Metal-modified hollow SAPO-34 molecular sieve and production method and application thereof

Abstract

The invention discloses a metal-modified hollow SAPO-34 molecular sieve and a production method and application thereof. The molecular sieve is of a structure with a locally-transparent surface and cubic hollow interior. Production of the molecular sieve comprises the steps of adopting a cheap organic amine as a template, introducing a structure promoter and a metal element, and conducting crystallization under a traditional hydrothermal condition. The synthesized SAPO-34 molecular sieve is high in crystallinity degree, the average grain size is 2-10 [mu]m, and the molecular sieve structure of the locally-transparent surface and the cubic hollow interior benefits diffusion and mass transfer of reactants and products in a catalytic reaction. A synthesized SAPO-34 molecular sieve catalyst is used for a reaction of methyl alcohol or dimethyl ether transformation to a low-carbon olefin, the ethylene selectivity and the propylene selectivity are high, and meanwhile, the metal-modified hollow SAPO-34 molecular sieve has the character of a long service life. The method is simple in process, fast, low in cost and suitable for industrial scale-up application.

Description

technical field [0001] The invention relates to the field of molecular sieve preparation and application, in particular to a metal-modified hollow SAPO-34 molecular sieve and its preparation method and application. Background technique [0002] In the 1980s, the patent US4440871 disclosed a series of silicoaluminophosphate molecular sieves SAPO-n. Among them, SAPO-34 molecular sieve has attracted a lot of attention from basic research to industrial application. It has been proved that SAPO-34 is a good methanol-to-olefin ( MTO) industrial catalyst. In US Pat. No. 4,310,440 and US Pat. No. 4,440,871, tetraethylammonium hydroxide template is mainly used in the synthesis of SAPO-34 molecular sieve, which is expensive. Chinese patents ZL93112230, ZL93112015 and ZL94110059 disclose the method of preparing SAPO-34 using triethylamine, diethylamine or a mixture of the two as a template. This type of template is relatively cheap and beneficial to industrial production, but using th...

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Problems solved by technology

Tetraethylammonium hydroxide templating agent is mainly used when synthesizing SAPO-34 molecular sieve in U.S. Patent US4310440 and US4440871, and its price is expensive

Chinese patents ZL93112230, ZL93112015 and ZL94110059 disclose the method of preparing SAPO-34 using triethylamine, diethylamine or a mixture of the two as a template. This type of template is relatively cheap and beneficial to industrial production, but using this type of template, Usually, the cubic SAPO-34 grains with relatively large size and relatively complete morphology are obtained, and the crystallinity is poor, and the lifetime in the MTO reaction is short, and the selectivity of olefin products is poor.

[0007] In summary, there are various problems in the synthesis and collection process of SAPO-34 molecular sieves in the prior art. Some molecular sieves have large crystal grains and low degree of crystallinity, which will affect the catalytic performance, but small crystal grains are difficult to collect and the yield is low. , some synthesis processes are complicated, and some technical routes are costly

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