Silicon carbide block with macroporous and mesoporous composite structure, and preparation method thereof

Abstract

The invention provides a preparation method of a silicon carbide block with a macroporous and mesoporous composite structure. The preparation method comprises the following steps: preparing the mixed solution of ethylene oxide, tetraethoxysilane and nitric acid in the mol ratio of x: 1: 0.25, wherein x is greater than or equal to 0.45 and less than or equal to 0.55; pouring the mixed solution into a die and sealing, demolding after standing, carrying out hydro-thermal treatment by using ammonium hydroxide to obtain a silicon oxide template, soaking the silicon oxide template into the methylbenzene solution of polycarbosilane, heating until the methylbenzene completely volatilizes, carrying out pyrolysis treatment under the protection of an insert gas to obtain a silicon carbide and silicon oxide composite block, and then carrying out soaking treatment by using hydrofluoric acid to obtain the silicon carbide block. The method provided by the invention is capable of directly obtaining the silicon carbide block with the macroporous and mesoporous composite structure, and avoids the problems of specific surface area reduction, diffusion resistance increase and pore blockage due to subsequent processing; besides, the silicon carbide block is adjustable in macroporous pore diameter and good in pore connectivity; as a result, the mass transfer resistance is greatly reduced and the catalytic efficiency is improved; and moreover, the preparation method is simple in preparation and convenient to operate.

Description

technical field [0001] The invention belongs to the technical field of catalyst carrier materials, and in particular relates to a silicon carbide block with a macropore and mesoporous composite structure and a preparation method thereof. Background technique [0002] Silicon carbide materials have high high temperature chemical stability, high temperature mechanical strength, high temperature thermal stability, thermal conductivity and low thermal expansion rate, and are ideal catalyst supports for high temperature and highly erosive catalytic processes. However, the specific surface area of ​​traditional silicon carbide materials is low, and the specific surface area of ​​the highest such as β-silicon carbide is only 20-30m 2 / g, can not meet the requirements of industrial catalytic engineering. [0003] At present, there are two main methods of increasing the specific surface area of ​​silicon carbide: (1) using nanostructured carbon and (1) reacting silicon dioxide at hi...

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Problems solved by technology

[0004] Although the above methods can effectively increase the specific surface area of ​​silicon carbide, the following problems still exist: (1) The products directly prepared by the above methods are all silicon carbide powders, which need to be pressed into silicon carbide blocks before actual use However, in the process of pressing and forming, the specific surface area will be reduced, the diffusion resistance will be increased, and the pores will be blocked; (2) the products obtained by the above methods only have a single mesopore, and the connectivity is relatively poor. In the process of high-speed fluid It will produce a large diffusion resistance and affect the catalytic efficiency

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