Method for preparing grade porous ZMS (Zeolite Socony Mobil)-5 molecular sieve by acid-base coupling

Abstract

The invention relates to a method for preparing a ZSM (Zeolite Socony Mobil)-5 in a grade structure, and specifically relates to a method for preparing a grade porous ZMS-5 molecular sieve by acid-base coupling. The method comprises the following steps: mixing commercial ZSM-5 and alkali liquor in proportion, and heating and stirring to form a suspension; filtering the suspension; washing the filter cakes by water or acidic liquor; and finally, carrying out ion exchange by using acidic ammonium salt liquor; and then, roasting to obtain the grade porous ZMS-5 molecular sieve. The method provided by the invention aims to prepare the ZSM-molecular sieve rich in secondary mesopores. Firstly, part of aluminum silicon species in the ZSM-5 is removed in an environment-friendly alkali treatment manner to prepare the ZSM-5 molecular sieve with a secondary pore structure. Based on the secondary pore formed, undefined structures on the surface of the ZSM-5 and in the duct are dissolved out by way of acid washing or ion exchange. Meanwhile, the pore volume and the specific surface area of the secondary mesopore-enriching ZSM-5 molecular sieve are improved. Through the acid-base coupling treatment, the distribution state of aluminum outside the framework on the surface of the ZSM-5 is improved, so that the secondary mesopore-enriching ZSM-5 molecular sieve prepared by the method has a huge application potential in catalytic cracking and hydrocracking.

Description

technical field [0001] The invention relates to a method for preparing ZSM-5 with hierarchical structure, in particular to a method for preparing ZSM-5 molecular sieve with hierarchical pores through acid-base coupling. Background technique [0002] ZSM-5 molecular sieve is a kind of aluminosilicate molecular sieve with MFI crystal structure, which is widely used in petrochemical field, such as catalytic cracking, diesel decondensation, xylene isomerization, etc. With the increasingly heavy crude oil, the macromolecules of crude oil cannot effectively contact the acidic active sites, and the adsorption and desorption of reactants and products in the pores are hindered, resulting in secondary cracking and increased coke production, making ZSM-5, etc. The active sites on the surface of the catalyst are covered, which leads to a decrease in the conversion rate of the reaction, and finally makes the catalyst deactivate rapidly. Therefore, developing high-efficiency ZSM-5 cataly...

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Problems solved by technology

Using high-temperature heat treatment method, during high-temperature treatment, the ZSM-5 molecular sieve with hierarchical pore structure is prone to structural collapse, and the mesopore structure disappears; water vapor treatment, as an ultra-stabilization treatment, has limited mesopores produced by catalytic cracking Y-type molecular sieve treatment, and at the same time Water vapor treatment enriches a large number of extra-framework aluminum species on the surface of Y-type molecular sieve; acid treatment destroys the crystal structure, dissolves amorphous Al species, and produces secondary mesopores, but ZSM-5 molecular sieve is relatively As far as molecular sieves are concerned, the aluminum content is low, so the secondary mesopores produced are also very limited, and at the same time, the acidity and acidity of ZSM-5 will be severely damaged; as a method of selective desiliconization, alkali treatment has been used in the preparation of secondary mesopores. reported in mesopores, but after alkali treatment, the surface of molecular sieves is enriched with a large number of extra-framework aluminum species, which is prone to carbon deposition in catalytic cracking, which limits its application in catalytic cracking processes

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