Study on synthesis of hierarchical ZSM-5 zeolite by seed method
Hierarchical nano-sized ZSM-5 aggregate zeolite was synthesized by seed-assisted method with sodium alumi-nate as aluminum source,silica sol as silicon source,Silicalite-1(S-1)as seeds and ammonium carbonate as auxiliary agent.The effects of the amount of ammonium carbonate,the amount of seed,the H2O/SiO2 ratio and the crystallization tem-perature on the physical properties of the hierarchical ZSM-5 zeolite were investigated.The characterization results of X-ray diffraction(XRD),scanning electron microscopy(SEM),and N2 adsorption-desorption indicated that the addition of ammonium carbonate reduced the pH value of the system,which slowed down the nucleation rate of the zeolite,and significantly reduced the relative crystallinity(RC)of ZSM-5.S-1 could increase the specific surface area and pore volume of ZSM-5 zeolite when it was added at a dosage of 5%～7%(mass fraction).Furthermore,the H2O/SiO2 ratio had a significant effect on the morphology of ZSM-5 zeolite.The hierarchical ZSM-5 zeolite with more concentrated mesoporous distribution could be synthesized with H2O/SiO2 ratio of 45.Due to the improved accessibility of active centers and reac-tants,as well as the reduced residence time of reaction products in the pores,the zeolite exhibited excellent stability and se-lectivity for the alkylation of trimethylbenzene with methanol compared with the ZSM-5-180 zeolite.
NETL
NSTL
万方数据
