Enhanced dispersion of Pt and Ni nanoparticles on ammonia-treated siliceous MFI zeolites for toluene hydrogenation

Abstract

In heterogeneous catalysis, the performance of supported metal catalysts is often limited by metal agglomeration. Herein, we tackle this challenge by loading Pt and Ni nanoparticles into the micropores of MFI zeolites possessing single-point defects created by ammonia/ammonium (NH₃/NH₄⁺) solution treatment. Characterization through infrared spectroscopy revealed the formation of silanol-nest defects, analogous to those produced by strong acid treatment in metallosilicate zeolites. Metal loading was performed by incipient wetness impregnation, both with and without silanol nests. The extent of silanol nests led to significant differences in Pt and Ni dispersion, as evidenced by hydrogen chemisorption and scanning transmission electron microscopy. Notably, the silanol nests enhanced catalytic activity of encapsulated Ni nanoparticles in toluene hydrogenation by 810-fold.