Method for preparing phosphor modified ZSM-5 sieve

Abstract

This invention relates to a method for preparing P-modified ZSM-5 molecular sieve. The method comprises: (1) performing heat-exchange on synthesized ZSM-5 molecular sieve with ammonium solution; (2) placing in a fixed bed reactor; (3) heating to evaporate and sublimate phosphorus oxide at 250-600 deg.C; (4) introducing air or inert gas into the fixed bed reactor as the carrier gas, and uniformly depositing phosphorus oxide onto ZSM-5 molecular sieve by chemical vapor deposition to obtain P-modified ZSM-5 molecular sieve. The method can uniformly deposit phosphorus oxide onto ZSM-5 molecular sieve, thus improving the hydrothermal activity and stability of ZSM-5 molecular sieve. The catalytic cracking catalysts with P-modified ZSM-5 molecular sieve as the active component have better catalytic activity and can bring higher olefin yields. The method has such advantages as easy operation, high controllability.

Description

technical field [0001] The invention belongs to the technical field of molecular sieve preparation, and particularly relates to a method for preparing phosphorus-modified ZSM-5 molecular sieves. More precisely, phosphorus oxides are uniformly deposited on ZSM-5 molecular sieves by chemical vapor deposition for chemical modification. Background technique [0002] Since the Mobil Petroleum Company of the United States invented ZSM-5 molecular sieve (USP 3702886) in 1972, due to its high silicon-aluminum ratio, unique pore structure and excellent thermal and hydrothermal stability, ZSM-5 molecular sieve has been used in It has been widely used in petrochemical processes such as shape-selective cracking, alkylation, isomerization, disproportionation, catalytic dewaxing, and etherification of hydrocarbons. The synthesis method of ZSM-5 molecular sieve has been developed from the classic organic method using organic ammonium as a template to the synthesis method without ammonium. ...

AI Technical Summary

Problems solved by technology

The disadvantage of its method is that if it is synthesized at high temperature, AlO 4 -5 grows well in the outer layer of ZSM-5, which easily leads to AlO 4 -5 independent crystallization, it is difficult to form a core / shell molecular sieve in the true sense; if synthesized at low temperature, AlO 4 -5 has a long crystallization time, resulting in excessive energy consumption

[0014] For ZSM-5 molecular sieve, due to the high ratio of silicon to aluminum in the framework and the unique pore structure, the amount of phosphorus introduced by ion exchange or impregnation is limited, and it is difficult to obtain phosphorus in the mode of solid-solid reaction or solid-colloid reaction. The molecular sieve product with uniform distribution of oxides affects its performance, and the molecular sieve modification in the prior art is an indispensable roasting process with high energy consumption after contacting with phosphorus oxides, which increases the production cost. cost