Silica microspheres doped with boron and having a hierarchical pore structure, and a preparation method and applications thereof

Abstract

The application belongs to the technical field of lubricant additives, and particularly relates to boron-doped silica microspheres with a hierarchical pore structure, a preparation method thereof and application. The boron-doped silica microspheres with a hierarchical pore structure provided by the application have a regular spherical morphology, good dispersibility, stable structure, and two different size pore structures, including ordered spherical pores and randomly distributed nanopore structures; the coexistence of the two different size pore structures improves the oil storage capacity of the modified silica microspheres as lubricant additives, facilitates the transmission and diffusion of lubricating oil, and improves the lubricating effect. In the application, an organic complex formed by mixing a surfactant and an acrylic acid homopolymer is used as a template, a silicic acid skeleton is formed through the interaction between a silicon source and the organic template, boron is introduced into the skeleton through the interaction between the silicic acid and a boron source, and the synthesis of boron-doped hierarchical mesoporous silica microspheres is realized through drying and calcination.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lubricant additives, and particularly relates to a boron-doped silica microsphere with a multi-level pore structure, a preparation method and application thereof. BACKGROUND

[0002] A lubricant is a lubricating medium used to reduce the friction resistance of a friction pair and slow down the wear of the friction pair. Adding a lubricant to the friction pair is an effective means to reduce friction and wear and prolong the service life of materials. In order to improve the lubricating efficiency of the lubricant and make up for the deficiency of the lubricant, it is usually necessary to add a lubricating additive to the lubricant. The current lubricating additive is mainly spherical mesoporous silica. The regular spherical morphology of the spherical mesoporous silica can play the role of a micro-bearing and a micro-ball during friction, change sliding friction into rolling friction, effectively reduce the friction coefficient, and the mesoporous structure in the spherical mesoporous silica material has good oil absorption and oil storage performance. The lubricating oil stored in the pore channel can be slowly released during friction to form an oil film on the surface of the friction pair to protect the metal friction pair. In order to further optimize and improve the comprehensive performance of the lubricant, researchers have developed boron-containing additives. For example, Chinese Patent CN105985844A discloses a biodegradable anti-wear hydraulic oil containing a boron-containing additive. The purpose is to improve the anti-wear performance and oxidation resistance of the hydraulic oil by adding the boron-containing additive, meet the complex and variable working conditions of the hydraulic system, and make the hydraulic oil have good biodegradability. For another example, Chinese Patent CN104893787A discloses a boron-containing lubricating additive with ultra-high hydrolytic stability, which solves the technical problem of easy hydrolysis of the boron-containing lubricating oil additive and improves the corrosion resistance and thermal stability of the lubricating oil.

[0003] However, the existing boron-containing lubricating oil additives mostly contain a single size of pore structure, which limits the oil storage capacity in the pore channel of the boron-containing lubricating oil additive and the transmission and diffusion performance of the lubricating oil, thereby reducing the anti-wear performance of the friction pair. SUMMARY

[0004] Therefore, the application provides a boron-doped silica microsphere with a multi-level pore structure, a preparation method and application thereof. The boron-doped silica microsphere with a multi-level pore structure contains two sizes of pore diameters, improves the oil storage capacity, facilitates the transmission and diffusion of the lubricating oil, and improves the lubricating effect.

[0005] In order to solve the above technical problems, the application provides a boron-doped silica microsphere with a multi-level pore structure, which comprises a silica skeleton, boron oxide loaded on the surface and / or in the pore channel of the silica skeleton, and in-situ doped boron in the silica skeleton.

[0006] The pore structure contained in the boron-doped silica microspheres with multi-level pore structure includes first pores and second pores; the average pore diameter of the first pores is 2.0-3.0 nm, and the average pore diameter of the second pores is 20-30 nm.

[0007] Preferably, the first pores are spherical pores, and the second pores are through pores with irregular shapes.

[0008] Preferably, the boron-doped silica microspheres with multi-level pore structure have an average diameter of 80-500 nm, a specific surface area of 302-535 m 2 / g, and a total pore volume of 0.59-0.76 cm 3 / g.

[0009] Preferably, the boron-doped silica microspheres with multi-level pore structure have a mass percentage of boron element of 2-5%.

[0010] The application further provides a preparation method of the boron-doped silica microspheres with multi-level pore structure.

[0011] The surfactant, the acrylic homopolymer and water are first mixed to obtain a template emulsion;

[0012] The template emulsion and an organic silicon source are secondly mixed for co-assembly to obtain a mixed suspension containing silicic acid oligomers and the template;

[0013] The mixed suspension containing the silicic acid oligomers and the template and a boron source aqueous solution are thirdly mixed, and then sequentially subjected to standing, solid-liquid separation, drying and calcination to obtain the boron-doped silica microspheres with multi-level pore structure.

[0014] Preferably, the acrylic homopolymer has an average molecular weight of 50,000-240,000 g / mol; and the surfactant is a cationic quaternary ammonium compound or a quaternary ammonium salt.

[0015] The mass ratio of the acrylic homopolymer to the surfactant is 40-180:44.

[0016] Preferably, the organic silicon source is tetraethyl orthosilicate or tetrapropyl orthosilicate.

[0017] The mass ratio of the organic silicon source to the acrylic homopolymer is 2:3-8.

[0018] The co-assembly is performed at a temperature of 20-45℃ for 5-30 min.

[0019] Preferably, the boron source is boric acid or ammonium borate.

[0020] The mass ratio of the boron source to the silicon source is 0.2-1:2.

[0021] The temperature of the standing is 80-100 DEG C, and the time is 12-48h.

[0022] Preferably, the temperature of the calcination is 500-800 DEG C, and the time is 5.5-6.5h.

[0023] The application further provides the application of the boron-doped silica microspheres with the multi-level pore structure in lubricant additives, heterogeneous catalysis or carbon dioxide gas adsorption.

[0024] The application provides a boron-doped silica microsphere with a multi-level pore structure, which comprises a silica framework, boron oxide loaded on the surface and / or in the channel of the silica framework and in-situ doped framework boron in the silica framework; the boron-doped silica microsphere with the multi-level pore structure contains pore structures including first pores and second pores; the average pore diameter of the first pores is 2.0-3.0nm, and the average pore diameter of the second pores is 20-30nm. The boron-doped silica microsphere with the multi-level pore structure provided by the application has a regular spherical morphology, good dispersibility and stable structure, and has two different sizes of pore structures, including ordered spherical pores and randomly distributed nanopores, and the randomly distributed nanopores do not destroy the order of the ordered mesopores; the coexistence of the two different sizes of pore structures improves the oil storage capacity of the boron-doped silica microsphere with the multi-level pore structure as a lubricant additive and is beneficial to the transmission and diffusion of lubricating oil, thereby improving the lubricating effect.

[0025] The application further provides a preparation method of the boron-doped silica microspheres with a multi-level pore structure, and the method comprises the following steps: first mixing a surfactant, an acrylic homopolymer and water to obtain a template emulsion; second mixing the template emulsion and an organic silicon source to perform co-assembly, so as to obtain a mixed suspension containing a silicic acid oligomer and a template; third mixing the mixed suspension containing the silicic acid oligomer and the template and a boron source aqueous solution, and then sequentially performing standing, solid-liquid separation, drying and calcination, so as to obtain the boron-doped silica microspheres with the multi-level pore structure. In the application, an organic complex formed by mixing a surfactant and an acrylic homopolymer is used as a template, a silicic acid skeleton is formed through the interaction between a silicon source and the organic template, and then boron is introduced into the skeleton through the interaction between the silicic acid and a boron source, so that the synthesis of the boron-doped multi-level mesoporous silica microspheres is realized through drying and calcination. In the application, the electrostatic interaction between the surfactant template and the polyacrylic acid is used for self-assembly, so as to form an ordered mesoporous template (the surfactant is used as a template); after the silicon source is added, the silicic acid oligomer is co-assembled with the template, so as to cause the dynamic phase separation of the polyacrylic acid from the organic template, and form irregular through holes. The preparation method provided by the application has simple process steps, the multi-level mesoporous boron-doped silica microspheres prepared by the method have rich pore structures, large specific surface area and total pore volume, good stability and a good application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A scanning electron microscope image of the boron-doped silica microspheres with a multi-level pore structure prepared in Example 1;

[0027] Figure 2 A transmission electron microscope image of the boron-doped silica microspheres with a multi-level pore structure prepared in Example 1;

[0028] Figure 3 Nitrogen adsorption-desorption curves and corresponding pore size distribution diagrams of the boron-doped silica microspheres with a multi-level pore structure prepared in Example 1, wherein A is a nitrogen adsorption-desorption curve diagram, and B is a pore size distribution diagram;

[0029] Figure 4 An XRD spectrum diagram of the boron-doped silica microspheres with a multi-level pore structure prepared in Example 1;

[0030] Figure 5 A nuclear magnetic resonance spectrum diagram of the boron-doped silica microspheres with a multi-level pore structure prepared in Example 1;

[0031] Figure 6 A thermogravimetric analysis curve diagram of the silica microspheres of Example 1 and Comparative Examples 2 and 4 after adsorbing lubricating oil;

[0032] Figure 7The scanning electron microscope image of the boron-doped silica microspheres with hierarchical pore structure prepared in Example 2;

[0033] Figure 8 The scanning electron microscope and transmission electron microscope images of the boron-doped silica microspheres with hierarchical pore structure prepared in Example 4, wherein the left side is the scanning electron microscope image and the right side is the transmission electron microscope image;

[0034] Figure 9 The scanning electron microscope image of the boron-doped silica microspheres with hierarchical pore structure prepared in Comparative Example 2;

[0035] Figure 10 The transmission electron microscope image of the boron-doped silica microspheres with hierarchical pore structure prepared in Comparative Example 2. DETAILED DESCRIPTION

[0036] The present application provides a boron-doped silica microsphere with hierarchical pore structure, which comprises a silica framework, boron oxide loaded on the surface and / or in the pore of the silica framework, and in-situ doped boron in the silica framework.

[0037] In the present application, the boron-doped silica microsphere with hierarchical pore structure contains pore structures including first pores and second pores; the average pore diameter of the first pores is 2.0-3.0 nm; and the average pore diameter of the second pores is 20-30 nm.

[0038] In the present application, the first pores are preferably spherical pores, and the second pores are preferably irregularly shaped through pores.

[0039] In the present application, the average diameter of the boron-doped silica microsphere with hierarchical pore structure is 80-500 nm, preferably 100-400 nm; the specific surface area of the boron-doped silica microsphere with hierarchical pore structure is preferably 302-535 m 2 / g, more preferably 350-500 m 2 / g; and the total pore volume of the boron-doped silica microsphere with hierarchical pore structure is preferably 0.59-0.76 cm 3 / g, more preferably 0.59-0.76 cm 3 / g.

[0040] In the present application, the mass percentage of boron in the boron-doped silica microsphere with hierarchical pore structure is preferably 2-5%, more preferably 3-5%.

[0041] The boron atom doped boron-doped mesoporous silica microspheres with multi-level pore structure provided by the application have the advantages of stable structure, regular spherical morphology, good dispersibility, two sizes of pore structure, large specific surface area and total pore volume, and a boron doping amount of up to 5%. The boron atom doped boron-doped mesoporous silica microspheres have good application prospects in the fields of heterogeneous catalysis, lubricating materials, CO2 gas adsorption and the like.

[0042] The application further provides a preparation method of the boron-doped mesoporous silica microspheres with multi-level pore structure.

[0043] The surfactant, the acrylic acid homopolymer and water are first mixed to obtain a template emulsion;

[0044] The template emulsion and an organic silicon source are secondly mixed to perform co-assembly, so as to obtain a mixed suspension containing a silicic acid oligomer and a template;

[0045] The mixed suspension containing the silicic acid oligomer and the template and a boron source aqueous solution are thirdly mixed, and then sequentially subjected to standing, solid-liquid separation, drying and calcination, so as to obtain the boron-doped mesoporous silica microspheres with multi-level pore structure.

[0046] In the application, the surfactant is preferably a cationic quaternary ammonium compound or a quaternary ammonium salt, and more preferably a cationic quaternary ammonium compound. In the application, the cationic quaternary ammonium compound is preferably tetradecyl ammonium chloride, chlorohexadecyl pyridine monohydrate, cetyltrimethylammonium bromide or dodecyltrimethylammonium bromide, and more preferably chlorohexadecyl pyridine monohydrate.

[0047] In the application, the average molecular weight of the acrylic acid homopolymer is preferably 50000-240000 g / mol, and more preferably 70000-200000 g / mol. The acrylic acid homopolymer is preferably provided in the form of a solution of acrylic acid homopolymer, and the mass concentration of the solution of acrylic acid homopolymer is preferably 30%.

[0048] In the application, the mass ratio of the acrylic acid homopolymer to the surfactant is preferably 40-180:44, and more preferably 50-160:44.

[0049] In the application, the water is preferably deionized water. In the application, the mass ratio of the water to the surfactant is preferably 70-190:1, and more preferably 72-185:1.

[0050] In the application, the first mixing is preferably performed under stirring. The application does not have special requirements for the stirring, as long as the mixing is uniform.

[0051] In the present application, the first mixing preferably further comprises: mixing the first mixing system and a pH regulator for pH adjustment. In the present application, the pH of the pH-adjusted system is preferably 8-11, more preferably 9-10. In the present application, the pH regulator is preferably an aqueous ammonia solution, and the mass concentration of the aqueous ammonia solution is preferably 25-28%. The present application does not have special limitations on the amount of the pH regulator, as long as the desired pH can be achieved. In the present application, the mixing is preferably carried out under stirring, and the temperature of the stirring is preferably 20-45℃, more preferably 25-40℃; the time of the stirring is preferably 25-35min, more preferably 30min. The present application adjusts the pH of the first mixing system to ensure that the template emulsion remains uniformly dispersed in a stable emulsion system.

[0052] After obtaining the template emulsion, the present application carries out a second mixing of the template emulsion and an organic silicon source for a co-assembly reaction to obtain a mixed suspension containing silicic acid oligomers and templates. In the present application, the organic silicon source is tetraethyl orthosilicate or tetrapropyl orthosilicate, more preferably tetraethyl orthosilicate. In the present application, the mass ratio of the organic silicon source to the acrylic homopolymer is preferably 2:3-8, more preferably 2:4-6.

[0053] In the present application, the temperature of the co-assembly is preferably 20-45℃, more preferably 25-40℃; the time of the co-assembly is preferably 5-30min, more preferably 10-25min. In the present application, the co-assembly is preferably accompanied by stirring, and the stirring speed is preferably 450-550r / min, more preferably 500r / min.

[0054] In the present application, the co-assembly preferably includes a hydrolysis polymerization reaction. In the present application, the organic silicon source is hydrolyzed to form orthosilicic acid, which is subjected to polycondensation to form silicic acid oligomers; the silicic acid oligomers are co-assembled with templates (surfactants and acrylic homopolymers) to form a silicic acid framework.

[0055] After obtaining the mixed suspension containing silicic acid oligomers and templates, the present application carries out a third mixing of the mixed suspension containing silicic acid oligomers and templates and an aqueous boric source solution, followed by static standing, solid-liquid separation, drying, and calcination to obtain the boron-doped silica microspheres with a hierarchical pore structure. In the present application, the boric source is preferably boric acid or ammonium borate, more preferably boric acid. In the present application, the mass ratio of the boric source to the silicon source is preferably 0.2-1:2, more preferably 0.5-0.6:2.

[0056] The boron source is dissolved in water to obtain a boron source aqueous solution in the present application. The water is preferably deionized water in the present application. The present application has no special requirements for the dissolution as long as complete dissolution is achieved. The mass concentration of the boron source aqueous solution is preferably 0.12-0.16 g / mL in the present application.

[0057] The third mixing is preferably accompanied by stirring in the present application, and the present application has no special requirements for the rotation speed of the stirring as long as uniform mixing is achieved.

[0058] The temperature of the standing is preferably 80-100℃, more preferably 85-95℃, and the time of the standing is preferably 12-48 h, more preferably 24-48 h in the present application. The template agent and the silicon acid oligomer-containing substance self-assemble to form a silica framework during the standing in the present application, and boron atoms are doped into the silica framework.

[0059] The present application has no special requirements for the solid-liquid separation, and a conventional method in the art can be used.

[0060] The temperature of the drying is preferably 60-80℃, more preferably 60-70℃, and the time of the drying is preferably 8-12 h, more preferably 10-12 h in the present application.

[0061] The temperature of the calcination is preferably 500-800℃, more preferably 500-700℃, and the time of the calcination is preferably 5.5-6.5 h, more preferably 6 h in the present application. The calcination is preferably performed in a muffle furnace in the present application. The template agent (the surfactant and the acrylic acid homopolymer) in the solid obtained by the solid-liquid separation can be removed by the calcination in the present application, and a pore structure with an average pore size of 2.0-3.0 nm and 20-30 nm is formed. Meanwhile, the boron source is converted into boron oxide by the calcination in the present application.

[0062] In the present application, the silicon source undergoes hydrolysis condensation reaction and co-assembles with the pore-forming template agent to form a silica skeleton with a hierarchical pore structure, and there is a certain interaction between the silicic acid and the boron source, which can introduce boron elements into the skeleton, and then further condense the silicic acid to form a boron-doped silicon dioxide material. After removing the organic pore-forming template agent by high-temperature calcination, a boron-doped hierarchical mesoporous silica microsphere with a hierarchical pore structure is prepared. The boron-doped hierarchical mesoporous silica microsphere provided by the present application has a regular shape, and the particle size can be adjusted. The material has a Pm-3n cubic mesostructure, and the ordered mesopore size is 2.0-3.0nm, while the nanopore size randomly distributed between the ordered mesopores is 20-30nm. The boron doping amount in the silica can reach 5%, the specific surface area is large, and the pore structure is rich, which is beneficial to the loading, storage and transportation of guest molecules. The boron-doped hierarchical mesoporous silica microsphere provided by the present application as a lubricating oil storage material shows excellent lubricating oil storage capacity. The preparation process provided by the present application is simple, low in cost, mild in reaction conditions, and easy to popularize.

[0063] The present application also provides the application of the boron-doped hierarchical mesoporous silica microsphere in lubricant additives, heterogeneous catalysis or carbon dioxide gas adsorption.

[0064] In order to further illustrate the present application, the technical solutions provided by the present application are described in detail below in conjunction with examples, but they should not be understood as limiting the scope of protection of the present application.

[0065] Example 1

[0066] 40mL of deionized water, 3g of acrylic acid homopolymer with a mass concentration of 30% (average molecular weight of 50000g / mol) and 0.55g of chlorohexadecylpyridine monohydrate were mixed under stirring to obtain a colorless transparent solution, then a 26% ammonia solution was added to adjust the pH value of the system to 9, forming a white suspension and a small amount of white agglomerates, and the system was stirred at 30℃ for 30min to obtain a template emulsion;

[0067] 2.1g of tetraethyl orthosilicate and the template emulsion were co-assembled at a temperature of 25℃ and a speed of 500r / min for 5min to obtain a mixed suspension containing silicic acid oligomers and template agents;

[0068] 0.60g of boric acid was dissolved in 5g of deionized water to obtain a boric acid aqueous solution; the boric acid aqueous solution and the mixed suspension containing silicic acid oligomers and template agents were stirred and mixed, and then placed at 80℃ for 48h;

[0069] The system after standing is solid-liquid separated, the solid obtained by the solid-liquid separation is dried at 60℃ for 12h, and then is placed in a muffle furnace and calcined at 500℃ for 6h to obtain the boron-doped silica microspheres with hierarchical pore structure.

[0070] Example 2

[0071] 100mL of deionized water, 3g of acrylic acid homopolymer with a mass concentration of 30% (average molecular weight of 50000g / mol) and 0.54g of chlorohexadecylpyridine monohydrate are mixed under stirring to obtain a colorless transparent solution, then a solution of ammonia with a mass concentration of 25-28% is added, the pH value of the system is adjusted to 8, a white suspension and a small amount of white agglomerates are formed, and the system is stirred at 20-45℃ for 30min to obtain a template emulsion;

[0072] 2.0g of tetraethyl orthosilicate and the template emulsion are co-assembled at a temperature of 35℃ and a rotating speed of 500r / min for 5-30min to obtain a mixed suspension containing silicic acid oligomers and templates;

[0073] 0.60g of boric acid is dissolved in 5g of deionized water to obtain a boric acid aqueous solution; the boric acid aqueous solution and the mixed suspension containing silicic acid oligomers and templates are stirred and mixed, and then are placed at 90℃ for 48h;

[0074] The system after standing is solid-liquid separated, the solid obtained by the solid-liquid separation is dried at 70℃ for 10h, and then is placed in a muffle furnace and calcined at 500℃ for 6h to obtain the boron-doped silica microspheres with hierarchical pore structure

[0075] Example 3

[0076] 40mL of deionized water, 3g of acrylic acid homopolymer with a mass concentration of 30% (average molecular weight of 50000g / mol) and 0.22g of chlorohexadecylpyridine monohydrate are mixed under stirring to obtain a colorless transparent solution, then a solution of ammonia with a mass concentration of 25% is added, the pH value of the system is adjusted to 8, a white suspension and a small amount of white agglomerates are formed, and the system is stirred at 20-45℃ for 30min to obtain a template emulsion;

[0077] 2.0g of tetraethyl orthosilicate and the template emulsion are co-assembled at a temperature of 25℃ and a rotating speed of 500r / min for 25min to obtain a mixed suspension containing silicic acid oligomers and templates;

[0078] 0.80g of boric acid is dissolved in 5g of deionized water to obtain a boric acid aqueous solution; the boric acid aqueous solution and the mixed suspension containing silicic acid oligomers and templates are stirred and mixed, and then are placed at 100℃ for 48h;

[0079] The system after standing is solid-liquid separated, and the solid obtained by the solid-liquid separation is dried at 60°C for 12h and then calcined in a muffle furnace at 500°C for 6h to obtain boron-doped silica microspheres with hierarchical pore structure.

[0080] Example 4

[0081] 40mL of deionized water, 6.0g of acrylic acid homopolymer with a mass concentration of 30% (average molecular weight of 50000g / mol) and 0.54g of chlorohexadecylpyridine monohydrate are mixed under stirring to obtain a colorless transparent solution, and then a 25-28% ammonia solution is added to adjust the pH value of the system to 10, forming a white suspension with a small amount of white agglomerates, which is stirred magnetically at 30°C for 30min to obtain a template emulsion;

[0082] 2.0g of tetraethyl orthosilicate and the template emulsion are co-assembled at a temperature of 25°C and a speed of 500r / min for 5min to obtain a mixed suspension containing silicic acid oligomers and templates;

[0083] 0.60g of boric acid is dissolved in 5g of deionized water to obtain a boric acid aqueous solution; the boric acid aqueous solution and the mixed suspension containing silicic acid oligomers and templates are stirred and mixed, and then left to stand at 90°C for 48h;

[0084] The system after standing is solid-liquid separated, and the solid obtained by the solid-liquid separation is dried at 60°C for 12h and then calcined in a muffle furnace at 500°C for 6h to obtain boron-doped silica microspheres with hierarchical pore structure.

[0085] Comparative Example 1

[0086] The modified silica microspheres are prepared according to the method of Example 1, except that the tetraethyl orthosilicate and the boric acid aqueous solution are added to the template emulsion at the same time.

[0087] Comparative Example 2

[0088] The modified silica microspheres are prepared according to the method of Example 1, except that the boric acid aqueous solution is added to the template emulsion first and then the tetraethyl orthosilicate is added.

[0089] Comparative Example 3

[0090] The modified silica microspheres are prepared according to the method of Example 1, except that the boric acid is directly mixed with the mixed suspension containing silicic acid oligomers and templates.

[0091] Comparative Example 4

[0092] Silica microspheres with a model of CAS:7440-21-3 purchased from Pioneer Nanometer are used as a comparative example.

[0093] The oil storage performance was evaluated as follows: The boron-doped silica microspheres with hierarchical porous structure prepared in Example 1 were placed in a round-bottom flask and vacuumed for 0.5 h. Perfluoropolyether lubricating oil was added to the round-bottom flask and kept under vacuum for 4 h. Then, the residual lubricating oil on the surface was washed away with petroleum ether. The mass ratio of lubricating oil to oil storage material was 5:1.

[0094] The boron-doped silica microspheres with a hierarchical porous structure prepared in Example 1 were examined by scanning electron microscopy (SEM), and the SEM images are shown below. Figure 1 As shown. From Figure 1 As can be seen, boron-doped silica microspheres with a hierarchical porous structure are regular spherical particles with good dispersibility and a particle size of 300–600 nm.

[0095] Transmission electron microscopy (TEM) was performed on the boron-doped silica microspheres with hierarchical porous structure prepared in Example 1, and the TEM images are shown below. Figure 2 As shown. From Figure 2 It can be clearly observed that boron-doped silica microspheres with hierarchical porous structures have both small and large nanopore structures.

[0096] Nitrogen adsorption was performed on the boron-doped silica microspheres with a hierarchical porous structure prepared in Example 1, and nitrogen adsorption-desorption curves and corresponding pore size distribution diagrams were obtained, as shown below. Figure 3 As shown, A is the nitrogen adsorption-desorption curve, and B is the pore size distribution diagram. From Figure 3 As can be seen, the boron-doped silica microspheres with a hierarchical porous structure prepared in Example 1 exhibit typical adsorption behavior of mesoporous materials. The specific surface area of ​​the silica microspheres prepared in Example 1, calculated using the BET method, is 535 m². 2 / g, total pore volume is 0.76cm³ 3 / g. Calculations using the BJH method show that the boron-doped silica microspheres with a hierarchical porous structure exhibit two pore size distributions: ordered mesopores with a pore size of approximately 2.5 nm and nanopores with a pore size of approximately 25 nm.

[0097] XRD analysis was performed on the boron-doped silica microspheres with a hierarchical porous structure prepared in Example 1, and the XRD patterns were obtained, as shown below. Figure 4 As shown. From Figure 4 As can be seen from Example 1, the boron-doped silica microspheres with a hierarchical porous structure exhibit three distinct diffraction peaks at 2θ = 1.5–2.5, corresponding to the (200), (210), and (211) diffraction planes of the cubic mesoscopic structure Pm-3n, respectively. This indicates the presence of an ordered mesoporous structure in the synthesized silica microspheres. In this invention… Figure 2In the middle of which the through hole of irregular shape can be observed, Figure 4 The small angle XRD proves that the spherical hole is arranged in order.

[0098] The boron-doped silica microspheres with hierarchical pore structure prepared in Example 1 are detected by nuclear magnetic resonance, and the 11B MAS nuclear magnetic resonance spectrum is obtained as shown in Figure 5 From Figure 5 It can be seen that the peak appearing at-2.8ppm of the boron-doped silica microspheres with hierarchical pore structure prepared in Example 1 corresponds to the four-coordinated boron (B[4]) in the TO4 site of the silica material skeleton, and the signal appearing at 0-15ppm can be attributed to the three-coordinated boron (B[3]) in the silica skeleton, which is similar to the isolated boron in the zeolite skeleton. In addition, the signal at 15-25ppm belongs to the boron oxide species in the silica material, indicating that the synthesized ordered mesoporous hierarchical pore silica material has both boron species introduced into the silica skeleton and boron oxide species.

[0099] The boron-doped silica microspheres with hierarchical pore structure prepared in Example 1 and the silica microspheres of Comparative Examples 2 and 4 are adsorbed with lubricating oil, and then thermogravimetric detection is performed, and the thermogravimetric analysis curve of the modified silica microspheres after adsorbing lubricating oil is obtained as shown in Figure 6 From Figure 6 It can be seen that the mass loss of the sample prepared in Example 1 in the temperature range of 250-600℃ accounts for about 50.4% of the total mass, which corresponds to the thermal decomposition range of the lubricating oil, indicating that the boron-doped silica microspheres with hierarchical pore structure prepared by adsorbing lubricating oil have an oil absorption amount of about 50.4%. Compared with the thermogravimetric analysis of the lubricating oil adsorption samples prepared in Comparative Examples 2 and 4, it can be seen that the sample of Comparative Example 2 has no regular spherical morphology and lacks ordered mesoporous and nanoporous structure, and the oil absorption amount is only 20%, while the sample of Comparative Example 4 is only a single pore size mesoporous silica, lacking a hierarchical pore structure, and the oil absorption amount is 31%.

[0100] The boron-doped silica microspheres with hierarchical pore structure prepared in Example 2 are detected by scanning electron microscopy, and the scanning electron microscope image is obtained as shown in Figure 7 From Figure 7 It can be seen that the silica microspheres prepared in Example 2 are a kind of spherical particles with regular morphology and good dispersibility, and the average diameter is 100-200nn. Compared with Figure 1 the boron-doped silica microspheres with hierarchical pore structure in Figure 7 have a larger particle size, which indicates that the amount of water in the reaction system has a significant effect on the particle size of the synthesized silica microspheres.

[0101] The boron-doped silica microspheres with hierarchical porous structure prepared in Example 4 were detected by scanning electron microscopy and transmission electron microscopy, and the scanning electron microscopy and transmission electron microscopy images were obtained as shown in Figure 8 Fig. 1, wherein the left side is the scanning electron microscopy image and the right side is the transmission electron microscopy image. It can be seen from Figure 8 Fig. 1 that the boron-doped silica prepared in Example 4 has a regular spherical morphology, good dispersibility, and the particle size is 500-800 nm, and a large number of mesoporous structures in the silica microspheres can be clearly observed. It is illustrated that in the reaction system of the present application, the silica microspheres with regular spherical morphology can be synthesized in a wide range of the amount of water-soluble acrylic homopolymer.

[0102] The modified silica microspheres prepared in Comparative Example 2 were detected by scanning electron microscopy, and the scanning electron microscopy image was obtained as shown in Figure 9 Fig. 2. It can be seen from Figure 9 Fig. 2 that the silica prepared in Comparative Example 2 is a block solid without regular morphology.

[0103] The modified silica microspheres prepared in Comparative Example 2 were detected by transmission electron microscopy, and the transmission electron microscopy image was obtained as shown in Figure 10 Fig. 3. It can be seen from Figure 10 Fig. 3 that the silica prepared in Comparative Example 2 has a porous structure inside the particles but the silica particles are not spherical in morphology. The adding time of the silicon source and the boron source can affect the morphology of the silica particles.

[0104] Although the above examples have made a detailed description of the present application, it is only a part of the examples of the present application, not all the examples, and other examples can be obtained according to the present examples without creativity, which all belong to the protection scope of the present application.

Claims

1. A method for preparing boron-doped silica microspheres with hierarchical pore structure, comprising the following steps: mixing a surfactant, an acrylic homopolymer, water and a pH regulator to obtain a template emulsion; the surfactant is a cationic quaternary ammonium compound; mixing the template emulsion and an organosilicon source to perform co-assembly, to obtain a mixed suspension containing silicic acid oligomers and templates; mixing the mixed suspension containing silicic acid oligomers and templates and an aqueous solution of a boron source, and then sequentially performing standing, solid-liquid separation, drying and calcination, to obtain boron-doped silica microspheres with hierarchical pore structure; the boron-doped silica microspheres with hierarchical pore structure comprise a silica framework, boron oxide loaded on the surface and / or in the pores of the silica framework, and framework boron in-situ doped in the silica framework; the boron-doped silica microspheres with hierarchical pore structure contain first pores and second pores; the average pore size of the first pores is 2.0-3.0 nm, and the average pore size of the second pores is 20-30 nm; the first pores are spherical pores, and the second pores are irregularly shaped through pores. 2.The boron-doped silica microspheres with hierarchical pore structure according to claim 1, wherein the mass percentage of boron in the boron-doped silica microspheres with hierarchical pore structure is 2-5%. 3.The boron-doped silica microspheres with hierarchical pore structure according to claim 1 or 2, wherein the average molecular weight of the acrylic homopolymer is 50,000-240,000 g / mol. 4.The boron-doped silica microspheres with hierarchical pore structure according to any one of claims 1-3, wherein the mass ratio of the acrylic homopolymer to the surfactant is 40-180:

44. 5.The boron-doped silica microspheres with hierarchical pore structure according to any one of claims 1-4, wherein the organosilicon source is tetraethyl orthosilicate or tetrapropyl orthosilicate. 6.The boron-doped silica microspheres with hierarchical pore structure according to any one of claims 1-5, wherein the mass ratio of the organosilicon source to the acrylic homopolymer is 2:3-8. 7.The boron-doped silica microspheres with hierarchical pore structure according to any one of claims 1-6, wherein the temperature of the co-assembly is 20-45℃, and the time is 5-30 min.

2. The method of claim 1, wherein, The boron-doped silica microspheres with the hierarchical pore structure have an average diameter of 80-500 nm, a specific surface area of 302-535 m 2 / g, and a total pore volume of 0.59-0.76 cm 3 / g.

3. The preparation method according to claim 1, characterized in that, 8.The boron-doped silica microspheres with hierarchical pore structure according to any one of claims 1-7, wherein the boron source is boric acid or ammonium borate; the mass ratio of the boron source to the organosilicon source is 0.2-1:2; the temperature of the standing is 80-100℃, and the time is 12-48 h.

4. The preparation method according to claim 1, characterized in that, 9.The boron-doped silica microspheres with hierarchical pore structure obtained by the method according to any one of claims 1-8, and application of the boron-doped silica microspheres with hierarchical pore structure in lubricant additives, heterogeneous catalysis or carbon dioxide gas adsorption.

5. The method of claim 1 or 4, wherein the compound is prepared by the method of claim 2 or 3. ​ 6. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. ​ ​ ​ 7. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. ​ ​ ​ 8. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. ​ ​

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