A kind of framework vanadium mcm-41 molecular sieve and its preparation method and application

Abstract

The invention relates to a skeleton vanadium MCM-41 molecular sieve. Vanadium atoms are uniformly distributed in a skeleton of the molecular sieve in a mode of VO4. The invention further relates to apreparation method of the skeleton vanadium MCM-41 molecular sieve. The content of vanadium in the V-MCM-41 molecular sieve prepared by interaction of a vanadium complex and an organic template reaches up to 13wt%, the V-MCM-41 molecular sieve still maintains a good hexagonal mesoporous duct structure and has high specific surface area, the active sites of the obtained molecular sieves are numerous, the activity of the molecular sieve is high, the service life of the molecular sieve is long, and the utilization rate of the molecular sieve is high.

Description

technical field [0001] The invention belongs to the technical field of molecular sieves, and in particular relates to a framework vanadium MCM-41 molecular sieve and its preparation method and application. Background technique [0002] Since Mobil successfully synthesized the MCM-41 mesoporous molecular sieve series materials with regular pore structure and narrow pore size distribution in 1992, they have shown great performance because of their larger specific surface area, pore volume, regular pore structure and uniform pore size distribution. The excellent catalytic performance has attracted great attention of researchers who study the synthesis of molecular sieves and their catalytic applications. However, pure silicon MCM-41 molecular sieve has a neutral skeleton structure, low acid content and acid strength, and poor hydrothermal stability, which limits its industrial application. [0003] In recent years, metal heteroatom precursors have been introduced during the fo...

AI Technical Summary

Problems solved by technology

Such as CN104003414A adopts the method that directly adds vanadium source doping to successfully synthesize V-MCM-41 molecular sieve, but the vanadium atom that obtains by this method is in molecular sieve and exists in the form of oxide mostly outside the framework of molecular sieve (existing in molecular sieve In the channel or on the surface of the molecular sieve), too much oxide not only blocks the channel of the molecular sieve, but also does not play the role of the catalytic center

At the same time, the blocked molecular sieve channels cannot provide space for the reactants to react, and the narrow channels will also cause a decrease in the diffusion of reactants and products, increase the probability of side reactions, cause carbon deposition on the catalyst, and cause catalyst deactivation

In addition, the direct doping method does not use any complexes, and it is very easy to directly precipitate vanadium atoms under the action of strong alkali in the subsequent crystallization process, so that they cannot enter the molecular sieve framework.

Most of the vanadium atoms in the molecular sieve prepared by the loading method are covered on the surface of the molecular sieve in the form of oxides, which will also block the pores of the molecular sieve and cannot function as a catalytic center.

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