A preparation method of spherical silicon dioxide

Abstract

The present invention belongs to the field of silica material preparation, and specifically relates to a method for preparing spherical silica, comprising the following steps: Step S1: mixing water glass, an organic solvent, and an emulsifier and emulsifying the mixture; Step S2: mixing the emulsified mixture with a polymerizer, reacting, and forming balls to obtain spherical silica gel; Step S3: mixing the spherical silica gel with a curing agent, performing solid-liquid separation after curing, washing the solid phase with water, and drying to obtain spherical silica; the emulsifier is a Span emulsifier or a mixed emulsifier comprising a Span emulsifier and polyethylene glycol distearate. The silica prepared by the present invention has a relatively stable skeleton, and has uniform particle size, pore volume, and pore size.

Description

Technical Field

[0001] The invention belongs to the field of silicon dioxide material preparation, and particularly relates to a method for preparing spherical silicon dioxide. Background Art

[0002] Spherical silica has relatively stable chemical properties and can be used as an additive, filler and adsorbent. It is widely used in food, pesticides, medicine, cosmetics, industrial purification, chromatography, biochemistry and colloid chemistry.

[0003] Spherical silica as a filler can greatly improve the rigidity, wear resistance, weather resistance, impact resistance, compression resistance, tensile strength, flame resistance, arc resistance, insulation properties and resistance to ultraviolet radiation of electronic products.

[0004] Spherical silica is used in column chromatography. A solution (liquid phase) containing a mixture of substances with different components is passed through a chromatographic column (also called a chromatography column or preparative column) equipped with a stationary phase (such as column chromatography silica) to separate the effective components of the solute in the liquid phase from the mixed state. Alternatively, the substance to be purified is passed through a preparative column along with a solvent so that the impurities therein are adsorbed by the stationary phase to produce a pure substance. Alternatively, the stationary phase is used to adsorb the desired substance components (such as adsorbing urokinase in urine), and then desorbed to obtain the desired product.

[0005] At present, the domestic spherical silica market is mainly occupied by foreign brands. Domestic spherical silica is less used due to limitations in production and performance.

[0006] The domestic production plan for silica is basically to precipitate it using industrial water glass and sulfuric acid under certain conditions, and it appears in an amorphous form. Its disadvantage is that the silica appears in a flaky stacking form, resulting in poor strength. During the drug purification process, the silica is easy to fall off small silica fragments, causing drug contamination.

[0007] Patent document CN111974369A discloses a column chromatography silica gel, a preparation method thereof, and an application thereof. Sulfuric acid and water glass are mixed to obtain a silica gel. After granulation, a pore-uniformizing agent is added to the silica gel. The final product is washed and dried. The dilute sodium silicate solution reacts with a strong acid and condenses into lumps of uneven size, resulting in an incomplete reaction. The resulting silica gel exhibits problems such as an unstable skeleton and pore collapse, leading to a low separation and purification rate. Summary of the Invention

[0008] Therefore, the technical problem to be solved by the present invention is to overcome the defects of uneven silica particle size and low separation and purification rate in the prior art, thereby providing a method for preparing spherical silica with uniform particle size, uniform pore volume and pore size, and high separation and purification rate when used as a chromatography column filler.

[0009] To this end, the present invention provides a method for preparing spherical silicon dioxide, comprising the following steps:

[0010] Step S1: mixing water glass, an organic solvent, and an emulsifier and emulsifying them; the emulsifier is a Span emulsifier or a mixed emulsifier including a Span emulsifier and polyethylene glycol distearate;

[0011] Step S2: mixing the emulsified mixture with a polymerizing agent, reacting, and molding into balls to obtain spherical silica gel;

[0012] Step S3: Spherical silica gel is mixed with a curing agent, solidified, and then solid-liquid separation is performed. The solid phase is washed with water and then dried to obtain spherical silica.

[0013] In the present invention, the term water glass is an aqueous solution of sodium silicate.

[0014] Furthermore, the emulsifier is a Span emulsifier or a mixed emulsifier including a Span emulsifier and polyethylene glycol distearate; preferably, the mass ratio of the Span emulsifier to the polyethylene glycol distearate in the mixed emulsifier is 10 to 20:1, more preferably 11 to 13:1.

[0015] Furthermore, the Span-type emulsifier is at least one of Span 10 (SP10), Span 20 (SP20), Span 40 (SP40), Span 60 (SP60), Span 80 (SP80) and Span 85 (SP85); preferably, the emulsifier is a mixed emulsifier including Span 20 and polyethylene glycol distearate.

[0016] Furthermore, the mass concentration of the water glass is 15% to 40%.

[0017] Furthermore, in step S3, the solid phase is washed with water until the pH value of the washing liquid is 4-7.5.

[0018] Furthermore, the organic solvent is one or more of C5-C11 normal alkanes and C5-C11 isoalkanes. Preferably, the organic solvent is one or more of n-pentane, n-hexane and isopentane.

[0019] Furthermore, the polymerization agent is sulfuric acid, preferably sulfuric acid with a mass concentration of 20% to 60%;

[0020] The curing agent is nitric acid, preferably nitric acid with a mass concentration of 50% to 80%.

[0021] Furthermore, in step S1, the mixed liquid is emulsified under stirring at a speed of 500-1000 r / min, and the emulsification time is 0.5-1.5 h; and / or, in step S2, the emulsified mixed liquid reacts with the polymerizer at a temperature of 40-60°C and a stirring speed of 200-400 r / min, and the reaction time is 40-50 min; and / or, in step S3, the curing conditions are first stirring for 20-30 min, then heating to 80-120°C, and then stirring for 30-50 min; and / or, in step S2, the conditions for plasticizing the balls are stirring at a speed of 500-1000 rpm for 30-60 min.

[0022] Furthermore, the mass ratio of the water glass, organic solvent, emulsifier, polymerizer and curing agent is 2-4:10-18:8-15:4-8:3-10.

[0023] Among them, the water washing adopts a combination of stirring water washing and flowing water washing. First, the silica gel is soaked in water, heated to 40-60°C, and washed 2-3 times with stirring at a speed of 200r / min, each washing time for 2-3 hours, and then washed with flowing water to make the pH value of the washing liquid reach 4-7.5.

[0024] The present invention also provides spherical silicon dioxide prepared by any of the above-mentioned preparation methods.

[0025] The technical solution of the present invention has the following advantages:

[0026] 1. The preparation method of spherical silica provided by the present invention is to obtain spherical silica by performing polymerization, plastic ball, solidification, solid-liquid separation, water washing and drying steps after emulsification. The present invention has found that water glass is emulsified by a Span emulsifier or a mixed emulsifier including a Span emulsifier and polyethylene glycol distearate and then undergoing polymerization reaction to make the reaction more sufficient. After sufficient emulsification, silica with smaller particle size can be made in the plastic ball. After plastic ball and solidification, it is washed to avoid the problem of uneven particle size. The above method helps to obtain spherical silica with good particle morphology, uniform pore volume and pore size, and uniform particle size distribution. The problem of skeleton destruction or pore collapse is significantly improved, so that the separation and purification rate is significantly improved.

[0027] 2. The method for preparing spherical silica provided by the present invention is to control the mass ratio of the Span emulsifier and polyethylene glycol distearate in the mixed emulsifier to be 11 to 13:1 during the emulsification stage; or when a mixed emulsifier including Span 20 and polyethylene glycol distearate is used, water glass can be better emulsified to form a stable and uniform suspension after emulsification, so that the water glass and sulfuric acid can be more fully contacted and reacted. The prepared silica has a more stable skeleton and uniform pore structure, and will not cause problems such as skeleton destruction or pore collapse; the spherical silica particles finally obtained have good morphology and uniform pore volume and pore size. Using this spherical silica gel as a column chromatography filler further improves the efficiency of separation and purification, avoids the problem of silica gel exploding particles, and causes dead adsorption or chromatographic column blockage.

[0028] 3. The present invention provides a method for preparing spherical silica, using nitric acid at a concentration of 50% to 80% by mass as a curing agent to further enhance the stability of the framework and control pore size, thereby improving the silica's adsorption properties. Washing the particles to a pH of 4-7.5 ensures uniform washing of the particles, consistent washing speed, and accurate endpoint determination. It also prevents small particles from entering the pipeline with the water flow and causing blockage, thereby improving the efficiency of the washing process.

[0029] 4. The spherical silica provided by the present invention can achieve a regular spherical shape in the process, and the particle size can reach 20 to 100 μm. When used as a chromatography column filler, it can withstand higher column pressures than silica with larger particles, further increasing the sample load and flow rate, thereby improving the production efficiency of the separation and purification process. Smaller particle size silica has a wider range of applications.

[0030] 5. The method for preparing spherical silica provided by the present invention has an advanced process, low raw material loss, low energy consumption in the production process, reduced raw material, labor and equipment costs, improved production efficiency, easy operation, and easy to industrialize, with an annual output of up to 500 tons. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Figure 1 1 is a process flow chart of embodiment 1 of the present invention. DETAILED DESCRIPTION

[0033] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0034] If specific experimental procedures or conditions are not specified in the examples, the procedures or conditions described in the literature in the field can be followed. Reagents or instruments used without manufacturer's indication are commercially available. Polyethylene glycol distearate in this invention was purchased from Shanghai Huijun Chemical Co., Ltd., with a content of >99%.

[0035] Example 1

[0036] This embodiment provides a method for preparing spherical silicon dioxide, which is as follows:

[0037] (1) Emulsification: 300 g of 15% water glass, 1400 g of n-pentane and 1200 g of SP80 were stirred and emulsified at 50° C. and 500 rpm for 1 h to obtain a mixed solution.

[0038] (2) Polymerization: 500 g of sulfuric acid with a mass concentration of 28% was added to the mixed solution obtained in step (1) under stirring at 50° C. and 200 r / min for reaction for 40 min.

[0039] (3) Molding balls: The reaction solution obtained in step (2) was stirred at 500 r / min for 60 min to form balls, thereby obtaining spherical silica gel with a particle size of 20 to 100 μm.

[0040] (4) Curing: Add 400 g of concentrated nitric acid with a mass concentration of 68% to the spherical silica gel and stir for 20 min. Raise the temperature to 100°C and maintain for 30 min. Allow to stand and separate the layers. Separate and collect the lower layer. Filter and collect the solid.

[0041] (5) Water washing and drying: washing with water until the pH value of the washing liquid reaches 5, then filtering through a suction filter and drying to obtain spherical silica.

[0042] Example 2

[0043] This embodiment provides a method for preparing spherical silicon dioxide, which is as follows:

[0044] (1) Take 300 g of 15% water glass, 1400 g of n-pentane, 1129.4 g of SP20 and 70.6 g of polyethylene glycol distearate, and stir and emulsify at 50°C and 500 r / min for 1 h.

[0045] (2) 500 g of 28% sulfuric acid was added to the mixture obtained in step (1) at 50° C. and 200 rpm, and stirred for 40 minutes. The mixture was then stirred at 500 rpm for 60 minutes to obtain spherical silica gel with a particle size of 20 to 100 μm.

[0046] (3) Add 400 g of concentrated nitric acid with a mass concentration of 68% to the spherical silica gel and stir for 20 minutes. Raise the temperature to 100° C. and maintain for 30 minutes. Allow to stand and separate the layers. Separate and collect the lower layer. Filter and collect the solid. Wash with water until the pH value of the washing liquid reaches 6. Then, filter and wash through a suction filter and dry to obtain spherical silica.

[0047] Example 3

[0048] This embodiment provides a method for preparing spherical silicon dioxide, which is as follows:

[0049] (1) Emulsification: 300 g of 30% water glass, 1800 g of n-pentane, 1411.8 g of SP20, and 88.2 g of polyethylene glycol distearate were mixed and stirred at 60° C. and 850 r / min for 2 h.

[0050] (2) Polymerization: 800 g of sulfuric acid with a mass concentration of 60% was added to the mixed solution obtained in step (1) at 50° C. and 400 r / min under stirring for 60 min.

[0051] (3) Plastic sphering: The reaction solution obtained in step (2) was stirred at 1000 r / min for 60 min to obtain spherical silica gel with a particle size of 20 to 100 μm.

[0052] (4) Solidification: add 1000 g of concentrated nitric acid with a mass concentration of 80% and stir for 20 minutes, heat to 120°C and maintain for 45 minutes, let it stand to separate the layers, separate and collect the lower layer, and collect the solid by filtration.

[0053] (5) Water washing and drying: washing with water until the pH value of the washing liquid reaches 7, and then filtering and drying to obtain spherical silica.

[0054] Example 4

[0055] This embodiment provides a method for preparing spherical silica, which is basically the same as Example 1, except that in step (1), 1100 g of SP20 and 100 g of polyethylene glycol distearate are used instead of 1200 g of SP80.

[0056] Comparative Example 1

[0057] This ratio provides a preparation method of spherical silica, which is basically the same as Example 1, except that in step (1), 1200 g of polyethylene glycol distearate is used instead of 1200 g of SP80.

[0058] Comparative Example 2

[0059] This ratio provides a preparation method of spherical silica, which is basically the same as Example 1, except that in step (1), no emulsifier SP80 is added.

[0060] Comparative Example 3

[0061] This embodiment provides a method for preparing spherical silica, which is basically the same as Example 2, except that in step (1), 70.6 g of polyethylene glycol monostearate is used instead of 70.6 g of polyethylene glycol distearate.

[0062] Experimental Example 1

[0063] The pore volume, average pore diameter and specific surface area of ​​the spherical silica obtained in each embodiment were tested with reference to the national standard GB / T34709-2017. The results are shown in the following table.

[0064] Table 1 Structure of spherical silica in various examples

[0065] project Pore ​​volume (ml / g) Average pore size (nm) <![CDATA[Specific surface area / (m 2 / g)]]> Example 1 0.81 6 390 Example 2 0.72 8 400 Example 3 0.73 8 410 Example 4 0.8 7 380

[0066] As can be seen from the above table, the spherical silica prepared in Examples 1-4 of the present invention has a larger pore diameter and pore volume, and a larger specific surface area.

[0067] Experimental Example 2

[0068] The particle size uniformity of the spherical silica prepared in each embodiment and comparative example was tested with reference to the national standard GB / T34709-2017.

[0069] Column chromatography was performed using 200 g of spherical silica prepared in each of the Examples and Comparative Examples as a chromatographic column filler to separate and purify a crude flax lignan product containing 30% of the same batch. The crude product was dissolved in xylene and eluted with dichloromethane to obtain the target flax lignan. The separation and purification rate was then calculated according to the following formula: Separation and purification rate = actual yield of target product after column purification / theoretical value of target product * 100%; where the theoretical value of target product = target product content in the crude product * crude product mass.

[0070] Table 2 Separation and purification rate of flax lignans

[0071] project Separation and purification rate / % Particle size uniformity Example 1 80 60％ Example 2 81 62％ Example 3 86 59％ Example 4 90 67％ Comparative Example 1 70 50％ Comparative Example 2 61 53％ Comparative Example 3 63 50％

[0072] As can be seen from Table 2 above, compared with Comparative Examples 1-3, the particle size uniformity of the spherical silica prepared in Examples 1-4 of the present invention is significantly improved, and the separation and purification rate is significantly improved. In particular, Examples 2-4 have a higher separation and purification rate by adopting the preferred emulsifier, among which Example 4 is the best.

[0073] Experimental Example 3

[0074] The spherical silica prepared in Example 3 was compared with a well-known German product. The total metal ion content was measured by ICP-MS, and the resistivity was measured using a resistivity meter. 200 g of the spherical silica prepared in Example 3 and the well-known German product were used as chromatography column fillers. A crude batch of liquid crystal monomer (TFT monomer) containing 30% of the same crude product was dissolved in xylene and then separated and purified using dichloromethane as the eluent. The separation and purification yields were calculated.

[0075] Table 3 Performance comparison with commercially available products

[0076]

[0077] As can be seen from the above table, compared with the existing spherical silica, the spherical silica prepared in Example 3 of the present invention has a higher separation and purification rate in separation and purification (increased by 0.5%), a lower total amount of metal ions (reduced by 28.5%), and a higher resistivity after sample purification (increased by 10.2%). In addition, it has the advantages of low price (reduced by 50%), short delivery cycle (reduced by more than 67%), and can be customized.

[0078] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing spherical silicon dioxide, characterized in that: The steps include: Step S1: mixing water glass, an organic solvent, and an emulsifier and emulsifying them, wherein the emulsifier comprises a mixed emulsifier of Span 20 and polyethylene glycol distearate; the mass ratio of Span 20 to polyethylene glycol distearate in the mixed emulsifier is 11-13:1; Step S2: mixing the emulsified mixture with a polymerizing agent, reacting, and molding into spherical silica gel; Step S3: Spherical silica gel is mixed with a curing agent, solidified, and solid-liquid separation is performed. The solid phase is washed with water and then dried to obtain spherical silica; the curing agent is nitric acid with a mass concentration of 50% to 80%; and the organic solvent is one or more of C5 to C11 normal alkanes and C5 to C11 isoalkanes.

2. The method for preparing spherical silicon dioxide according to claim 1, wherein The mass concentration of the water glass is 15% to 40%.

3. The method for preparing spherical silicon dioxide according to claim 1, wherein In step S3, the solid phase is washed with water until the pH value of the washing liquid is 4-7.

5.

4. The method for preparing spherical silicon dioxide according to claim 1, wherein The organic solvent is one or more of n-pentane, n-hexane and isopentane.

5. The method for preparing spherical silicon dioxide according to claim 1, wherein The polymerization agent is sulfuric acid with a mass concentration of 20% to 60%.

6. The method for preparing spherical silicon dioxide according to claim 1, wherein In step S1, the mixed liquid is emulsified under stirring at a speed of 500-1000 r / min, and the emulsification time is 0.5-1.5 h; and / or, in step S2, the emulsified mixed liquid reacts with the polymerizer at a temperature of 40-60°C and a stirring speed of 200-400 r / min, and the reaction time is 40-50 min; and / or, in step S3, the curing conditions are: stirring for 20-30 min, heating to 80-120°C, and stirring for 30-50 min; and / or, in step S2, the conditions for plasticizing the balls are stirring at a rotation speed of 500-1000 rpm for 30-60 min.

7. The method for preparing spherical silicon dioxide according to claim 1, wherein The mass ratio of the water glass, organic solvent, emulsifier, polymerizer and curing agent is 2-4:10-18:8-15:4-8:3-10.

8. Spherical silicon dioxide obtained by the preparation method described in any one of claims 1 to 7.

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