High-iron content Fe-ZSM-5 molecular sieve preparation method

Abstract

The invention discloses a preparation method of a high-iron content Fe-ZSM-5 molecular sieve. The method is characterized in that under condition that an organic amine template agent is not used, an appropriate silicon source, an alkali source, an aluminium source, and an iron source are selected, seed crystal is added, a hydro-thermal synthesis method, crystallization at constant temperature is carried out to obtain a NaFe-ZSM-5 molecular sieve slurry with the frame containing iron, the slurry is subjected to exchange washing through an acidic solution to obtain low-sodium Fe-ZSM-5, the low-sodium Fe-ZSM-5 and inorganic iron salt liquid are uniformly mixed, and steps of exchange washing at the constant temperature, drying and roasting are carried out to obtain the high-iron content hydrogen-type Fe-ZSM-5; the organic amine template agent is not used, a plurality of the inorganic silicon source, the alkali source, the aluminium source, and the iron source are subjected to the hydro-thermal synthesis method and ion exchange to prepare the Fe-ZSM-5 molecular sieve with an iron content being more than 6%, operation step is less, industrial production is easily realized, and environment pollution problem due to removal of the template agent is not generated. The iron content is increased on the surface of the molecular sieve through a primary ion exchange method, the iron element in and out of the frame of the molecular sieve can be uniformly distributed, and the relative crystallization degree of the Fe-ZSM-5 molecular sieve can be kept in a maximum degree.

Description

technical field [0001] The invention relates to the technical field of molecular sieves, in particular to a method for preparing Fe-ZSM-5 molecular sieves with high iron content. Background technique [0002] Metal-modified zeolite catalysts are currently an important class of catalysts for the selective catalytic reduction of nitrogen oxides. Catalysts prepared with metal-modified molecular sieves such as copper and iron have shown good activity in selective denitration, and the NOx conversion rate is high. At present, the metal-modified molecular sieve catalysts used for selective denitrification include Cu-ZSM-5, Cu-SSZ-13, Fe-ZSM-5, Fe-BETA, Fe-ZSM-5, etc., Cu- ZSM-5 contains 2% water vapor in the reaction raw material, which will seriously affect its catalytic activity, while the automobile exhaust contains up to 10% to 16% water vapor, which greatly affects the NO x The conversion rate of molecular sieves such as SSZ-13 and BETA is introduced into the template during ...

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Problems solved by technology

[0003] The current Fe-ZSM-5 molecular sieve mainly has the following problems in the synthesis: first, the template agent is used, because the cost of the template agent is very high, which greatly increases the production cost of the molecular sieve, and there is environmental pollution in the template agent removal process Second, the iron content of the Fe-ZSM-5 molecular sieve synthesized by the current in-situ synthesis method is not high, generally below 3%, and generally requires at least two exchanges and repeated roasting to make Fe-ZSM-5 Molecular sieves are loaded with higher iron content, but repeated roasting is likely to cause defects in the crystal skeleton of Fe-ZSM-5 molecular sieves, affecting the crystallinity of the product and ultimately affecting its catalytic performance; third, although the existing method of solid impregnation can improve Iron content of Fe-ZSM-5 molecular sieve, but most of its active sites exist on the surface of molecular sieve, resulting in low catalytic activity of molecular sieve

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