A method for synthesizing high softening point silicon oxide
By adding titanium and zirconium compounds and subjecting the process to high-temperature calcination during the synthesis of silica, the problems of poor density and low softening point of synthesized silica were solved, thus achieving the preparation of silica with a high softening point and improving the performance of quartz crucibles.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA CATALYST HLDG CO LTD
- Filing Date
- 2024-05-11
- Publication Date
- 2026-08-04
AI Technical Summary
Synthetic silica has poor density and a low softening point, making it difficult to meet the performance requirements of quartz crucibles in the photovoltaic field.
Titanium compounds and/or zirconium compounds are added during the synthesis of silicon dioxide. After drying and pulverizing, the silicon dioxide is calcined at high temperature to form silicon dioxide with a high softening point.
It significantly improves the density and softening point of synthetic quartz sand, enhancing its application potential in the photovoltaic field.
Abstract
Description
Technical Field
[0001] This invention relates to the field of silicon oxide synthesis technology, and in particular to a method for synthesizing silicon oxide with a high softening point. Background Technology
[0002] Semiconductors and photovoltaics account for 36% and 34% of global high-purity silica sand sales, respectively, making them the two largest demanders. In the semiconductor field, high-purity silica materials are mainly used in the production of semiconductor silicon wafers, typically requiring silica sand purity of 6N or higher. In the photovoltaic field, silica sand is mainly used to make quartz crucibles for pulling single-crystal silicon rods. To ensure the performance of the single-crystal silicon rods and the service life of the quartz crucibles, strict requirements are placed on the purity, impurities, hydroxyl groups, gas-liquid inclusions, particle size, and uniformity of the silica sand.
[0003] In recent years, due to the rapid development of photovoltaic technology and the scarcity of high-quality quartz deposits, high-purity quartz sand has been in severe shortage. With increasing demand and rising prices, the production technology of quartz sand for photovoltaic applications has become a research hotspot for major manufacturers. Mitsubishi Chemical of Japan has obtained synthetic silica with a purity of 6N or higher through the sol-gel process and applied it to the semiconductor field. Inspired by Mitsubishi Chemical, researchers have attempted to use synthetic quartz sand to make quartz crucibles. By further improving the purity of silica and reducing the content of hydroxyl groups and gas-liquid inclusions, they aim to improve the performance of synthetic silica and apply it to the manufacture of quartz crucibles.
[0004] After conducting long-term research on synthetic silica, the applicant discovered that synthetic silica differs significantly from naturally formed quartz sand in its internal structure. Synthetic silica has an amorphous internal structure, resulting in substantial differences in strength, density, and softening point compared to natural quartz sand. Furthermore, higher purity does not necessarily improve the performance of quartz crucibles; the quartz sand used for crucible production requires a certain impurity content to ensure sufficient density and softening point. Summary of the Invention
[0005] To improve the problems of poor density and low softening point of synthesized silica, this invention provides a method for synthesizing silica with a high softening point.
[0006] The technical solution of this invention: A method for synthesizing high softening point silicon dioxide, comprising the following steps:
[0007] In the process of preparing silica sol by hydrolysis of tetraalkoxysilane or by hydrolysis of water glass, titanium compounds and / or zirconium compounds are added. The resulting silica sol is gelled, dried, pulverized, and calcined at 900~1600 °C to obtain the silicon oxide.
[0008] The amount of titanium compound and / or zirconium compound added is 0.0001 to 0.001% (mass fraction) based on the amount of silicon dioxide.
[0009] The titanium compound is selected from at least one of TiBr4, TiCl4, Ti(SO4)2, and alkyl titanate.
[0010] The zirconium compound is selected from at least one of ZrCl4, ZrOCl2, Zr(OH)4, ZrBr4, and Zr(SO4)2.
[0011] Some specific methods for synthesizing high softening point silicon dioxide involve calcination temperatures of 1400~1600 ℃.
[0012] Some specific methods for synthesizing high softening point silicon dioxide involve calcination temperatures of 1100~1300 ℃.
[0013] Some specific methods for synthesizing high softening point silica involve adding titanium compounds and / or zirconium compounds in amounts of 0.0003 to 0.001%.
[0014] Some specific methods for synthesizing high softening point silica, wherein the alkyl titanate is selected from tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, and tetrabutyl titanate.
[0015] Some specific methods for synthesizing high softening point silicon oxide, wherein the tetraalkoxysilane is tetramethoxysilane or tetraethoxysilane.
[0016] Some specific methods for synthesizing high softening point silica, wherein the silica content in the water glass is 20%~30% by mass.
[0017] The beneficial effects of the present invention are as follows: The present invention provides a method for synthesizing high softening point silica. This method significantly improves the density and softening point of the synthesized silica by adding a small amount of titanium compound and / or zirconium compound during the synthesis of silica sand. In particular, silica sand with the addition of titanium compound and zirconium compound at the same time has a better softening point and density. Detailed Implementation
[0018] In a specific embodiment, the amount of titanium compound and zirconium compound added is calculated based on the mass of silicon dioxide. For example, 0.0001% TiBr4 is added to 5 kg of water glass with a mass concentration of 30%, and the amount of TiBr4 added is 0.15 g. Example 1
[0019] 0.0001% (based on the mass of silica) of TiBr4 was added to 30% water glass. After stirring, 2 mol / L hydrochloric acid solution was added dropwise to maintain the pH value of the system below 2. The mixture was stirred at room temperature for 1.5 h. The reaction mixture was aged at 65 °C for 24 h to obtain silica gel. After washing the silica gel with water, it was dried at 165 °C for 15 h and then crushed into particles with a diameter of 40-80 mesh. The particles were then calcined at 1200 °C for 6 h to obtain silica. Example 2
[0020] The preparation method is the same as in Example 1, except that the amount of TiBr4 added is 0.0003%. Example 3
[0021] The preparation method is the same as in Example 1, except that the amount of TiBr4 added is 0.0005%. Example 4
[0022] The preparation method is the same as in Example 1, except that the amount of TiBr4 added is 0.001%. Example 5
[0023] The preparation method is the same as in Example 3, and the calcination temperature is 1500℃. Example 6
[0024] 0.0001% (based on the mass of silica) of ZrCl4 was added to 30% water glass. After stirring evenly, 2 mol / L hydrochloric acid solution was added dropwise to maintain the pH value of the system below 2. The mixture was stirred at room temperature for 1.5 h. The reaction mixture was aged at 65 ℃ for 24 h to obtain silica gel. After washing the silica gel with water, it was dried at 165 ℃ for 15 h and then crushed into particles with a diameter of 40~80 mesh. The particles were then calcined at 1200 ℃ for 6 h to obtain silica. Example 7
[0025] The preparation method is the same as in Example 6, except that the amount of ZrCl4 added is 0.0005%. Example 8
[0026] The preparation method is the same as in Example 6, and the calcination temperature is 1400℃. Example 9
[0027] Add 0.0003% (based on the mass of silica) ZrCl4 and 0.0003% TiBr4 to 30% water glass. After stirring evenly, add 2 mol / L hydrochloric acid solution dropwise, keeping the pH of the system below 2. Stir at room temperature for 1.5 h. Age the reaction mixture at 65 ℃ for 24 h to obtain silica gel. After washing the silica gel with water, dry it at 165 ℃ for 15 h and crush it into particles with a diameter of 40~80 mesh. Calcine it at 1200 ℃ for 6 h to obtain silica. Example 10
[0028] Add 5g of 2mol / L hydrochloric acid to 2kg of water, then simultaneously add 0.0005% tetrabutyl titanate and 500g of 99.999% pure tetramethoxysilane. React at room temperature for 6 hours. After distilling to remove the organic alcohol and 30% water produced by hydrolysis, age at 60℃ for 24 hours to obtain a gel. Wash with water, dry at 160℃ for 15 hours, crush to 40-80 mesh, and calcine at 1200℃ for 6 hours to obtain the silica product. Example 11
[0029] The preparation method is the same as in Example 9, and the calcination temperature is 1600℃.
[0030] Comparative Example 1
[0031] Add 2 mol / L hydrochloric acid solution dropwise to 30% water glass, keep the pH of the system less than 2, stir at room temperature for 1.5 h, age the reaction mixture at 65℃ for 24 h to obtain silica gel, wash the silica gel with water, dry it at 165 ℃ for 15 h, crush it into particles with a diameter of 40~80 mesh, and calcine it at 1200℃ for 6 h to obtain silica.
[0032] Comparative Example 2
[0033] Add 5g of 2 mol / L hydrochloric acid to 2 kg of water, then add 500g of 99.999% pure tetramethoxysilane dropwise. React at room temperature for 6 h. After distilling to remove the organic alcohol and 30% water produced by hydrolysis, age at 60℃ for 24 h to obtain a gel. Wash with water, dry at 160℃ for 15 h, crush to 40~80 mesh, and calcine at 1200℃ for 6 h to obtain the silica product.
[0034] Test case
[0035] The pore size, density, and softening point of the silica solid powders obtained in Examples 1-10 and Comparative Examples 1-2 were determined. The pore size distribution of the samples from the examples and comparative examples was analyzed using an ASAP 2460 surface area and pore size analyzer manufactured by Micromeritics. Sample density was determined using the tap density method. The softening point was determined by placing 2g of sample in a quartz crucible, heating the crucible, and recording the temperature at which the sample began to melt. Each sample was measured three times, and the average value was taken. Specific data are shown in Table 1.
[0036] Table 1 Performance parameters of silicon oxide in the examples and comparative examples
[0037] sample Pore size / nm Density / g / cm³ Softening point / ℃ Example 1 1~2 2.20 1680 Example 2 1~2 2.23 1683 Example 3 1~2 2.25 1692 Example 4 1~2 2.28 1705 Example 5 1~2 2.35 1710 Example 6 1~2 2.21 1708 Example 7 1~2 2.26 1712 Example 8 1~2 2.37 1710 Example 9 1~2 2.30 1705 Example 10 1~2 2.24 1702 Comparative Example 1 1~5 2.20 1470 Comparative Example 2 1~5 2.20 1480 .
[0038] As can be seen from the data in Table 1, the addition of small amounts of Ti and Zr compounds can significantly improve the density and softening point of silica. The method provided by this invention offers further possibilities for the application of synthetic quartz sand in the photovoltaic field.
Claims
1. A method for synthesizing high softening point silicon dioxide, characterized in that, The following steps are adopted: In the process of preparing silica sol by hydrolysis of tetraalkoxysilane or by hydrolysis of water glass, titanium compounds and / or zirconium compounds are added. After the obtained silica sol is gelled, dried, pulverized, and then calcined at 900~1600 °C, the silicon oxide is obtained. The amount of titanium compound and / or zirconium compound added is 0.0001% to 0.001% based on the amount of silicon dioxide. The titanium compound is selected from at least one of TiBr4, TiCl4, Ti(SO4)2, and alkyl titanate; The zirconium compound is selected from at least one of ZrCl4, ZrOCl2, Zr(OH)4, ZrBr4, and Zr(SO4)2.
2. The method for synthesizing high softening point silicon dioxide according to claim 1, characterized in that, The roasting temperature is 1400~1600 ℃.
3. The method for synthesizing high softening point silicon oxide according to claim 1, characterized in that, The roasting temperature is 1100~1300 ℃.
4. The method for synthesizing high softening point silicon dioxide according to any one of claims 1-3, characterized in that, The amount of titanium compound and / or zirconium compound added is 0.0003~0.001%.
5. The method for synthesizing high softening point silicon dioxide according to any one of claims 1-3, characterized in that, The alkyl titanate is selected from at least one of tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, and tetraisopropyl titanate.
6. The method for synthesizing high softening point silicon dioxide according to any one of claims 1-3, characterized in that, The tetraalkoxysilane is either tetramethoxysilane or tetraethoxysilane.
7. The method for synthesizing high softening point silicon dioxide according to any one of claims 1-3, characterized in that, The water glass contains 20% to 30% silica by mass.
8. The method for synthesizing high softening point silicon dioxide according to any one of claims 1-3, characterized in that, After the silica sol is gelled and dried, it is pulverized to 40-80 mesh.