Small-grain multi-level porous ith structure silica-alumina molecular sieve and its preparation method and application

Abstract

The invention provides a hierarchically porous ITH structural silica-alumina molecular sieve with small crystal grains as well as a preparation method and an application thereof. The ITH structural silica-alumina molecular sieve comprises the following elements: silicon, germanium, aluminium, and oxygen, wherein SiO2 / Al2O3 (mol ratio)=10-2000, and GeO2 / SiO2 (mol ratio)=0.001-2.0; wherein, the small crystal grains show that volume intermediate value of crystal grains is 0.5-10[mu]m, and the hierarchically pores comprise micropores and mesoporous. The hierarchically porous ITH structural silica-alumina molecular sieve with small crystal grains has good hydro-thermal stability; and when the molecular sieve is applied to a reaction for preparation of alkene by a MTO method, the molecular sieve has the advantages of high propylene selectivity, good low carbon selectivity, long service life of catalysts, and the like.

Description

technical field [0001] The invention relates to a silicon-alumina molecular sieve with a small-grain multi-level hole ITH structure and a preparation method and application thereof. Background technique [0002] Low-carbon olefins, especially ethylene and propylene, are important basic organic chemical raw materials and play a pivotal role in modern petroleum and chemical industries. The traditional production route of ethylene and propylene relies too much on petroleum resources. Petroleum is a non-renewable resource, and its distribution is uneven. There are problems of unstable short-term supply and insufficient long-term storage, which restricts the traditional process of preparing low carbon olefins such as ethylene and propylene, and the contradiction between supply and demand becomes increasingly prominent. Therefore, it is imminent to develop a new technology that can replace the traditional preparation of low-carbon olefins. Countries all over the world have devote...

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Problems solved by technology

In 2006, R.Castaneda et al. (J.Catal.2006,238,79~87) reported a method for directly synthesizing silicon-aluminum molecular sieves with ITH structure, but silicon and aluminum sources were limited to tetraethyl orthosilicate and isopropyl Alcohol aluminum (Aluminum Isopropoxide, AIP), used templating agent is very expensive, simultaneously, the amount of water that requires in the synthesis system is less (H 2 O / SiO 2 The molar ratio is generally less than 10), and the hydrolysis process inevitably loses water, so the formed colloid is relatively viscous, and it is not easy to stir evenly, resulting in poor repeatability of the synthesis process

However, the total selectivity of low-carbon olefins in this case is poor, only in the range of 66.5% to 76.5%; although the catalyst life is up to 20 days, it can be seen from the data given in the specific examples that the life of the catalyst obtained in this case Basically, it is about 8 to 15 days, and it needs to be continuously recycled and regenerated by complex fluidized bed technology, which is difficult to meet the actual industrial needs

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