Synthetic zeolites, such as FAU Y and MFI ZSM-5 zeolites, are industrially important solid acid catalysts, especially in petrochemical fluid catalytic cracking (FCC) for producing gasoline range and gaseous (such as propylene) products. Reactivity, selectivity and accessibility are import features of bulk zeolites, being critical to determine the performance of industrial FCC catalysts. Specifically to address accessibility issues associated with the microporous zeolites (or diffusion limitation in the framework), various strategies are being developed and explored to enhance the rate of diffusion reactants/produces into/from the zeolites, such as the design of nanozeolites, the templating method to prepare zeolites with mesoporous features and the post-synthesis modification methods to prepare hierarchical zeolites. Among these developments, the post-synthesis methods (such as dealumination and desilication) are robust and practical with low-cost implications, and used by the industrial, being deemed as unlikely to have breakthrough development. In this keynote presentation, by revisiting the mechanisms of dealumination of low Si/Al Y zeolite and the desilication of ZSM-5 zeolite, we propose new strategies to improve the old techniques further with relevant findings to show the developed hierarchical mesoporous FAU Y and mesoporous low Si/Al ratio hollow ZSM-5 zeolites, as well as their catalytic performance in model cracking reactions.

Revisiting the old dealumination and desilication of synthetic zeolites: Way forward

2019 Fall National Meeting

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