Method for synthesizing metal-modified SAPO-34 molecular sieve

Abstract

The invention discloses a method for synthesizing a metal-modified SAPO-34 molecular sieve. The method comprises the following steps: preparing a metal salt into an aqueous solution; adding an aluminum source to be stirred uniformly; then, filtering, washing, drying, calcining at a low temperature, and then re-dispersing in a small amount of water; sequentially adding a phosphorus source, a silicon source and a template agent; stirring to form a gel mixture; and ageing, crystallizing, washing, drying and calcining to prepare the metal-modified SAPO-34 molecular sieve. The metal-modified SAPO-34 molecular sieve prepared in the invention has relatively high crystallinity, shows high low-carbon olefin selectivity when use for catalyzing reaction of preparing olefin from methanol, has the advantages of high ethylene selectivity, yield, low synthesis costs and easy industrial large-scale production.

Description

technical field [0001] The invention relates to the field of SAPO-34 molecular sieves, in particular to a synthesis method for high and low-carbon olefins selective metal-modified SAPO-34 molecular sieves and an application in catalytic methanol-to-olefins reaction. Background technique [0002] SAPO-34 molecular sieve is made of [SiO 4 ], [AlO 4 ], [PO 4 ] The microporous crystal composed of tetrahedral units has a chabazite (CHA) eight-membered ring channel structure with a pore diameter of about 0.38nm. It has a suitable acid center and good thermal and hydrothermal stability. It is an excellent methanol production Catalyst for low carbon olefins. [0003] In order to continuously improve the performance of SAPO-34 molecular sieve in catalytic methanol to olefins reaction, it is necessary to modify SAPO-34 molecular sieve. At present, the modification methods of SAPO-34 molecular sieve mainly include metal doping; preparation of hierarchical porous structure SAPO-34 m...

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Problems solved by technology

Chinese patent (101555022) reacts a metal salt solution with a template to form a complex, then adds a phosphorus source, an aluminum source, a silicon source, etc. to form a gel, then hydrothermally ages and crystallizes to prepare a metal-modified SAPO-34 molecular sieve , showed excellent catalytic performance in the reaction process of methanol to olefins, but did not mention the hydrothermal stability of SAPO-34 molecular sieve after metal modification. In the actual industrial application process, the hydrothermal stability of molecular sieve is the most important factor affecting the device. A very important indicator of whether it can run stably for a long time

However, the performance of the catalyst produced by this kind of modification method is unstable, and the performance of the catalyst decreases seriously after repeated regeneration.

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