Method for preparing SAPO-34 molecular sieve

Abstract

The invention provides a method for preparing a SAPO-34 molecular sieve. The method comprises the following steps of: 1, uniformly mixing a proper amount of phosphorus source, aluminum source, silicon source, template, auxiliary template and water at a proper temperature and under a stirring condition to obtain mixed solution, of which a molar ratio of all components, namely, the molar ratio of Rto F- to SiO2 to Al2O3 to P2O5 to H2O, is a:b:c:1:d:e, wherein R represents the template, a is 0.2 to 5.0, b is 0 to 1.0, c is 0.2 to 1.5, d is 0.2 to 2.0 and e is 20 to 200; 2, ageing the mixed solution; and putting the aged mixed solution in a crystallization kettle, sealing the crystallization kettle, heating the mixed solution to a crystallization temperature, and crystallizing the mixed solution at the constant crystallization temperature; 3, performing centrifugal separation of the crystallized mixed solution, filtering, washing the mixed solution until a pH value of the mixed solution is 7 to 8, and drying a solid sample to obtain the SAPO-34 raw powder; and 4, baking the SAPO-34 raw powder at the temperature of between 450 and 650 DEG C for 4 to 8 hours to obtain the SAPO-34 molecular sieve. The SAPO-34 molecular sieve prepared by the method is characterized by high crystallinity and can show better low carbon olefin selectivity in an MTO reaction.

Description

technical field [0001] The invention relates to a preparation method of SAPO-34 molecular sieve, more specifically, relates to a method for preparing SAPO-34 molecular sieve by using fluoride as an auxiliary template agent. Background technique [0002] SAPO-n molecular sieve is a new series of silicoaluminophosphate molecular sieves (USP 4440871, USP 4499327) researched and developed by Union Carbide Corporation (UCC) in 1984. The sol is an aluminum source, a phosphorus source and a silicon source, and is obtained by first obtaining an organic amine / aluminum phosphate / silicon complex with a microporous phase by hydrothermal crystallization, and then removing the template (organic amine) by roasting. At present, SAPO molecular sieves have been reported to have 13 three-dimensional microporous framework structures, and SAPO-34 is one of them. Its structure is similar to chabazite, with three-dimensional intersecting channels, and the pore diameter is about 0.38nm. It belongs ...

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Problems solved by technology

For the technology of preparing SAPO-34 molecular sieves using sodium fluoride and potassium fluoride with low toxicity and more obvious mineralization effect as auxiliary templating agent, there is no report yet

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