Method for preparing silicon dioxide based on gas-liquid two-phase interface method

Abstract

The invention provides a method for preparing silicon dioxide based on a gas-liquid two-phase interface method. The method comprises the following steps: S1, providing an alcohol-water solution; s2, mixing an additive into the alcohol-water solution to obtain a reaction solution; the additive comprises an alkali material; s3, loading silicon tetrachloride gas in the inert gas, and then controlling the inert gas to continuously aerate the reaction liquid; s4, stopping aeration in the reaction liquid to obtain a stop solution; s5, aging the stop solution to obtain an aged solution; and S6, carrying out solid-liquid separation on the aged liquid to obtain a silicon dioxide primary product. According to the method, silicon dioxide is prepared through a silicon tetrachloride gas-liquid two-phase interface reaction, the problems that silicon tetrachloride is high in hydrolysis rate, high in dangerousness and the like are solved according to the gas-liquid interface principle, and the silicon dioxide which is high in dispersity, spheroidization degree and purity, controllable in morphology and uniform in particle size distribution is prepared.

Description

Technical Field

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

[0002] Silicon tetrachloride (SiCl 4 ) is an important industrial chemical, widely used in electronics, optical communications, chemicals, new energy and other fields. Silicon tetrachloride is a typical by-product of the polysilicon production process. If it cannot be recycled efficiently, 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 produce white smoke (the main component is HCl), which will cause serious harm to the environment, including pollution of water sources and soil. At present, the resource utilization of silicon tetrachloride is mainly converted into high-purity silicon tetrachloride, silicon oxide or trichlorosilane. Among them, trichlorosilane is mainly prepared by hydrogen reduction method and can be used in the production of polysilicon; the main process for converting silicon tetrachloride into silicon dioxide is hydrogen-oxygen combustion method and direct oxidation method. Under appropriate process conditions, silicon dioxide materials used in ceramics, optical glass and other fields can be prepared.

[0003] Silica materials are widely used in ceramics, rubber, plastics, coatings, pigments and catalyst carriers due to their unique properties such as high surface hydroxyl groups, high surface energy, large specific surface area, high thermal stability, good dispersion performance, thermal resistance and electrical resistance. At present, the production process of silica powder mainly includes two methods: gas phase method and wet method. Gas phase silica is mainly prepared by hydrolysis of chlorosilane at high temperature, and the reaction is usually carried out 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 high. The wet process is to generate a precipitate through the neutralization reaction of sodium silicate and acid, and then obtain the silica product through aging, washing, drying and crushing. This method has simple equipment and low cost, but the particle size and distribution of the product are difficult to control, and the purity is usually lower than that of the gas phase product.

[0004] Using silicon tetrachloride as a silicon source to prepare silicon dioxide powder can improve resource utilization, reduce production energy consumption, and reduce pollution emissions. For example, the Chinese invention patent application with publication number CN102795630A uses the reverse microemulsion method to prepare silicon dioxide, creates a reverse microemulsion system by compounding organic substances such as the NP series and TX series, adds silicon tetrachloride after microemulsification treatment for hydrolysis, and then obtains silicon dioxide particles through demulsification treatment and drying. Although the above patent application uses silicon tetrachloride as a silicon source to prepare silicon dioxide, the process is complicated and uses a large amount of organic substances such as the NP series and TX series, which easily affects the purity of the silicon dioxide product, and the uniformity of the spheroidization degree and particle size distribution also needs to be improved.

[0005] In view of this, it is necessary to provide a method for preparing silicon dioxide based on the gas-liquid two-phase interface method to solve or at least alleviate the technical problems that a large amount of organic matter affects the purity of the silicon dioxide product and the process is complicated. Summary of the invention

[0006] The main purpose of the present invention is to provide a method for preparing silicon dioxide based on a gas-liquid two-phase interface method, aiming to solve the technical problems that a large amount of organic matter affects the purity of the silicon dioxide product and the process is complicated.

[0007] To achieve the above object, the present invention provides a method for preparing silicon dioxide based on a gas-liquid two-phase interface method, comprising the steps of: S1, providing an alcohol aqueous solution; S2, adding an additive to the alcohol aqueous 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 the reaction liquid; S4, when the pH of the reaction solution reaches 6.5-8.2, aeration into the reaction solution is stopped to obtain a stop solution; S5, aging the stop solution to obtain an aged solution; S6, separating the aged liquid into solid and liquid to obtain a primary product of silicon dioxide.

[0008] Furthermore, the volume concentration of alcohol substances in the alcohol aqueous solution is 30-60%; the alcohol aqueous solution includes an aqueous solution of polar alcohol substances; and the polar alcohol substances include ethanol.

[0009] Furthermore, the alkali material includes one or more of ammonia water and sodium hydroxide; when the alkali material is ammonia water, the volume ratio of the ammonia water to the alcohol aqueous solution is 1:15-25; when the alkali material is sodium hydroxide, the mass volume ratio of the sodium hydroxide to the alcohol aqueous solution is 0.1-0.5g:150mL.

[0010] Furthermore, the additive also includes an active agent; the mass volume ratio of the active agent to the alcohol aqueous solution is 0.05-1g:150mL; the active agent includes one or more of a cationic surfactant and a non-ionic surfactant; the cationic surfactant includes hexadecyltrimethylammonium bromide; the non-ionic surfactant includes a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

[0011] Furthermore, the step S6 also includes: calcining the primary silicon dioxide product to obtain a silicon dioxide product; the calcination is carried out under the protection of a second inert gas, the calcination temperature is 400-700° C., and the calcination time is 0.2-3 h.

[0012] Furthermore, the step S6 further comprises: before the calcination, washing and drying the primary silicon dioxide product in sequence; the drying comprises vacuum drying; and the temperature of the vacuum drying is 50-100°C.

[0013] Furthermore, the gas flow rate of the first inert gas is 50-600 L / h.

[0014] Furthermore, the duration of the continuous aeration is 0.15-20 min; the first inert gas is aerated into the reaction liquid through an aeration head, and the pore size of the aeration head is 0.1-50 μm.

[0015] Furthermore, during the continuous aeration, the temperature of the reaction liquid is 10-50° C.; during the continuous aeration, the reaction liquid is stirred.

[0016] Furthermore, the aging time is 5-30 minutes, the aging temperature is 20-50° C., and the aging is carried out under stirring.

[0017] Compared with the prior art, the present invention has at least the following advantages: The present invention proposes for the first time the silicon tetrachloride gas-liquid interface method for preparing high-purity silicon dioxide powder; the reaction process of the present invention is mild, and the hydrolysis process of silicon tetrachloride is controlled by gas-liquid interface reaction, which overcomes the problems of fast hydrolysis rate and high danger of silicon tetrachloride, and improves resource utilization. In addition, the silicon dioxide product of the present invention has high purity and spheroidization, and the process is simple; specifically, the present invention prepares silicon dioxide with high dispersibility and controllable morphology and particle size, and the product has high purity, regular morphology, high spheroidization, and uniform particle size and pore size distribution; further, the particle size distribution of silicon dioxide powder in the present invention at 0.1-0.2um can even reach 100%, and high-purity ordered mesoporous silicon dioxide powder is obtained. In addition, the entire process of the present invention does not produce three wastes, does not generate waste or pollution, and has good environmental protection and economy; the overall process is simple, the conditions are mild and controllable, the energy consumption is low, the practical application prospects are broad, and it has the potential for promoting industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0019] Figure 1 A process flow chart for preparing a silicon dioxide product in a certain embodiment of the present invention; Figure 2 1 is a SEM image of the silicon dioxide product in Example 1 of the present invention; in the figure, (a) is a SEM image under a scanning electron microscope, and (b) is another SEM image under a scanning electron microscope; Figure 3 This is a particle size distribution diagram of the silicon dioxide product in Example 1 of the present invention; in the figure, the columns represent the percentage of particles in different particle size ranges, and the curve is a cumulative distribution curve; Figure 4 1 is a SEM image of the silicon dioxide product in Example 2 of the present invention; in the figure, (a) is a SEM image under a scanning electron microscope, and (b) is another SEM image under a scanning electron microscope; Figure 5 This is a particle size distribution diagram of the silicon dioxide product in Example 2 of the present invention; in the figure, the columns represent the percentage of particles in different particle size ranges, and the curve is a cumulative distribution curve; Figure 6 The figures are SEM images of the silicon dioxide products in Comparative Example 1 and Example 3 of the present invention; in the figures, (a) is the SEM image of the silicon dioxide product in Comparative Example 1, and (b) is the SEM image of the silicon dioxide product in Example 3; Figure 7 This is a particle size distribution diagram of the silicon dioxide product in Example 3 of the present invention; in the figure, the columns represent the percentage of particles in different particle size ranges, and the curve is a cumulative distribution curve; Figure 8 1 is a SEM image of the silicon dioxide product in Example 4 of the present invention; in the figure, (a) is a SEM image under a scanning electron microscope, and (b) is another SEM image under a scanning electron microscope; Fig. 9 This is a particle size distribution diagram of the silicon dioxide product in Example 4 of the present invention; in the figure, the columns represent the percentage of particles in different particle size ranges, and the curve is a cumulative distribution curve; Fig.10 1 is a SEM image of the silicon dioxide product in Example 5 of the present invention; in the figure, (a) is a SEM image under a scanning electron microscope, and (b) is another SEM image under a scanning electron microscope; Fig.11 This is a TEM image of the silicon dioxide product in Example 5 of the present invention; Fig.12 This is a particle size distribution diagram of the silicon dioxide product in Example 5 of the present invention; in the figure, the columns represent the percentage of particles in different particle size ranges, and the curve is a cumulative distribution curve; Fig.13 The SEM image of the silicon dioxide 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; Fig.14 1 is a SEM image of the silicon dioxide product in Comparative Example 3 of the present invention; in the image, (a) is a SEM image under a scanning electron microscope, and (b) is another SEM image under a scanning electron microscope.

[0020] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with the implementation methods and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions 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 creative work are within the scope of protection of the present invention.

[0022] Furthermore, the technical solutions between the various embodiments of the present invention may be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in the field. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0023] When the embodiments give a numerical range, it should be understood that, unless otherwise specified in the present invention, the two 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 are in accordance with the technical personnel in this field of the prior art and the description of the present invention. Any method, equipment and material of the prior art similar to or equivalent to the method, equipment and material 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 gas washing bottle is adjusted accordingly as needed to enable the experiment to be carried out normally; and the reaction time is based on the endpoint pH of the reaction solution, such as: the reaction time in comparative example 2 is extended to 8 minutes.

[0024] The present invention mainly aims at the problems existing in the existing process of preparing silicon dioxide powder from silicon tetrachloride, such as great technical difficulty and danger, high cost, serious environmental impact, poor product stability, uneven particle size, low spheroidization degree, irregular morphology, high equipment requirements, etc., and proposes an innovative gas-liquid two-phase interface method.

[0025] See also Figure 1 It is understood that the present invention provides a method for preparing silicon dioxide based on a gas-liquid two-phase interface method, comprising the steps of: S1, providing an alcohol aqueous solution.

[0026] In the present invention, the volume concentration of the alcohol substance in the alcohol aqueous solution is 30-60%, and further, the volume concentration of the alcohol substance in the alcohol aqueous solution is 45-55%.

[0027] In the present invention, the alcohol aqueous solution includes an aqueous solution of polar alcohol substances; the polar alcohol substances include ethanol; specifically, the alcohol aqueous solution is prepared from ethanol and water, and ethanol is the alcohol substance in the alcohol aqueous solution.

[0028] S2, mixing an additive into the alcohol aqueous solution to obtain a reaction solution.

[0029] In the present invention, the process of mixing the additive into the alcohol aqueous solution comprises: adding the additive into the alcohol aqueous solution and mixing, the mixing speed may be 200-800rpm or 300-600rpm, and the mixing time may be 10-50min or 10-30min.

[0030] In the present invention, the additive includes an alkali material; and after the additive is mixed into the reaction solution, the pH value 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.

[0031] In the present invention, the alkali material includes one or more of ammonia water and sodium hydroxide, and further sodium hydroxide. In certain embodiments, when the alkali material is ammonia water, the volume ratio of the ammonia water to the alcohol aqueous solution is 1:15-25, and further 1:18-22; the ammonia water is analytically pure ammonia water; in the present invention, the concentration of analytically pure ammonia water is 25-28%; in certain embodiments, when the alkali material is sodium hydroxide, the mass volume ratio of the sodium hydroxide to the alcohol aqueous solution is 0.1-0.5g:150mL, and further 0.1-0.25g:150mL.

[0032] In the present invention, the additive also includes an active agent; the mass volume ratio of the active agent to the alcohol aqueous solution is 0.05-1g:150mL, further 0.1-0.5g:150mL or 0.15-0.3g:150mL; the active agent includes one or more of a cationic surfactant and a non-ionic surfactant; the cationic surfactant includes hexadecyltrimethylammonium bromide; the non-ionic surfactant includes a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer; the active agent includes one or more of hexadecyltrimethylammonium bromide (CTAB) and a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer (P123); further, the active agent is hexadecyltrimethylammonium bromide.

[0033] S3, loading silicon tetrachloride gas in a first inert gas, and then controlling the first inert gas to continuously aerate the reaction liquid.

[0034] 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 the reaction liquid includes: placing silicon tetrachloride liquid in a closed container, introducing the first inert gas into the closed container, and then allowing the first inert gas to flow out of the closed container, thereby loading silicon tetrachloride gas in the first inert gas; after the first inert gas flows out of the closed container, controlling the first inert gas to continue aerating the reaction liquid. Further, placing silicon tetrachloride liquid in a closed container at a temperature of 20-50°C (specifically room temperature); further, the process of introducing the first inert gas into the closed container includes: introducing the first inert gas above the liquid surface of the silicon tetrachloride liquid in the closed container.

[0035] 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.

[0036] In the present invention, the duration of the continuous aeration is 0.15-20 minutes, preferably 0.15-10 minutes or 0.15-2 minutes or 0.8-1.2 minutes; the present invention generates a gas-liquid interface reaction 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 size of the aeration head is 0.1-50 μm, further 10-40 μm, and further 25-35 μm; the shape of the aeration head can be flat or cylindrical.

[0037] In the present invention, when the continuous aeration is performed, the temperature of the reaction liquid is 10-50°C, further 20-50°C or 20-40°C, specifically room temperature; when the continuous aeration is performed, the reaction liquid is stirred at a stirring rate of 50-600rpm, preferably 300-600rpm.

[0038] In the present invention, the specific process of step S3 includes: placing silicon tetrachloride liquid in a gas washing bottle, connecting the gas inlet end in the bottle to the gas path of the first inert gas, and passing the first inert gas into the interior of the gas washing bottle through the gas path; connecting the gas outlet end of the gas washing bottle to an aeration head, and inserting the aeration head into the interior of the reaction liquid; and passing the first inert gas (such as argon) as a carrier gas to expose the volatilized silicon tetrachloride gas in the gas washing bottle into the reaction liquid to perform a gas-liquid interface reaction.

[0039] S4, when the pH of the reaction solution reaches 6.5-8.2 (further 6.8-8.2, further 7-8 or 6.8-7.2), aeration into the reaction solution is stopped to obtain a stop solution.

[0040] S5, aging the stop solution to obtain an aged solution.

[0041] In the present invention, the aging time 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, and the stirring rate of the aging process is 50-500rpm, further 150-350rpm.

[0042] S6, separating the aged liquid into solid and liquid to obtain a primary silica product; in the present invention, the primary silica product is a powder; the separated liquid (filtrate) obtained after the solid-liquid separation can be used as a water distribution medium for the reaction liquid.

[0043] In the present invention, the step S6 further comprises: washing, drying and calcining the primary silica product in sequence to obtain a silica product; in the present invention, the silica product is a powder; the drying comprises vacuum drying, the vacuum drying temperature is 50-100°C, preferably the vacuum drying temperature is 60-85°C; the calcination is carried out under the protection of a second inert gas, the calcination temperature is 400-700°C (further 500-600°C), and the calcination time is 0.2-3h (further 0.5-2h or 0.8-1.2h); the second inert gas comprises argon. In the present invention, when the additive does not contain the active agent, the calcination may not be carried out, that is, the step S6 further comprises: washing and drying the primary silica product in sequence.

[0044] In the present invention, the chemical reaction equations involved include: . It should be noted that liquid silicon tetrachloride will undergo a violent hydrolysis reaction when in contact with water, and the hydrolysis rate is relatively fast, making it difficult to achieve precise control of the silicon dioxide product. The present invention cleverly constructs a gas-liquid interface to regulate the hydrolysis reaction rate; moreover, the present invention improves the particle size uniformity and purity of silicon dioxide; the gas-liquid interface method reduces the industrial process, has low production energy consumption, reduces the emission of harmful substances, meets environmental protection requirements, and provides a green and efficient solution for the preparation of high-purity silicon dioxide powder from silicon tetrachloride.

[0045] The following are specific examples of the present invention: Example 1 A method for preparing silicon dioxide powder, comprising the steps of: S1, mix 50 mL of water and 52 mL of ethanol evenly to obtain an alcohol-water solution.

[0046] S2, add 5 mL of analytical pure ammonia water to the alcohol aqueous solution, and stir magnetically at 300 rpm for 15 min to obtain a reaction solution (the pH of the reaction solution is 11.5).

[0047] S3, take 2mL of silicon tetrachloride liquid and place it in a washing bottle at room temperature, the air inlet end of the washing bottle is connected to the argon gas line, and argon gas is continuously introduced into the washing bottle through the argon gas line (into the bottle from the top of the silicon tetrachloride liquid), and the argon flow rate is 120L / h; the air outlet end of the washing bottle is connected to the aeration head, the aeration head is cylindrical, the pore size is 30μm, and the aeration head is inserted into the reaction liquid; after the argon gas flows out of the washing bottle, it carries silicon tetrachloride gas and enters the reaction liquid through the aeration head, so that a gas-liquid interface reaction is carried out during the continuous aeration process; the gas-liquid interface reaction is carried out at room temperature, and the reaction liquid is stirred during the reaction at a rotation speed of 500rpm.

[0048] S4, when the pH of the reaction solution reaches 8 (end point pH of the reaction solution, reaction time 30s), close the argon gas line to stop the reaction and obtain the stop solution.

[0049] S5, subjecting the stop solution to an aging reaction 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.

[0050] S6, centrifugally separating the aged liquid, and washing the separated solids with pure water and ethanol for three times respectively, and then drying them in a vacuum drying oven at 80° C., and obtaining a nano-scale silica product after testing.

[0051] In this example, the SEM analysis and particle size distribution of the nano-silicon dioxide product are shown in Figure 2-Figure 3 As shown, it can be seen that although the silicon dioxide powder prepared by using ammonia water as an alkaline catalyst for the hydrolysis of silicon tetrachloride at the two-phase interface has agglomeration phenomenon, the single particle size is small and belongs to nano-scale spherical particles.

[0052] In the nano-scale silicon dioxide product of this embodiment, the purity of silicon dioxide is 96.8%, and the obtained silicon dioxide powder has high purity and low content of impurities.

[0053] Example 2 A method for preparing silicon dioxide powder, comprising the steps of: S1, mix 50 mL of water and 52 mL of ethanol evenly to obtain an alcohol-water solution.

[0054] S2, add 5 mL of analytical pure ammonia water to the alcohol aqueous solution, and stir magnetically at 300 rpm for 15 min to obtain a reaction solution (the pH of the reaction solution is 11.5).

[0055] S3, take 2mL of silicon tetrachloride liquid and place it in a washing bottle at room temperature, the air inlet end of the washing bottle is connected to the argon gas line, and argon gas is continuously introduced into the washing bottle through the argon gas line (into the bottle from the top of the silicon tetrachloride liquid), and the argon flow rate is 400L / h; the air outlet end of the washing bottle is connected to the aeration head, the aeration head is cylindrical, and the pore size is 30μm, and the aeration head is inserted into the reaction liquid; after the argon gas flows out of the washing bottle, it carries silicon tetrachloride gas and enters the reaction liquid through the aeration head, so that a gas-liquid interface reaction is carried out during the continuous aeration process; the gas-liquid interface reaction is carried out at room temperature, and the reaction liquid is stirred during the reaction at a rotation speed of 500rpm.

[0056] S4, when the pH of the reaction solution reaches 8 (end point pH of the reaction solution, reaction time 15s), close the argon gas line to stop the reaction and obtain the stop solution.

[0057] S5, subjecting the stop solution to an aging reaction 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.

[0058] S6, centrifugally separating the aged liquid, and washing the separated solids with pure water and ethanol for three times respectively, and then drying them in a vacuum drying oven at 80° C., and obtaining a micron-sized silica product after testing.

[0059] In this example, the SEM analysis and particle size distribution of the micron-sized silica product are shown in Figure 4-Figure 5 As shown, it can be seen that: with the increase of carrier gas flow rate, the particle size of the silica particles obtained in this embodiment increases to the micron level, the particle shape is spherical and ellipsoidal, the surface is relatively smooth, although a small number of particles are agglomerated, the particle size distribution is relatively concentrated, and the particle size of most particles is about 3µm.

[0060] Example 3 A method for preparing silicon dioxide powder, comprising the steps of: S1, mix 72 mL of water and 78 mL of ethanol evenly to obtain an alcohol-water solution.

[0061] S2, add 0.34 g of NaOH to the alcohol aqueous solution, and stir magnetically at 500 rpm for 20 min to obtain a reaction solution (the pH of the reaction solution is 12.2).

[0062] S3, take 3mL of silicon tetrachloride liquid and place it in a washing bottle at room temperature, the air inlet end of the washing bottle is connected to the argon gas line, and argon gas is continuously introduced into the washing bottle through the argon gas line (into the bottle from the top of the silicon tetrachloride liquid), and the argon flow rate is 150L / h; the air outlet end of the washing bottle is connected to the aeration head, the aeration head is cylindrical, the pore size is 30μm, and the aeration head is inserted into the reaction liquid; after the argon gas flows out of the washing bottle, it carries silicon tetrachloride gas and enters the reaction liquid through the aeration head, so that a gas-liquid interface reaction is carried out during the continuous aeration process; the gas-liquid interface reaction is carried out at room temperature, and the reaction liquid is stirred during the reaction at a rotation speed of 500rpm.

[0063] S4, when the pH of the reaction solution reaches 8 (end point pH of the reaction solution, reaction time 40s), close the argon gas line to stop the reaction and obtain the stop solution.

[0064] S5, subjecting the stop solution to an aging reaction 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.

[0065] S6, centrifugally separating the aged liquid, and washing the separated solids with pure water and ethanol for three times respectively, and then drying them in a vacuum drying oven at 80° C., and obtaining a nano-scale silica product after testing.

[0066] In this example, the SEM analysis of the nano-silicon dioxide product is shown in Figure 6 As shown in part (b), the particle size distribution is shown in Figure 7 As shown, it can be seen that sodium hydroxide as an alkaline catalyst for the hydrolysis of silicon tetrachloride at the two-phase interface can also prepare nano-scale silicon dioxide powder. Although the obtained particles are partially agglomerated and adhered, they are obviously spheroidized and the particle size distribution is relatively concentrated.

[0067] Example 4 A method for preparing silicon dioxide powder, comprising the steps of: S1, mix 72 mL of water and 78 mL of ethanol evenly to obtain an alcohol-water solution.

[0068] S2, add 0.17 g of NaOH to the alcohol aqueous solution, and stir magnetically at 500 rpm for 20 min to obtain a reaction solution (the pH of the reaction solution is 12).

[0069] S3, take 3mL of silicon tetrachloride liquid and place it in a washing bottle at room temperature, the air inlet end of the washing bottle is connected to the argon gas line, and argon gas is continuously introduced into the washing bottle through the argon gas line (into the bottle from the top of the silicon tetrachloride liquid), and the argon flow rate is 150L / h; the air outlet end of the washing bottle is connected to the aeration head, the aeration head is cylindrical, the pore size is 30μm, and the aeration head is inserted into the reaction liquid; after the argon gas flows out of the washing bottle, it carries silicon tetrachloride gas and enters the reaction liquid through the aeration head, so that a gas-liquid interface reaction is carried out during the continuous aeration process; the gas-liquid interface reaction is carried out at room temperature, and the reaction liquid is stirred during the reaction at a rotation speed of 500rpm.

[0070] S4, when the pH of the reaction solution reaches 7 (end point pH of the reaction solution, reaction time 1 min), close the argon gas line to stop the reaction and obtain the stop solution.

[0071] S5, subjecting the stop solution to an aging reaction 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.

[0072] S6, centrifugally separating the aged liquid, and washing the separated solids with pure water and ethanol for three times respectively, and then drying them in a vacuum drying oven at 80° C., and obtaining a submicron silicon dioxide product after testing.

[0073] In this example, the SEM analysis and particle size distribution of the submicron silica product are shown in Figure 8-Figure 9 As shown, it can be seen that by reducing the amount of alkaline catalyst sodium hydroxide, silicon tetrachloride can be hydrolyzed at the gas-liquid two-phase interface to obtain submicron silica spheres with high spheroidization degree, narrow particle size distribution and high dispersion.

[0074] Example 5 A method for preparing silicon dioxide powder, comprising the steps of: S1, mix 72 mL of water and 78 mL of ethanol evenly to obtain an alcohol-water solution.

[0075] S2, add 0.17 g of NaOH and 0.22 g of CTAB to the alcohol aqueous solution, and stir magnetically at 600 rpm for 20 min to obtain a reaction solution (the pH of the reaction solution is 12).

[0076] S3, take 3mL of silicon tetrachloride liquid and place it in a washing bottle at room temperature, the air inlet end of the washing bottle is connected to the argon gas line, and argon gas is continuously introduced into the washing bottle through the argon gas line (into the bottle from the top of the silicon tetrachloride liquid), and the argon flow rate is 150L / h; the air outlet end of the washing bottle is connected to the aeration head, the aeration head is cylindrical, the pore size is 30μm, and the aeration head is inserted into the reaction liquid; after the argon gas flows out of the washing bottle, it carries silicon tetrachloride gas and enters the reaction liquid through the aeration head, so that a gas-liquid interface reaction is carried out during the continuous aeration process; the gas-liquid interface reaction is carried out at room temperature, and the reaction liquid is stirred during the reaction at a rotation speed of 500rpm.

[0077] S4, when the pH of the reaction solution reaches 7 (end point pH of the reaction solution, reaction time 1 min), close the argon gas line to stop the reaction and obtain the stop solution.

[0078] S5, subjecting the stop solution to an aging reaction 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.

[0079] S6, centrifugally separating the aged liquid, and washing the separated solid (initial silica product) with pure water and ethanol for 3 times respectively, and then drying it in a vacuum drying oven at 80°C. After drying, calcining it at 550°C in an argon atmosphere for 1 hour to remove the active agent, and obtaining a submicron silica product after testing.

[0080] In this embodiment, see Fig.10 As shown in the figure, it can be seen that: under the control of the surfactant, the hydrolysis of silicon tetrachloride prepared monodisperse submicron spherical silica, the particles have high spheroidization degree and uniform distribution. Although some samples are stacked in layers, the particles have obvious edges and smooth surfaces; see Figure 11-Figure 12 As shown, it can be seen that the obtained spherical silica particles have a narrow particle size distribution, orderly arrangement of mesopores, and have high application potential.

[0081] In this embodiment, the surfactant CTAB is introduced into the liquid phase system. Based on the self-assembly behavior of the amphiphilic surfactant, silicon tetrachloride is hydrolyzed to prepare ordered mesoporous monodisperse submicron spherical silica. The particles have high spheroidization degree and narrow particle size distribution, and the particle size distribution in the range of 0.1-0.2 μm reaches 100%.

[0082] In the silicon dioxide product of this embodiment, the silicon dioxide purity is 99.45%, and the obtained silicon dioxide powder has high purity and low impurity salt content.

[0083] Comparative Example 1 Compared with Example 3, in this comparative example, the endpoint pH of the reaction solution was adjusted to 2, and other conditions remained unchanged to obtain a silicon dioxide product.

[0084] See also Figure 6 As shown in part (a), the silica product obtained in this comparative example has collapsed shape, uneven particle size distribution, and obvious agglomeration between particles. This is mainly because the hydrolysis product of silicon tetrachloride, silicic acid, is stable in the pH range of 2-3, and the condensation process is slow and irregular. Under neutral conditions, silicic acid tends to condense to form Si-O-Si bonds.

[0085] Comparative Example 2 Compared with Example 5, the endpoint pH of the reaction solution was adjusted to 2, and other conditions remained unchanged to obtain a silicon dioxide product.

[0086] See also Fig.13 As shown, in the silicon dioxide product obtained in this comparative example, the silicon dioxide particles have poor morphology, uneven particle size distribution, and obvious agglomeration and adhesion.

[0087] In the silicon dioxide product of this comparative example, the silicon dioxide purity is 88.74%, the obtained silicon dioxide powder has low purity and high content of impurities.

[0088] Comparative Example 3 Compared with Example 1, in this comparative example, the alcohol aqueous solution was adjusted to water, and other conditions remained unchanged to obtain a silicon dioxide product.

[0089] See also Fig.14 As shown, in the silicon dioxide product obtained in this comparative example, the silicon dioxide particles are adhered and aggregated to each other, the morphology is poor, and no spherical particles are generated. Mainly because the role of ethanol in the silicon tetrachloride hydrolysis system is dispersion, dissolution and thickening, etc., the presence of alcohol is one of the key factors in preparing high-quality spherical particles. Adding an appropriate amount of ethanol to the reaction system can help control the reaction process and control the size and dispersion of the particles.

[0090] The above technical solutions of the present invention are only preferred embodiments of the present invention, and the patent scope of the present invention is not limited thereto. All equivalent structural changes made by using the contents of the present invention specification and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing silicon dioxide based on a gas-liquid two-phase interface method, characterized in that: Includes steps: S1, providing an alcohol aqueous solution; S2, adding an additive to the alcohol aqueous 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 the reaction liquid; S4, when the pH of the reaction solution reaches 6.5-8.2, aeration into the reaction solution is stopped to obtain a stop solution; S5, aging the stop solution to obtain an aged solution; S6, separating the aged liquid into solid and liquid to obtain a primary product of silicon dioxide.

2. The method for preparing silicon dioxide based on the gas-liquid two-phase interface method according to claim 1, characterized in that: The volume concentration of alcohol substances in the alcohol aqueous solution is 30-60%; the alcohol aqueous solution includes an aqueous solution of polar alcohol substances; and the polar alcohol substances include ethanol.

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

4. The method for preparing silicon dioxide based on the gas-liquid two-phase interface method according to claim 1, characterized in that: The additive also includes an active agent; the mass volume ratio of the active agent to the alcohol aqueous solution is 0.05-1g:150mL; the active agent includes one or more of a cationic surfactant and a non-ionic surfactant; the cationic surfactant includes hexadecyltrimethylammonium bromide; the non-ionic surfactant includes a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

5. The method for preparing silicon dioxide based on the gas-liquid two-phase interface method according to claim 1, characterized in that: The step S6 further comprises: calcining the primary silicon dioxide product to obtain a silicon dioxide product; the calcination is performed under the protection of a second inert gas, the calcination temperature is 400-700° C., and the calcination time is 0.2-3 hours.

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

7. The method for preparing silicon dioxide based on the gas-liquid two-phase interface method according to claim 1, characterized in that: The gas flow rate of the first inert gas is 50-600 L / h.

8. The method for preparing silicon dioxide based on the gas-liquid two-phase interface method according to claim 1, characterized in that: The duration of the continuous aeration is 0.15-20 minutes; the first inert gas is aerated into the reaction liquid through an aeration head, and the aperture of the aeration head is 0.1-50 μm.

9. The method for preparing silicon dioxide based on the gas-liquid two-phase interface method according to claim 1, characterized in that: During the continuous aeration, the temperature of the reaction liquid is 10-50° C.; during the continuous aeration, the reaction liquid is stirred.

10. The method for preparing silicon dioxide based on the gas-liquid two-phase interface method according to claim 1, characterized in that: The aging time is 5-30 minutes, the aging temperature is 20-50° C., and the aging is carried out under stirring.

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