Hierarchical pore ZSM-5 molecular sieve and synthetic method thereof

Abstract

The invention discloses a hierarchical pore ZSM-5 molecular sieve and a synthetic method thereof. The hierarchical pore ZSM-5 molecular sieve is formed by the accumulation of crystalline grains with order nano-layered structures and is integrally structured. The synthetic method comprises the following steps of: with quaternary ammonium salt as a structure-directing agent (SDA), tetraethoxysilane (TEOS) as a silicon source, aluminium isopropoxide (AIP) as an aluminum source, and potassium hydroxide (KOH) as an alkali source, adding a cationic surface active agent (CSF) to prepare a synthetic liquid with the molar ratio of (20-100) SiO2: (1-3) Al2O3: (10-30) SDA: (10-50) KOH: (1,000-3,000) H2O: (1-10) CSF; adding 10 to 20% of Silicalite-1 molecular sieve seed crystal gel; performing hydrothermal crystallization according to the conventional method; processing a product by washing, drying and roasting to obtain the ZSM-5 molecular sieve. The molecular sieve is an agglomeration which is formed by the self-assembly under mutual effect of CSF, seed crystal gel and an inorganic species and is of a lamella and hierarchical zeolite structure; the molecular sieve is relatively high in specific surface area, relatively short in a diffusion path and relatively high in stability. The preparation method also has the advantages of high degree of crystallinity, high yield and simple operation steps, and is easy to separate.

Description

technical field [0001] The invention relates to the technical field of molecular sieve synthesis, in particular to a multi-level porous ZSM-5 molecular sieve with a monolithic nanosheet structure and a synthesis method thereof. Background technique [0002] U.S. Mobil Corporation reported the synthesis of ZSM-5 molecular sieve for the first time in 1972 (USP3702886), because of its ordered microporous structure, larger specific surface area, higher thermal and hydrothermal stability, skeleton acid center, It has become one of the most widely used catalysts in industry due to its excellent properties such as exchanged cations. However, the smaller micropore channels of the microporous ZSM-5 molecular sieve prevent larger molecules from entering the zeolite channels for adsorption and catalytic reactions, and limit the diffusion of macromolecules. In order to overcome the limitation of a single channel, researchers have considered solutions that combine the characteristics of...

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Problems solved by technology

[0004] However, the synthetic nanosheet structure hierarchical porous ZSM-5 molecular sieve reported in the literature is a micron-sized powder, and it is necessary to add a binder to make it shape or improve its strength.

The use of additives will block the pores of the molecular sieve, resulting in a reduction in the content of the active components of the catalyst, thereby reducing its catalytic performance

Although some researchers have prepared monolithic catalysts, multi-step treatment or addition of special carriers is required in the synthesis process, complicated operating procedures, high synthesis costs, etc. are still difficulties that require customer service.

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