Method for preparing small-grain sapo molecular sieve, product and use thereof

Abstract

The invention relates to a method for preparing a small granulated SAPO molecular sieve, a product prepared through the method, and a use of the product. The method concretely includes the following steps: preprocessing a raw material SAPO molecular sieve to form granules with the granularity of 10-800nm in order to obtain a crystallization precursor with low crystallization degree; mixing an organic amine template R and water with optional silicon, aluminum and phosphorus sources to prepare a crystallization liquid, or using a mother liquor obtained after separating a product in the preparation process of the SAPO molecular sieve as the crystallization liquid; and mixing the crystallization precursor with the crystallization liquid, carrying out a hydrothermal reaction, and separating to obtain the small granulated SAPO molecular sieve. The method allows the small granulated SAPO molecular sieve to be simply prepared without using an organic amine template tetraethylammonium hydroxide, and the product prepared in the invention has the advantages of obvious prolongation of the catalysis life of a reaction of oxygen-containing compounds, such as methanol, to olefin as a catalyst, and obvious selectivity increase as a catalyst.

Description

technical field [0001] The invention relates to the field of molecular sieves and preparation methods thereof, in particular to a method for preparing small-grain SAPO molecular sieves, products obtained by the method and uses thereof. Background technique [0002] Since Union Carbide successfully developed a series of aluminum phosphate molecular sieves and their derivatives in 1982 (Pat: USP4310440, USP4,440,871), aluminum phosphate molecular sieves and their heteroatom-substituted derivatives have been widely concerned by researchers. It is one of the research hotspots in the field of materials science and catalysis. Especially the SAPO-n (n is the model) series silicoaluminophosphate molecular sieve: its skeleton is made of PO 2 + , AlO 2 - and SiO 2 Composed of tetrahedrons, Si atoms enter the neutral aluminum phosphate molecular sieve structure through substitution, so that it generates a net negative charge. According to different synthesis conditions and differ...

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Problems solved by technology

These research results imply that it is difficult to synthesize nano-molecular sieves by this method while simultaneously controlling the composition of the resulting molecular sieves.

[0007] In view of the difficulties in the preparation of small-grain SAPO molecular sieves, including high cost, complicated synthesis process, difficult control of composition, poor crystallinity, low yield, etc., and problems such as a large amount of industrial wastewater produced in the production of SAPO molecular sieves, the inventors thought of If the SAPO molecular sieve is pretreated into a molecular sieve precursor whose crystal structure has been partially destroyed and the particle size becomes smaller, and then the crystal structure is repaired through secondary crystallization, it will be possible to obtain a high-crystallinity SAPO molecular sieve with a particle size of nanoscale

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