A method for preparing silica based on the gas-liquid two-phase interface method

Abstract

The present invention provides a method for preparing silica based on the gas-liquid two-phase interface method, comprising the steps of: S1, providing an aqueous alcohol solution; S2, mixing an additive into the aqueous alcohol solution to obtain a reaction solution; the additive includes an alkali material; S3, loading silicon tetrachloride gas in the inert gas, and then controlling the inert gas to continuously aerate into the reaction solution; S4, stopping aerating into the reaction solution to obtain a termination solution; S5, aging the termination solution to obtain an aged solution; S6, separating the solid and liquid of the aged solution to obtain a primary silica product. The present invention prepares silica through the gas-liquid two-phase interface reaction of silicon tetrachloride, and overcomes problems such as fast hydrolysis rate and high danger of silicon tetrachloride by using the gas-liquid interface principle, and prepares silica with high dispersibility, spheroidization degree and purity, controllable morphology and uniform particle size distribution.

Description

Technical Field

[0001] The present invention relates to the field of utilization of silicon tetrachloride, and particularly to a method for preparing silicon dioxide based on a gas-liquid two-phase interface method. Background Art

[0002] Silicon tetrachloride (SiCl4) is an important industrial chemical, which is widely used in fields such as electronics, optical communication, chemical industry, and new energy. Silicon tetrachloride is a typical by-product in the production process of polysilicon. If it cannot be efficiently recycled, it will cause serious waste of resources. In addition, silicon tetrachloride is a highly corrosive and volatile chemical. Once leaked, it will quickly react with water vapor in the air to form white smoke (mainly composed of HCl), causing serious harm to the environment, including polluting water sources and soil. At present, the resource utilization of silicon tetrachloride is mainly to convert it into high-purity silicon tetrachloride, silicon oxides, trichlorosilane, etc. Among them, trichlorosilane is mainly prepared by the hydrogen reduction method and can be used in the production of polysilicon. The main processes for converting silicon tetrachloride into silicon dioxide are the hydrogen-oxygen combustion method and the direct oxidation method. Under appropriate process conditions, silicon dioxide materials for fields such as ceramics and optical glass can be prepared.

[0003] Silicon dioxide materials have specific properties in terms of having many surface hydroxyl groups, large surface energy, large specific surface area, high thermal stability, good dispersion performance, thermal resistance, electrical resistance, etc., and are widely used in fields such as ceramics, rubber, plastics, coatings, pigments, and catalyst carriers. At present, the production processes of silicon dioxide powder mainly include the gas phase method and the wet method. Gas phase silicon dioxide is mainly prepared by hydrolyzing chlorosilane at high temperature, and the reaction usually takes place in a hydrogen-oxygen flame. The characteristics of this process are small product particle size, uniform distribution, and high purity, but the equipment investment is large, the energy consumption is high, and the production cost is relatively high. The wet process is to generate a precipitate by the neutralization reaction of sodium silicate and acid, and then obtain the silicon dioxide product through aging, washing, drying, and pulverization. This method has simple equipment and low cost, but it is difficult to control the particle size and distribution of the product, and the purity is usually lower than that of the gas phase method product.

[0004] Using silicon tetrachloride as a silicon source to prepare silicon dioxide powder can improve resource utilization rate, reduce production energy consumption, and reduce pollution emissions. For example, the Chinese patent application with the publication number CN102795630A uses the reverse microemulsion method to prepare silicon dioxide. By compounding organic substances such as NP series and TX series to create a reverse microemulsion system, after microemulsification treatment, silicon tetrachloride is added for hydrolysis, and then through steps such as demulsification treatment and drying, silicon dioxide particles are obtained. Although the above patent application uses silicon tetrachloride as a silicon source to obtain silicon dioxide, the process is complex, a large amount of organic substances such as NP series and TX series are used, which easily affects the purity of the silicon dioxide product, and the sphericity and the uniformity of the particle size distribution also need to be improved.

[0005] In view of this, it is necessary to provide a method for preparing silica based on the gas-liquid two-phase interface method to solve or at least alleviate the technical problems that a large amount of organic substances affect the purity of silica products and the process is cumbersome. Summary of the Invention

[0006] The main object of the present invention is to provide a method for preparing silica based on the gas-liquid two-phase interface method, aiming to solve the above-mentioned technical problems that a large amount of organic substances affect the purity of silica products and the process is cumbersome.

[0007] To achieve the above object, the present invention provides a method for preparing silica based on the gas-liquid two-phase interface method, comprising the steps of:

[0008] S1, providing an aqueous alcohol solution;

[0009] S2, mixing an additive into the aqueous alcohol solution to obtain a reaction solution; the additive includes an alkali material, and the pH of the reaction solution is 10 - 13;

[0010] S3, loading silicon tetrachloride gas in a first inert gas, and then controlling the first inert gas to continuously aerate into the reaction solution;

[0011] S4, when the pH of the reaction solution reaches 6.5 - 8.2, stop aerating into the reaction solution to obtain a termination solution;

[0012] S5, aging the termination solution to obtain an aging solution;

[0013] S6, separating the solid and liquid of the aging solution to obtain a primary silica product.

[0014] Further, the volume concentration of the alcohol substance in the aqueous alcohol solution is 30 - 60%; the aqueous alcohol solution includes an aqueous solution of a polar alcohol substance; the polar alcohol substance includes ethanol.

[0015] Further, the alkali material includes one or more of ammonia water and sodium hydroxide; when the alkali material is the ammonia water, the volume ratio of the ammonia water to the aqueous alcohol solution is 1:15 - 25; when the alkali material is the sodium hydroxide, the mass-volume ratio of the sodium hydroxide to the aqueous alcohol solution is 0.1 - 0.5 g:150 mL.

[0016] Further, the additive further includes an active agent; the mass-volume ratio of the active agent to the aqueous alcohol solution is 0.05 - 1 g:150 mL; the active agent includes one or more of a cationic surfactant and a non-ionic surfactant; the cationic surfactant includes cetyltrimethylammonium bromide; the non-ionic surfactant includes a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer.

[0017] Further, the step S6 further includes: calcining the crude silica to obtain a silica product; the calcination is carried out under the protection of a second inert gas, the temperature of the calcination is 400 - 700 °C, and the duration of the calcination is 0.2 - 3 h.

[0018] Further, the step S6 further includes: before the calcination, washing and drying the crude silica in sequence; the drying includes vacuum drying; the temperature of the vacuum drying is 50 - 100 °C.

[0019] Further, the gas flow rate of the first inert gas is 50 - 600 L / h.

[0020] Further, the duration of the continuous aeration is 0.15 - 20 min; the first inert gas is aerated into the reaction solution through an aeration head, and the pore diameter of the aeration head is 0.1 - 50 μm.

[0021] Further, when the continuous aeration is carried out, the temperature of the reaction solution is 10 - 50 °C; when the continuous aeration is carried out, the reaction solution is stirred.

[0022] Further, the duration of the aging is 5 - 30 min, the temperature of the aging is 20 - 50 °C, and the aging is carried out under stirring conditions.

[0023] Compared with the prior art, the present invention has at least the following advantages:

[0024] The present invention first proposes a method for preparing high-purity silica powder by the silicon tetrachloride gas-liquid interface method; the reaction process of the present invention is mild, and the hydrolysis process of silicon tetrachloride is controlled by the gas-liquid interface reaction, overcoming the problems of fast hydrolysis rate and high danger of silicon tetrachloride, and improving the resource utilization rate. Moreover, the silica product of the present invention has high purity and sphericity, and the process is simple; specifically, the present invention prepares silica with high dispersibility, controllable morphology and particle size, high product purity, regular morphology, high sphericity, and uniform particle size and pore size distribution; further, the particle size distribution of the silica powder in the present invention in the range of 0.1 - 0.2 μm can even reach 100%, and high-purity ordered mesoporous silica powder is obtained. In addition, no three wastes are generated in the whole process of the present invention, no waste or pollution is generated, and the environmental protection and economy are good; the overall process is simple, the conditions are mild and controllable, the energy consumption is low, the actual application prospect is broad, and it has the potential to promote industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can be obtained based on the structures shown in these drawings.

[0026] Figure 1 It is the process flow diagram for preparing silica products in a certain embodiment of the present invention;

[0027] Figure 2 It is the SEM image of the silica product in Example 1 of the present invention; in the figure, (a) is a certain SEM image under the scanning electron microscope, and (b) is another SEM image under the scanning electron microscope;

[0028] Figure 3 It is the particle size distribution diagram of the silica product in Example 1 of the present invention; in the figure, the columns represent the proportion of the number of particles in different particle size ranges, and the curve is the cumulative distribution curve;

[0029] Figure 4 It is the SEM image of the silica product in Example 2 of the present invention; in the figure, (a) is a certain SEM image under the scanning electron microscope, and (b) is another SEM image under the scanning electron microscope;

[0030] Figure 5 It is the particle size distribution diagram of the silica product in Example 2 of the present invention; in the figure, the columns represent the proportion of the number of particles in different particle size ranges, and the curve is the cumulative distribution curve;

[0031] Figure 6 It is the SEM image of the silica products in Comparative Example 1 and Example 3 of the present invention; in the figure, (a) is the SEM image of the silica product in Comparative Example 1, and (b) is the SEM image of the silica product in Example 3;

[0032] Figure 7 It is the particle size distribution diagram of the silica product in Example 3 of the present invention; in the figure, the columns represent the proportion of the number of particles in different particle size ranges, and the curve is the cumulative distribution curve;

[0033] Figure 8 It is the SEM image of the silica product in Example 4 of the present invention; in the figure, (a) is a certain SEM image under the scanning electron microscope, and (b) is another SEM image under the scanning electron microscope;

[0034] Figure 9 It is the particle size distribution diagram of the silica product in Example 4 of the present invention; in the figure, the columns represent the proportion of the number of particles in different particle size ranges, and the curve is the cumulative distribution curve;

[0035] Figure 10 SEM image of the silica product in Example 5 of the present invention; in the figure, (a) is a certain SEM image under a scanning electron microscope, and (b) is another SEM image under a scanning electron microscope;

[0036] Figure 11 TEM image of the silica product in Example 5 of the present invention;

[0037] Figure 12 Particle size distribution diagram of the silica product in Example 5 of the present invention; in the figure, the columns represent the proportion of the number of particles in different particle size ranges, and the curve is the cumulative distribution curve;

[0038] Figure 13 SEM image of the silica product in Comparative Example 2 of the present invention; in the figure, (a) is a certain SEM image under a scanning electron microscope, and (b) is another SEM image under a scanning electron microscope;

[0039] Figure 14 SEM image of the silica product in Comparative Example 3 of the present invention; in the figure, (a) is a certain SEM image under a scanning electron microscope, and (b) is another SEM image under a scanning electron microscope.

[0040] The realization, functional characteristics and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Specific embodiments

[0041] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0042] Moreover, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0043] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention, based on the understanding of those skilled in the art of the present technology field of the prior art and the description of the present invention, any methods, devices, and materials similar to or equivalent to those described in the embodiments of the present invention can also be used to implement the present invention. In the comparative examples of the present invention, the amount of silicon tetrachloride liquid in the washing bottle is adjusted correspondingly according to needs to ensure the normal progress of the experiment; and, the reaction time is based on the pH at the end point of the reaction solution. For example, the reaction time in Comparative Example 2 is extended to 8 min.

[0044] The present invention mainly aims at the problems existing in the process of preparing silicon dioxide powder from silicon tetrachloride, such as high technical difficulty and danger, high cost, serious environmental impact, poor product stability, uneven particle size, low sphericity, irregular morphology, and high equipment requirements, and proposes an innovative gas-liquid two-phase interface method.

[0045] See Figure 1 For understanding, the present invention provides a method for preparing silicon dioxide based on the gas-liquid two-phase interface method, including the steps:

[0046] S1, providing an aqueous alcohol solution.

[0047] In the present invention, the volume concentration of the alcohol in the aqueous alcohol solution is 30 - 60%, and further, the volume concentration of the alcohol in the aqueous alcohol solution is 45 - 55%.

[0048] In the present invention, the aqueous alcohol solution includes an aqueous solution of a polar alcohol; the polar alcohol includes ethanol; specifically, the aqueous alcohol solution is prepared from ethanol and water, and ethanol is the alcohol in the aqueous alcohol solution.

[0049] S2, mixing an additive into the aqueous alcohol solution to obtain a reaction solution.

[0050] In the present invention, the process of mixing the additive into the aqueous alcohol solution includes: adding the additive to the aqueous alcohol solution and mixing, the mixing speed can be 200 - 800 rpm or 300 - 600 rpm, and the mixing duration can be 10 - 50 min or 10 - 30 min.

[0051] In the present invention, the additive includes an alkaline material; and after mixing the additive in the present invention, the pH of the reaction solution is 10 - 13, further 11 - 12.5, further 11 - 12.5 or 11.5 - 12.2 or 11.9 - 12.1.

[0052] In the present invention, the alkali material includes one or more of ammonia water and sodium hydroxide, and further is sodium hydroxide. In certain embodiments, when the alkali material is the ammonia water, the volume ratio of the ammonia water to the aqueous alcohol solution is 1:15 - 25, and further is 1:18 - 22; the ammonia water is analytical pure ammonia water; in the present invention, the concentration of the analytical pure ammonia water is 25 - 28%; in certain embodiments, when the alkali material is the sodium hydroxide, the mass - volume ratio of the sodium hydroxide to the aqueous alcohol solution is 0.1 - 0.5 g:150 mL, and further is 0.1 - 0.25 g:150 mL.

[0053] In the present invention, the additive further includes an active agent; the mass - volume ratio of the active agent to the aqueous alcohol solution is 0.05 - 1 g:150 mL, and further is 0.1 - 0.5 g:150 mL or 0.15 - 0.3 g:150 mL; the active agent includes one or more of a cationic surfactant and a non - ionic surfactant; the cationic surfactant includes cetyltrimethylammonium bromide; the non - ionic surfactant includes poly(ethylene oxide) - poly(propylene oxide) - poly(ethylene oxide) triblock copolymer; the active agent includes one or more of cetyltrimethylammonium bromide (CTAB) and poly(ethylene oxide) - poly(propylene oxide) - poly(ethylene oxide) triblock copolymer (P123); further, the active agent is cetyltrimethylammonium bromide.

[0054] S3, load silicon tetrachloride gas in the first inert gas, and then control the first inert gas to continuously aerate into the reaction solution.

[0055] In the present invention, the process of loading silicon tetrachloride gas in the first inert gas and then controlling the first inert gas to aerate into the reaction solution includes: placing silicon tetrachloride liquid in a closed container, introducing the first inert gas into the closed container, and then making the first inert gas flow out of the closed container, so as to load silicon tetrachloride gas in the first inert gas; after the first inert gas flows out of the closed container, control the first inert gas to continuously aerate into the reaction solution. Further, the silicon tetrachloride liquid is placed in a closed container at a temperature of 20 - 50 °C (specifically, at room temperature); further, the process of introducing the first inert gas into the closed container includes: introducing the first inert gas above the liquid level of the silicon tetrachloride liquid in the closed container.

[0056] In the present invention, the gas flow rate of the first inert gas is 50 - 600 L / h, further 100 - 200 L / h, or 100 - 180 L / h, or 140 - 160 L / h; during specific operation, the gas flow rate of the first inert gas introduced into the closed container is 50 - 600 L / h, further 100 - 200 L / h, or 100 - 180 L / h, or 140 - 160 L / h; the first inert gas includes argon.

[0057] In the present invention, the duration of continuous aeration is 0.15 - 20 min, preferably 0.15 - 10 min, or 0.15 - 2 min, or 0.8 - 1.2 min; in the present invention, a gas-liquid interface reaction occurs during the continuous aeration. In a specific implementation form, the first inert gas is aerated into the reaction liquid through an aeration head, and the pore diameter of the aeration head is 0.1 - 50 μm, further 10 - 40 μm, and still further 25 - 35 μm; the shape of the aeration head can be flat or cylindrical.

[0058] When the present invention performs the continuous aeration, the temperature of the reaction liquid is 10 - 50 °C, further 20 - 50 °C or 20 - 40 °C, and specifically can be at room temperature; when performing the continuous aeration, the reaction liquid is stirred, and the stirring rate is 50 - 600 rpm, preferably 300 - 600 rpm.

[0059] In the present invention, the specific process of step S3 includes: placing silicon tetrachloride liquid in a washing bottle, connecting the gas inlet end inside the bottle to the gas path of the first inert gas, and introducing the first inert gas into the inside of the washing bottle through the gas path; connecting the gas outlet end of the washing bottle to an aeration head, and inserting the aeration head into the inside of the reaction liquid; introducing the first inert gas (such as argon) as a carrier gas to expose the volatilized silicon tetrachloride gas in the washing bottle into the reaction liquid to carry out a gas-liquid interface reaction.

[0060] S4. When the pH of the reaction liquid reaches 6.5 - 8.2 (further 6.8 - 8.2, still further 7 - 8 or 6.8 - 7.2), stop aerating the reaction liquid to obtain a termination liquid.

[0061] S5. Age the termination liquid to obtain an aged liquid.

[0062] In the present invention, the aging duration is 5 - 30 min, preferably 10 - 20 min; the aging temperature is 20 - 50 °C, further 20 - 35 °C; the aging is carried out under stirring conditions, and the stirring rate during the aging process is 50 - 500 rpm, further 150 - 350 rpm.

[0063] S6. Solid-liquid separate the aging solution to obtain the primary silica product. In the present invention, the primary silica product is in powder form. The separated liquid (filtrate) obtained after solid-liquid separation can be recycled as the water for preparing the reaction solution.

[0064] In the present invention, step S6 further includes: sequentially washing, drying, and calcining the primary silica product to obtain a silica product. In the present invention, the silica product is in powder form. The drying includes vacuum drying, and the temperature of the vacuum drying is 50 - 100°C, preferably 60 - 85°C. The calcining is carried out under the protection of a second inert gas, the temperature of the calcining is 400 - 700°C (further 500 - 600°C), and the duration of the calcining is 0.2 - 3 h (further 0.5 - 2 h or 0.8 - 1.2 h). The second inert gas includes argon. In the present invention, when the additive does not contain the active agent, the calcining may not be carried out, that is, step S6 further includes: sequentially carrying out the washing and the drying on the primary silica product.

[0065] In the present invention, the involved chemical reaction equations include: . It should be noted that when liquid-phase silicon tetrachloride contacts water, a violent hydrolysis reaction will occur, and the hydrolysis rate is relatively fast, making it difficult to precisely control the silica product. The present invention ingeniously constructs a gas-liquid interface to control the hydrolysis reaction rate. Moreover, the present invention improves the particle size uniformity and purity of silica. The industrial process of the gas-liquid interface method is reduced, the production energy consumption is low, and the emission of harmful substances is reduced, meeting the environmental protection requirements, providing a green and efficient solution for the field of preparing high-purity silica powder from silicon tetrachloride.

[0066] The following are specific examples of the present invention:

[0067] Example 1

[0068] A method for preparing silica powder, the steps of which are:

[0069] S1. Mix 50 mL of water and 52 mL of ethanol evenly to obtain an aqueous ethanol solution.

[0070] S2. Add 5 mL of analytical pure ammonia water to the aqueous ethanol solution, and magnetically stir at a rate of 300 rpm for 15 min to obtain a reaction solution (the pH of the reaction solution is 11.5).

[0071] S3. Take 2 mL of silicon tetrachloride liquid and place it in a washing bottle at room temperature. Connect the inlet end of the washing bottle to an argon gas line, and continuously introduce argon gas into the washing bottle through the argon gas line (introduce it into the bottle from above the silicon tetrachloride liquid). The argon gas flow rate is 120 L / h. Connect the outlet end of the washing bottle to an aeration head. The aeration head is cylindrical with a pore diameter of 30 μm, and the aeration head is inserted into the reaction solution. After the argon gas flows out of the washing bottle, it carries silicon tetrachloride gas and enters the reaction solution through the aeration head, so as to carry out a gas-liquid interface reaction during continuous aeration. The gas-liquid interface reaction is carried out at room temperature, and the reaction solution is stirred during the reaction process at a rotation speed of 500 rpm.

[0072] S4. When the pH of the reaction solution reaches 8 (the end pH of the reaction solution, the reaction time is 30 s), close the argon gas line and stop the reaction to obtain a termination solution.

[0073] S5. Age the termination solution at 30 °C to obtain an aged solution; the stirring rate during the aging process is 300 rpm, and the aging time is 15 min.

[0074] S6. Centrifuge the aged solution, wash the separated solid matter 3 times with pure water and ethanol respectively, and then place it in a vacuum drying oven at 80 °C for drying. After detection, a nano-scale silica product is obtained.

[0075] In this example, for the SEM analysis and particle size distribution of the nano-scale silica product, see Figures 2 - 3 As shown, it can be seen that although the silica powder prepared with ammonia water as the base catalyst for the hydrolysis of silicon tetrachloride at the two-phase interface has an agglomeration phenomenon, the single particle size is small and it belongs to nano-scale spherical particles.

[0076] In the nano-scale silica product of this example, the purity of silica is 96.8%, and the obtained silica powder has a high purity and a low content of miscellaneous salts.

[0077] Example 2

[0078] A method for preparing silica powder, the steps of which are as follows:

[0079] S1. Mix 50 mL of water and 52 mL of ethanol evenly to obtain an alcohol aqueous solution.

[0080] S2. Add 5 mL of analytical pure ammonia water to the alcohol aqueous solution, and magnetically stir at a rate of 300 rpm for 15 min to obtain a reaction solution (the pH of the reaction solution is 11.5).

[0081] S3. Take 2 mL of silicon tetrachloride liquid and place it in a washing bottle at room temperature. Connect the inlet end of the washing bottle to an argon gas pipeline, and continuously introduce argon gas into the washing bottle through the argon gas pipeline (introduce it into the bottle from above the silicon tetrachloride liquid). The argon gas flow rate is 400 L / h. Connect the outlet end of the washing bottle to an aeration head. The aeration head is cylindrical with a pore diameter of 30 μm, and the aeration head is inserted into the reaction solution. After the argon gas flows out of the washing bottle, it carries silicon tetrachloride gas and enters the reaction solution through the aeration head, so as to carry out a gas-liquid interface reaction during continuous aeration. The gas-liquid interface reaction is carried out at room temperature, and the reaction solution is stirred during the reaction process at a rotation speed of 500 rpm.

[0082] S4. When the pH of the reaction solution reaches 8 (the end pH of the reaction solution, the reaction time is 15 s), close the argon gas pipeline and stop the reaction to obtain a termination solution.

[0083] S5. Age the termination solution at 30 °C to obtain an aged solution. The stirring rate during the aging process is 300 rpm, and the aging time is 15 min.

[0084] S6. Centrifuge the aged solution, wash the separated solid matter 3 times with pure water and ethanol respectively, and then place it in a vacuum drying oven at 80 °C for drying. After testing, a micron-sized silica product is obtained.

[0085] In this example, the SEM analysis and particle size distribution of the micron-sized silica product are shown in Figures 4 - 5 As can be seen, as the carrier gas flow rate increases, the particle size of the silica particles obtained in this example becomes larger, reaching the micron level. The particle shape is spherical and ellipsoidal, and the surface is relatively smooth. Although a small number of particles have agglomeration phenomena, the particle size distribution is relatively concentrated, and the particle size of most particles is about 3 μm.

[0086] Example 3

[0087] A method for preparing silica powder, the steps of which are as follows:

[0088] S1. Mix 72 mL of water and 78 mL of ethanol evenly to obtain an alcohol-water solution.

[0089] S2. Add 0.34 g of NaOH to the alcohol-water solution and magnetically stir it at a rate of 500 rpm for 20 min to obtain a reaction solution (the pH of the reaction solution is 12.2).

[0090] S3. Place 3 mL of silicon tetrachloride liquid in a washing bottle at room temperature. Connect the inlet end of the washing bottle to an argon gas pipeline, and continuously introduce argon into the washing bottle through the argon gas pipeline (introduce it into the bottle from above the silicon tetrachloride liquid), with an argon flow rate of 150 L / h. Connect the outlet end of the washing bottle to an aeration head. The aeration head is cylindrical with a pore diameter of 30 μm, and the aeration head is inserted into the reaction solution. After the argon flows out of the washing bottle, it carries silicon tetrachloride gas and enters the reaction solution through the aeration head, so as to carry out a gas-liquid interface reaction during continuous aeration. The gas-liquid interface reaction is carried out at room temperature, and the reaction solution is stirred during the reaction process at a rotation speed of 500 rpm.

[0091] S4. When the pH of the reaction solution reaches 8 (the end pH of the reaction solution, reaction time 40 s), close the argon gas pipeline, stop the reaction, and obtain a termination solution.

[0092] S5. Age the termination solution at 30 °C to obtain an aged solution; the stirring rate during the aging process is 300 rpm, and the aging time is 15 min.

[0093] S6. Centrifuge the aged solution, wash the separated solid matter 3 times with pure water and ethanol respectively, and then place it in a vacuum drying oven at 80 °C for drying. After detection, a nano-scale silica product is obtained.

[0094] In this example, the SEM analysis of the nano-scale silica product is shown in Figure 6 part (b) of, and the particle size distribution is shown in Figure 7 It can be seen that sodium hydroxide can also prepare nano-scale silica powder as the base catalyst for the hydrolysis of silicon tetrachloride at the two-phase interface. Although some of the obtained particles are agglomerated and adhered, the spheroidization is obvious and the particle size distribution is relatively concentrated.

[0095] Example 4

[0096] A method for preparing silica powder, the steps of which are as follows:

[0097] S1. Mix 72 mL of water and 78 mL of ethanol evenly to obtain an alcohol aqueous solution.

[0098] S2. Add 0.17 g of NaOH to the alcohol aqueous solution and magnetically stir it at a rate of 500 rpm for 20 min to obtain a reaction solution (the pH of the reaction solution is 12).

[0099] S3. Take 3 mL of silicon tetrachloride liquid and place it in a washing bottle at room temperature. Connect the inlet end of the washing bottle to an argon gas pipeline, and continuously introduce argon gas into the washing bottle through the argon gas pipeline (introduce it into the bottle from above the silicon tetrachloride liquid). The argon gas flow rate is 150 L / h. Connect the outlet end of the washing bottle to an aeration head. The aeration head is cylindrical with a pore diameter of 30 μm, and the aeration head is inserted into the reaction solution. After the argon gas flows out of the washing bottle, it carries silicon tetrachloride gas and enters the reaction solution through the aeration head, so as to carry out a gas-liquid interface reaction during continuous aeration. The gas-liquid interface reaction is carried out at room temperature, and the reaction solution is stirred during the reaction process at a rotation speed of 500 rpm.

[0100] S4. When the pH of the reaction solution reaches 7 (the end pH of the reaction solution, the reaction time is 1 min), close the argon gas pipeline and stop the reaction to obtain a termination solution.

[0101] S5. Carry out an aging reaction on the termination solution at 30 °C to obtain an aging solution; the stirring rate during the aging process is 300 rpm, and the aging time is 15 min.

[0102] S6. Centrifuge the aging solution, wash the separated solid matter with pure water and ethanol three times respectively, and then place it in a vacuum drying oven at 80 °C for drying. After detection, a submicron-sized silica product is obtained.

[0103] In this example, for the SEM analysis and particle size distribution of the submicron-sized silica product, see Figures 8 - 9 As shown, it can be seen that by reducing the dosage of the alkali catalyst sodium hydroxide, the hydrolysis of silicon tetrachloride based on the gas-liquid two-phase interface can obtain submicron-sized silica spheres with high sphericity, narrow particle size distribution, and high dispersity.

[0104] Example 5

[0105] A method for preparing silica powder, the steps of which are as follows:

[0106] S1. Mix 72 mL of water and 78 mL of ethanol evenly to obtain an alcohol-water solution.

[0107] S2. Add 0.17 g of NaOH and 0.22 g of CTAB to the alcohol-water solution, and magnetically stir at a rate of 600 rpm for 20 min to obtain a reaction solution (the pH of the reaction solution is 12).

[0108] S3. Take 3 mL of silicon tetrachloride liquid and place it in a washing bottle at room temperature. Connect the inlet end of the washing bottle to an argon gas pipeline, and continuously introduce argon gas into the washing bottle through the argon gas pipeline (introduce it into the bottle from above the silicon tetrachloride liquid). The argon gas flow rate is 150 L / h. Connect the outlet end of the washing bottle to an aeration head. The aeration head is cylindrical with a pore diameter of 30 μm, and the aeration head is inserted into the reaction solution. After the argon gas flows out of the washing bottle, it carries silicon tetrachloride gas and enters the reaction solution through the aeration head, thereby carrying out a gas-liquid interface reaction during continuous aeration. The gas-liquid interface reaction is carried out at room temperature, and the reaction solution is stirred during the reaction process at a rotation speed of 500 rpm.

[0109] S4. When the pH of the reaction solution reaches 7 (the end-point pH of the reaction solution, reaction time 1 min), close the argon gas pipeline to stop the reaction and obtain a termination solution.

[0110] S5. Age the termination solution at 30 °C to obtain an aged solution. The stirring rate during the aging process is 300 rpm, and the aging time is 15 min.

[0111] S6. Centrifuge the aged solution, wash the separated solid matter (crude silica) three times each with pure water and ethanol, then place it in a vacuum drying oven at 80 °C for drying, and then calcine it in an argon atmosphere at 550 °C for 1 h to remove the active agent. After testing, a submicron-sized silica product is obtained.

[0112] In this example, as shown in Figure 10 it can be seen that: under the regulation of the active agent, monodisperse submicron-sized spherical silica is prepared by the hydrolysis of silicon tetrachloride. The sphericity of the particles is high, the distribution is uniform. Although some samples show a stacked state layer by layer, the particle edges are obvious and the surface is smooth. As shown in Figures 11 - 12 it can be seen that: the obtained spherical silica particles have a narrow particle size distribution, the mesopores are orderly arranged, and they have high application potential.

[0113] In this example, in the liquid phase system, the surfactant CTAB is introduced. Based on the self-assembly behavior of the amphiphilic surfactant, monodisperse submicron-sized spherical silica with ordered mesopores is prepared by the hydrolysis of silicon tetrachloride. The sphericity of the particles is high, the particle size distribution is narrow, and the particle size distribution reaches 100% in the range of 0.1 - 0.2 μm.

[0114] In the silica product of this example, the purity of silica is 99.45%, and the obtained silica powder has a high purity and a low content of miscellaneous salts.

[0115] Comparative Example 1

[0116] Compared with Example 3, in this comparative example, the end-point pH of the reaction solution is adjusted by 2, and other conditions remain unchanged to obtain a silica product.

[0117] See Figure 6 As shown in part (a) of Figure 6 , the shape of the silica product obtained in this comparative example collapsed, the particle size distribution was uneven, and there was obvious agglomeration between particles. This is mainly because the hydrolysis product of silicon tetrachloride, silicic acid, is stably present in the range of pH = 2-3, and the condensation process is slow and irregular. Under neutral conditions, silicic acid tends to condense to form Si-O-Si bonds.

[0118] Comparative Example 2

[0119] In this comparative example, compared with Example 5, the end-point pH of the reaction solution was adjusted to 2, and other conditions remained unchanged to obtain a silica product.

[0120] See Figure 13 As shown, in the silica product obtained in this comparative example, the morphology of the silica particles is poor, the particle size distribution is uneven, and the agglomeration and adhesion phenomena are obvious.

[0121] In the silica product of this comparative example, the purity of silica is 88.74%, and the obtained silica powder has a low purity and a high content of miscellaneous salts.

[0122] Comparative Example 3

[0123] In this comparative example, compared with Example 1, the aqueous alcohol solution was adjusted to water, and other conditions remained unchanged to obtain a silica product.

[0124] See Figure 14 As shown, in the silica product obtained in this comparative example, the silica particles adhered and aggregated to each other, the morphology was poor, and no spherical particles were formed. This is mainly because the role of ethanol in the silicon tetrachloride hydrolysis system is dispersion, dissolution, thickening, etc. The presence of alcohol is one of the key factors for preparing high-quality spherical particles. The addition of an appropriate amount of ethanol to the reaction system can help control the reaction process, control the particle size and dispersion.

[0125] In the above technical solutions of the present invention, the above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made under the technical concept of the present invention by using the content of the specification and drawings of the present invention, or directly / indirectly applied to other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method for preparing silica based on the gas-liquid two-phase interface method, characterized in that, Including the steps: S1, providing an aqueous alcohol solution; S2, mixing an additive into the aqueous alcohol solution to obtain a reaction solution; the additive includes an alkali material, and the pH of the reaction solution is 10 - 13; S3, loading silicon tetrachloride gas in a first inert gas, and then controlling the first inert gas to continuously aerate into the reaction solution; S4, when the pH of the reaction solution reaches 6.5 - 8.2, stopping aerating into the reaction solution to obtain a termination solution; S5, aging the termination solution to obtain an aged solution; S6, performing solid - liquid separation on the aged solution to obtain a primary silica product.

2. The method for preparing silica based on the gas-liquid two-phase interface method according to claim 1, wherein, The volume concentration of the alcohol substance in the aqueous alcohol solution is 30 - 60%; the aqueous alcohol solution includes an aqueous solution of a polar alcohol substance; the polar alcohol substance includes ethanol.

3. The method for preparing silica based on the gas-liquid two-phase interface method according to claim 1, wherein The alkali material includes one or more of ammonia water and sodium hydroxide; when the alkali material is the ammonia water, the volume ratio of the ammonia water to the aqueous alcohol solution is 1:15 - 25; when the alkali material is the sodium hydroxide, the mass - volume ratio of the sodium hydroxide to the aqueous alcohol solution is 0.1 - 0.5 g:150 mL.

4. The method for preparing silica based on the gas-liquid two-phase interface method according to claim 1, characterized in that, The additive further includes an active agent; the mass - volume ratio of the active agent to the aqueous alcohol solution is 0.05 - 1 g:150 mL; the active agent includes one or more of a cationic surfactant and a non - ionic surfactant; the cationic surfactant includes cetyltrimethylammonium bromide; the non - ionic surfactant includes poly(ethylene oxide) - poly(propylene oxide) - poly(ethylene oxide) triblock copolymer.

5. The method for preparing silica based on the gas-liquid two-phase interface method according to claim 1, characterized in that, The step S6 further includes: calcining the primary silica product to obtain a silica product; the calcining is carried out under the protection of a second inert gas, the temperature of the calcining is 400 - 700 °C, and the duration of the calcining is 0.2 - 3 h.

6. The method for preparing silica based on the gas-liquid two-phase interface method according to claim 5, characterized in that, The step S6 further includes: before carrying out the calcining, washing and drying the primary silica product in sequence; the drying includes vacuum drying; the temperature of the vacuum drying is 50 - 100 °C.

7. The method for preparing silica based on the gas-liquid two-phase interface method according to claim 1, wherein The gas flow rate of the first inert gas is 50 - 600 L / h.

8. The method for preparing silica based on the gas-liquid two-phase interface method according to claim 1, wherein The duration of the continuous aeration is 0.15 - 20 min; the first inert gas aerates into the reaction solution through an aeration head, and the pore diameter of the aeration head is 0.1 - 50 μm.

9. The method for preparing silica based on the gas-liquid two-phase interface method according to claim 1, wherein When carrying out the continuous aeration, the temperature of the reaction solution is 10 - 50 °C; when carrying out the continuous aeration, the reaction solution is stirred.

10. The method for preparing silica based on the gas-liquid two-phase interface method according to claim 1, wherein, The duration of the aging is 5 - 30 min, the temperature of the aging is 20 - 50 °C, and the aging is carried out under stirring conditions.

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