Ultra-high-field solid-state NMR spectroscopy unveils the effects of the microwave-assisted post-synthetic treatments of FAU Y on the structural integrity of the resulting zeolites with mesoporosity, as well as the role of various framework and extra framework species in the performance in catalytic cracking reactions.

Abstract

Ultra-high-field solid-state NMR spectroscopy (1.0 GHz, 23.5 T) was employed to reveal the structural evolution of aluminum species and thus their correlations to catalytic cracking performance of Y zeolites after post-synthetic treatments. Microwave-assisted treatments, including chelating dealumination and NH₄OH treatment, induced significant changes in both framework and extra-framework aluminum species. NMR analysis identified that the interaction between extra-framework Al(V/VI) and Brønsted acid sites (BAS) play a crucial role in enhancing catalytic efficiency. The hierarchical zeolite Y-MWNH3-0.1–30 exhibited superior catalytic cracking performance, achieving high yields of light hydrocarbons (C₁–C₄), and excellent selectivity toward BTX during the cracking of bulky molecules. These findings provide new insights into how post-synthetic modifications can be used to tune aluminum species distribution and acid site interaction, optimizing zeolite catalysts for hydrocarbon conversion performance.