A high-purity silica and its preparation method

Abstract

The application provides a preparation method of high-purity silicon dioxide, comprising the following steps: S1, preparing fine silicon powder as raw material; preparing weak alkali solution with pH value of 7-8 for standby; S2, stirring and mixing the fine silicon powder in the step S1 with the alkali solution, slowly reacting the fine silicon powder with the weak alkali to produce hydrogen gas, expanding the volume of the silicon powder and forming a porous silicon powder preform; S3, drying the porous silicon powder preform obtained in the step S2, then heating and reacting the porous silicon powder preform in an oxygen atmosphere, heating to a temperature of 1000-1500 DEG C and then keeping the temperature, and after the keeping temperature, cooling the product to obtain a high-purity silicon dioxide preform; S4, crushing, screening, cleaning and drying the high-purity silicon dioxide preform obtained in the step S3 to obtain high-purity silicon dioxide. The high-purity silicon dioxide prepared by the method has high purity, and the preparation method has low cost, high efficiency, high commercial value and high popularization value.

Description

Technical Field

[0001] This invention relates to the field of silica purification and processing technology, and more specifically, to a high-purity silica and its preparation method. Background Technology

[0002] High-purity quartz sand is scarce, and its purification technology has a high barrier to entry. The raw materials for high-purity quartz sand mainly come from vein quartzite and granite pegmatite, whose quartz crystals have a coarse grain size and are easily liberated, making them ideal raw materials for processing into high-purity quartz sand. However, not all corresponding mines can produce high-purity quartz sand. In fact, only a very small number of granite pegmatites and vein quartzites meet the requirements for producing high-purity quartz sand. This leads some in the market to simply understand high-purity quartz sand as a commodity. In reality, besides the relatively scarce mineral supply, the highly complex purification technology is another major hurdle. Due to the relatively unstable supply of raw materials, few companies have spent considerable time exploring and improving purification processes. The process first requires crushing the raw materials, then separating impurities from the minerals (magnetic separation and flotation), and finally using chemical treatment methods to remove impurities from gas inclusions and crystal lattices. Currently, only Unimin, TQC, and Quartz Group can supply high-purity quartz sand in large quantities with stable quality, and this situation has persisted to this day.

[0003] Even if breakthroughs are achieved in the synthesis of high-purity silica sand, its initial application will likely be at the semiconductor level. To alleviate the tight supply of high-purity silica sand, the market has high hopes for its artificial synthesis, achieved through chemical vapor deposition of silicon tetrachloride. Since silicon tetrachloride is a byproduct of polysilicon production, its supply should theoretically not be a bottleneck. Currently, only one Japanese company can mass-produce high-purity silica sand, and its high price is a major obstacle to its widespread adoption.

[0004] Patent CN110357115A discloses a method for preparing nano-silica from crystalline silicon diamond wire cutting waste. The method involves acid washing to remove impurities from the crystalline silicon diamond wire cutting waste, followed by water washing and drying to produce impurity-removed cutting waste. This waste is then mixed evenly with silicon micropowder to form a mixed raw material. Finally, the mixed raw material is smelted at 1500–3000°C. The flue gas is then treated with a dust removal device to collect the dust, which is then air-cooled to room temperature to obtain nano-silica. However, the smelting temperature required in the reaction is as high as nearly 3000°C, which places high demands on the reaction equipment and reaction conditions, resulting in low production efficiency and high production costs. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing high-purity silica, so as to solve the problems of high requirements for reaction equipment and reaction conditions, low production efficiency and high production cost of conventional methods.

[0006] To address the above problems, this invention provides a method for preparing high-purity silica, comprising the following steps:

[0007] S1: Prepare fine silica powder as raw material; prepare an alkaline solution with a pH of 7-8 for later use;

[0008] S2: The fine silicon powder from step S1 is stirred and mixed with the alkaline solution. The fine silicon powder and the weak alkaline solution undergo a slow chemical reaction to produce hydrogen gas, which causes the silicon powder to expand in volume and form a porous silicon powder preform.

[0009] S3: The porous silicon powder preform obtained in step S2 is dried, and then the porous silicon powder preform is heated and reacted in an oxygen atmosphere. After heating to a temperature of 1000-1500℃, it is kept at the temperature. After the temperature is kept at the temperature, the product is cooled to obtain a high-purity silicon dioxide preform.

[0010] S4: The high-purity silica preform obtained in step S3 is crushed, sieved, washed and dried to obtain high-purity silica.

[0011] As a preferred embodiment, in step S1, the impurity content of the fine silicon powder is less than 1 ppm, and the particle size is 10-1000 nm.

[0012] As a preferred embodiment, in step S1, the alkaline solution is one or more of ammonia water and organic bases, and the organic bases include ethylenediamine, diethylamine and triethylamine.

[0013] As a preferred embodiment, the concentration of the alkaline solution is 0.1%-1%.

[0014] As a preferred embodiment, in step S2, the mass ratio of the fine silicon powder to the alkaline solution is (1-2):1.

[0015] As a preferred embodiment, in step S2, after the mixture is stirred and homogenized, the initial temperature of the reaction between the fine silicon powder and the weak alkaline solution is controlled at 20-40℃, and the reaction time is 1-5 hours.

[0016] As a preferred embodiment, in step S3, the bulk density of the porous silicon powder preform after drying is 1-2 g / cm³. 3 .

[0017] As a preferred embodiment, in step S3, the drying conditions are: drying at a temperature of 50-200°C for 1-5 hours.

[0018] As a preferred embodiment, in step S3, the heating rate of the heating reaction is 5-10℃ / min, and the holding time is 1-10 hours.

[0019] Another technical problem that this invention aims to solve is to provide a high-purity silicon dioxide to address the issues of low purity and unstable quality in silicon dioxide prepared by conventional methods.

[0020] To address the aforementioned problems, the present invention also provides a high-purity silica, which is prepared by the above-described preparation method, and the high-purity silica has a purity greater than or equal to 99.9% and a particle size of 10-1000 nm.

[0021] Compared to existing technologies and background technologies, the beneficial effects of this invention are as follows: This invention provides a method for preparing high-purity silica by pre-preparing a porous silica preform from high-purity ultrafine silica powder. The porous silica preform has a large internal specific surface area, allowing the silica particles to undergo a sufficient oxidation reaction with oxygen during the high-temperature oxidation stage, transforming them into silica. The prepared silica has high purity and low preparation cost, meeting the needs of semiconductor and photovoltaic applications, replacing the monopoly of imported high-purity quartz sand. Furthermore, the reaction conditions of this invention are relatively simple, requiring no cumbersome steps or harsh conditions, making it environmentally friendly. The high-purity silica prepared by this invention has high purity, relatively uniform particle size, and stable quality, possessing high commercial and promotional value. Attached Figure Description

[0022] Figure 1 This is a scanning electron microscope image of the silicon dioxide prepared according to the present invention. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention provides a method for preparing high-purity silicon dioxide, comprising the following steps:

[0025] S1: Prepare fine silica powder as raw material; prepare an alkaline solution with a pH of 7-8 for later use;

[0026] S2: The fine silicon powder in step S1 is stirred and mixed with the alkaline solution. Under static conditions, the fine silicon powder and the weak alkaline solution produce a slow chemical reaction to generate hydrogen gas and release heat, causing the volume of the silicon powder to expand and form a porous silicon powder preform.

[0027] S3: The porous silicon powder preform obtained in step S2 is dried, and then the porous silicon powder preform is heated and reacted in an oxygen atmosphere. After heating to a temperature of 1000-1500℃, it is kept at the temperature. After the temperature is kept at the temperature, the product is cooled to obtain a high-purity silicon dioxide preform.

[0028] S4: The high-purity silica preform obtained in step S3 is crushed, sieved, washed and dried to obtain high-purity silica.

[0029] As a preferred embodiment, in step S1, the impurity content of the fine silicon powder is less than 1 ppm, and the particle size is 10-1000 nm.

[0030] As a preferred embodiment, in step S1, the alkaline solution is one or more of ammonia water and organic bases, and the organic bases include ethylenediamine, diethylamine and triethylamine.

[0031] As a preferred embodiment, the concentration of the alkaline solution is 0.1%-1%.

[0032] As a preferred embodiment, in step S2, the mass ratio of the fine silica powder to the alkaline solution is 1-2:1.

[0033] As a preferred embodiment, in step S2, after stirring and mixing evenly, the initial temperature of the reaction is controlled at 20-40℃, and the reaction time is 1-5 hours.

[0034] As a preferred embodiment, in step S3, the bulk density of the porous silicon powder preform after drying is 1-2 g / cm³. 3 .

[0035] As a preferred embodiment, in step S3, the drying conditions are: drying at a temperature of 50-200°C for 1-5 hours.

[0036] As a preferred embodiment, in step S3, the heating rate of the heating reaction is 5-10℃ / min, and the holding time is 1-10 hours.

[0037] The present invention also provides a high-purity silicon dioxide, which is prepared by the above preparation method, and the purity of the high-purity silicon dioxide is greater than or equal to 99.9% and the particle size is 10-1000 nm.

[0038] The following description elaborates on the above-mentioned technical solution of the present invention with reference to specific data:

[0039] Example 1:

[0040] This embodiment provides a high-purity silicon dioxide and its preparation method:

[0041] The high-purity silica is prepared by the following method, and the purity of the high-purity silica is greater than or equal to 99.9%, and the particle size is 50-100 nm.

[0042] The preparation method includes the following steps:

[0043] S1: Prepare fine silicon powder as raw material; prepare an alkaline solution with pH 7.5 for later use; the impurity content of the fine silicon powder is less than 1 ppm and the particle size is 10-50 nm; the alkaline solution is ammonia water; the concentration of the alkaline solution is 0.5%;

[0044] S2: The fine silicon powder from step S1 is stirred and mixed with the alkaline solution, and the fine silicon powder expands in volume to form a porous silicon powder preform; the mass ratio of the fine silicon powder to the alkaline solution is 1:1; after stirring evenly, the initial temperature of the reaction is controlled at 30°C and the reaction time is 3 hours.

[0045] S3: The porous silicon powder preform obtained in step S2 is dried, and the average bulk density of the dried porous silicon powder preform is 1.5 g / cm³. 3 The drying conditions are: drying at 125°C for 1 hour;

[0046] The porous silica preform was then heated in an oxygen atmosphere at a heating rate of 7.5°C / min. The porous silica preform was then heated to 1250°C and held at that temperature for 5 hours. After the holding period, the product was allowed to cool to obtain a high-purity silica preform.

[0047] S4: The high-purity silica preform obtained in step S3 is crushed, sieved, washed and dried to obtain high-purity silica.

[0048] Example 2:

[0049] This embodiment provides a high-purity silicon dioxide and its preparation method:

[0050] The high-purity silica is prepared by the following method, and the purity of the high-purity silica is greater than or equal to 99.9%, and the particle size is 300-500 nm.

[0051] The preparation method includes the following steps:

[0052] S1: Prepare fine silicon powder as raw material; prepare an alkaline solution with pH 7.5 for later use; the impurity content of the fine silicon powder is less than 1 ppm and the particle size is 100-300 nm; the alkaline solution is ethylenediamine; the concentration of the alkaline solution is 0.3%;

[0053] S2: The fine silicon powder from step S1 is stirred and mixed with the alkaline solution. After the fine silicon powder expands in volume, it forms a porous silicon powder preform. The mass ratio of the fine silicon powder to the alkaline solution is 1:1. After stirring and mixing, the initial reaction temperature is controlled at 20°C and the reaction time is 1 hour.

[0054] S3: The porous silicon powder preform obtained in step S2 is dried, and the bulk density of the dried porous silicon powder preform is 1.4 g / cm³. 3 The drying conditions are as follows: drying at 50°C for 3 hours;

[0055] The porous silica preform was then heated in an oxygen atmosphere at a heating rate of 5°C / min. The porous silica preform was then heated to 1000°C and held at that temperature for 1 hour. After the holding period, the product was allowed to cool to obtain a high-purity silica preform.

[0056] S4: The high-purity silica preform obtained in step S3 is crushed, sieved, washed and dried to obtain high-purity silica.

[0057] Example 3:

[0058] This embodiment provides a high-purity silicon dioxide and its preparation method:

[0059] The high-purity silica is prepared by the following method, and the purity of the high-purity silica is greater than or equal to 99.9%, and the particle size is 500-800 nm.

[0060] The preparation method includes the following steps:

[0061] S1: Prepare fine silica powder as raw material; prepare an alkaline solution with pH 7.8 for later use; the impurity content of the fine silica powder is less than 1 ppm and the particle size is 300-600 nm; the alkaline solution is ammonia water; the concentration of the alkaline solution is 1%;

[0062] S2: The fine silicon powder from step S1 is stirred and mixed with the alkaline solution. After the volume of the fine silicon powder expands, a porous silicon powder preform is formed. The mass ratio of the fine silicon powder to the alkaline solution is 1:1. After stirring and mixing, the initial temperature of the reaction is controlled at 40°C, and the reaction time is 5 hours.

[0063] S3: The porous silicon powder preform obtained in step S2 is dried, and the bulk density of the dried porous silicon powder preform is 1.6 g / cm³. 3 The drying conditions are: drying at 200°C for 1 hour;

[0064] The porous silica preform was then heated in an oxygen atmosphere at a heating rate of 10°C / min. The porous silica preform was then heated to 1500°C and held at that temperature for 10 hours. After the holding period, the product was allowed to cool to obtain a high-purity silica preform.

[0065] S4: The high-purity silica preform obtained in step S3 is crushed, sieved, washed and dried to obtain high-purity silica.

[0066] Figure 1 This is a scanning electron microscope image of the silicon dioxide prepared in the above embodiments of the present invention.

[0067] Comparative Example 1:

[0068] A comparative example provides silicon dioxide and its preparation method:

[0069] The silica is prepared by the following method, and the high-purity silica has a purity of less than 99.9% and a particle size of 500-1100 nm.

[0070] The preparation method includes the following steps:

[0071] S1: Prepare fine silica powder as raw material; prepare an alkaline solution with pH 8.5 for later use; the impurity content of the fine silica powder is less than 1 ppm and the particle size is 500-800 nm; the alkaline solution is ammonia water; the concentration of the alkaline solution is 1%;

[0072] S2: The fine silicon powder from step S1 is stirred and mixed with the alkaline solution, and the fine silicon powder expands in volume to form a porous silicon powder preform; the mass ratio of the fine silicon powder to the alkaline solution is 1:1; after stirring and mixing, the initial temperature of the reaction is controlled at 40°C, and the reaction time is 5 hours.

[0073] S3: The porous silicon powder preform obtained in step S2 is dried, and the bulk density of the dried porous silicon powder preform is 0.8 g / cm³. 3 The drying conditions are: drying at 200°C for 1 hour;

[0074] The porous silicon powder preform was then heated and reacted in an oxygen atmosphere at a heating rate of 10°C / min. The porous silicon powder preform was then heated to 1300°C and held at that temperature for 10 hours. After the holding period, the product was allowed to cool to obtain a silicon oxide preform.

[0075] S4: The silica preform obtained in step S3 is crushed, sieved, washed and dried to obtain a powder containing silica and silicon particles.

[0076] Comparative Example 2:

[0077] A comparative example provides silicon dioxide and its preparation method:

[0078] The silica is prepared by the following method, and the high-purity silica has a purity of less than 99.9% and a particle size of 200-800 nm.

[0079] The preparation method includes the following steps:

[0080] S1: Prepare fine silica powder as raw material; prepare an alkaline solution with pH 7.5 for later use; the impurity content of the fine silica powder is less than 1 ppm and the particle size is 300-500 nm; the alkaline solution is ammonia water; the concentration of the alkaline solution is 1%;

[0081] S2: The fine silicon powder from step S1 is stirred and mixed with the alkaline solution, and the fine silicon powder expands in volume to form a porous silicon powder preform; the mass ratio of the fine silicon powder to the alkaline solution is 1:1; after stirring and mixing, the initial temperature of the reaction is controlled at 40°C, and the reaction time is 5 hours.

[0082] S3: The porous silicon powder preform obtained in step S2 is dried, and the bulk density of the dried porous silicon powder preform is 1.8 g / cm³. 3 The drying conditions are: drying at 200°C for 1 hour;

[0083] The porous silicon powder preform was then heated and reacted in an oxygen atmosphere at a heating rate of 10°C / min. The porous silicon powder preform was then heated to 1800°C and held at that temperature for 10 hours. After the holding period, the product was allowed to cool to obtain a silicon oxide preform.

[0084] S4: The silica preform obtained in step S3 is crushed, sieved, washed and dried to obtain a powder containing silica and silica.

[0085] Comparative Example 3:

[0086] A comparative example provides silicon dioxide and its preparation method:

[0087] The silica is prepared by the following method, and the high-purity silica has a purity of less than 99.9% and a particle size of 300-1200 nm.

[0088] The preparation method includes the following steps:

[0089] S1: Prepare fine silica powder as raw material; prepare an alkaline solution with pH 7.5 for later use; the impurity content of the fine silica powder is less than 1 ppm and the particle size is 300-500 nm; the alkaline solution is ammonia water; the concentration of the alkaline solution is 1%;

[0090] S2: The fine silicon powder from step S1 is stirred and mixed with the alkaline solution, and the fine silicon powder expands in volume to form a porous silicon powder preform; the mass ratio of the fine silicon powder to the alkaline solution is 1:5; after stirring and mixing, the initial temperature of the reaction is controlled at 40°C, and the reaction time is 5 hours.

[0091] S3: The porous silicon powder preform obtained in step S2 is dried, and the bulk density of the dried porous silicon powder preform is 3.1 g / cm³. 3 The drying conditions are: drying at 200°C for 1 hour;

[0092] The porous silicon powder preform was then heated and reacted in an oxygen atmosphere at a heating rate of 10°C / min. The porous silicon powder preform was then heated to 1500°C and held at that temperature for 10 hours. After the holding period, the product was allowed to cool to obtain a silicon oxide preform.

[0093] S4: The silica preform obtained in step S3 is crushed, sieved, washed and dried to obtain a powder containing silica and silicon particles.

[0094] Table 1 shows the purity and particle size test results of the silica prepared in the examples and comparative examples:

[0095] Table 1: Purity and particle size test results of silica prepared in the examples and comparative examples

[0096] sample Particle size (nm) purity(%) Example 1 50-100 99.95 Example 2 300-500 99.93 Example 3 500-800 99.92 Comparative Example 1 500-1100 96.2 Comparative Example 2 200-800 95.3 Comparative Example 3 300-1200 93.7

[0097] Through further comparison of the examples and comparative examples, the silica prepared under the conditions used in Example 1 has the most uniform particle size. The silica prepared in Examples 1-3 has a higher purity than that of the comparative examples under conditions not controlled by this invention. This further proves that the silica obtained within the preparation method of this invention has higher purity and more controllable and uniform particle size. It also proves that this invention solves the problems of high requirements for reaction equipment and reaction conditions, low production efficiency and high production cost of conventional methods, and provides a method for preparing silica with high purity and low cost.

[0098] While the disclosure is as stated above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and all such changes and modifications will fall within the protection scope of this invention.

Claims

1. A method for producing high purity silicon dioxide, characterized by: The method comprises the following steps: S1: preparing fine silicon powder as raw material; preparing weak alkali solution with pH of 7-8 for standby; S2: mixing the fine silicon powder in step S1 with the weak alkali solution by stirring, and after the fine silicon powder reacts with the weak alkali solution, the fine silicon powder is expanded in volume and forms a porous silicon powder preform; S3: drying the porous silicon powder preform obtained in step S2, and then heating and reacting the porous silicon powder preform in an oxygen atmosphere, heating to a temperature of 1000-1500℃ and then keeping the temperature, and after keeping the temperature, cooling the product to obtain a high-purity silicon dioxide preform; S4: obtaining high-purity silicon dioxide by crushing, screening, washing and drying the high-purity silicon dioxide preform obtained in step S3. In step S1, the particle size of the fine silicon powder is 10-600 nm. In step S2, the mass ratio of the fine silicon powder to the alkali solution is (1-2):

1.

2. The method of producing high purity silicon dioxide according to claim 1, characterized by: In step S1, the impurity content of the fine silicon powder is less than 1 ppm.

3. The method of producing high purity silicon dioxide according to claim 1, characterized by: In step S1, the alkali solution is one or both of ammonia and organic base, and the organic base includes ethylenediamine, diethylamine and triethylamine.

4. The method of producing high purity silicon dioxide according to claim 3, characterized by: The concentration of the alkali solution is 0.1%-1%.

5. The method of claim 1, wherein: In step S2, the reaction conditions of the fine silicon powder with the weak alkali solution are as follows: the initial temperature of the reaction is controlled to be 20-40℃, and the reaction time is 1-5 hours.

6. The method of producing high purity silicon dioxide according to claim 1, characterized by: In step S3, the bulk density of the porous silicon powder preform after the drying treatment is 1-2 g / cm3.

7. The method of claim 1, wherein: In step S3, the drying treatment is performed at a temperature of 50-200℃ for 1-5 hours.

8. The method of claim 1, wherein: In step S3, the heating rate of the heating reaction is 5-10℃ / min, and the holding time is 1-10 hours.

9. High purity silicon dioxide characterized in that: The high-purity silicon dioxide is prepared by the method of any one of claims 1-8, and the purity of the high-purity silicon dioxide is greater than or equal to 99.9%, and the particle size is 10-1000 nm.

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