for preparing a silicon-aluminum composite sol with controllable particle size as described in claim 1, characterized in that, The concentration of aluminum alkoxide in the alcohol dispersion is 20-30%.

7. The method for preparing a silicon-aluminum composite sol with controllable particle size as described in claim 1, characterized in that, The steps for preparing an aluminum nitrate solution include: adding aluminum nitrate nonahydrate to deionized water at room temperature and stirring until dissolved, wherein the concentration of aluminum nitrate in the aluminum nitrate solution is 12-20%.

8. The method for preparing a silicon-aluminum composite sol with controllable particle size as described in claim 1, characterized in that, Under stirring conditions, the aluminum nitrate solution is added to the silicon-aluminum alkoxide mixture, and the stirring time is 1 to 1.5 hours, while the stirring speed is 80 to 120 r / min.

9. The method for preparing a silicon-aluminum composite sol with controllable particle size as described in claim 1, characterized in that, The hydrolysis reaction is carried out at a temperature of 50–70°C, for a reaction time of 3–6 h, and with a stirring speed of 80–120 r / min.

10. The method for preparing a silicon-aluminum composite sol with controllable particle size as described in claim 1, characterized in that, The aging reaction is carried out at a temperature of 70–90°C, for a reaction time of 2–4 hours, and with a stirring speed of 80–120 r / min.

Images