Method for synthesizing SAPO-34 molecular sieve by taking A type zeolite as silicon source

Abstract

The invention provides a method for synthesizing SAPO-34 molecular sieve by taking A type zeolite as a silicon source. According to the method, phosphoric acid is used as a phosphorus source, pseudo-boehmite is used as an aluminum source, the A type zeolite is used as the silicon source, and an organic template agent is diethylamine, morpholine, cyclohexane, triethylamine or the like; the phosphoric acid, the aluminum source, the silicon source, the organic template agent and water are prepared into synthetic gel according to the molar ratio of Al2O3:H3PO4:SiO2:R:H2O as 1.0:2.0:(0.1-1.0):(2.0-3.0):(50-100); and the synthetic gel is subjected to hydrothermal crystallization for 3-6 days at the temperature of 200 DEG C and under self-generated pressure, and then is cooled, washed, separated and dried at room temperature to obtain a product. By using the method, the SAPO-34 molecular sieve product with higher crystallinity and more uniform silicon distribution on a framework is obtained.

Description

technical field [0001] The invention relates to the synthesis of silicoaluminophosphate molecular sieve SAPO-34. Specifically, type A zeolite is used as the silicon source to synthesize the SAPO-34 molecular sieve with more uniform silicon distribution on the skeleton. Background technique [0002] Silicoaluminophosphate molecular sieve SAPO-34 made of PO 4 , AlO 4 and SiO 4 The tetrahedron constitutes a three-dimensional framework structure, and the SAPO-34 molecular sieve has a medium-strength acid center and an eight-membered ring microporous structure, which shows excellent catalytic performance in the reaction of methanol to light olefins. [0003] The most commonly used silicon source for synthesizing SAPO-34 molecular sieve is silica sol (Microporous and Mesoporous Materials 114 (2008) 416-423), and other silicon sources can also be used, such as gas phase silica, thin layer chromatography, gas phase silica, etc. . But when above-mentioned silicon source forms rea...

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Problems solved by technology

But when above-mentioned silicon source forms reaction mixture gel, silicon source is in highly aggregated state, even if use the tetraethyl orthosilicate of molecular state as silicon source, it also can be hydrolyzed and condensed at first to form aggregation state (Microporous and Mesoporous Materials2009, 126, 1), so that the silicon source cannot enter the framework in a highly dispersed form during the formation of the molecular sieve structure, which affects the quantity and form of silicon entering the framework, resulting in uneven distribution of silicon in the synthesized SAPO-34 molecular sieve, which is difficult to control, thereby affecting its catalytic performance

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