CN119390077A

CN119390077A - A kind of silicon dioxide core-shell microsphere and preparation method thereof

Info

Publication number: CN119390077A
Application number: CN202510005556.8A
Authority: CN
Inventors: 吴大朋
Original assignee: Ningbo University
Current assignee: Ningbo University
Priority date: 2025-01-03
Filing date: 2025-01-03
Publication date: 2025-02-07

Abstract

The present invention provides a silicon dioxide core-shell microsphere and a preparation method thereof, the preparation method comprising the following steps: S1, using acrylamide as a raw material, polymerizing and modifying a polyacrylamide gel layer of a set thickness on the outer surface of a silicon dioxide solid microsphere; S2, dispersing the microsphere obtained in step S1 in an aqueous solution, adding a diamine organic compound, hydrolyzing part of the amide bonds of the polyacrylamide gel layer, and forming a polyorganic amine gel layer; S3, dispersing the microsphere obtained in step S2 in an orthosilicate solution, hydrolyzing the orthosilicate in the polyorganic amine gel layer, and depositing silicon dioxide nanoparticles; S4, calcining the microsphere obtained in step S3 at a high temperature, removing organic matter, and cross-linking the silicon dioxide nanoparticles to obtain silicon dioxide core-shell microspheres. The preparation method of the present invention can accurately control the shell thickness and shell porosity, and can improve the mechanical strength of the entire core-shell microsphere.

Description

Silica core-shell microsphere and preparation method thereof

Technical Field

The invention relates to the technical field of liquid chromatographic separation materials, in particular to a silicon dioxide core-shell microsphere and a preparation method thereof.

Background

Core-shell silica fillers, which may also be referred to as surface porous silica fillers, consist of an inner solid core structure and an outer porous shell structure, first proposed by Horvath et al in the last 60 th century. Core-shell silica microspheres then rapidly attract attention from researchers due to their particular structure. The company Dupont, merck and Waters first developed Zipax, perisorb, corasil brand first generation core-shell silica gel microspheres. Halo chromatography columns were developed by ADVANCED MATERIAL Technology limited in us 2007, the packing being 2.7 μm core-shell silica microspheres formed from a 1.7 μm solid core combined with a 0.5 μm porous shell. Compared with the full-porous silica microspheres with the same diameter, the porous silica core-shell microspheres can shorten the mass transfer distance of an analyte in a fixed phase in the chromatographic separation process, reduce mass transfer resistance, improve separation efficiency by more than one time, and shorten chromatographic separation time by more than half.

The prior art discloses a preparation method of a plurality of core-shell type silicon dioxide microspheres, such as silica gel nano particles are electrostatically adsorbed by urea resin and then calcined at high temperature to prepare the core-shell type silicon dioxide microspheres, the patent CN201610655630.1 adopts two quaternary ammonium salts with different carbon branched chain lengths as co-template agents to prepare the core-shell microspheres with larger radioactive mesoporous structures, and the patent CN201810160294.2 adopts silicon dioxide polymer core-shell composite microspheres as templates to successfully prepare the silicon dioxide core-shell microspheres through a sol-gel process.

However, the existing preparation method has the following problems that (1) the thickness controllability of the shell layer is poor, and the thickness of the shell layer cannot be accurately controlled no matter in a urea resin/silica gel nanoparticle self-assembly method or a radial mesoporous shell layer method. (2) The shell layer has poor mechanical strength, the content of silicon dioxide in the shell layer of the urea resin/silica gel nano particle self-assembly method is low, so that the mechanical strength is low, and the core-shell silicon dioxide is easy to break during high-pressure filling and subsequent high-pressure separation.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to develop a novel core-shell type silicon dioxide microsphere preparation technology, which can accurately control the thickness of a shell layer and improve the integral mechanical strength of the microsphere.

In order to achieve the above purpose, the invention provides a preparation method of silica core-shell microspheres, which comprises the following steps:

S1, taking acrylamide as a raw material, and polymerizing and modifying a polyacrylamide gel layer with a set thickness on the outer surface of a silicon dioxide solid microsphere;

s2, dispersing the microspheres obtained in the step S1 in an aqueous solution, and adding a diamino organic compound to hydrolyze part of amide bonds of the polyacrylamide gel layer to form a poly-organic amine gel layer;

S3, dispersing the microspheres obtained in the step S2 in an orthosilicate solution, hydrolyzing the orthosilicate in a poly-organic amine gel layer, and depositing silica nanoparticles;

And S4, calcining the microsphere obtained in the step S3 at a high temperature, removing organic matters, and crosslinking the silicon dioxide nano particles to obtain the silicon dioxide core-shell microsphere.

According to the preparation method disclosed by the invention, the polyacrylamide gel layer is controllably grown on the surface of the silicon dioxide solid microsphere, and then the shell layer is prepared by hydrolysis, so that the thickness and the porosity of the shell layer can be accurately controlled, and on the other hand, the content of the silicon dioxide of the shell layer can be increased by increasing the addition amount of the orthosilicate, so that the mechanical strength of the shell layer is improved. Therefore, compared with the prior art, the preparation method provided by the invention can obviously improve the accuracy of shell thickness and shell porosity control and improve the mechanical strength of the whole core-shell microsphere.

In a preferred or alternative embodiment, in the step S1, the preparation method of the polyacrylamide gel layer is selected from one of atom transfer radical polymerization, radical polymerization and reversible deactivation radical polymerization, preferably atom transfer radical polymerization.

In a preferred or alternative embodiment, in the step S1, the diameter of the silica solid microsphere is 0.1-10 μm, and the thickness of the polyacrylamide gel layer is 1-1000 nm.

The thickness of the polyacrylamide gel layer can be precisely controlled by utilizing the surface atom transfer polymerization growth and only quantitatively controlling the addition amount of the acrylamide monomer and the silica solid microsphere.

In a preferred or alternative embodiment, in the step S2, the hydrolysis degree of the polyacrylamide gel layer is 10% -90%.

In a preferred or alternative embodiment, the molar ratio of the orthosilicate used in the step S3 to the acrylamide used in the step S1 is 0.1-2.0:1.

The deposition amount of the silicon dioxide nano particles in the gel layer can be controlled by controlling the hydrolysis degree of the polyacrylamide gel layer and the addition amount of the orthosilicate, and finally the porosity of the shell layer is controlled.

In a preferred or alternative embodiment, in the step S4, the calcination temperature is 300 to 1000 ℃ and the calcination time is 0.5 to 48 hours. By selecting proper sintering temperature and sintering time, the mechanical strength of the shell layer can be improved.

In a preferred or alternative embodiment, in the step S2, the diamine-based organic compound is selected from one or more of ethylenediamine, propylenediamine, butylenediamine, pentyldiamine, hexamethylenediamine.

In a preferred or alternative embodiment, in the step S3, the orthosilicate is selected from one or more of methyl orthosilicate, ethyl orthosilicate, and isopropyl orthosilicate.

The invention also provides a silicon dioxide core-shell microsphere prepared by the preparation method, which comprises a solid silicon dioxide core layer and a porous silicon dioxide shell layer. Preferably, the porosity of the porous silica shell layer is 10% -90%. The silicon dioxide core-shell microsphere has the advantages of accurate and controllable shell thickness and porosity and high mechanical strength.

In summary, compared with the prior art, the invention has the following beneficial effects:

(1) The thickness of the shell layer is precisely controllable, namely a gel layer is controllably grown on the surface of the silica solid microsphere, and then the shell layer is prepared by hydrolysis, and the thickness of the porous silica shell layer can be controlled by only controlling the thickness of the polyacrylamide gel layer.

(2) The porosity of the shell layer is precisely controllable, the deposition amount of the silica nano particles in the gel layer can be controlled by controlling the addition amount of the orthosilicate and the silica solid ball modified with the poly-organic amine gel layer, and finally the porosity of the shell layer is controlled.

(3) The shell layer has high mechanical strength, and the content of silicon dioxide in the shell layer can be increased by increasing the addition amount of the tetrasilicate in a proper porosity range, so that the mechanical strength of the shell layer can be increased, and the mechanical strength of the shell layer can be increased by selecting proper sintering temperature and sintering time.

Drawings

FIG. 1 is an electron micrograph of silica core shell microspheres of example 1.

FIG. 2 is a chromatogram of silica core-shell microsphere chromatography column reversed phase chromatography for alkylbenzene separation in example 2.

Detailed Description

In order that the above objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It should be noted that the following examples are only for illustrating the implementation method and typical parameters of the present invention, and are not intended to limit the scope of the parameters described in the present invention, so that reasonable variations are introduced and still fall within the scope of the claims of the present invention.

It should be noted that endpoints and any values of the ranges disclosed herein are not limited to the precise range or value, and that such range or value should be understood to include values approaching such range or value. For numerical ranges, one or more new numerical ranges may be found between the endpoints of each range, between the endpoint of each range and the individual point value, and between the individual point value, in combination with each other, and are to be considered as specifically disclosed herein.

The specific embodiment of the invention provides a silicon dioxide core-shell microsphere and a preparation method thereof, which are used for solving the problems of poor shell thickness controllability, poor shell mechanical strength and the like of the silicon dioxide core-shell microsphere in the prior art. The preparation method comprises the following steps:

s1, taking acrylamide as a raw material, and polymerizing and modifying a polyacrylamide gel layer with a set thickness on the outer surface of the silicon dioxide solid microsphere.

In a specific embodiment, the method for preparing the polyacrylamide gel layer is selected from one of atom transfer radical polymerization, radical polymerization and reversible deactivation radical polymerization, preferably atom transfer radical polymerization.

In the specific embodiment, the diameter of the silica solid microspheres is 0.1-10 mu m, the thickness of the polyacrylamide gel layer can be accurately controlled by quantitatively controlling the addition amount of the acrylamide monomer and the silica solid microspheres by utilizing surface atom transfer polymerization growth, and the typical thickness of the polyacrylamide gel layer is 1-1000 nm.

S2, dispersing the microspheres obtained in the step S1 in an aqueous solution, adding a diamino organic compound, and hydrolyzing part of amide bonds of polyacrylamide to form a poly-organic amine gel layer.

In a specific embodiment, the degree of hydrolysis of the polyacrylamide gel layer can be controlled by controlling the relationship between the amount of the diamine-based organic compound added and the amount of the acrylamide monomer.

In a specific embodiment, the diamino organic compound may be selected from ethylenediamine, propylenediamine, butylenediamine, pentylene diamine, hexylenediamine, and the like. The hydrolysis temperature is controlled to be 20-90 ℃ and the hydrolysis time is controlled to be 1-24 h. Preferably, the hydrolysis degree of the polyacrylamide gel layer is 10% -90%.

S3, dispersing the microspheres obtained in the step S2 in an orthosilicate solution, hydrolyzing the orthosilicate in a gel layer, and depositing silica nanoparticles.

By controlling the addition of the orthosilicate, the deposition amount of the silica nanoparticles in the gel layer can be controlled, and finally the porosity of the shell layer can be controlled. In a proper porosity range, the content of the shell silicon dioxide can be increased by increasing the addition amount of the tetrasilicate, so that the shell mechanical strength is improved. In a specific embodiment, the molar ratio of the orthosilicate to the acrylamide is 0.1-2.0:1, preferably 0.4-1.0:1.

In particular embodiments, the orthosilicate may be selected from methyl orthosilicate, ethyl orthosilicate, isopropyl orthosilicate, and the like. The hydrolysis is carried out at room temperature for 1-24 hours, preferably for 1-100 hours, and preferably for 12-64 hours.

S4, calcining the microsphere obtained in the step S3 at a high temperature, removing organic matters, and crosslinking the silica nanoparticles to obtain the silica core-shell microsphere taking porous silica as a shell layer.

In a specific embodiment, the calcination temperature is 300-1000 ℃ and the calcination time is 0.5-48 h. By selecting proper sintering temperature and sintering time, the mechanical strength of the shell layer can be improved.

The silica core-shell microsphere prepared by the method comprises a solid silica core layer and a porous silica shell layer, wherein the thickness and the porosity of the shell layer are controllable, the typical porosity of the porous silica shell layer is 10% -90%, the shell layer has high mechanical strength, can bear high pressure, and meets the use requirements of high-pressure filling and high-pressure separation.

The technical scheme and effect of the present invention are described below by specific examples.

Example 1

The preparation process of the core-shell silica microsphere comprises the following steps:

(1) 10mL of 70% methanol solution is prepared, 1g of (3-bromopropyl) triethoxysilane modified solid silica microsphere with the diameter of 1.5 μm is added, 0.2g of acrylamide, 0.02g of N, N-methylene bisacrylamide is added, nitrogen bubbling is performed for half an hour to remove oxygen, 0.1% cuprous bromide and 0.1% of initiator by mass are added, the reaction is carried out for 24 hours at room temperature in a sealed manner, the product is collected and washed with water, and the surface of the solid silica microsphere is dried in vacuum at 50 ℃ to form a polyacrylamide gel layer with the thickness of 100 nm.

(2) Dispersing the microspheres obtained in the step (1) in an aqueous solution, adjusting the pH to 7 by using 0.1M hydrochloric acid, adding 0.2mL of 37% formaldehyde solution, reacting for 3 hours at room temperature, then adding 0.6mL of ethylenediamine, uniformly mixing, reacting for 12 hours at 50 ℃, enabling the hydrolysis degree of a polyacrylamide gel layer to be 60%, centrifugally collecting the microspheres after the hydrolysis of the polyacrylamide, washing the microspheres to be neutral by using methanol and water, and drying the microspheres in vacuum at 50 ℃ to obtain the silica microspheres modified with the polypropylene organic amine gel layer.

(3) Dispersing the microspheres obtained in the step (2) in 10mL of 60% ethanol solution, adding 0.4mL of ethyl orthosilicate, reacting for 48 hours at room temperature in a sealed manner under the mechanical stirring of 400r/min, collecting microspheres after hydrolysis of the ethyl orthosilicate, washing the microspheres with ethanol and water to be neutral, and vacuum drying the microspheres at 50 ℃ to obtain the silica core-shell microspheres with silica nanoparticles deposited in the gel layer.

(4) And (3) placing the microspheres obtained in the step (3) into a muffle furnace, heating to 600 ℃ at a heating rate of 2 ℃ per minute, maintaining for 6 hours, and slowly cooling to room temperature to obtain the silica core-shell microspheres with solid silica core layers and porous silica shell layers.

The silica core-shell microsphere prepared in this example was subjected to electron microscopy, and the result is shown in FIG. 1, wherein the thickness of the shell layer is 100nm, the porosity is 60%, and the diameter of the core is 1.5. Mu.m.

The silica core-shell microsphere prepared in this example was subjected to nitrogen adsorption test, the specific surface area of the microsphere was 50m ²/g, and the pore diameter was 8.5nm.

Example 2

The preparation method of the core-shell silica microsphere liquid chromatographic column comprises the following steps:

(1) 1g of the silica core-shell microsphere prepared in example 1 was weighed, washed with 6M hydrochloric acid, pure water and ethanol in this order, and dried in a vacuum oven at 80℃overnight.

(2) Collecting the microspheres treated in the step (1), adding 20ml of toluene solution of octadecyl dimethyl chlorosilane with the concentration of 5%, adding 5ml of pyridine, and putting the microspheres into an oven for reaction for 12 hours at the temperature of 100 ℃.

(3) Repeating the step (2) for two times, collecting the product, cleaning and drying in vacuum to obtain the core-shell silica microsphere modified by the reversed phase chromatographic stationary phase.

(4) Dispersing the microspheres obtained in the step (3) into methanol, filling the microspheres into a stainless steel column tube with an inner diameter of 2.1mm and a tube length of 50mm by adopting a homogenization method under the pressure of 40MPa, and obtaining the core-shell silica liquid chromatographic column modified by the reversed phase chromatographic stationary phase.

Five alkylbenzenes were separated using the core-shell silica liquid chromatography column prepared in example 2 under conditions of acetonitrile/water (65:35), flow rate of 0.2mL/min, and detection wavelength of 210nm. As shown in FIG. 2, the 5 kinds of compounds were toluene (FIG. 1), ethylbenzene (FIG. 2), propylbenzene (FIG. 3), butylbenzene (FIG. 4) and pentylbenzene (FIG. 5), respectively. The chromatographic dead time is about 1.5min, and the alkylbenzene small molecules are effectively separated on a core-shell silica liquid chromatographic column.

Example 3

(1) 10mL of 70% methanol solution is prepared, 1g of (3-bromopropyl) triethoxysilane modified solid silica microsphere with the diameter of 2 mu m is added, 0.5g of acrylamide and 0.05g of N, N-methylene bisacrylamide are added, nitrogen bubbling is performed for half an hour to remove oxygen, 0.1% of cuprous bromide and 0.1% of initiator by mass are added, the reaction is carried out for 24 hours at room temperature in a sealed manner, the product is collected and washed by water, and the solid silica microsphere surface is dried in vacuum at 50 ℃ to form a polyacrylamide gel layer with the thickness of 180 nm.

(2) Dispersing the microspheres obtained in the step (1) in an aqueous solution, adjusting the pH to 7 by using 0.1M hydrochloric acid, adding 0.2mL of 37% formaldehyde solution, reacting for 3 hours at room temperature, then adding 0.8mL of ethylenediamine, uniformly mixing, reacting for 12 hours at 50 ℃, enabling the hydrolysis degree of a polyacrylamide gel layer to be 40%, centrifugally collecting the microspheres after the hydrolysis of the polyacrylamide, washing the microspheres to be neutral by using methanol and water, and drying the microspheres in vacuum at 50 ℃ to obtain the silica microspheres modified with the poly-organic amine gel layer.

(3) Dispersing the microspheres obtained in the step (2) in 10mL of 60% ethanol solution, adding 0.8mL of ethyl orthosilicate, reacting for 48 hours at room temperature in a sealed manner under the mechanical stirring of 400r/min, collecting microspheres after hydrolysis of the ethyl orthosilicate, washing the microspheres with ethanol and water to be neutral, and vacuum drying the microspheres at 50 ℃ to obtain the silica core-shell microspheres with silica nanoparticles deposited in the gel layer.

(4) And (3) placing the microspheres obtained in the step (3) into a muffle furnace, heating to 800 ℃ at a heating rate of 2 ℃ per minute, maintaining for 4 hours, and slowly cooling to room temperature to obtain the silica core-shell microspheres with solid silica core layers and porous silica shell layers.

The silica core-shell microsphere prepared in this example was subjected to electron microscopy, the shell thickness was 180nm, the porosity was 40%, and the core diameter was 2. Mu.m.

Example 4

(1) 1g of the silica core-shell microsphere prepared in example 3 was weighed, washed with 6M hydrochloric acid, pure water and ethanol in this order, and dried in a vacuum oven at 80℃overnight.

The five alkylbenzenes of toluene, ethylbenzene, propylbenzene, butylbenzene and pentylbenzene were separated by the core-shell silica liquid chromatography column prepared in example 4 under the conditions of acetonitrile/water (65:35), a flow rate of 0.2mL/min and a detection wavelength of 210nm. The chromatographic dead time is about 1.6 min, and alkylbenzene small molecules are effectively separated on a core-shell silica liquid chromatographic column.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.

Claims

1. A method for preparing silicon dioxide core-shell microspheres, characterized in that it comprises the following steps:

S1, using acrylamide as a raw material, polymerizing and modifying a polyacrylamide gel layer of a set thickness on the outer surface of the silica solid microspheres;

S2, dispersing the microspheres obtained in step S1 in an aqueous solution, adding a diamine-based organic compound to hydrolyze part of the amide bonds of the polyacrylamide gel layer to form a polyorganic amine gel layer;

S3, dispersing the microspheres obtained in step S2 in an orthosilicate solution, allowing the orthosilicate to hydrolyze in the polyorganoamine gel layer to deposit silicon dioxide nanoparticles;

S4, calcining the microspheres obtained in step S3 at high temperature to remove organic matter, and cross-linking the silica nanoparticles to obtain silica core-shell microspheres.

2. The method for preparing silica core-shell microspheres according to claim 1, characterized in that in the step S1, the preparation method of the polyacrylamide gel layer is selected from one of atom transfer radical polymerization, free radical polymerization, and reversible deactivation radical polymerization.

3. The method for preparing silica core-shell microspheres according to claim 2, characterized in that, in the step S1, the diameter of the silica solid microspheres is 0.1-10 μm, and the thickness of the polyacrylamide gel layer is 1-1000 nm.

4. The method for preparing silica core-shell microspheres according to claim 1, characterized in that in the step S2, the degree of hydrolysis of the polyacrylamide gel layer is 10% to 90%.

5. The method for preparing silicon dioxide core-shell microspheres according to claim 1, wherein the molar ratio of the orthosilicate used in step S3 to the acrylamide used in step S1 is 0.1-2.0:1.

6. The method for preparing silica core-shell microspheres according to claim 1, characterized in that in the step S4, the calcination temperature is 300-1000°C and the calcination time is 0.5-48h.

7. The method for preparing silica core-shell microspheres according to any one of claims 1 to 6, characterized in that in the step S2, the diamine organic compound is selected from one or more of ethylenediamine, propylenediamine, butylenediamine, pentamethylenediamine, and hexamethylenediamine.

8. The method for preparing silicon dioxide core-shell microspheres according to any one of claims 1 to 6, characterized in that in the step S3, the orthosilicate is selected from one or more of methyl orthosilicate, ethyl orthosilicate, and isopropyl orthosilicate.

9. A silica core-shell microsphere, characterized in that it is prepared by the preparation method according to any one of claims 1 to 8, and comprises a solid silica core layer and a porous silica shell layer.

10 . The silica core-shell microspheres according to claim 9 , wherein the porosity of the porous silica shell layer is 10% to 90%.