Method for synthesizing ultrathin ZSM-5 molecular sieve nanosheets under low temperature and normal pressure

Abstract

The invention discloses a method for synthesizing an ultrathin ZSM-5 molecular sieve according to a low-temperature and normal-pressure hydrothermal method. Trace ammonium salt, silicon sol, a fluorine source and an aluminum source which serve as raw materials are subjected to hydrothermal synthesis. The method is characterized by comprising the following steps: stirring a template agent (ammoniumsalt), a silicon source and a certain amount of water uniformly at room temperature, sequentially adding the aluminum source and the fluorine source, and stirring and performing pre-crystallization at 50 to 100 DEG C for 1 to 50 hours; performing crystallization at 50 to 100 DEG C for 12 to 240 hours; after the reaction ends, cooling a reaction kettle to room temperature and then centrifuging, washing and drying the products. According to the method, the synthesis temperature is low, the synthesis pressure is low or normal pressure, the use amount of the template agent is small, skeleton heteroatoms can be regulated and controlled, and the thickness of a nanometer sheet can be regulated and controlled effectively. The crystallinity degree of the ultrathin nanometer sheet-like ZSM-5 molecular sieve is high, the synthesis cost is greatly saved due to a trace amount of template agent, the use of a high-pressure reaction kettle can be avoided due to low temperature and normal pressure, and the method is favorable for industrial amplification production and has strong industrial promotion prospect.

Description

technical field [0001] The invention belongs to the technical field of synthesis of zeolite molecular sieves, in particular to a method for synthesizing ultrathin nanosheet ZSM-5 molecular sieves under low temperature and normal pressure conditions. Background technique [0002] It is well known that ZSM-5 molecular sieves exhibit different catalytic effects due to different axial orientations. Among them, the nanosheet ZSM-5 molecular sieve (grows relatively fast along the a-axis direction, that is, the (010) crystal plane is large, but grows very slowly along the b-axis direction, and the (100) crystal plane and (X0Z) crystal plane are small. , with a hexagonal flake-like cross-section) compared with other shapes of MFI zeolites, it shows good separation and permeability performance and excellent anti-carbon deposition ability. [0003] At present, the commonly used methods for synthesizing sheet-like ZSM-5 sieves include layered silicate exfoliation method and hydrotherm...

AI Technical Summary

Problems solved by technology

[0008] In addition, the low-temperature synthesis of ZSM-5 molecular sieve membranes is also involved in the published patent (CN201010220350.0), but the focus of this method is to synthesize molecular sieve membranes containing carbon tubes. The synthesis temperature is 90-180 ° C, but the The synthesis conditions in the examples are all at 150°C, and no examples below 100°C or even 100°C have been seen

Images