Photochemically modified high-surface-activity nano-spherical silica and preparation method thereof

Abstract

The present invention discloses a photochemically modified high-surface-activity nano-spherical silica and a preparation method thereof, belonging to the field of nano-silica technology. Photochemical etching is used to act on silica powder, so that active hydroxyl groups that are conducive to coupling reactions are uniformly formed on the silica surface, and the specific surface area of ​​the spherical silica is increased. The coupling reaction is directly carried out under weakly alkaline conditions, and the degree of reaction between the active hydroxyl groups and the coupling groups is controlled by changes in coupling agent concentration, reaction temperature, and reaction time, thereby controlling the hydrophilicity and hydrophobicity of the product. The modified nano-spherical silica obtained has good dispersibility, fluidity, lipophilicity, and high surface chemical activity, and can be used in materials such as adhesives, sealants, composite surfactant functionalities, functional nanomaterial carriers, and nano-oil displacement agents. The entire preparation process is simple, the yield is high, and pollution emissions are low.

Description

Technical Field

[0001] The invention belongs to the technical field of nano-silicon dioxide, and particularly relates to a photochemically modified high-surface-activity nano-spherical silicon dioxide and a preparation method thereof. Background Art

[0002] Silica powder is required to be ultrafine, high-purity, with uniform particle size distribution and no serious agglomeration. At present, the main methods for preparing spherical silica powder include sol-gel method, spray pyrolysis method, hydrothermal method, modified Bayer process, etc. At present, the existing technology can use solution method to prepare ultrafine silica powder. The product morphology is good and the particle size is small, but there are disadvantages such as multiple steps, high water consumption, high emissions, and high impurity ion content. The halosilane combustion hydrolysis method is used to prepare fumed silica. Although the process steps are relatively simple and the product appearance is smaller, the process produces acidic hydrogen halide gas as a by-product, which causes certain pollution. At the same time, the silica particles are very prone to produce dendritic structures that are difficult to separate, resulting in poor fluidity. Even after modification, it is difficult to separate.

[0003] During oil recovery, nanoflooding technology allows injection water to reach any corner of the reservoir, significantly increasing recovery rates. Without changing the waterflooding system, it can be used for strategic replacement in the later stages of development of medium- and high-permeability reservoirs, as well as for effective waterflooding of low-, ultra-, and ultra-low-permeability and tight reservoirs. The modified nano-spherical silica proposed in this paper holds promise for application in the field of nanoflooding. Summary of the Invention

[0004] In view of the above problems, the present invention provides a method for preparing photochemically modified high-surface-activity nano-spherical silica, comprising the following steps:

[0005] The nano-spherical silica raw material is mixed with a heated alkaline etching solution, and the interface of the mixed solution is photochemically micro-etched using ultraviolet light. After etching, the silica is separated and filtered out using a filter membrane;

[0006] The filtered silica is cleaned of excess etching solution and etching impurities on the surface, washed until the pH of the liquid is 8.5-10, and dried to obtain hydroxylated nano-spherical silica with a micro-etched surface;

[0007] The hydroxylated nano-spherical silica after surface micro-etching is dispersed to form a weak alkaline solution, and a silane coupling agent is added to the weak alkaline solution under ultraviolet light irradiation to carry out a coupling reaction to obtain modified nano-spherical silica with high surface activity.

[0008] Furthermore, the mass of the nano-spherical silicon dioxide raw material is 10-50% of the mass of the alkaline etching solution;

[0009] The mass of the silane coupling agent is 10-20% of the mass of the weak alkaline solution.

[0010] Furthermore, the method further includes performing a pretreatment before mixing the nano-spherical silica raw material with the heated alkaline etching solution, comprising:

[0011] cleaning and drying the nano-spherical silica raw material;

[0012] Heat the alkaline etching solution to 50-80°C.

[0013] Furthermore, the alkaline etching solution is selected from a sodium hydroxide solution and / or a potassium hydroxide solution with a concentration of 1-5 mol / L;

[0014] A calcium carbonate powder filter bag is further added to the alkaline etching solution, and the mass of the calcium carbonate powder is 1-5% of the mass of the alkaline etching solution.

[0015] Furthermore, the photochemical surface micro-etching is performed for 0.5-2 hours.

[0016] Furthermore, removing excess etching solution and etching impurities remaining on the surface of the filtered silicon dioxide specifically comprises: dispersing, washing and filtering the filtered silicon dioxide in a cleaning solution to remove excess etching solution and etching impurities remaining on the surface.

[0017] Furthermore, the cleaning solution is an acidic cleaning solution with a pH value between 2 and 3, and is composed of 1% acetic acid, 20% ethanol, and 79% pure water by mass fraction.

[0018] Furthermore, obtaining the modified high-surface-activity nano-spherical silica comprises the following steps:

[0019] Hydroxylated nano-spherical silica and a silane coupling agent are reacted under ultraviolet light to generate hydrophobically modified nano-spherical silica with high surface activity;

[0020] The hydrophobically modified nano-spherical silica with high surface activity is washed, filtered and dried to obtain modified nano-spherical silica with high surface activity.

[0021] Furthermore, the coupling reaction time is 0.5-5h, and the coupling reaction temperature is 30-60°C.

[0022] Furthermore, the silane coupling agent includes any one or more combinations of ethyltrimethoxysilane, n-propyltrimethoxysilane and trimethyloxyphenylsilane.

[0023] On the other hand, the present invention also discloses a photochemically modified high-surface-activity nano-spherical silica prepared by the preparation method.

[0024] Furthermore, the nano-spherical silica raw material is spherical, and the single particle size is 10-100 nm.

[0025] The photochemically modified high-surface-activity nano-spherical silicon dioxide can be used in the preparation of oil-displacing agents, adhesives, sealants, composite surfactants and functional nano-material carriers.

[0026] Beneficial effects of the present invention:

[0027] The present invention utilizes photochemical etching to act on silica powder, uniformly forming active hydroxyl groups on the silica surface that are beneficial for coupling reactions. This also increases the specific surface area of ​​the spherical silica. The coupling reaction proceeds directly under weakly alkaline conditions. The degree of reaction between the active hydroxyl groups and the coupling groups is controlled by varying the coupling agent concentration, reaction temperature, and reaction time, thereby controlling the hydrophilicity and hydrophobicity of the product. The resulting modified nano-spherical silica exhibits excellent dispersibility, fluidity, lipophilicity, and high surface chemical activity. It can be used in adhesives, sealants, composite surfactants, functional nanomaterial carriers, and other materials. Upon maturity, it is expected to become a new generation of nano-oil displacement agent products.

[0028] The preparation method of the photochemically modified high-surface-activity nano-spherical silicon dioxide provided by the present invention has the advantages of simple process, high yield and low pollution emission.

[0029] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the 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.

[0031] Figure 1 A schematic diagram showing the preparation method of the photochemically modified high-surface-activity nano-spherical silica proposed in the present invention is shown;

[0032] Figure 2 The scanning electron microscope image of the photochemically modified high-surface-activity nano-spherical silica prepared in Example 1 of the present invention is shown;

[0033] Figure 3The Fourier transform infrared spectrum (FTIR) of the nano-spherical silica raw material in step S1 in Example 1 of the present invention is shown;

[0034] Figure 4 shows the Fourier transform infrared spectrum of the hydroxylated nano-spherical silica after surface microetching in step S2 of Example 1 of the present invention;

[0035] Figure 5 The Fourier transform infrared spectrum of the modified high-surface-activity nano-spherical silica prepared in Example 1 of the present invention is shown. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings 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 making creative efforts shall fall within the scope of protection of the present invention.

[0037] One of the purposes of the present invention is to provide a method for preparing photochemically modified high surface activity nano-spherical silica. Figure 1 As shown, the following steps are included:

[0038] S1, pretreatment, cleaning and drying the nano-spherical silica raw material; in an etching device, heating the alkaline etching solution to 50-80° C., stirring and mixing the nano-spherical silica raw material with the alkaline etching agent at a mass ratio of 10-50%, wherein the mass of the nano-spherical silica raw material is 10-50% of the alkaline etching agent, while stirring, turning on the ultraviolet lamp so that its light energy acts on the interface between the raw material and the etching solution, and performing photochemical surface micro-etching for 0.5-2 hours. After etching, the silica is separated and filtered out using a filter membrane;

[0039] In step S1, the etchant is sodium hydroxide and / or potassium hydroxide at a concentration of 1-5 mol / L. A calcium carbonate powder filter bag is added to the etching solution at a mass ratio of 1-5%. The calcium carbonate can react the free silicate anions obtained by the reaction to form calcium silicate, thereby maintaining a relatively stable pH value of the solution and reducing insoluble matter. In the present invention, the etchant concentration and etching time are controlled. If the etching time is too long or the etching solution concentration is too high, excessive etching will result, significantly affecting the morphology and size of the nanoparticles and causing unnecessary losses. If the etching time is too long or the etching solution concentration is too low, the etching effect will be insignificant.

[0040] S2. In a cleaning device, the filtered silica is dispersed in a cleaning solution, washed, and filtered 2-5 times to remove excess etching solution and etching impurities on the surface, and the solution is washed until the pH value is about 8.5-10, and then dried at 50-100° C. to obtain hydroxylated nano-spherical silica after surface micro-etching;

[0041] The cleaning solution in step S2 is an acidic cleaning solution with a pH value between 2.5 and 3.5, and is composed of 1% acetic acid, 20% ethanol and 79% pure water by mass.

[0042] S3. Disperse and mix the hydroxylated nano-spherical silica in the solution and then add it to the modification device to form a weak alkaline solution. While stirring, turn on the light source so that its light energy acts on the interface between the raw material and the etching solution. Add a silane coupling agent and react with it for 0.5-5 hours. The reaction temperature is 30-60°C. The mass of the silane coupling agent is 10-20% of the weak alkaline solution to produce hydrophobically modified nano-spherical silica with high surface activity. The small-sized modified nano-spherical silica with high surface activity is obtained by washing, filtering and drying through a collecting device.

[0043] In step S3, the silane coupling agent includes any one or more combinations of ethyltrimethoxysilane, n-propyltrimethoxysilane and trimethyloxyphenylsilane.

[0044] Example 1

[0045] S1. Pretreatment: Clean and dry a nano-spherical silica raw material with an average particle size of 50 nm; in an etching device, heat the alkaline etching solution to 60° C., stir and disperse the nano-spherical silica raw material with a 2 mol / L NaOH etchant at a mass ratio of 50%, add a 5% by mass calcium carbonate powder filter bag to the etching device, and while stirring, turn on an ultraviolet lamp with a wavelength of 290 nm and a power of 600 W to perform photochemical surface micro-etching for 0.5 h. After etching, separate and filter out the silica using a filter membrane;

[0046] S2. In a cleaning device, the filtered silica is dispersed in a cleaning solution of 1% acetic acid, 20% ethanol, and 79% pure water, washed, and filtered once, and then washed and filtered three times with pure water to remove excess etching solution and etching impurities on the surface. The solution is washed until the pH value is about 10, and then dried at 80° C. to obtain hydroxylated nano-spherical silica after surface micro-etching;

[0047] S3. Disperse and mix the hydroxylated nano-spherical silica in the solution, then add it to the modification device. While stirring, turn on a light source with a wavelength of 340 nm and a power of 300 W to allow light energy to act on the interface between the raw material and the etching solution. Add 15% by weight of n-propyltrimethoxysilane and react with it for 5 hours to produce hydrophobically modified nano-spherical silica with high surface activity. Pass through a collection device, rinse with pure water three times, filter, and dry at 80°C for 5 hours to obtain small-sized modified nano-spherical silica with high surface activity.

[0048] The contact angles of the spherical silica raw material, the hydroxylated nano-spherical silica after surface micro-etching (i.e., the contact angle after etching), and the modified high-surface-activity nano-spherical silica (i.e., the contact angle after modification) in steps S1, S2, and S3 are 137°, 58°, and 153°, respectively.

[0049] Example 2

[0050] S1. Pretreatment: Clean and dry a nano-spherical silica raw material with an average particle size of 10 nm; in an etching device, heat the alkaline etching solution to 80° C., stir and disperse the nano-spherical silica raw material with a 1 mol / L NaOH etchant at a mass ratio of 10%, add a 5% by mass calcium carbonate powder filter bag to the etching device, and while stirring, turn on an ultraviolet lamp with a wavelength of 290 nm and a power of 500 W to perform photochemical surface micro-etching for 0.25 h. After etching, separate and filter out the silica using a filter membrane;

[0051] S2. In a cleaning device, the filtered silica is dispersed in a cleaning solution of 1% acetic acid, 20% ethanol, and 79% pure water, washed, and filtered once, and then washed and filtered three times with pure water to remove excess etching solution and etching impurities on the surface. The solution is washed until the pH value is about 8.5, and then dried at 80° C. to obtain hydroxylated nano-spherical silica after surface micro-etching;

[0052] S3. Disperse and mix the hydroxylated nano-spherical silica in the solution, then add it to the modification device. While stirring, turn on a light source with a wavelength of 400nm and a power of 200W to allow light energy to act on the interface between the raw material and the etching solution. Add 5% by weight of n-propyltrimethoxysilane and react with it for 3 hours to produce hydrophobically modified nano-spherical silica with high surface activity. Pass through a collection device, rinse with pure water three times, filter, and dry at 80°C for 5 hours to obtain small-sized modified nano-spherical silica with high surface activity.

[0053] The contact angles of the spherical silica raw material, the hydroxylated nano-spherical silica after surface micro-etching, and the modified nano-spherical silica with high surface activity in steps S1, S2, and S3 are 137°, 82°, and 142°, respectively.

[0054] Example 3

[0055] The preparation was carried out according to the method of Example 1, except that the etchant was a mixture of potassium hydroxide and sodium hydroxide in a substance amount ratio of 1:1 with a total of 2 mol / L, to obtain modified high-surface-activity nano-spherical silica.

[0056] The contact angles of the spherical silica raw material, the hydroxylated nano-spherical silica after surface micro-etching, and the modified high-surface-activity nano-spherical silica in steps S1, S2, and S3 are 137°, 55°, and 155°, respectively.

[0057] Example 4

[0058] The preparation was carried out according to the method of Example 1, except that potassium hydroxide was used as the etchant, to obtain modified nano-spherical silica with high surface activity.

[0059] The contact angles of the spherical silica raw material, hydroxylated nano-spherical silica after surface micro-etching, and modified nano-spherical silica with high surface activity are 137°, 57°, and 155°, respectively.

[0060] Example 5

[0061] The preparation was carried out according to the method of Example 1, except that ethyltrimethoxysilane was used as the silane coupling agent, to obtain modified high-surface-activity nano-spherical silica.

[0062] The stable contact angles of spherical silica raw material, hydroxylated nano-spherical silica after surface micro-etching, and modified nano-spherical silica with high surface activity are 137°, 58°, and 127°, respectively.

[0063] Example 6

[0064] The preparation was carried out according to the method of Example 1, except that the silane coupling agent was a mixture of ethyltrimethoxysilane, n-propyltrimethoxysilane and trimethyloxyphenylsilane in a mass ratio of 1:1:1, to obtain modified high-surface-activity nano-spherical silica.

[0065] The stable contact angles of spherical silica raw material, hydroxylated nano-spherical silica after surface micro-etching, and modified nano-spherical silica with high surface activity are 137°, 58°, and 142°, respectively.

[0066] Example 7 uses a hydrophobic modifier containing a phenyl group for coupling.

[0067] S1. Pretreatment: Clean and dry a nano-spherical silica raw material with an average particle size of 50 nm; in an etching device, heat the alkaline etching solution to 50° C., stir and disperse the nano-spherical silica raw material with a 1 mol / L NaOH etchant at a mass ratio of 10%, add a 5% by mass calcium carbonate powder filter bag to the etching device, and while stirring, turn on an ultraviolet lamp with a wavelength of 290 nm and a power of 600 W to perform photochemical surface micro-etching for 2 hours. After etching, separate and filter out the silica using a filter membrane;

[0068] S2. In a cleaning device, the filtered silica is dispersed in a cleaning solution of 1% acetic acid, 20% ethanol, and 79% pure water, washed, and filtered once, and then washed and filtered three times with pure water to remove excess etching solution and etching impurities on the surface. The solution is washed until the pH value is about 8.5, and then dried at 80° C. to obtain hydroxylated nano-spherical silica after surface micro-etching;

[0069] S3. Disperse and mix the hydroxylated nano-spherical silica in the solution, then add it to the modification device. While stirring, turn on a light source with a wavelength of 400nm and a power of 200W to allow light energy to act on the interface between the raw material and the etching solution. Add 10% by weight of trimethyloxyphenylsilane and react for 5 hours to produce hydrophobically modified nano-spherical silica with high surface activity. Pass through a collection device, rinse with pure water three times, filter, and dry at 80°C for 5 hours to obtain small-sized modified nano-spherical silica with high surface activity.

[0070] The stable contact angles of the spherical silica raw material, the hydroxylated nano-spherical silica after surface micro-etching, and the modified nano-spherical silica with high surface activity in steps S1, S2, and S3 are 137°, 65°, and 163°, respectively.

[0071] Comparative Example 1

[0072] The preparation was carried out according to the method of Example 1, except that no ultraviolet light source was used to assist the reaction during etching, thereby obtaining modified nano-spherical silica with high surface activity.

[0073] The stable contact angles of the spherical silica raw material, the hydroxylated nano-spherical silica after surface micro-etching, and the modified nano-spherical silica with high surface activity in steps S1, S2, and S3 are 137°, 135°, and 135°, respectively.

[0074] Test Example 1

[0075] The modified high surface activity nano spherical silica in Examples 1-7 was characterized by scanning electron microscopy. The results showed that the prepared modified high surface activity nano spherical silica was spherical, with a single particle size of 10-100 nm. The SEM image of the modified high surface activity nano spherical silica in Example 1 is as follows: Figure 2 shown.

[0076] Test Example 2

[0077] The products of the nano-spherical silica preparation process in Example 1 were detected by infrared spectroscopy, and the detection results were as follows: Figure 3 、 Figure 4 and Figure 5 As shown, Figure 3 is the Fourier transform infrared spectrum of the nano-spherical silica in step S1 of Example 1, Figure 4 is the Fourier transform infrared spectrum of the hydroxylated nano-spherical silica obtained in step S2 of Example 1, Figure 5 This is the Fourier transform infrared spectrum of the modified high-surface-activity nano-spherical silica obtained in step S3 of Example 1.

[0078] Test Example 3

[0079] The hydrophobicity of the modified, highly surface-active nano-spherical silica prepared in Examples 1-7 and Comparative Example 1 was tested. The nano-spherical silica of the present invention was pressed into a flake-like solid using a mechanical tablet press. Pure water was dropped onto the solid surface and the contact angle was measured (the contact angles in the above examples were measured using the same method). The results are shown in Table 1:

[0080] Table 1

[0081] Implementation Method Contact angle after etching Contact angle after modification Example 1 58° 153° Example 2 82° 142° Example 3 55° 155° Example 4 57° 155° Example 5 58° 127° Example 6 58° 142° Example 7 65° 163° Comparative Example 1 135° 135°

[0082] From the above results, it can be seen that the modified high-surface-activity nano-spherical silica prepared by the preparation method proposed in the present invention has good hydrophobicity and high surface chemical activity test, and the main function of calcium carbonate is to adsorb silicate ions, converting the poorly soluble silicate ions into soluble carbonate ions, reducing insoluble matter, and has no significant effect on the hydrophobicity of the product.

[0083] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing photochemically modified high-surface-activity nano-spherical silica, characterized in that: include: The nano-spherical silica raw material is mixed with a heated alkaline etching solution, and the interface of the mixed solution is photochemically micro-etched using ultraviolet light. After etching, the silica is separated and filtered out using a filter membrane; The filtered silica is cleaned of excess etching solution and etching impurities on the surface, washed until the pH of the liquid is 8.5-10, and dried to obtain hydroxylated nano-spherical silica with a micro-etched surface; The hydroxylated nano-spherical silica after surface micro-etching is dispersed to form a weak alkaline solution, and a silane coupling agent is added to the weak alkaline solution under ultraviolet light irradiation to carry out a coupling reaction to obtain modified nano-spherical silica with high surface activity.

2. The method for preparing photochemically modified high-surface-activity nano-spherical silica according to claim 1, characterized in that: The mass of the nano-spherical silica raw material is 10-50% of the mass of the alkaline etching solution; The mass of the silane coupling agent is 10-20% of the mass of the weak alkaline solution.

3. The method for preparing photochemically modified high-surface-activity nano-spherical silica according to claim 1, characterized in that: The method further includes performing a pretreatment before mixing the nano-spherical silicon dioxide raw material with the heated alkaline etching solution, including: cleaning and drying the nano-spherical silica raw material; Heat the alkaline etching solution to 50-80°C.

4. The method for preparing photochemically modified high-surface-activity nano-spherical silica according to claim 1, characterized in that: The alkaline etching solution is selected from a sodium hydroxide solution and / or a potassium hydroxide solution with a concentration of 1-5 mol / L; A calcium carbonate powder filter bag is further added to the alkaline etching solution, and the mass of the calcium carbonate powder is 1-5% of the mass of the alkaline etching solution.

5. The method for preparing photochemically modified high-surface-activity nano-spherical silica according to claim 1, characterized in that: The time for performing the photochemical surface micro-etching is 0.5-2 hours.

6. The method for preparing photochemically modified high-surface-activity nano-spherical silica according to claim 1, characterized in that: Remove excess etching solution and etching impurities from the filtered silicon dioxide surface, specifically: The filtered silicon dioxide is dispersed in a cleaning solution, cleaned and filtered to remove excess etching solution and etching impurities remaining on the surface.

7. The method for preparing photochemically modified high-surface-activity nano-spherical silica according to claim 6, characterized in that: The cleaning solution is an acidic cleaning solution with a pH value between 2 and 3, and is composed of 1% acetic acid, 20% ethanol and 79% pure water in mass fraction.

8. The method for preparing photochemically modified high-surface-activity nano-spherical silica according to claim 1, characterized in that: The method for obtaining modified high-surface-activity nano-spherical silica comprises the following steps: Hydroxylated nano-spherical silica and a silane coupling agent are reacted under ultraviolet light to generate hydrophobically modified nano-spherical silica with high surface activity; The hydrophobically modified nano-spherical silica with high surface activity is washed, filtered and dried to obtain modified nano-spherical silica with high surface activity.

9. The method for preparing photochemically modified high-surface-activity nano-spherical silica according to claim 1, characterized in that: The coupling reaction time is 0.5-5h, and the coupling reaction temperature is 30-60°C.

10. The method for preparing photochemically modified high-surface-activity nano-spherical silica according to claim 1, characterized in that: The silane coupling agent includes any one or more combinations of ethyltrimethoxysilane, n-propyltrimethoxysilane and trimethyloxyphenylsilane.

11. A photochemically modified high surface activity nano-spherical silica, characterized in that: The method according to any one of claims 1 to 10 is used for preparation.

12. The photochemically modified high surface activity nano-spherical silica according to claim 11, characterized in that: The nano-spherical silicon dioxide raw material is spherical, and the single particle size is 10-100nm.

13. Use of the photochemically modified high-surface-activity nano-spherical silica according to claim 11 or 12 in the preparation of oil-displacing agents, adhesives, sealants, composite surfactants and functional nano-material carriers.

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