Synthesis And Application Of Hierarchical ZSM-5 Zeolite

Hierarchical ZSM-5 zeolite as a good shape-selecting catalyst has wide industrial applications.The hotspot is how to synthesize hierarchical ZSM-5 zeolite with simple and inexpensive method.In this paper,mesoporous silica spheres were used as silicon source and sacrificial template to synthesis hierarchical ZSM-5 zeolite,and the sample were applied in MTA reaction.First,mesoporous silica spheres were prepared by a modified Stober method and used as silicon source for subsequent experiments.The hierarchical ZSM-5 zeolite was synthesized by steam-assisted crystallization method.The influence of time,temperature,aluminum source and amount of template agent on synthesis was discussed.Compared the structural properties of synthetic samples under both sodium-free and sodium conditions.The sodium-free method can obtain the desired crystal structure.Two samples were used in the MTA reaction,the selectivity of BTX and aromatics in sodium-free sample improved 23 and 22 percentage points compared with the sodium sample,respectively.The sodium-free sample showed more excellent catalytic activity than sodium method sample.Secondly,the modified steam-assisted crystallization device used a multi-layer crystallization method to facilitate crystallization.Hydrothermal synthesis and steam-assisted crystallization were used to obtain samples with different morphologies.The water steam-assisted crystallization sample WV-ZSM-5 had obvious concave defects and the hydrothermal synthesis sample HT-ZSM-5 was a typical hexagonal prism structure.Two samples were used in the MTA reaction,the selectivity of BTX and aromatic were not much different.The lifetime of WV-ZSM-5 improved 73.8%compared with HT-ZSM-5.WV-ZSM-5 showed more excellent catalytic stability.Finally,the microporous ZSM-5 was modified by Fenton reagent.It was found that the crystallinity of the sample after Fenton reagent treatment was improved.The addition of mesopores increased the average crystal pore size from 2.7 nm to 4.0 nm,and the acid amount increased significantly.