The role of Al species on the formation of hierarchical morphology of ZSM-11 zeolite

Hierarchically structured ZSM-11 zeolites composed of numerous nanorods can be generated by employing TBA+ as a template in the Al species containing systems. Herein, we report on the positive function of Al species on the formation of the hierarchical morphology of ZSM-11. To reveal the influence of Al species on the crystal morphology, a recrystallization process was conducted after adding Al species into a well crystallized silicalite-2 mixture and the evolution process was tracked by XRD, SEM, TEM, FTIR and N2 adsorption. It has been found that the presence of Al species has a great influence on the behaviour of TBA+, which causes a certain amount of TBA+ adhered on the surface of the newly formed Si-Al framework fragments to suppress the aggregation of fragments to form a large single-like crystal. These results have improved our cognition on the mechanism of hierarchical ZSM-11 crystallization and may contribute to the preparation of materials with controlled morphology. [Display omitted] •Hierarchical ZSM-11 was obtained by recrystallizing an Al + silicalite-2 mixture.•TBA+ plays a crucial role in inducing the formation of hierarchical morphology.•Al is necessary for the hierarchical structure by affecting the behavior of TBA+.