Preparation method of high-purity nanometer silicon dioxide

Abstract

The present application relates to C01B chemical production technical field, more specifically, the present application provides a kind of preparation method of high-purity nanometer silicon dioxide.The present application provides a kind of preparation method of high-purity nanometer silicon dioxide, including the high-temperature furnace pretreatment of the silicon residue with impurity content of 5-25%, four times of pickling with dilute hydrochloric acid, while it is ultrasonic atomization and high-temperature plasma treatment, prepared the nanometer silicon dioxide with purity of 99.999%, while nanometer silicon dioxide has excellent sphericity.Compared with prior art, the method for preparing high-purity nanometer silicon dioxide provided by the present application reduces the waste of silicon resources in industrial production process on the one hand, on the other hand, the entire synthesis process is simple, the action time is short, greatly improves the production efficiency of preparing high-purity nanometer silicon dioxide, provides a new method for producing high-purity nanometer silicon dioxide.

Description

Technical Field

[0001] This invention relates to the field of CO1B chemical production technology, and more specifically, this invention provides a method for preparing high-purity nano-silica. Background Technology

[0002] With the rapid development of the electronics industry, aerospace technology, fiber optic communications, and other fields, the performance requirements for substrates are becoming increasingly stringent. Nano-silica, as an important basic raw material, directly affects the performance of the substrate through its purity. Existing nano-silica technologies suffer from two main limitations: firstly, their purity cannot meet the growing needs of industrial technology; secondly, the synthesis of high-purity nano-silica involves complex processes, hindering large-scale industrial production and severely limiting the application scope of high-purity nano-silica.

[0003] Chinese invention patent CN108203096A discloses a method for preparing high-purity silica. This patent uses diatomaceous earth and ammonium fluoride as raw materials and focuses on solving the problem of poor safety in the synthesis process of silica preparation in the prior art. However, the method requires the purchase of a large amount of diatomaceous earth with a silica content of 95wt% as the main raw material, which greatly increases the synthesis cost and is not conducive to the nationwide promotion and use of the method.

[0004] Chinese invention patent with publication number CN112938989A discloses a high-purity silica for optical coating and its preparation process. In this patent, water glass is used as the silicon source, which focuses on solving the problem of poor refractive index and light transmittance of optical coating in the prior art. However, the reaction time of the solution is long, and the high-purity silica prepared is only suitable for the field of optical coating, and its application range is narrow.

[0005] Chinese invention patent CN108516556A discloses a method for preparing high-purity silica using silicon slag. In this patent, waste generated during the production of organosilicon is used as the silicon source to obtain silica with a purity of 99.99%. However, the particle size and sphericity of the silica are not well reflected. In addition, carbon dioxide is introduced in the preparation method, which may lead to problems in controlling the amount of carbon dioxide introduced.

[0006] On the other hand, silicon slag is generated during the production of phosphate fertilizer. Direct discharge or burial of this slag will not only cause environmental pollution but also result in the loss of a large amount of silicon resources. Therefore, developing a method to prepare high-purity nano-silica using silicon slag generated during phosphate fertilizer production as a raw material is of profound significance. Summary of the Invention

[0007] To address the above problems, this invention provides a method for preparing high-purity nano-silica, comprising the following steps:

[0008] S1: Place the silicon slag in a high-temperature furnace with water vapor to obtain pretreated silicon slag A;

[0009] S2: Wash the silicon slag A described in S1 with dilute acid and adjust the pH to 6.5-7 to obtain silicon slag B;

[0010] S3: After adding the silicon slag B and binder mentioned in S2 to the ultrasonic atomizer, a carrier gas is added to obtain an aerosol.

[0011] S4: The aerosol described in step (3) is transported to a high-temperature plasma by airflow, cooled to room temperature, and then screened to obtain the high-purity nano-silica.

[0012] In some preferred embodiments, the moisture content of the silicon slag in S1 is 5-60%.

[0013] In some preferred embodiments, the impurity content in the silicon slag described in S1 is 5-25%.

[0014] In some preferred embodiments, the impurities include aluminum fluoride, calcium chloride, and fluorosilicic acid.

[0015] In order to eliminate some of the fluorine atoms in the silicon slag and improve the recovery rate of silicon in the silicon slag, in some preferred embodiments, the temperature of the high-temperature furnace in S1 is 350-450℃.

[0016] In some preferred embodiments, the dilute acid washing in S2 is performed 3-5 times.

[0017] In some preferred embodiments, the dilute acid in S2 is at least one of dilute nitric acid and dilute hydrochloric acid.

[0018] In some preferred embodiments, the molar concentration of the dilute acid in S2 is 0.1-1 mol / L.

[0019] The applicant discovered that when using silicon slag generated during phosphate fertilizer production as the silicon source for preparing high-purity nano-silicon, the slag contains 5-25% impurities. Using existing techniques, it is difficult to guarantee that the prepared nano-silicon will achieve a purity of 99.999% while maintaining good sphericity. This reduces the recovery rate of silicon slag and wastes silicon resources. To improve the recovery rate of silicon slag and prepare high-purity nano-silicon, after extensive consideration and innovative experiments, the applicant unexpectedly discovered that treating the silicon slag first in a high-temperature furnace and then in dilute acid, especially at 400°C with dilute hydrochloric acid, can significantly improve the purity of the nano-silicon. The applicant speculates that the possible reason is that when silicon slag with an impurity content of 5-25% is placed in a high-temperature furnace at 400°C, the aluminum fluoride and calcium fluoride in the impurities undergo hydrolysis with the water vapor in the high-temperature furnace to generate metal oxides and hydrogen fluoride gas. The hydrogen fluoride gas automatically overflows, thereby removing some of the fluorine atoms from the silicon slag. After washing with dilute hydrochloric acid four times, the metal ions in the silicon slag can be fully removed, significantly reducing the impurity content in the silicon slag. This allows the prepared nano-silica to maintain excellent sphericity while also having high purity, providing a new strategy for the production of high-purity nano-silica.

[0020] In some preferred embodiments, the adhesive in S3 is at least one of hydroxypropyl methylcellulose, polyvinyl acetate, ethylene-acrylic acid copolymer, and acrylic resin.

[0021] In order to make the nano-silica have a uniformly distributed particle size range, in some more preferred embodiments, the adhesive in S3 is polyvinyl acetate and acrylic resin, and the mass ratio of polyvinyl acetate to acrylic resin is (0.2-0.8):(1.1-1.9).

[0022] In some preferred embodiments, the mass ratio of the acrylic resin, polyvinyl acetate and acrylic resin is 0.4:1.5.

[0023] In some preferred embodiments, the average molecular weight of polyvinyl acetate is 400,000-600,000.

[0024] In some preferred embodiments, the acid value of the acrylic resin is 5-15 mg KOH / g.

[0025] In some preferred embodiments, the mass ratio of silicon slag B to binder in S3 is 100:(1-3).

[0026] In order to ensure that the adhesive and silicon slag B can work together effectively and improve their compatibility, in some preferred embodiments, the atomization rate of the ultrasonic atomizer in S3 is 1.2-2 mL / min.

[0027] In some preferred embodiments, the carrier gas flow rate in S3 is 100-180 mL / min.

[0028] In some preferred embodiments, the carrier gas in S3 is at least one of argon and nitrogen.

[0029] In some preferred embodiments, the airflow velocity in S4 is 10-20 L / min.

[0030] In order to ensure that the prepared nano-silica has both high purity and good sphericity, thereby enhancing its application prospects in the industrial field, in some preferred embodiments, the temperature of the high-temperature plasma in S4 is 1900-2200℃.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The method for preparing high-purity nano-silica of the present invention uses silicon slag with an impurity content of 5-25% as raw material for preparing nano-silica. It is added to a high-temperature furnace at 400°C for treatment. On the one hand, it can remove some of the fluorine atoms in the silicon slag. On the other hand, it converts aluminum fluoride and calcium fluoride in the impurities into aluminum oxide and calcium oxide, which prepares for the next step of dilute acid washing and effectively reduces the impurity content in the silicon slag.

[0033] 2. The method for preparing high-purity nano-silica of the present invention involves washing silicon slag A after it has been treated in a high-temperature furnace at 400°C with dilute hydrochloric acid. In particular, washing it four times can significantly improve the purity of nano-silica and effectively remove metallic impurities from the silicon slag. The purity of the prepared nano-silica can reach 99.999%.

[0034] 3. The method for preparing high-purity nano-silica of the present invention requires strict control of the pH in S2 to be 6.5-7, in order to avoid the formation of metal oxides in the system that are difficult to remove, resulting in residual metal particles in the nano-silica and affecting the application range of the nano-silica.

[0035] 4. The method for preparing high-purity nano-silica of the present invention involves treating silicon slag with a water content of 5-60% through multiple processes, including high-temperature furnace, dilute acid washing, ultrasonic atomization, and high-temperature plasma treatment. This significantly improves the purity of nano-silica while also providing good sphericity, thus providing a high-performance basic raw material for the field of electronic technology.

[0036] 5. The method for preparing high-purity nano-silica of the present invention provides a new approach for synthesizing high-purity nano-silica. On the other hand, the synthesis process is simple and suitable for large-scale preparation, promotion and sales. Moreover, the raw materials are by-products from the preparation of phosphate fertilizers, which can be recycled and reused, effectively solving the waste of silicon resources in the actual production process. Attached Figure Description

[0037] Figure 1 Scanning electron microscope image of high-purity nano-silica with an average particle size of 280 nm prepared in Example 1. Detailed Implementation

[0038] Example 1

[0039] Example 1 provides a method for preparing high-purity nano-silica, comprising the following steps:

[0040] S1: Place the silicon slag in a high-temperature furnace with water vapor to obtain pretreated silicon slag A;

[0041] S2: Wash the silicon slag A described in S1 with dilute acid and adjust the pH to 6.5-7 to obtain silicon slag B;

[0042] S3: After adding the silicon slag B and binder mentioned in S2 to the ultrasonic atomizer, a carrier gas is added to obtain an aerosol.

[0043] S4: The aerosol described in step (3) is transported to a high-temperature plasma by airflow, cooled to room temperature, and then screened to obtain the high-purity nano-silica.

[0044] The moisture content of the silicon slag in S1 is 59%.

[0045] The impurity content in the silicon slag described in S1 is 10%.

[0046] The temperature of the high-temperature furnace described in S1 is 400℃.

[0047] The dilute acid washing process described in S2 is performed four times.

[0048] The dilute acid mentioned in S2 is dilute hydrochloric acid, purchased from Guangzhou Deshu Chemical Co., Ltd.

[0049] The adhesive described in S3 is polyvinyl acetate and acrylic resin, with a mass ratio of polyvinyl acetate to acrylic resin of 0.4:1.5. The polyvinyl acetate was purchased from Shanghai Sigma-Aldrich Trading Co., Ltd., with an average molecular weight of 500,000; the acrylic resin was purchased from Sanmu Group, model BS-9360, with an acid value of 6-10.

[0050] The mass ratio of silicon slag B to binder in S3 is 100:2.

[0051] The atomization rate of the ultrasonic atomizer described in S3 is 1.6 mL / min.

[0052] The carrier gas flow rate in S3 is 175 mL / min.

[0053] The carrier gas mentioned in S3 is argon.

[0054] The airflow velocity in S4 is 15 L / min.

[0055] The temperature of the high-temperature plasma described in S4 is 2100℃.

[0056] The scanning electron microscope image of the high-purity nano-silica with an average particle size of 280 nm described in S4 is shown below. Figure 1 .

[0057] Performance testing

[0058] The purity of the high-purity silica prepared in Example 1 was tested:

[0059] The testing method was as follows: X-ray fluorescence spectrometry was used to determine the content of each element in silicon dioxide;

[0060] The X-ray fluorescence spectrometer is model Epsilon1.

[0061] The high-purity silica prepared in Example 1 has a purity of 99.999%.

Claims

1. A method for preparing high-purity nano-silica, characterized in that, Includes the following steps: S1: Place the silicon slag in a high-temperature furnace with water vapor to obtain pretreated silicon slag A; S2: Wash the silicon slag A described in S1 with dilute hydrochloric acid and adjust the pH to 6.5-7 to obtain silicon slag B; S3: After adding the silicon slag B and binder mentioned in S2 to the ultrasonic atomizer, a carrier gas is added to obtain an aerosol. S4: The aerosol described in S3 is transported to a high-temperature plasma by an airflow, cooled to room temperature, and then screened to obtain the high-purity nano-silica. The silicon slag is silicon slag produced during the production of phosphate fertilizer. The silicon slag has a moisture content of 5-60% and an impurity content of 5-25%. The impurities include aluminum fluoride, calcium fluoride and fluorosilicic acid. The temperature of the high-temperature furnace in S1 is 350-450℃; the temperature of the high-temperature plasma is 1900-2200℃.

2. The method for preparing high-purity nano-silica according to claim 1, characterized in that, The dilute hydrochloric acid washing process described in S2 is performed 3-5 times.

3. The method for preparing high-purity nano-silica according to claim 1, characterized in that, The concentration of the dilute hydrochloric acid in S2 is 0.1-1 mol / L.

4. The method for preparing high-purity nano-silica according to claim 1, characterized in that, The adhesive described in S3 is at least one of hydroxypropyl methylcellulose, polyvinyl acetate, ethylene-acrylic acid copolymer, and acrylic resin.

5. The method for preparing high-purity nano-silica according to claim 4, characterized in that, The average molecular weight of the polyvinyl acetate is 400,000-600,000.

6. The method for preparing high-purity nano-silica according to claim 4, characterized in that, The acid value of the acrylic resin is 5-15 mg KOH / g.

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