Gradient pore HZSM-5 (hydrogen zeolite socony mobile-5) molecular sieve and preparation method thereof

Abstract

The invention provides a gradient pore HZSM-5 molecular sieve and a preparation method thereof. The preparation method takes natural clay minerals as raw materials to synthesize a microporous NaZSM-5molecular sieve without application of template agent, performs alkali treatment on the microporous NaZSM-5 molecular sieve through crystallized mother liquid to prepare a gradient pore NaZSM-5 molecular sieve, and performs acid exchange on the gradient pore NaZSM-5 molecular sieve through acid liquor to obtain the gradient pore HZSM-5 molecular sieve. The invention also provides the gradient poreHZSM-5 molecular sieve prepared through the method. The preparation method of the gradient pore HZSM-5 molecular sieve does not require any template agent as well as additional alkali source during alkali treatment and has no discharge of acid liquor or alkali liquor during the whole process, thereby greatly reducing the production cost of molecular sieves and improving the environmental properties of the preparation process; the prepared gradient pore HZSM-5 molecular sieve is rich in micro-mesoporous composite gradient pore structures.

Description

technical field [0001] The invention relates to a molecular sieve and a preparation method thereof, in particular to a step-pore HZSM-5 molecular sieve and a preparation method thereof, belonging to the technical field of molecular sieve preparation. Background technique [0002] Mobil Corporation of the United States successfully synthesized ZSM-5 molecular sieve (US 3702886) for the first time in 1972. Because of its unique three-dimensional pore structure, shape-selective catalytic performance, excellent thermal and hydrothermal stability, and high catalytic activity, it is widely used It is used in many fields such as petrochemical industry, fine chemical industry and environmental protection. [0003] However, the smaller micropores of microporous ZSM-5 molecular sieves (micropores with a pore size of less than 2nm, macropores with a pore size of more than 50nm, and mesoporous pores with a pore size of 2-50nm) prevent larger molecules from entering the molecular sieve c...

AI Technical Summary

Problems solved by technology

CN101723403A discloses a method for synthesizing a stepped pore ZSM-5 molecular sieve compounded by mesopores and micropores. In the method, chemical reagents are used as silicon-aluminum sources, organic amines are used as microporous templates, and polysaccharide compounds and their derivatives are used as Mesoporous templates are used to synthesize step-pore ZSM-5 molecular sieves. The synthetic material includes micropores of 0.5-0.6nm and mesopores of 5-100nm (large), but the hydrothermal crystallization time of this method is longer (3-14 days)

This process requires the use of a large amount of NH 4 + solution, high-temperature roasting will produce a large amount of pollutants NOx, and high-temperature roasting is also a process of high energy consumption

In addition, the zeolite crystallization mother liquor usually contains a large amount of unreacted silica-alumina species and templates, and often requires special treatment to meet the emission standards, which not only causes waste of materials, but also increases process costs

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