Catalyst for catalyzing conversion of silicon tetrachloride and preparation method thereof

Abstract

The invention provides a catalyst for catalyzing conversion of silicon tetrachloride and a preparation method thereof, the catalyst has a core-shell structure, the core comprises a catalyst carrier, and the shell comprises an active component; wherein the active component comprises a silicon-copper multi-component alloy, elemental copper and nano ceramic, and the silicon-copper multi-component alloy comprises silicon, copper, transition metal elements and / or rare earth elements. The catalyst disclosed by the invention is applied to a cold hydrogenation reaction process, silicon tetrachloride directly reacts with an active component silicon-copper phase and elemental copper in the catalyst, so that the catalytic reaction time is greatly shortened, and the catalytic reaction rate and the conversion rate can be effectively improved; the catalyst prepared by the preparation method of mechanical alloying has the advantages of abundant pore diameters, fine crystal grains and high defect density.

Description

technical field [0001] The invention relates to the technical field of polysilicon production, in particular to a catalyst for catalyzing the conversion of silicon tetrachloride and a preparation method thereof. Background technique [0002] A large amount of by-products of silicon tetrachloride and hydrogen chloride will be produced during the production of polysilicon, among which silicon tetrachloride is highly polluting and cannot be discharged directly. Hydrogen silicon, that is, the use of hydrochlorination reaction to catalytically convert silicon tetrachloride into trichlorosilane, and then carry out rectification and purification. The catalyst is the most critical factor determining the conversion rate of hydrochlorination. [0003] At present, the silicon tetrachloride (STC) cold hydrogenation process adopted by domestic polysilicon manufacturers is carried out in a fluidized bed reactor. Among many catalysts, copper-based catalysts are a type of catalyst with high...

AI Technical Summary

Problems solved by technology

[0004] Yet, in the fluidized bed reactor, there are following problems in the catalytic conversion of silicon tetrachloride: (1) in the fluidized bed reactor, cuprous chloride particle size gradually reduces, is limited by the fluidized bed filtration system, The small cuprous chloride cannot be fully utilized and flows into the back-end system. It is discarded together with unreacted silicon powder in the slurry process as waste treatment, and it is difficult to separate from other components in the raffinate, causing a lot of waste; ( 2) During the catalytic reaction, cuprous chloride and silicon powder are contacted by collision instead of direct contact, the contact time is short, cuprous chloride diffuses, the reaction is insufficient, and the amount of silicon-copper phase generated by in situ reaction is small , resulting in lower catalytic efficiency; (3) The catalytically active components are formed in situ during the cold hydrogenation reaction, while cuprous chloride and metal silicon powder have large particle and grain sizes, small grain boundary areas, and defects There are fewer centers, and the reactivity between metal silicon powder and cuprous chloride is low, resulting in a small amount of silicon-copper phase formed, a low density of silicon-copper interfaces and other defect centers; (4) catalytic reaction process Electron migration, the adsorption and dissociation efficiency of silicon tetrachloride on the catalyst needs to be further improved; (5) The catalytic conversion temperature of silicon tetrachloride is relatively high (500-550 ° C), which is easy to cause grain growth and lead to active center (6) In the fluidized bed, silicon tetrachloride is catalytically hydrogenated to generate trichlorosilane and hydrogen chloride is generated at the same time, hydrogen chloride reacts with silicon powder to generate trichlorosilane, and during the production process of metal silicon powder, metal silicon melt The solidification rate is slower, resulting in a larger grain size, and the lower reactivity leads to insufficient reaction of silicon powder

[0005] In recent years, the industry has developed a supported catalyst prepared by supporting monovalent copper ions with molecular sieve, silica, aluminum oxide, etc. Compared with the pure cuprous chloride catalyst, the unit consumption of cuprous chloride significantly reduced, but still failed to effectively solve the above problems