Preparation method of hierarchical pore SSZ-13 molecular sieve

Abstract

The invention belongs to the field of molecular sieve catalysts, and particularly relates to a preparation method of a hierarchical pore SSZ-13 molecular sieve. The preparation method comprises the following steps: selecting an SSZ-13 molecular sieve synthesized by a traditional hydrothermal synthesis method as raw powder, grinding and uniformly mixing the SSZ-13 molecular sieve with NH4F, KF, NH4HF2, NaF, Na2SiF6 and other solid fluorides, standing at a certain temperature for a period of time, washing and drying to obtain the mesoporous-microporous composite pore channel molecular sieve. TheSSZ-13 molecular sieve obtained by the preparation method has the advantages of microporous zeolite, diffusion of macromolecules in mesopores and the like, and has wide application in the fields of methanol-to-olefin, petrochemical engineering, tail gas purification and the like.

Description

technical field [0001] The invention belongs to the field of molecular sieves, and in particular relates to a preparation method of a hierarchically porous SSZ-13 molecular sieve with micropores and mesopores. Background technique [0002] Low-carbon olefins, especially ethylene and propylene, are important raw materials for the modern petrochemical industry. In recent years, their demand has increased dramatically worldwide. At present, low-carbon olefins are mainly derived from the steam cracking of petroleum hydrocarbons. Due to the increasing shortage of petroleum resources, the methanol-to-olefins (MTO) technology using coal, natural gas, and biomass as carbon sources has attracted extensive attention. The traditional SSZ-13 molecular sieve catalyst has a CHA topology and has become one of the best catalysts for the MTO reaction because of its special pore structure and high selectivity for low-carbon olefins. In the 1980s, American chemist Zones first synthesized micr...

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Problems solved by technology

Patents CN106745036A, CN106830007B and CN106745035B use polyquaternium salts, long-chain silanes and amphiphilic organosilanes as crystallization synthesis reaction aids respectively, by regulating the molarity of alkali source, silicon source, aluminum source, template agent, polyquaternium salt and water Proportioning, using segmented dynamic / static crystallization, synthesized a high-crystallinity hierarchical SSZ-13 molecular sieve with ordered distribution of micropores and mesopores, but this is easy to block the channels, the synthesis method is cumbersome, and the cost is relatively high. high

[0004] Literature (RSCAdv., 2019, 9:77-86) prepared hierarchical SSZ-13 by changing the calcination conditions and then using NaOH solution at 65°C for 30 minutes, but desiliconization by alkali treatment would lead to a decrease in the crystallinity of molecular sieves. And when SSZ-13 molecular sieve is applied to MTO reaction, the catalyst life can not be improved

[0005] Literature (Microporous and Mesoporous Materials.2016.07.045.) using HF-NH 4 F etched SAPO-34 molecular sieve with CHA topology under ultrasonic conditions to successfully synthesize hierarchical porous SAPO-34 molecular sieve, but the HF and NH 4 F is all liquid, its preparation method is complicated, and can cause the waste of a part of water resource

[0006] The in situ synthesis method is adopted in the above-mentioned process of preparing the multi-stage SSZ-13 molecular sieve, the hard template will block the multi-stage pores and reduce the catalytic performance of the catalyst, the alkali treatment in the post-treatment method will cause the crystallinity of the molecular sieve to decrease, and the fluorine The etching method is complex and will cause waste of water resources

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