Composite modified molecular sieve improving activity and hydrothermal stability and preparation method thereof

Abstract

The invention discloses a composite modified molecular sieve improving activity and hydrothermal stability and a preparation method thereof. The preparation method is characterized by comprising the following steps of: adding the molecular sieve into phosphorus aqueous solution, reacting the molecular sieve for some time at a certain pH value and temperature and under a certain pressure, and filtering, drying and roasting the reaction product to obtain a phosphorus modified molecular sieve; and adding the phosphorus modified molecular sieve into the aqueous solution which contains rear-earth ions, reacting the molecular sieve for some time at a certain pH value and temperature and under a certain pressure, and filtering, washing, drying and roasting the reaction product to obtain the composite modified molecular sieve. The modified molecular sieve has a dry basis content of 88 to 99 weight percent, a silica alumina ratio of 15 to 250, 0.01 to 10 weight percent of phosphorus and 0.01 to 10 weight percent of rear earth. A model catalyst prepared through the composite modified molecular sieve has higher hydrothermal stability and micro activity than a model catalyst which contains anunmodified molecular sieve and a molecular sieve which is modified by other methods.

Description

technical field [0001] The invention belongs to the technical field of molecular sieve modification, in particular to a composite modified molecular sieve with improved activity and hydrothermal stability and a preparation method. Background technique [0002] In recent years, researchers and manufacturers of refining catalysts at home and abroad have long been committed to improving the performance of FCC catalysts by using molecular sieves with various types of structures, and increasing the yield of low-carbon olefins in FCC units. This is because steam cracking, the traditional main method for producing ethylene and propylene, is carried out through free radical reaction, with high temperature and strict requirements on raw materials. However, the cost of producing low-carbon olefins by catalytic cracking is relatively low, and it is currently a hot spot in research at home and abroad to increase the production of low-carbon olefins. Functional shape-selective molecular...

AI Technical Summary

Problems solved by technology

[0021] However, when the current conventional phosphorus-modified molecular sieves introduce the second modified component through ion exchange, the phosphorus element in the molecular sieve will be lost in large quantities and the purpose of the two-component modified molecular sieve cannot be achieved, thereby affecting the stability of the molecular sieve and Catalytic activity

Similarly, when rare earth modified molecular sieves are prepared by conventional impregnation or exchange methods, the rare earths are only adsorbed on the surface of the molecular sieve and are easily lost during post-treatment, contaminating other components in the catalyst.

Images