Tailoring the Morphology of MTW Zeolite Mesocrystals: Intertwined Classical/Nonclassical Crystallization

The morphology and porosity of zeolite play a significant role in the activity and selectivity of catalytic reactions. It is a dream to optionally modulate zeolite morphology by regulating the crystallization process on the basis of comprehensively understanding the mechanisms. Herein, a series of MTW zeolite mesocrystals can be consciously fabricated with morphologies from a dense structure to a loose one of an oriented nanocrystallite aggregate by changing the H2O/SiO2 ratio. Their intertwined classical/nonclassical crystallization processes are investigated comprehensively. The results indicate that the crystallization of MTW zeolite takes place by a chain of events, including the formation of wormlike particles (WLPs), their aggregation, and crystallization of aggregates. MTW with a loose structure mainly crystallizes by an internal reorganization after a fast aggregation of WLPs in a concentrated system. On the other hand, the dense MTW is realized via the co-occurrence of a coalescence of the participating WLPs during its crystal growth with a slower rate in a dilute system. Moreover, the advantages of MTW with a loose structure are confirmed through cumene cracking and 1,2,4-trimethylbenzene transformation. This method could pave the way for the synthesis of other zeolites with diverse morphologies and/or mesoporosities via subtle regulation of the crystallization pathway.