Preparation method of wear-resistant porous silicon-aluminum ball

Abstract

The invention provides a preparation method of wear-resistant porous silicon-aluminum balls, and belongs to the field of surface modification of porous ceramic materials. The silicon-aluminum ball is bonded with phosphate glass through organic-inorganic hybridization, and a wear-resistant porous shell layer is formed on the surface of the silicon-aluminum ball. On the premise that the pore structure is reserved, the wear rate is reduced by 40%, and the dual requirements of a catalysis / adsorption scene for wear resistance and mass transfer performance are met.

Description

Technical Field

[0001] This invention belongs to the field of surface modification of porous ceramic materials, and specifically relates to a method for secondary spraying of multifunctional sol on the surface of a pre-formed silicon-aluminum sphere, followed by low-temperature curing to form a core-shell structure wear-resistant layer. Background Technology

[0002] Due to their excellent mechanical strength, thermal stability, and chemical stability, silica-alumina microspheres are widely used as catalyst supports and adsorbents in petrochemical, environmental protection, and other fields. In practical industrial applications, these silica-alumina microspheres typically need to operate for extended periods in harsh environments such as fluidized beds and moving beds, where there is intense collision, friction, and airflow erosion. Therefore, wear resistance (usually characterized by the wear index) is a crucial performance indicator, directly determining the catalyst's lifespan and the stability of the equipment operation.

[0003] To achieve high mechanical strength and wear resistance, the traditional method for preparing silicon-aluminum spheres in the industry commonly uses aluminum sol as a binder. After spray granulation, the aluminum sol forms a robust alumina bridging network during calcination, tightly binding the silicon-aluminum raw material particles together, thus endowing the silicon-aluminum spheres with excellent wear resistance. However, this method has an inherent drawback that is difficult to overcome: while forming a strong binding phase, the colloidal particles of the aluminum sol severely clog the pores inside the silicon-aluminum spheres, resulting in a lower specific surface area and smaller pore volume of the obtained product. Although this densified structure ensures strength, it sacrifices the most critical surface active sites and mass transport channels for catalyst supports or adsorbents, severely limiting their catalytic activity and adsorption efficiency.

[0004] To improve the specific surface area and pore volume of aluminosilicate spheres, silica sol was used instead of aluminosilicate as a binder. The colloidal properties of silica sol reduce its pore-blocking effect during bonding, thus indeed improving the specific surface area and pore volume of the resulting aluminosilicate spheres. However, the skeletal structure formed by silica sol as a binder is generally weaker than that formed by aluminosilicate, leading to a significant decrease in the wear resistance of the aluminosilicate spheres, making it difficult to meet the stringent mechanical strength requirements of industrial applications. Summary of the Invention

[0005] To address the above technical problems, this invention provides a method for preparing a wear-resistant porous shell layer on the surface of a silicon-aluminum sphere. Using silicon-aluminum spheres as the substrate, a porous shell layer with high specific surface area and low wear rate is constructed through a four-step process of surface activation, functional sol preparation, spraying, and gradient curing.

[0006] This invention provides a wear-resistant porous silicon-aluminum ball, which has a core-shell structure, including a shell and a matrix. The shell and the matrix are chemically bonded to form an organic-inorganic hybrid structure. The matrix is ​​a silicon-aluminum ball, and the shell is a porous ceramic.

[0007] Furthermore, the shell thickness is 50~100μm.

[0008] The wear-resistant porous silicon-aluminum spheres have a specific surface area of ​​150~250m². 2 / g, pore volume 0.3~1.0cm 3 / g, pore size 5~20nm, wear index 0.1%~20%.

[0009] The present invention also provides a method for preparing the above-mentioned wear-resistant porous silica-alumina spheres. The method includes spraying a functional sol onto the surface of the silica-alumina spheres. The functional sol contains silica sol, organosilane, pore-forming agent, phosphate binder and silane coupling agent. The total mass of the functional sol is 3% to 10% of the carrier mass.

[0010] Furthermore, the preparation process of the functional sol includes hydrolyzing organosilane and silica sol, and then adding pore-forming agent, phosphate binder, silane coupling agent and curing catalyst. The mass ratio of silica sol, organosilane, pore-forming agent, phosphate binder, silane coupling agent and curing catalyst is (22~35):(10~15):(2~5):(3~6):(1~2):(0.5~1.5).

[0011] Furthermore, the organosilane is selected from at least one of methyltrimethoxysilane (MTMS), vinyltriethoxysilane (VTES), and γ-aminopropyltriethoxysilane; The pore-forming agent is selected from at least one of cetyltrimethylammonium bromide (CTAB), polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and polyacrylamide (PAM); The phosphate binder is selected from at least one of aluminum dihydrogen phosphate and magnesium phosphate; The silane coupling agent is selected from at least one of aminosilane (KH-550), γ-methacryloyloxypropyltrimethoxysilane (KH-570), epoxysilane (KH-560), and vinylsilane (A-151), and the amount added is 1wt%~2wt% of the functional sol mass; The curing catalyst is selected from at least one of organotin catalysts and peroxide initiators.

[0012] Furthermore, the curing catalyst is dibutyltin dilaurate (DBTDL) and / or benzoyl peroxide (BPO).

[0013] Furthermore, the functional sol has a pH value of 4.5~5.5 and a viscosity of 15~25 mPa·s.

[0014] Furthermore, the hydrolysis temperature is 30~50℃ and the time is 1~3 h.

[0015] Furthermore, the preparation process of the spray coating includes preheating the steam-treated silicon-aluminum spheres for later use, applying the functional sol to the substrate surface by spraying, and then curing.

[0016] Furthermore, during spraying, the silicon-aluminum spheres preheated to 80~150℃ are pressure-sprayed and coated 2~5 times at a distance of 15~25 cm and a single-pass weight gain rate of 1wt%~3wt%, with a total thickness of 50~110μm. Each pass is flash-dried at 120~180℃ for 2~5 min and then cured.

[0017] Furthermore, the conditions for the steam treatment include a temperature of 80-90°C, a humidity of 60%-85%, and a treatment time of 30-60 minutes.

[0018] Furthermore, the coating is applied at least twice, and a curing treatment is performed after each coating. The curing treatment conditions include heating to 500~650℃ at a heating rate of ≤3℃ / min, setting at least two heat preservation platforms during the process, and maintaining the temperature for 2~5 hours after reaching the final temperature.

[0019] Furthermore, the preparation process of the silicon-aluminum spheres includes: (1) Add acid to sodium silicate solution to adjust pH, and form silica gel after aging treatment; (2) An acidic aluminum salt solution is introduced into the silica gel, and an alkaline solution is added dropwise to adjust the pH to generate aluminum silicate precipitate. The aluminum silicate precipitate is crystallized and then filtered and washed until neutral to obtain a filter cake. (3) Add binder and dispersant to the filter cake, add acid to adjust pH, and spray mold.

[0020] Furthermore, the acid solution is selected from at least one of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, and formic acid, with a concentration of 5wt% to 20wt%; the alkaline solution is ammonia water with a concentration of 5wt% to 20wt%.

[0021] Furthermore, the aging treatment temperature is 30~60℃, and the aging treatment time is 0.5~2h.

[0022] Furthermore, the acidic aluminum salt solution is at least one of aluminum sulfate, aluminum nitrate, and aluminum chloride, with a concentration of 10wt% to 40wt%, and the mass ratio of the acidic aluminum salt to sodium silicate is (0.5~1):1.

[0023] Furthermore, in step (2), the pH is 6~9, the crystallization temperature is 50~80℃, and the crystallization time is 0.5~4h.

[0024] Further, the binder is selected from at least one of sodium metasilicate pentahydrate, water glass, silica sol, and ethyl silicate (TEOS), the dispersant is AD8098, and the mass ratio of the filter cake, binder and dispersant is 1:(0.01~0.15):(0.01~0.03).

[0025] Furthermore, in step (3), the spray molding temperature is 150~180℃.

[0026] The present invention has the following beneficial effects: This invention forms a wear-resistant, porous shell on the surface of aluminosilicate spheres by bonding with a phosphate glass phase. The shell and the substrate are chemically bonded to form an organic-inorganic hybrid structure. While preserving the porous structure, the wear rate is reduced by 40%, meeting the dual requirements of wear resistance and mass transfer performance in catalytic / adsorption applications. Detailed Implementation

[0027] The following embodiments will further illustrate the present invention, but are not intended to limit the invention.

[0028] AD8098 was purchased from Dongguan Aoda Environmental Protection New Materials Co., Ltd. Example 1

[0029] Carrier preparation and pretreatment: 66.7g of sodium silicate solution (13%) was adjusted to pH 9.5 with sulfuric acid solution (20%) and aged at room temperature for 45 min to obtain a gel solution. 307.71g of aluminum sulfate was added to 842.74g of water to prepare an aluminum sulfate solution, which was then added to the above gel solution. Ammonia solution (20%) was added to adjust the pH of the slurry to 6. After crystallization at 60℃ for 2 h, the solution was washed with deionized water until neutral, and the filter cake was reserved. 13g of sodium metasilicate was added to the filter cake as a binder, along with 11.02g of dispersant (AD8098) and 36.5g of nitric acid (20%) to adjust the pH of the gel to 9, and spray-dried to obtain an amorphous silica-alumina carrier. The amorphous silica-alumina carrier was placed in a steam treatment tank and treated with saturated steam at 150℃ and 85% RH for 50 min. After treatment, it was rinsed with deionized water until neutral and dried at 120℃ for 2 hours for later use.

[0030] Preparation of the multifunctional sol: Add 12.0 g MTMS and 4.0 g VTES to 35.0 g silica sol and hydrolyze by stirring in a 40°C water bath for 2.0 h. Add 3.0 g CTAB and 2.0 g PVA fibers, followed by 4.0 g aluminum dihydrogen phosphate, and stir for 15 min until transparent. Finally, add 2.0 g KH-550, 0.2 g DBTDL, and 0.8 g BPO, and stir for 30 min.

[0031] The multifunctional sol was sprayed onto the surface of the aluminosilicate spheres. The spheres were preheated to 110°C, and the sol was sprayed in three coats at a distance of 20 cm using a pressure spray gun (each coat flash-drying at 150°C for 4 min). Curing was carried out by gradient heating to 550°C at a rate of 100°C / h and holding at that temperature for 2 h, with subsequent holding times at 150°C, 250°C, and 400°C for 60 minutes each. The resulting aluminosilicate sphere shell thickness was 75 μm. Performance parameters are shown in Table 1. Example 2

[0032] Carrier preparation and pretreatment: 96g of sodium silicate solution (15% concentration) was adjusted to pH 9.5 with sulfuric acid solution (20% concentration), and aged at room temperature for 30 min to obtain a gel solution. 307.71g of aluminum sulfate was added to 842.74g of water to prepare an aluminum sulfate solution, which was then added to the above gel solution. Ammonia solution (20% concentration) was added to adjust the pH of the slurry to 6. After crystallization at 45℃ for 2 h, the slurry was washed with deionized water until neutral, and the filter cake was reserved. 8.26g of sodium metasilicate was added to the filter cake as a binder, 11.02g of dispersant (AD8098) and 9.48g of nitric acid (20% concentration) were added to adjust the pH of the gel to 9, and the amorphous silica-alumina carrier was obtained by spraying. The amorphous silica-alumina carrier was placed in a steam treatment tank and treated with saturated steam at 130℃ and 85% RH for 50 min. After treatment, it was rinsed with deionized water until neutral and dried at 120℃ for 2 hours for later use.

[0033] Preparation of the multifunctional sol: Add 10g MTMS and 4.0g VTES to 28g silica sol and hydrolyze by stirring in a 35℃ water bath for 4 h. Add 2.5g CTAB and 2.5g PVA fibers, followed by 3g aluminum dihydrogen phosphate, and stir for 15 min until transparent. Finally, add 2.0g KH-550, 0.2g DBTDL, and 0.8g BPO, and stir for 30 min.

[0034] The multifunctional sol was sprayed onto the surface of the aluminosilicate spheres. The spheres were preheated to 130°C, and the sol was sprayed in four coats at a distance of 20 cm using a pressure spray gun (each coat flash-drying at 150°C for 4 min). Curing was carried out by gradient heating to 600°C at a rate of 100°C / h and holding at that temperature for 2 h, with subsequent holding times at 150°C, 250°C, and 400°C for 60 minutes each. The resulting aluminosilicate sphere shell thickness was 98 μm. Performance parameters are shown in Table 1. Example 3

[0035] Carrier preparation and pretreatment: The pH of 116g of sodium silicate solution (20%) was adjusted to 9.5 using sulfuric acid solution (20%), and aged at room temperature for 60 min to obtain a gel solution. 307.71g of aluminum sulfate was dissolved in 842.74g of water to prepare an aluminum sulfate solution, which was then added to the above gel solution. Ammonia solution (20%) was added to adjust the pH of the slurry to 6. After crystallization at 45℃ for 4 h, the solution was washed with deionized water until neutral, and the filter cake was reserved. 8.26g of sodium metasilicate was added to the filter cake as a binder, along with 11.02g of dispersant (AD8098) and 9.48g of nitric acid (20%) to adjust the pH of the gel to 9, and spray-dried to obtain an amorphous silica-alumina carrier. The amorphous silica-alumina carrier was placed in a steam treatment tank and treated with saturated steam at 130℃ and 85% RH for 50 min. After treatment, it was rinsed with deionized water until neutral and dried at 120℃ for 2 hours for later use.

[0036] Preparation of the multifunctional sol: Add 10g MTMS and 3.0g VTES to 30g silica sol and hydrolyze by stirring in a 45℃ water bath for 4 h. Add 1.5g CTAB and 1.5g PVA fiber, followed by 5g aluminum dihydrogen phosphate, and stir for 15 min until transparent. Finally, add 2.0g KH-550, 0.2g DBTDL, and 0.8g BPO, and stir for 30 min.

[0037] The multifunctional sol was sprayed onto the surface of the aluminosilicate spheres. The spheres were preheated to 130°C, and the sol was sprayed in two coats at a distance of 20 cm using a pressure spray gun (each coat flash-drying at 150°C for 4 min). Curing was carried out by gradient heating to 650°C at a rate of 100°C / h and holding at that temperature for 2 h, with subsequent holding times at 150°C, 250°C, and 400°C for 60 minutes each. The resulting aluminosilicate sphere shell thickness was 52 μm. Performance parameters are shown in Table 1. Comparative Example 1

[0038] Carrier preparation and pretreatment: The pH of 66.7 g of sodium silicate solution (13%) was adjusted to 9.5 with sulfuric acid solution (20%), and aged at room temperature for 45 min to obtain a gel solution. 307.71 g of aluminum sulfate was added to 842.74 g of water to prepare an aluminum sulfate solution, which was then added to the above gel solution. Ammonia solution (20%) was added to adjust the pH of the slurry to 6. After crystallization at 60℃ for 2 h, the solution was washed with deionized water until neutral, and the filter cake was reserved. 13 g of sodium metasilicate was added to the filter cake as a binder, along with 11.02 g of dispersant (AD8098) and 36.5 g of nitric acid (20%) to adjust the pH of the gel solution to 9. Amorphous silica-alumina carriers were obtained by spraying. The temperature was gradually increased to 550℃ and held for 2 h, with subsequent holding times at 150℃, 250℃, and 400℃ for 60 min each. The performance parameters of the obtained silica-alumina spheres are shown in Table 1.

[0039] Table 1

[0040] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A wear-resistant porous silicon-aluminum ball, characterized in that, The wear-resistant porous silicon-aluminum sphere has a core-shell structure, including a shell and a matrix. The shell and the matrix are chemically bonded to form an organic-inorganic hybrid structure. The matrix is ​​a silicon-aluminum sphere, and the shell is a porous ceramic.

2. The wear-resistant porous silicon-aluminum ball according to claim 1, characterized in that, The shell thickness is 50~100μm; And / or, the specific surface area of ​​the wear-resistant porous silica-alumina spheres is 150~250m². 2 / g, pore volume 0.3~1.0cm 3 / g, pore size 5~20nm, wear index 0.1%~20%.

3. A method for preparing the wear-resistant porous aluminosilicate spheres according to claim 1 or 2, characterized in that, The preparation method includes spraying a functional sol onto the surface of aluminosilicate spheres. The functional sol contains silica sol, organosilane, pore-forming agent, phosphate binder, and silane coupling agent. The total mass of the functional sol is 3% to 10% of the carrier mass.

4. The preparation method according to claim 3, characterized in that, The preparation process of the functional sol includes hydrolyzing organosilane and silica sol, and then adding pore-forming agent, phosphate binder, silane coupling agent and curing catalyst. The mass ratio of silica sol, organosilane, pore-forming agent, phosphate binder, silane coupling agent and curing catalyst is (22~35):(10~15):(2~5):(3~6):(1~2):(0.5~1.5).

5. The preparation method according to claim 4, characterized in that, The organosilane is selected from at least one of methyltrimethoxysilane, vinyltriethoxysilane, and γ-aminopropyltriethoxysilane; The pore-forming agent is selected from at least one of hexadecyltrimethylammonium bromide, polyvinyl alcohol, polyethylene glycol, polyvinylpyrrolidone, and polyacrylamide; The phosphate binder is selected from at least one of aluminum dihydrogen phosphate and magnesium phosphate; The silane coupling agent is selected from at least one of aminosilane, γ-methacryloyloxypropyltrimethoxysilane, epoxysilane, and vinylsilane, and is added in an amount of 1 wt% to 2 wt% of the functional sol mass. The curing catalyst is selected from at least one of organotin catalysts and peroxide initiators, preferably dibutyltin dilaurate and / or benzoyl peroxide.

6. The preparation method according to claim 4 or 5, characterized in that, The functional sol has a pH value of 4.5~5.5 and a viscosity of 15~25 mPa·s; And / or, the hydrolysis temperature is 30~50℃ and the time is 1~3 h.

7. The preparation method according to any one of claims 3 to 6, characterized in that, The preparation process of the spray coating includes preheating the steam-treated silicon-aluminum spheres for later use, coating the functional sol onto the substrate surface by spraying, and then curing. Preferably, during spraying, the silicon-aluminum spheres preheated to 80~150℃ are pressure-sprayed and coated 2~5 times at a distance of 15~25 cm and a single-pass weight gain rate of 1 wt%~3 wt%, with a total thickness of 50~110 μm. Each pass is flash-dried at 120~180℃ for 2~5 min and then cured.

8. The preparation method according to claim 7, characterized in that, The conditions for steam treatment include a temperature of 80-90°C, a humidity of 60%-85%, and a treatment time of 30-60 minutes. Each coating is followed by a curing process. The curing process includes heating to 500-650°C at a rate of ≤3°C / min, with at least two heat preservation platforms set up during the process, and holding at the final temperature for 2-5 hours.

9. The preparation method according to any one of claims 3 to 8, characterized in that, The preparation process of the silicon-aluminum spheres includes: (1) Add acid to sodium silicate solution to adjust pH, and form silica gel after aging treatment; (2) An acidic aluminum salt solution is introduced into the silica gel, and an alkaline solution is added dropwise to adjust the pH to generate aluminum silicate precipitate. The aluminum silicate precipitate is crystallized and then filtered and washed until neutral to obtain a filter cake. (3) Add binder and dispersant to the filter cake, add acid to adjust pH, and spray mold.

10. The preparation method according to claim 9, characterized in that, The acid solution is selected from at least one of sulfuric acid, hydrochloric acid, nitric acid, acetic acid, and formic acid, with a concentration of 5wt% to 20wt%; the alkaline solution is ammonia water with a concentration of 5wt% to 20wt%. And / or, the aging treatment temperature is 30~60℃, and the aging treatment time is 0.5~2h; And / or, the acidic aluminum salt solution is at least one of aluminum sulfate, aluminum nitrate, and aluminum chloride, with a concentration of 10wt% to 40wt%, and the mass ratio of the acidic aluminum salt to sodium silicate is (0.5 to 1): 1; And / or, in step (2), the pH is 6~9, the crystallization temperature is 50~80℃, and the crystallization time is 0.5~4h; And / or, the binder is selected from at least one of sodium metasilicate pentahydrate, water glass, silica sol, and ethyl silicate, the dispersant is AD8098, and the mass ratio of the filter cake, binder, and dispersant is 1:(0.01~0.15):(0.01~0.03). And / or, in step (3), the spray molding temperature is 150~180℃.

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