Preparation method of monodisperse porous silicon dioxide microspheres

Abstract

The invention discloses a preparation method of monodisperse porous silicon dioxide microspheres. The preparation method comprises the following steps: carrying out cationization modification on monodisperse porous polymer microspheres; the method comprises the following steps: adding alkaline amino acid into pure water, and dispersing the surface cationized monodisperse porous polymer microspheres in the alkaline amino acid; adding a silicon dioxide precursor into the solution in one step to prepare polymer-silicon dioxide composite microspheres, filtering, washing and drying; and calcining the polymer-silicon dioxide composite microspheres in a distributed manner, and removing the organic polymer to obtain the monodisperse porous silicon dioxide microspheres. One-step feeding and stable reaction of a silicon dioxide precursor are realized by adjusting the solvent environment and alkaline conditions in the synthesis process of the polymer-silicon dioxide composite microspheres. The problems that the reaction process is tedious and difficult to control and microspheres are prone to agglomerate are solved.

Description

Technical Field

[0001] The invention relates to the technical field of silicon dioxide microsphere preparation, and more particularly to a method for preparing monodisperse porous silicon dioxide microspheres. Background Art

[0002] Porous silica microspheres have large specific surface area, good acid and alkali resistance, excellent thermal stability and other properties, and are widely used in many fields. For example, they are used as support frameworks for catalytic conversion, enzyme immobilization and liquid chromatography. With the continuous improvement of downstream application technology requirements, the requirements for the control of particle size and pore structure of porous silica microspheres are also getting higher and higher.

[0003] At present, the traditional sol-gel method can be used to prepare monodisperse silica microspheres with a size of tens to hundreds of nanometers, but it is difficult to exceed 1 micron, and the pores are small, so pore expansion treatment is usually required. The polymerization-induced gel aggregation method is difficult to achieve precise control of particle size and pores due to harsh conditions. Therefore, the use of template method to synthesize micron-scale monodisperse porous silica microspheres has received widespread attention and research.

[0004] Chinese patent application CN201610614254.1 discloses a method for preparing mesoporous silica microspheres by template method, the steps of which are: placing porous polymer microspheres in an aqueous solution of lower alcohol, catalyzing and stepwise dripping of the lower alcohol solution of silica precursor to obtain polymer-silica composite microspheres; then calcining in steps to remove the organic polymer to obtain porous silica microspheres. The document Jiwei, Chen, et al. "Fabrication of Monodisperse Porous Silica Microspheres with Tunable Particle Size and Pore Size for Protein Separation." Acs Applied Bio Materials (2018): acsabm.8b00088- synthesizes polymer-silica composite microspheres through porous microspheres modified with quaternary ammonium salt surfaces, and uses a peristaltic pump to drip TEOS ethanol solution in the presence of ammonia water. However, these methods are all carried out in an alcohol-water system, and it is necessary to form composite microspheres by distributed dripping of silica precursors, which makes the process cumbersome and difficult to control. This is a widespread and urgent problem to be solved in the synthesis process of polymer-silica composite microspheres. Summary of the invention

[0005] In view of this, the present invention provides a method for preparing monodisperse porous silica microspheres, which achieves one-step feeding and stable reaction of silica precursor by adjusting the solvent environment and alkaline conditions during the synthesis of polymer-silica composite microspheres, thereby solving the problems of complicated and difficult-to-control reaction process and easy agglomeration of microspheres.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] A method for preparing monodisperse porous silica microspheres comprises the following steps:

[0008] (1) cationic modification of monodisperse porous polymer microspheres;

[0009] (2) adding basic amino acids into pure water to disperse the surface cationized monodisperse porous polymer microspheres therein;

[0010] (3) adding a silica precursor to the above solution in one step to prepare polymer-silica composite microspheres, filtering, washing, and drying;

[0011] (4) Distributing and calcining the polymer-silica composite microspheres, and removing the organic polymer to obtain monodisperse porous silica microspheres.

[0012] Preferably, the monodisperse porous polymer microspheres in step (1) are poly(glycidyl methacrylate) microspheres.

[0013] The above-mentioned preferred advantageous effects include: high activity of epoxy functional groups, easy to achieve various cationic modifications

[0014] Preferably, the particle size of the monodisperse porous polymer microspheres in step (1) is 1-50 μm.

[0015] Preferably, the cationic modification in step (1) is modification by short-chain polyethyleneimine or trimethylamine.

[0016] The beneficial effects brought about by the above-mentioned optimization include: small molecular weight, easy modification, and high degree of cationization.

[0017] Preferably, the mass ratio of the monodisperse porous polymer microspheres to polyethyleneimine or trimethylamine is 1:(1-10).

[0018] Preferably, the basic amino acid in step (2) is lysine and / or arginine.

[0019] The beneficial effects brought about by the above-mentioned preference include: the side chain has an amino group, which provides a relatively strong alkaline environment.

[0020] Preferably, the amount of basic amino acid added to the pure water in step (2) is 0.5-10 mg / ml.

[0021] Preferably, the silicon dioxide precursor in step (2) of the method is selected from methyl orthosilicate and / or ethyl orthosilicate.

[0022] Preferably, the distributed calcination in step (4) is:

[0023] 25-200℃, heating rate 5℃ / min;

[0024] 200-300℃, heating rate 2℃ / min;

[0025] 300℃, keep warm for 2h;

[0026] 300-400℃, heating rate 5℃ / min;

[0027] 400-500℃, heating rate 2℃ / min;

[0028] 500℃, keep warm for 2h;

[0029] 500-700℃, heating rate 5℃ / min;

[0030] 700℃, keep warm for 4h.

[0031] The beneficial effects brought about by the above-mentioned optimization include: sufficient calcination and high strength.

[0032] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The raw materials are cheap and easy to obtain, and the cost is low;

[0034] 2. Simple process, mild reaction conditions and low energy consumption;

[0035] 3. The post-processing process is easy and environmentally friendly.

[0036] 4. The product has high yield and good quality.

[0037] The present invention makes the synthesis reaction of polymer-silicon dioxide composite microspheres mild and stable by adjusting the process of catalytic synthesis of polymer-silicon dioxide composite microspheres. Pure water is selected as a solvent for the reaction, thereby avoiding the use of alcohol organic reagents, and energy saving and environmental protection. Alkaline amino acids are used to provide an alkaline environment, thereby avoiding the operational danger of using inorganic bases such as ammonia water. The cumbersome process of dripping a silicon dioxide precursor is removed, and a one-step addition method is adopted to make the reaction simple. At the same time, the phenomenon of agglomeration in the reaction process can be effectively prevented, and the filling of silicon dioxide can be promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0039] Figure 1 This is a scanning electron microscope image of monodisperse silica microspheres of Example 6, wherein the particle size is 15 μm;

[0040] Figure 2 The scanning electron microscope images of the silica microspheres of Example 7, wherein the left image is the polymer-silica composite microspheres before calcination, and the right image is the silica microspheres after calcination;

[0041] Figure 3 This is a scanning electron micrograph of monodisperse silica microspheres of Example 8, wherein the particle size is 10 μm;

[0042] Figure 4 This is a scanning electron microscope image of the silica microspheres of Comparative Example 1, wherein the left image is a scanning electron microscope image of the polymer-silica composite microspheres before calcination, and the right image is a scanning electron microscope image of the silica microspheres after calcination. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example 1 Synthesis of monodisperse porous glycidyl methacrylate (PGMA) microspheres

[0045] Take 1g of 5 micron PGMA seed microspheres and dissolve them in 60ml 0.5% PVA aqueous solution and pour them into a three-necked flask. Take 4mL GMA, 3mL EGDMA, 2.5mL toluene, 1.5ml DBP, 0.5ml cyclohexanol, and 60㎎ AIBN and mix them in a beaker by ultrasonication. Pour them into 60ml water containing 0.35% PVA and 0.05% SDS, put them into an ultrasonic crusher, ultrasonicate them at 760W for 5 minutes, pour them into a three-necked flask, stir and swell at 39℃ for 24h, then heat to 74℃ and react for 16 hours. 10 micron porous PGMA microspheres were separated.

[0046] Example 2 Synthesis of monodisperse porous glycidyl methacrylate (PGMA) microspheres

[0047] Take 1g of 5 micron PGMA seed microspheres and dissolve them in 60ml 0.5% PVA aqueous solution and pour them into a three-necked flask. Take 7mL GMA, 3mL EGDMA, 3mL toluene, 2ml DBP, and 100㎎ AIBN and mix them in a beaker by ultrasonication. Pour them into 60ml water containing 0.35% PVA and 0.05% SDS, put them into an ultrasonic crusher, ultrasonicate them at 760W for 5 minutes, pour them into a three-necked flask, stir and swell at 39℃ for 24h, then heat to 74℃ and react for 16 hours. 15 micron porous PGMA microspheres were separated.

[0048] Example 3 Synthesis of monodisperse porous glycidyl methacrylate (PGMA) microspheres

[0049] Take 1g of 3-micron PGMA seed microspheres and dissolve them in 60ml 0.5% PVA aqueous solution and pour them into a three-necked flask. Take 5.2mL GMA, 1.35mL EGDMA, 1.7mL toluene, and 70㎎ AIBN and mix them in a beaker by ultrasonication. Pour them into 60ml water containing 0.35% PVA and 0.05% SDS, put them into an ultrasonic crusher, ultrasonicate them at 760W for 5 minutes, pour them into a three-necked flask, stir and swell at 39℃ for 24h, then heat to 74℃ and react for 16 hours. 8-micron porous PGMA microspheres were separated.

[0050] Example 4 Synthesis of monodisperse porous glycidyl methacrylate microspheres functionalized on polyethyleneimine surface

[0051] 10 g of 15 μm monodisperse porous glycidyl methacrylate microspheres were added to a 250 mL three-necked round-bottom flask, 150 mL of water was added, 100 g of PEI 600 was added and mixed evenly, and the mixture was reacted at 80 °C and 150 rpm for 12 h. The mixture was washed three times with distilled water and dried at 50 °C for 12 h to obtain porous glycidyl methacrylate microspheres functionalized with polyethyleneimine.

[0052] Example 5 Synthesis of monodisperse porous glycidyl methacrylate microspheres functionalized with trimethylamine

[0053] Take 2.5g of 10 micron monodisperse porous glycidyl methacrylate microspheres and add them to a 100mL three-necked round-bottom flask. Add 45mL of water, 5g of trimethylamine hydrochloride, and 2.13g of sodium hydroxide, mix well, and react at 54 degrees Celsius and 150rpm for 24h. Wash three times with distilled water and dry at 50℃ for 12h to obtain trimethylamine-functionalized porous glycidyl methacrylate microspheres.

[0054] Example 6 Synthesis of monodisperse porous silica microspheres

[0055] Take 0.5g of 15μm polyethyleneimine surface functionalized microspheres (Example 4) and place them in a 100mL three-necked round-bottom flask, add 25mL of deionized water, ultrasonically disperse for 30min, and add 25mg of lysine. After stirring and dissolving, add 1.5ml of tetraethoxysilane to the three-necked round-bottom flask. After adding, continue stirring and reacting for 24h. After the reaction is completed, wash with ethanol and water alternately three times and dry at 50℃ for 12h. The dried composite microspheres were placed in a muffle furnace and heated step by step, with the steps of 25-200℃ (5℃ / min), 200-300℃ (2℃ / min), 300℃ (2h), 300-400℃ (5℃ / min), 400-500℃ (2℃ / min), 500℃ (2h), 500-700℃ (5℃ / min), 700℃ (4h), and finally 15μm monodisperse porous silica microspheres were obtained. The average pore size of the microspheres is 150 angstroms, the pore volume is 0.62 cubic meters / gram, and the specific surface area is 154 square meters / gram. Figure 1 Shown are the obtained monodisperse porous silica microspheres, with an average particle size of 15 μm;

[0056] Example 7 Synthesis of monodisperse porous silica microspheres

[0057] Take 0.5g of 8μm-diameter trimethylamine surface functionalized microspheres and place them in a 100mL three-necked round-bottom flask, add 25mL of deionized water, ultrasonically disperse for 30min, and add 25mg of lysine. After stirring and dissolving, add 1.5ml of tetraethoxysilane to the three-necked round-bottom flask. After adding, continue stirring and reacting for 24h. After the reaction, wash alternately with ethanol and water three times, and dry at 50℃ for 12h. Place the dried composite microspheres in a muffle furnace and heat them step by step, with the step-by-step method of 25-200℃ (5℃ / min), 200-300℃ (2℃ / min), 300℃ (2h), 300-400℃ (5℃ / min), 400-500℃ (2℃ / min), 500℃ (2h), 500-700℃ (5℃ / min), 700℃ (4h), and finally obtain 6μm monodisperse porous silica microspheres. Figure 2 As shown, the left picture shows the composite microspheres before calcination, with a particle size of 8 microns. The right picture shows the silica microspheres after calcination, the particle size and pore structure of the microspheres have changed, and the average particle size has been reduced to 6μm;

[0058] Example 8 Synthesis of Monodisperse Porous Silica Microspheres

[0059] Take 0.5g of 10μm-diameter microspheres with trimethylamine surface functionalization and place them in a 100mL three-necked round-bottom flask, add 25mL of deionized water, ultrasonically disperse for 30min, and add 25mg of lysine. After stirring and dissolving, add 1.5ml of tetraethoxysilane to the three-necked round-bottom flask. After adding, continue stirring and reacting for 24h. After the reaction, wash alternately with ethanol and water three times, and dry at 50℃ for 12h. Place the dried composite microspheres in a muffle furnace and heat them step by step, with the step-by-step method of 25-200℃ (5℃ / min), 200-300℃ (2℃ / min), 300℃ (2h), 300-400℃ (5℃ / min), 400-500℃ (2℃ / min), 500℃ (2h), 500-700℃ (5℃ / min), 700℃ (4h), and finally obtain 10μm monodisperse porous silica microspheres. Figure 3 The obtained monodisperse porous silica microspheres are shown, with an average particle size of 10 μm; the average pore size of the microspheres is 60 angstroms, the pore volume is 0.81 cubic meters per gram, and the specific surface area is 573 square meters per gram.

[0060] Example 9 Synthesis of Monodisperse Porous Silica Microspheres

[0061] Take 0.5g of 10μm microspheres with trimethylamine surface functionalization and place them in a 100mL three-necked round-bottom flask, add 25mL of deionized water, ultrasonically disperse for 30min, and add 25mg of lysine. After stirring and dissolving, add 3ml of tetraethoxysilane to the three-necked round-bottom flask. After adding, continue stirring and reacting for 24h. After the reaction is completed, wash with ethanol and water alternately three times and dry at 50℃ for 12h. The dried composite microspheres were placed in a muffle furnace and heated step by step in the following steps: 25-200°C (5°C / min), 200-300°C (2°C / min), 300°C (2h), 300-400°C (5°C / min), 400-500°C (2°C / min), 500°C (2h), 500-700°C (5°C / min), 700°C (4h), and finally 10 μm monodisperse porous silica microspheres were obtained with an average pore diameter of 120 angstroms, a pore volume of 1.1 cubic meters per gram, and a specific surface area of ​​599 square meters per gram.

[0062] Example 10 Synthesis of monodisperse porous silica microspheres

[0063] Take 0.5g of 10μm microspheres with trimethylamine surface functionalization and place them in a 100mL three-necked round-bottom flask, add 25mL deionized water, ultrasonically disperse for 30min, and add 25mg lysine. After stirring and dissolving, add 3ml tetraethoxysilane to the three-necked round-bottom flask. After adding, continue stirring and reacting for 24h. After the reaction, wash with ethanol and water alternately three times and dry at 50℃ for 12h. The dried composite microspheres are placed in a muffle furnace and heated step by step, with the step-by-step method of 25-200℃ (5℃ / min), 200-300℃ (2℃ / min), 300℃ (2h), 300-400℃ (5℃ / min), 400-500℃ (2℃ / min), 500℃ (2h), 500-700℃ (5℃ / min), 700℃ (4h), and finally obtain 12μm monodisperse porous silica microspheres. The average particle size is 12 μm; the average pore size of the microspheres is 160 angstroms, the pore volume is 1.1 cubic meters per gram, and the specific surface area is 472 square meters per gram.

[0064] Comparative Example 1 Synthesis of monodisperse porous silica microspheres

[0065] Take 0.5g of 8μm microspheres with trimethylamine surface functionalization and place them in a 100mL three-necked round-bottom flask, add 20mL ethanol, 5ml deionized water, ultrasonically disperse for 30min, and add 0.5ml ammonia water. After stirring and dissolving, add 1.5ml tetraethoxysilane to the three-necked round-bottom flask. After adding, continue stirring and reacting for 24h. The reaction showed serious agglomeration. After the reaction was completed, wash it alternately with ethanol and water three times and dry it at 50℃ for 12h. The dried composite microspheres were placed in a muffle furnace and heated step by step in the following steps: 25-200°C (5°C / min), 200-300°C (2°C / min), 300°C (2h), 300-400°C (5°C / min), 400-500°C (2°C / min), 500°C (2h), 500-700°C (5°C / min), 700°C (4h), and finally 9μm hollow silica microspheres were obtained. Figure 4 The middle left picture shows the composite microspheres before calcination, with a particle size of 9 microns. The right picture shows the silica microspheres after calcination. It can be seen that when tetraethoxysilane is added once in a conventional alcohol and water system, the silica formed cannot penetrate into the interior, and eventually a core-shell structure composite microsphere is formed and agglomeration occurs. After calcination, hollow silica microspheres are formed, the average particle size does not change, and a large number of microspheres are broken.

[0066] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0067] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing monodisperse porous silica microspheres, characterized in that: The following steps are involved: (1) cationic modification of monodisperse porous polymer microspheres; (2) adding basic amino acids into pure water to disperse the surface cationized monodisperse porous polymer microspheres therein; (3) adding a silica precursor to the above solution in one step to prepare polymer-silica composite microspheres, filtering, washing, and drying; (4) Distributing and calcining the polymer-silica composite microspheres, and removing the organic polymer to obtain monodisperse porous silica microspheres.

2. The method for preparing monodisperse porous silica microspheres according to claim 1, characterized in that: The monodisperse porous polymer microspheres in step (1) are poly(glycidyl methacrylate) microspheres.

3. The method for preparing monodisperse porous silica microspheres according to claim 1, characterized in that: The particle size of the monodisperse porous polymer microspheres in step (1) is 1-50 μm.

4. The method for preparing monodisperse porous silica microspheres according to claim 1, characterized in that: The cationic modification in step (1) is carried out by polyethyleneimine or trimethylamine modification.

5. The method for preparing monodisperse porous silica microspheres according to claim 4, characterized in that: The mass ratio of the monodisperse porous polymer microspheres to polyethyleneimine or trimethylamine is 1:(1-10).

6. The method for preparing monodisperse porous silica microspheres according to claim 1, characterized in that: The basic amino acid in step (2) is lysine and / or arginine.

7. The method for preparing monodisperse porous silica microspheres according to claim 1, characterized in that: In step (2), the amount of basic amino acid added to pure water is 0.5-10 mg / ml.

8. The method for preparing monodisperse porous silica microspheres according to claim 1, characterized in that: In step (2) of the method, the silicon dioxide precursor is selected from methyl orthosilicate and / or ethyl orthosilicate.

9. The method for preparing dispersed porous silica microspheres according to claim 1, characterized in that: The distributed calcination in step (4) is: 25-200℃, heating rate 5℃ / min; 200-300℃, heating rate 2℃ / min; 300℃, keep warm for 2h; 300-400℃, heating rate 5℃ / min; 400-500℃, heating rate 2℃ / min; 500℃, keep warm for 2h; 500-700℃, heating rate 5℃ / min; 700℃, keep warm for 4h.

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