Supporting Metal Nanoparticles within Preformed Small-and Medium-pore Zeolites and Their Analogues assistedby Mercaptoamine

초록

Zeolite-encapsulated metal nanoparticle catalysts have attracted much attention for their enhanced resistance to sintering, poisoning, and coking in catalytic reactions. Herein, I will introduce a comprehensive method for encapsulating metal nanoparticles within pre-existing zeolites via post-synthetic modification. This strategy involves supporting both anionic and cationic precursors to zeolites and zeolite analogues that have been grafted with 2-aminoethanethiol (AET). In this process, the thiol (?SH) groups in AET ligands can coordinate with metal centers, while the amine groups were dynamically attached to the walls of the micropores through acid-base interactions, ensuring a uniform distribution of the metal-AET complex within the zeolite framework. During impregnation, conducted in near-neutral conditions, larger ligands (like Cl- and NO3-) bound to metal centers are partially substituted with smaller OH- ligands, improving the accessibility to the metal precursors. These processes successfully encapsulated Au, Rh, and Ni within the 8MR-CHA, 10MR-*MRE, 10MR-MFI, and 8-MR SAPO-34 zeolite analogues. Following a sequential activation process, small metal nanoparticles (1?2 nm in diameter) were uniformly distributed throughout the zeolite framework. Containment within small micropores also protects the nanoparticles against thermal sintering and prevents fouling of the metal surfaces by coke, thus resulting in high catalytic performance toward n-dodecane hydroisomerization and methane decomposition.