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

Abstract

The invention discloses photochemical modified nano spherical silicon dioxide with high surface activity and a preparation method thereof, and belongs to the technical field of nano silicon dioxide. A photochemical etching method is utilized to act on silicon dioxide powder, so that active hydroxyl groups beneficial to coupling reaction are uniformly formed on the surface of silicon dioxide; the specific surface area of the spherical silicon dioxide is increased, the coupling reaction is directly carried out under a weakly alkaline condition, and the reaction degree of the active hydroxyl and the coupling group is controlled through the change of the concentration of the coupling agent, the reaction temperature and the reaction time, so that the hydrophilic and hydrophobic capacities of the product are controlled. The obtained modified nano spherical silicon dioxide has good dispersity, fluidity, lipophilicity and high surface chemical activity, can be used in materials such as adhesives, sealants, composite surfactant functional materials, functional nano material carriers and nano oil displacement agents, and is simple in whole preparation process, high in yield and small in pollution emission.

Description

Technical Field

[0001] The invention belongs to the technical field of nano silicon dioxide, and particularly relates to 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, uniform in particle size distribution, and without serious agglomeration. At present, the main methods for preparing spherical silica powder are 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, the particle size is small, but there are disadvantages such as many processes, large 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, there is acidic hydrogen halide gas as a by-product in the process, which has certain pollution. At the same time, the silica particles are very easy to produce dendritic structures that are difficult to separate, resulting in poor fluidity, and it is difficult to separate even after modification.

[0003] In the process of oil extraction, nano-oil flooding technology can inject water into any corner of the oil reservoir, greatly improving the recovery rate. Without changing the water flooding operation system, it can be used for strategic replacement in the late stage of medium and high permeability oil reservoir development, and can also be used for effective water flooding of low / ultra-low / ultra-low permeability and dense oil reservoirs. The modified nano-spherical silica proposed in the present invention is expected to be applied in the field of nano-oil flooding. Summary of the invention

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

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

[0006] Remove excess etching solution and etching impurities from the filtered silicon dioxide, wash until the pH of the liquid is 8.5-10, and dry to obtain hydroxylated nano-spherical silicon dioxide with micro-etching on the 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 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 comprises pre-treating the nano-spherical silicon dioxide raw material before mixing it 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] Further, 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 also 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 a time of 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] Further, obtaining the modified high surface active 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 nanometer spherical silica with high surface activity is washed, filtered and dried to obtain modified nanometer 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 nano-spherical silicon dioxide with high surface activity prepared by the preparation method.

[0024] Furthermore, the nano-spherical silica raw material is spherical, and a 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 uses a photochemical etching method to act on silicon dioxide powder, so that the surface of silicon dioxide uniformly forms active hydroxyl groups that are beneficial to the coupling reaction, and increases the specific surface area of ​​spherical silicon dioxide. The coupling reaction is directly carried out under weak alkaline conditions, and the reaction degree of the active hydroxyl group and the coupling group is controlled by changing the concentration of the coupling agent, the reaction temperature, and the reaction time, thereby controlling the hydrophilicity and hydrophobicity of the product. The obtained modified nano spherical silicon dioxide has good dispersibility, fluidity, lipophilicity and high surface chemical activity, and can be used in materials such as adhesives, sealants, composite surfactants, functional nano material carriers, etc., and is expected to form a new generation of nano oil displacement products after maturity.

[0028] The preparation method of the photochemically modified high-surface-activity nano-spherical silicon dioxide provided by the 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 partly become apparent from the description, or 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 briefly introduces 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 creative work.

[0031] Figure 1 A schematic diagram showing a method for preparing photochemically modified high-surface-activity nano-spherical silica proposed in the present invention;

[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 The Fourier transform infrared spectrum of the hydroxylated nano-spherical silicon dioxide after surface microetching in step S2 of Example 1 of the present invention is shown;

[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] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] One of the purposes of the present invention is to provide a method for preparing photochemically modified high surface active 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 to make its light energy act on the interface between the raw material and the etching solution, and performing photochemical surface micro-etching for 0.5-2h, and after etching, using a filter membrane to separate and filter out the silica;

[0039] In step S1, the etchant is sodium hydroxide and / or potassium hydroxide, and the concentration is 1-5 mol / L, wherein a calcium carbonate powder filter bag with a mass ratio of 1-5% is added to the etching solution, and calcium carbonate can react the free silicate anions obtained by the reaction to obtain calcium silicate, maintain the pH value of the solution relatively stable, and reduce 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, it will cause excessive etching and significantly affect the morphology and size of the nanoparticles, causing unnecessary losses; if the etching time is too long or the etching solution concentration is too low, the etching effect is not obvious.

[0040] S2. In a cleaning device, the filtered silicon dioxide is dispersed, cleaned, and filtered 2-5 times in a cleaning liquid to remove excess etching liquid and etching impurities on the surface, and the liquid is cleaned until the pH value is about 8.5-10, and dried at 50-100° C. to obtain hydroxylated nano-spherical silicon dioxide 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 fraction.

[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 to react with it for 0.5-5h. 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, washing and drying the nano-spherical silica raw material with an average particle size of 50nm; in an etching device, heating the alkaline etching solution to 60°C, stirring and mixing the nano-spherical silica raw material with 2mol / LNaOH etching agent at a mass ratio of 50%, adding a calcium carbonate powder filter bag at a mass ratio of 5% in the etching device, turning on the ultraviolet lamp while stirring, with a wavelength of 290nm and a power of 600W, performing photochemical surface micro-etching for 0.5h, and separating and filtering out the silica using a filter membrane after etching;

[0046] S2. In a cleaning device, the filtered silica is dispersed, washed, and filtered once in a cleaning solution of 1% acetic acid, 20% ethanol, and 79% pure water, and then washed and filtered three times with pure water to remove excess etching solution and etching impurities remaining on the surface, and then washed until the pH of the liquid is about 10, and 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 and add it to the modification device. While stirring, turn on the light source to make its light energy act on the interface between the raw material and the etching solution. The wavelength is 340nm and the power is 300W. Add 15% by mass of n-propyltrimethoxysilane and react with it for 5h to produce hydrophobically modified nano-spherical silica with high surface activity. Through the collection device, wash with pure water 3 times, filter, and dry at 80℃ for 5h 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, washing and drying the nano-spherical silica raw material with an average particle size of 10nm; in an etching device, heating the alkaline etching solution to 80°C, stirring and mixing the nano-spherical silica raw material with 1mol / LNaOH etching agent at a mass ratio of 10%, adding a calcium carbonate powder filter bag at a mass ratio of 5% in the etching device, turning on the ultraviolet lamp with a wavelength of 290nm and a power of 500W while stirring, performing photochemical surface micro-etching for 0.25h, and separating and filtering out the silica using a filter membrane after etching;

[0051] S2. In a cleaning device, the filtered silica is dispersed, washed, and filtered once in a cleaning solution of 1% acetic acid, 20% ethanol, and 79% pure water, and then washed and filtered three times with pure water to remove excess etching solution and etching impurities remaining on the surface, and then washed until the pH of the liquid is about 8.5, and 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 and add it to the modification device. While stirring, turn on the light source to make its light energy act on the interface between the raw material and the etching solution, with a wavelength of 400nm and a power of 200W. Add 5% by mass of n-propyltrimethoxysilane and react with it for 3h to produce hydrophobically modified nano-spherical silica with high surface activity. Through the collection device, wash with pure water 3 times, filter, and dry at 80℃ for 5h 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 high-surface-activity nano-spherical silica 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 active 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 the etchant was potassium hydroxide, to obtain modified high-surface-active nano-spherical silica.

[0059] 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 were 137°, 57°, and 155°, respectively.

[0060] Example 5

[0061] The preparation was carried out according to the method of Example 1, except that the silane coupling agent was ethyltrimethoxysilane, to obtain modified high-surface-active 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 active 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, washing and drying the nano-spherical silica raw material with an average particle size of 50nm; in an etching device, heating the alkaline etching solution to 50°C, stirring and mixing the nano-spherical silica raw material with 1mol / LNaOH etching agent at a mass ratio of 10%, adding a calcium carbonate powder filter bag at a mass ratio of 5% in the etching device, turning on the ultraviolet lamp with a wavelength of 290nm and a power of 600W while stirring, and performing photochemical surface micro-etching for 2h, and separating and filtering out the silica with a filter membrane after etching;

[0068] S2. In a cleaning device, the filtered silica is dispersed, washed, and filtered once in a cleaning solution of 1% acetic acid, 20% ethanol, and 79% pure water, and then washed and filtered three times with pure water to remove excess etching solution and etching impurities remaining on the surface, and then washed until the pH of the liquid is about 8.5, and 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 and add it to the modification device, while stirring, turn on the light source so that its light energy acts on the interface between the raw material and the etching solution, the wavelength is 400nm, and the power is 200W. Add 10% by mass of trimethyloxyphenylsilane and react with it for 5h to produce hydrophobically modified nano-spherical silica with high surface activity. Through the collection device, wash with pure water 3 times, filter, and dry at 80℃ for 5h 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 silicon dioxide 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 silicon dioxide preparation process in Example 1 were detected by infrared spectroscopy. 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 high-surface-activity 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 solid using a mechanical tablet press, and pure water was dropped onto the solid surface to measure the contact angle (the contact angle in the above examples was measured using the same method). The results are shown in Table 1:

[0080] Table 1

[0081] Implementation 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] It can be seen from the above results 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, converting the poorly soluble silicate ions into easily soluble carbonate ions, reducing insoluble matter, and having 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 substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions 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 silicon dioxide raw material is mixed with the heated alkaline etching solution, and the interface of the mixed solution is photochemically micro-etched by ultraviolet light, and the silicon dioxide is separated and filtered out by a filter membrane after etching; Remove excess etching solution and etching impurities from the filtered silicon dioxide, wash until the pH of the liquid is 8.5-10, and dry to obtain hydroxylated nano-spherical silicon dioxide with micro-etching on the 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 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 active nano spherical silica according to claim 1, characterized in that: The mass of the nano-spherical silicon dioxide 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 active nano spherical silica according to claim 1, characterized in that: The method further includes pre-treating the nano-spherical silicon dioxide raw material before mixing it 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 active 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 also 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 active nano spherical silica according to claim 1, characterized in that: The photochemical surface micro-etching time is 0.5-2h.

6. The method for preparing photochemically modified high surface active 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, cleaned and filtered in a cleaning solution to remove excess etching solution and etching impurities remaining on the surface.

7. The method for preparing photochemically modified high surface active 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 active nano spherical silica according to claim 1, characterized in that: The process for obtaining modified high surface active 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 nanometer spherical silica with high surface activity is washed, filtered and dried to obtain modified nanometer spherical silica with high surface activity.

9. The method for preparing photochemically modified high surface active 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 active 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 is prepared by any one of claims 1 to 10.

12. The photochemically modified high surface active 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 as claimed in claim 11 or 12 in the preparation of oil-displacing agents, adhesives, sealants, composite surfactants and functional nano-material carriers.

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