Large-Mesopore Catalysts Synthesized via Calcination and Hydrothermal Treatment of Zinc-Meso-Y Zeolite Composites

Mesoporous Y (Meso-Y) zeolites are an emerging class of catalysts with mesopores (typically smaller than 9 nm in diameter) for accommodating sterically bulky reactant molecules, such as those commonly encountered in biomass and polymer waste upcycling. Here, in this manuscript, we report the synthesis, physicochemical characterization, and catalysis of novel Meso-Y zeolites consisting of tunable mesopores ranging from 9 to 20 nm in diameter and mesopore volumes of approximately 0.6 cm3/g. Our synthetic approach involves partial dissolution of the zeolite framework and zinc redistribution during calcination and hydrothermal treatment (HT) of conventional Meso-Y zeolites. The synthesis proceeds through an intermediate zinc-rich zincoaluminosilicate (ZnAlSi) phase, which was characterized by scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDX) before HT as a phase partially separated from the zeolite in syntheses involving high zinc concentrations. SEM-EDX characterization of these materials after HT demonstrates large mesopores, accompanied by zinc levels redistributing to the same uniformly low values throughout the material. Data from SEM, scanning transmission electron microscopy–energy-dispersive X-ray spectroscopy (STEM-EDS), and high-angle annular dark-field–scanning transmission electron microscopy (HAADF-STEM) show the synthesis of large mesopores after HT within the zeolite. H/D exchange and n-decane hydroconversion data prove acid-site accessibility in our catalysts under thermodynamically and kinetically controlled conditions, respectively, which is similar to a conventional Meso-Y control catalyst.