Method for preparing high-purity nanometer silicon dioxide by taking high-purity silicon tetrachloride as material

Abstract

The invention discloses a method for preparing high-purity nanometer silicon dioxide by taking high-purity silicon tetrachloride as the material, which includes the steps of adding high-purity silicon tetrachloride to absolute ethanol solution or methanol solution while stirring under minus 20-20 DEG C, dripping ultrapure water-ethanol solution or methanol solution which contains 0.1-0.5wt% of polyvinyl alcohol to above mixture according to the reaction proportion to produce colorless transparent sol; seasoning or condensing under reduced pressure to obtain colorless transparent gel; and alcohol leaching and deacidifying the colorless transparent gel until the pH reaches 4-7, then filtrating, freezing, drying and dealcoholizing to obtain high-purity nanometer silicon dioxide powder, wherein the ethanol or methanol filtered out in the alcohol leaching process and the ethanol or methanol removed in the freezing and drying processes are rectified to obtain ethanol or methanol which is returned for use again. Through the method, no metal impurity is introduced into the production; the purity of the nanometer silicon dioxide prepared through the method can be above 99.999%; the total content of metal impurities is less than 10ppm; the grain size can reach 20nm-80nm; the production process is simple; the equipment investment is less; the production cost is low; and the method is easy for industrial production.

Description

technical field [0001] The invention relates to a method for preparing high-purity nano high-purity silicon dioxide by using high-purity silicon tetrachloride as a raw material. Background technique [0002] High-purity silica usually means that the content of metal impurities contained in silica is particularly low, generally below 10ppm or even 1ppm. Its main uses are as fillers for integrated circuit packaging agents and for the manufacture of high-purity quartz glass, optical fiber optical instruments, SiO2 film and low cost solar grade polysilicon raw material. With the rapid development of the photovoltaic industry and the continuous improvement of solar-grade polysilicon production technology, the demand for high-purity silicon dioxide differentiation continues to increase. [0003] At present, there are mainly the following methods for preparing nano-silica powder: (1) Silicon tetrachloride high-temperature gas-phase oxidation method: the disadvantage of this method...

AI Technical Summary

Problems solved by technology

[0003] At present, there are mainly the following methods for preparing nano-silica powder: (1) Silicon tetrachloride high-temperature gas-phase oxidation method: the disadvantage of this method is that it needs to be carried out at a high temperature greater than 1000 ° C, the equipment investment is large, the particles are large, and the product The purity is difficult to meet the requirements; (2) the chemical precipitation method, carbonization reaction method, and reverse micellar solution method using silicates as raw materials. Although these methods have low raw material costs, they all have shortcomings such as complex production processes and difficult control of product purity; (3) Use silica sol as raw material spray drying method or gelation-drying method, the production process is simple, but because in the commercial silica sol as raw material, metal impurity content is higher, is difficult to remove, and product purity is low, if adopt expensive high Pure silica sol as a raw material will also lead to high production costs; (4) the sol-gel method using ethyl silicate (ETOS) as a raw material is that ethyl silicate is hydrolyzed to generate silica sol and gel, and then High-temperature treatment produces ultra-fine silica powder, which has high purity and can control the content of metal ions below 10ppm. The disadvantage is that the raw material ethyl silicate is expensive, resulting in high production costs.