Method for preparing silicon-aluminum-phosphorus molecular sieve from montmorillonite, product obtained by method and application thereof

Abstract

The invention relates to a method for preparing a silicon-aluminum-phosphorus molecular sieve from montmorillonite, a molecular sieve product obtained by the method and application thereof. The method comprises the following steps of: activating the montmorillonite with alkaline solution; mixing the activated montmorillonite, an aluminum source, a phosphorus source, a template and de-ionized water; and performing hydrothermal crystallization reaction on the mixture, wherein the product after the crystallization comprises a small-sized silicon-aluminum-phosphorus molecular sieve grown on a laminar structure and free silicon-aluminum-phosphorus molecular sieve. The silicon-aluminum-phosphorus molecular sieve prepared from the montmorillonite serving as a raw material is partially the small-sized silicon-aluminum-phosphorus molecular sieve grown on the laminar structure, so the influence of internal diffusion of reactant molecules and product molecules can be effectively reduced; and the silicon-aluminum-phosphorus molecular sieve is partially the free silicon-aluminum-phosphorus molecular sieve. An active skeletal silicon source formed by activating the montmorillonite with the alkaline solution contributes to forming a small-grain silicon-aluminum-phosphorus molecular sieve on the surface of the montmorillonite laminar structure and diffusing the reactant molecules and the product molecules; and the montmorillonite is widely distributed in China and has low cost, so the cost for synthesizing the silicon-aluminum-phosphorus molecular sieve is reduced.

Description

technical field [0001] The present invention relates to molecular sieves, more particularly to silicon aluminum phosphorus molecular sieves. Background technique [0002] The US patent USP4440871 in 1984 disclosed that a certain proportion of silicon source, aluminum source, phosphorus source and template were mixed, and hydrothermal crystallization at 100-250 ° C was used to synthesize a variety of new silicon aluminum phosphate series (SAPO-n) molecular sieves . [0003] Since the grain size has a great influence on the product selectivity of the MTO reaction, many scholars have devoted themselves to the development of small particle size molecular sieve catalysts. EP-A-541915 describes in specification that small particle size catalyst is beneficial to low carbon olefins (C 2 ~C 4 ), and disclosed that the small-grain SAPO-34 was obtained by stirring the crystallization mixture to reduce the intramolecular diffusion resistance. Exxon Mobil Chemical Patent Company disc...

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Problems solved by technology

[0008] Although montmorillonite has been used as a silicon source in the synthesis of other molecular sieves, there has been no report on the synthesis of silicon-aluminum-phosphorus molecular sieves using montmorillonite as a silicon source.

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