A kind of preparation method of fe-zsm-5 molecular sieve with high iron content

Abstract

The invention discloses a method for preparing the Fe-ZSM-5 molecular sieve with high iron content of the present invention. Firstly, under the condition of not using an organic amine template, select a suitable silicon source, alkali source, aluminum source, iron source, and add crystal seeds , using a hydrothermal synthesis method, constant temperature crystallization to obtain a NaFe-ZSM-5 molecular sieve slurry containing iron in the skeleton, the slurry is exchanged and washed with an acidic solution to obtain a low-sodium Fe-ZSM-5, and then mixed with an inorganic iron salt solution evenly, Constant temperature exchange washing and drying, roasting to obtain high iron content hydrogen Fe-ZSM-5; without using organic amine template agent, using a variety of inorganic silicon sources, aluminum sources, iron sources and seeds to prepare iron by hydrothermal synthesis and ion exchange Fe-ZSM-5 molecular sieve with a content of more than 6% has few operation steps, is easy to realize industrial production, and does not cause environmental pollution caused by removing the template agent; the application improves the molecular sieve surface by an ion exchange method. The iron content is increased, so that the iron elements inside and outside the molecular sieve framework are evenly distributed, and the relative crystallinity of the Fe-ZSM-5 molecular sieve is retained to the greatest extent.

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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