Preparation method of highly dispersed hierarchical pore H-ZSM-5 molecular sieve of framework metal

Abstract

The invention discloses a preparation method of a highly dispersed hierarchical pore H-ZSM-5 molecular sieve of a framework metal. The preparation method comprises the following steps: treating carbonblack by oxidation treatment to prepare hydrophilic carbon black as a hard template; preparing a nanoscale double metal specie by a space limitation method as a metal source of doping the framework;synthesizing a metal framework doped hierarchical pore H-ZSM-5 molecular sieve by one-step in-situ hydro-thermal synthesis; and preparing an H type molecular sieve by means of Na type molecular sieveion exchange. The H-ZSM-5 molecular sieve prepared by the method retains the advantages of a microporous molecular sieve and regular mesoporous ducts are added in the structure, so that the mass transfer performance of the molecular sieve is improved. The method solves the problems of degree of crystallinity and destroy of active center of a parent body of the molecular sieve as a result of a post-treatment method. The active metal sites of the molecular sieve are increased by isomorphous substitution of the nano metal specie, so that the reaction performance of the catalyst is improved. The dosage of a reagent caused by regulating / modifying the molecular sieve structure for many times is saved, and the catalyst preparation process flow is shortened.

Description

technical field [0001] The invention relates to a method for preparing a framework metal highly dispersed hierarchical porous H-ZSM-5 molecular sieve, which belongs to the field of catalytic material synthesis. Background technique [0002] The H-ZSM-5 molecular sieve developed by Mobil in the 1970s, because of its high specific surface area, excellent ion exchange performance, strong acidity and shape-selective catalytic ability, is often used as a catalytic material and widely used in catalysis, ion exchange and separation fields. Although the H-ZSM-5 molecular sieve has such excellent catalytic performance, its micropores are smaller than 0.6 nm, and its mass transfer diffusion severely limits its catalytic application. The synthesis of microporous-mesoporous materials with dual pore size distribution is an important pore system engineering. Hierarchical pore H-ZSM-5 molecular sieve can optimize the pore properties of catalysts and the synergistic effect of active sites,...

AI Technical Summary

Problems solved by technology

However, through metal surface modification of molecular sieves, the interaction ability between the metal ion precursor and the molecular sieve carrier is weak. During the heat treatment or reduction process, the metal is easy to diffuse into the surface or pores of the carrier, resulting in the migration and aggregation of the active metal components and Segregation phenomenon, forming larger metal particles, partially blocking the pores of mesoporous molecular sieves, the uneven and disordered distribution of such metal particles on the carrier determines its poor thermal stability

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