Method for preparing pure finely porous molecular sieve psosessing even distribution of acid strength

Abstract

A millipore HZSM-5 molecular sieve with uniform acid strength distribution features that the HZSM-5 molecular sieve taken from market is synthesized again in the aqueous solution of 3-valence al salt at 90-120 deg.C for 10-14 hr.

Description

technical field [0001] This patent application relates to a method for preparing molecular sieves, in particular to a method for preparing a pure microporous HZSM-5 molecular sieve with uniform acid strength distribution. Background technique [0002] Secondary synthesis of commercially available molecular sieves to reconstruct the pore structure and acid properties of molecular sieves is one of the effective ways to improve the separation effect of molecular sieves and increase their shape-selective properties. Exploring new secondary synthesis methods and research on synthesis effects are becoming a hot topic in the field of catalysis and separation. At present, the commonly used molecular sieve post-treatment methods include: high-temperature water vapor and / or acid filtration washing treatment, and lye hot reflux treatment. The former causes the release of aluminum from the molecular sieve framework, increases the ratio of silicon to aluminum in the framework, and forms...

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Problems solved by technology

The aforementioned dealumination treatment, whether it is high-temperature water vapor or acid washing, will cause the original number of acidic number of the molecular sieve to decrease, the micropores will be partially blocked, and the distribution of the acid strength of the molecular sieve cannot be effectively controlled.

Recently, it has been reported in the literature (S.vanDonk, A.H.Janssen, J.H.Bitter, and K.P.de Jong, Catal.Rev.2003, 45, 297-319) that the molecular sieve after dealumination is treated in acidic or alkaline solution, or the High silica-alumina molecular sieves exposed to AlCl 3 or AlBr 3 The number of acid sites of molecular sieves can be partially restored or increased in steam, but the pore structure and acid properties of the treated molecular sieves cannot fully meet the requirements, and there is a big problem whether the non-framework aluminum species are really re-entered into the molecular sieve lattice. controversy

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