Method for synthesizing high-purity large-particle quartz sand for photovoltaics

Abstract

The application discloses a synthesis method of high-purity large-particle quartz sand for photovoltaic, which comprises the following steps: using three kinds of organosilanes as silicon sources, using two kinds of organic alkalis to provide an alkaline environment, hydrolyzing under mild conditions, and combining with subsequent gravity sedimentation, freeze drying and step secondary calcination processes to prepare high-purity quartz sand products. The method has the advantages of simple operation, low cost, environmental friendliness and suitability for industrialization. Through the hydrolysis of the organosilanes, the method can reduce the introduction of metal impurities to a certain extent and improve the purity of the quartz sand. Through the step secondary calcination temperature, the content of the high-purity quartz sand inclusions is reduced, and the content of impurity elements such as Al, Li, Na and K is lower. The high-purity quartz sand for photovoltaic has regular morphology and a particle size of 160-230 mu m.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-purity quartz sand preparation, and particularly relates to a synthesis method of high-purity large-particle quartz sand for photovoltaics. BACKGROUND

[0002] China is the world's largest importer of high-purity quartz sand, with an import volume accounting for about 70% of the world's total imports. There are technical barriers in the production of high-purity quartz sand in China. Due to the important position of high-purity quartz sand in key emerging industries, it will directly affect the development of China's semiconductor chips, photovoltaics and silicon industries, and other key emerging industries. Therefore, it is urgent to develop the preparation technology of high-purity quartz sand.

[0003] High-purity quartz sand products mainly include quartz crucibles, quartz tubes, quartz boats, quartz ingots, quartz fibers and quartz bell jars. With the recovery of the global economy and the acceleration of industrialization, especially in the construction, new energy, semiconductor, optical fiber, photovoltaic, aerospace and weapon equipment industries, the demand for quartz sand continues to grow. The technical research of artificial synthesis of quartz sand will promote the industrial upgrading of the quartz sand industry and to some extent solve the problem of shortage of quartz sand. Artificial synthesis of quartz sand is necessary for resource stability, solving the "neck" problem and technological development and innovation. In the field of photovoltaics, in 2021, China's new photovoltaic power generation grid-connected installed capacity was about 53 million kilowatts, ranking first in the world for nine consecutive years. It is estimated that by 2027, market demand will grow to 39,400 tons, with a compound growth rate of 10.2% from 2022 to 2025. With the intensification of market competition and the increasing strictness of environmental protection policies, the quartz sand industry will accelerate the optimization and upgrading of industrial structure. The preparation of high-purity quartz sand as one of the important development directions of the industry will attract more attention and investment.

[0004] The national standard GB / T32649-2016 for high-purity quartz sand used in photovoltaics specifies that the particle size should be within the range of 70–350 μm, with a cumulative mass fraction of ≥90% within this range, and a cumulative mass fraction of less than 1% for particles smaller than 100 μm or larger than 300 μm. The strict requirements for the particle size distribution of quartz sand in the photovoltaic field stem from its impact on the quality and efficiency of photovoltaic products. As a crucial raw material in photovoltaic modules, the particle size distribution of quartz sand directly affects key properties of photovoltaic materials such as light transmittance, electrical conductivity, and thermal conductivity. For example, Chinese patent CN115974086A discloses a method for preparing high-packed quartz sand with a particle size distribution of 75–150 μm using a single organosilane as the silicon source; however, this method yields relatively small quartz sand particles. Smaller particle sizes may lead to excessively small gaps between the quartz sand particles, reducing the light scattering effect in the material. This results in some light not being effectively absorbed, increasing light reflection and transmission losses, thus affecting photovoltaic efficiency. In addition, Chinese patent CN116375040A discloses a method for preparing quartz sand particles with a particle size of 75–250 μm via a low-temperature two-step hydrolysis method. However, the resulting quartz sand has an excessively wide particle size distribution, which can lead to inconsistent optical paths within the photovoltaic material, affecting light absorption and conversion efficiency. Furthermore, it may also cause uneven shrinkage and expansion of the photovoltaic material during preparation, thus affecting the dimensional stability and mechanical properties of the product. Summary of the Invention

[0005] The purpose of this invention is to provide a method for synthesizing high-purity, large-particle photovoltaic quartz sand.

[0006] To achieve the above objectives, the present invention provides a method for synthesizing high-purity, large-particle quartz sand, comprising the following steps:

[0007] Step 1: Mix the non-polar solvent and high-purity water evenly, add the organosilane and stir continuously. After mixing evenly, slowly add the organic base and stir evenly to obtain a transparent solution containing organosilane.

[0008] Step 2: Hydrolyze the transparent solution containing organosilanes from Step 1 at 20–40°C for 1–5 h to obtain a silica dispersion;

[0009] Step 3: Centrifuge and wash the silica dispersion from Step 2. Freeze-dry the resulting precipitate at -5 to -10°C for 10 to 15 hours, thaw it, and then freeze-dry it at -15 to -20°C for 5 to 8 hours. After thawing, large-particle-size SiO2 powder is obtained.

[0010] Step 4: The large particle size SiO2 powder of step 3 is placed in a heating furnace for primary calcination and secondary calcination, the primary calcination is calcined at 350-500℃ for 2-5h, the secondary calcination is calcined at 1100-1600℃ for 4-6h, to obtain high-purity quartz sand with particle size of 160-230μm.

[0011] In the above step 1, the non-polar solvent is selected from any two of ethanol, methanol, isopropanol; preferably the non-polar solvent is selected from any two of ethanol, methanol, isopropanol in a volume ratio of 1:1-3 mixture.

[0012] In the above step 1, the organosilane is selected from any three of tetraethyl orthosilicate, tetramethyl orthosilicate, methyltrimethoxysilane, methylsilane; preferably the organosilane is selected from any three of tetraethyl orthosilicate, tetramethyl orthosilicate, methyltrimethoxysilane, methylsilane in a volume ratio of 1:1-3:1-3 mixture.

[0013] In the above step 1, the organic base is selected from any two of ammonia, triethanolamine, N-methyl pyrrolidone; preferably the organic base is selected from any two of ammonia, triethanolamine, N-methyl pyrrolidone in a volume ratio of 1:1-2 mixture.

[0014] In the above step 1, further preferably the volume ratio of high-purity water, non-polar solvent, organosilane, organic base is 5-15:20-40:1:1-3.

[0015] In the above step 3, the centrifugal washing is first centrifuged at 5000-10000r / min for 5-10min with distilled water, and then centrifuged at 5000-7000r / min for 8-15min with distilled water.

[0016] In the above step 4, preferably the heating rate of the primary calcination is 5-10℃ / min, and the heating rate of the secondary calcination is 10-20℃ / min.

[0017] The beneficial effects of the present application are as follows:

[0018] 1、The present application uses three kinds of organosilanes as a silicon source, which can introduce various functional groups on the surface of silicon dioxide. These functional groups can endow silicon dioxide with special properties such as hydrophilicity, hydrophobicity, catalytic activity, and adsorption performance. By controlling the reaction conditions (such as temperature, time, stirring speed, etc.), the particle size distribution of silicon dioxide can be adjusted. Compared with silicon dioxide prepared by a single organosilane, the complex system is more likely to obtain particles with uniform particle size and narrow distribution range. In the process of preparing silicon dioxide by complexing multiple organosilanes, the emission of harmful substances can be reduced. At the same time, by optimizing the reaction conditions and subsequent treatment process, the waste can also be reduced, recycled and harmlessly treated.

[0019] 2、The hydrolyzed silica dispersion liquid of the present application is used to prepare high-purity quartz sand products through gravity sedimentation, freeze-drying, and high-temperature calcination processes. By using a two-stage calcination temperature, the content of high-purity quartz sand inclusions is reduced, and the content of impurity elements such as Al, Li, Na, and K is lower, obtaining a high-purity quartz sand for photovoltaics with regular morphology and a particle size of 160-230 μm. The particle size distribution of the quartz sand directly affects the key properties of photovoltaic materials such as light transmittance, electrical conductivity, and thermal conductivity. The quartz sand in this particle size range exhibits good filling and flow properties in photovoltaic applications, and can also ensure uniform distribution during the preparation process, reducing the adverse effects caused by excessively large or small particle sizes. In addition, the regularity of the morphology of the quartz sand also has a significant impact on its photovoltaic performance. Quartz sand with regular morphology generally has higher light transmittance, thereby improving the photoelectric conversion efficiency, i.e., converting more solar energy into electrical energy. In addition, quartz sand with regular morphology is easier to control in size and shape during processing, improving processing efficiency and yield, thereby reducing production costs. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a scanning electron microscope image of the SiO2 powder prepared in Comparative Example 1.

[0021] Figure 2 is a scanning electron microscope image of the SiO2 powder prepared in Example 1.

[0022] Figure 3 is a scanning electron microscope image of the quartz sand prepared in Example 1.

[0023] Figure 4 is a scanning electron microscope image of the quartz sand prepared in Example 2. DETAILED DESCRIPTION

[0024] The present application will be described in detail below with reference to the accompanying drawings and examples, but the scope of protection of the present application is not limited to these examples.

[0025] Comparative Example 1

[0026] Step 1: 120 mL of ethanol and 40 mL of high-purity water were uniformly mixed, then 4 mL of tetraethyl orthosilicate was added while stirring, and after mixing evenly, 6 mL of ammonia water was slowly added and stirred evenly to obtain a transparent solution containing tetraethyl orthosilicate.

[0027] Step 2: The transparent solution containing tetraethyl orthosilicate in Step 1 was hydrolyzed at 30°C for 4 h to obtain a silica dispersion liquid.

[0028] Step 3: The silica dispersion solution of Step 2 was centrifuged at 5000 r / min for 10 min with distilled water, and then centrifuged at 6000 r / min for 15 min with distilled water. The obtained precipitate was freeze-dried at -10°C for 10 h, thawed, and then freeze-dried at -20°C for 5 h. After thawing, the SiO2 powder was obtained. As shown in FIG. 1, the size of the prepared SiO2 was about 300 nm. Figure 1

[0029] Step 4: The SiO2 powder of Step 3 was placed in a heating furnace for primary calcination and secondary calcination. The primary calcination was calcined at 400°C for 3 h, and the heating rate of the primary calcination was 10°C / min. The secondary calcination was calcined at 1300°C for 5 h, and the heating rate of the secondary calcination was 20°C / min. The quartz sand was obtained.

[0030] Example 1

[0031] Step 1: 80 mL of ethanol, 40 mL of methanol, and 40 mL of high-purity water were uniformly mixed, and then 1 mL of tetraethyl orthosilicate, 1 mL of tetramethyl orthosilicate, and 2 mL of methyltrimethoxysilane were added while stirring. After uniform mixing, 3 mL of ammonia water and 3 mL of triethanolamine were slowly added and stirred uniformly to obtain a transparent solution containing organosilane.

[0032] Step 2: The transparent solution containing organosilane in Step 1 was hydrolyzed at 30°C for 4 h to obtain a silica dispersion solution.

[0033] Step 3: The silica dispersion solution of Step 2 was centrifuged at 5000 r / min for 10 min with distilled water, and then centrifuged at 6000 r / min for 15 min with distilled water. The obtained precipitate was freeze-dried at -10°C for 10 h, thawed, and then freeze-dried at -20°C for 5 h. After thawing, the large-particle-size SiO2 powder was obtained. As shown in FIG. 2, the size of the prepared SiO2 was about 5 μm. Figure 2

[0034] Step 4: The large-particle-size SiO2 powder of Step 3 was placed in a heating furnace for primary calcination and secondary calcination. The primary calcination was calcined at 400°C for 3 h, and the heating rate of the primary calcination was 10°C / min. The secondary calcination was calcined at 1300°C for 5 h, and the heating rate of the secondary calcination was 20°C / min. The high-purity large-particle quartz sand with a particle size of 160-230 μm (see FIG. 3) was obtained, and the total amount of metal elements was less than 100 ppb (see Table 1). Figure 3

[0035] ​​​According to the embodiment 1 and the comparative example 1, it is found that, compared with using single organosilane, organic base and non-polar solvent, the growth of SiO2 crystal nucleus is facilitated by mixing multiple organosilanes, non-polar solvents and organic bases in a certain proportion in the technical solution of the present application, and quartz sand particles with regular morphology and large particle size can be obtained.

[0036] Table 1 Metal element detection results of the quartz sand product prepared in the embodiment 1

[0037] Element B A1 Gr Cu K Li Na Mn Ti Mg Ca Fe Ni Content (ppb) 9 17 0 0 5 0 18 0 0 0 25 8 0

[0038] Embodiment 2

[0039] Step 1: 30 mL of ethanol, 90 mL of methanol and 40 mL of high-purity water were uniformly mixed, then 1.5 mL of tetraethyl orthosilicate, 1.5 mL of tetramethyl orthosilicate and 1 mL of methyltrimethoxysilane were added while continuously stirring, and after uniform mixing, 2.5 mL of ammonia water and 3.5 mL of triethanolamine were slowly added and uniformly stirred to obtain a transparent solution containing organosilanes.

[0040] Step 2: After the transparent solution containing organosilanes in step 1 was hydrolyzed at 30°C for 4 h, a silica dispersion liquid was obtained.

[0041] Step 3: The silica dispersion liquid in step 2 was first centrifuged at 5000 r / min for 10 min using distilled water, and then centrifuged at 6000 r / min for 15 min using distilled water, and the obtained precipitate was freeze-dried at -10°C for 10 h, then thawed, and then freeze-dried at -20°C for 5 h, and after thawing, a large-particle-size SiO2 powder was obtained.

[0042] Step 4: The large-particle-size SiO2 powder in step 3 was placed in a heating furnace for primary calcination and secondary calcination, the primary calcination was calcined at 400°C for 3 h, and the heating rate of the primary calcination was 10°C / min; the secondary calcination was calcined at 1300°C for 5 h, and the heating rate of the secondary calcination was 20°C / min, to obtain high-purity large-particle quartz sand with a particle size of 160-230 μm (see Figure 4 ).

[0043] Embodiment 3

[0044] Step 1: 60 mL of ethanol, 60 mL of isopropyl alcohol and 40 mL of high-purity water were uniformly mixed, then 1.5 mL of tetraethyl orthosilicate, 2 mL of tetramethyl orthosilicate and 1.5 mL of methylsilane were added while continuously stirring, and after uniform mixing, 3 mL of N-methylpyrrolidone and 3 mL of triethanolamine were slowly added and uniformly stirred to obtain a transparent solution containing organosilanes.

[0045] Step 2: After the transparent solution containing organosilanes in step 1 was hydrolyzed at 20°C for 5 h, a silica dispersion liquid was obtained.

[0046] Step 3: The silica dispersion liquid of step 2 was centrifuged at 6000 r / min for 8 min with distilled water, then centrifuged at 5000 r / min for 10 min with distilled water, the obtained precipitate was freeze-dried at -5℃ for 15 h, then thawed, and freeze-dried at -15℃ for 8 h, and then thawed to obtain a large-particle-size SiO2 powder.

[0047] Step 4: The large-particle-size SiO2 powder of step 3 was placed in a heating furnace for primary calcination and secondary calcination, the primary calcination was calcined at 450℃ for 2 h, the heating rate of the primary calcination was 8℃ / min; the secondary calcination was calcined at 1400℃ for 5 h, the heating rate of the secondary calcination was 15℃ / min, and a high-purity large-particle quartz sand with a particle size of 160-230 μm was obtained.

Claims

1. A method for synthesizing high-purity, large-particle photovoltaic quartz sand, characterized in that, The method consists of the following steps: Step 1: Mix the non-polar solvent and high-purity water evenly, add the organosilane and stir continuously. After mixing evenly, slowly add the organic base and stir evenly to obtain a transparent solution containing organosilane. The nonpolar solvent is selected from any two of ethanol, methanol, and isopropanol in a volume ratio of 1:1 to 3; The organosilane is selected from any three of tetraethyl orthosilicate, tetramethyl orthosilicate, methyltrimethoxysilane, and methylsilane in a volume ratio of 1:1 to 3:1 to 3; The organic base is selected from any two of ammonia, triethanolamine, and N-methylpyrrolidone in a volume ratio of 1:1 to 2. Step 2: Hydrolyze the transparent solution containing organosilanes from Step 1 at 20–40°C for 1–5 h to obtain a silica dispersion; Step 3: Centrifuge and wash the silica dispersion from Step 2. Freeze-dry the resulting precipitate at -5 to -10°C for 10 to 15 hours, thaw it, and then freeze-dry it at -15 to -20°C for 5 to 8 hours. After thawing, large-particle-size SiO2 powder is obtained. Step 4: Place the large-particle-size SiO2 powder from Step 3 into a heating furnace for primary and secondary calcination. The primary calcination is carried out at 350–500℃ for 2–5 hours, and the secondary calcination is carried out at 1100–1600℃ for 4–6 hours to obtain high-purity quartz sand with a particle size of 160–230 μm.

2. The method for synthesizing high-purity, large-particle photovoltaic quartz sand according to claim 1, characterized in that, In step 1, the volume ratio of the high-purity water to the non-polar solvent, organosilane, and organic base is 5-15:20-40:1:1-3.

3. The method for synthesizing high-purity, large-particle photovoltaic quartz sand according to claim 1, characterized in that, In step 3, the centrifugal washing involves first centrifuging with distilled water at 5000-10000 r / min for 5-10 min, and then centrifuging with distilled water at 5000-7000 r / min for 8-15 min.

4. The method for synthesizing high-purity, large-particle photovoltaic quartz sand according to claim 1, characterized in that, In step 4, the heating rate of the initial calcination is 5-10℃ / min.

5. The method for synthesizing high-purity, large-particle photovoltaic quartz sand according to claim 1, characterized in that, In step 4, the heating rate of the secondary calcination is 10-20℃ / min.

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