(521dl) Modulating the Physicochemical Attributes of ZSM-5 Using Multivalent Ions-Assisted Synthesis
AIChE Annual Meeting
2023
2023 AIChE Annual Meeting
Catalysis and Reaction Engineering Division
Poster Session: Catalysis and Reaction Engineering (CRE) Division
Wednesday, November 8, 2023 - 3:30pm to 5:00pm
Electron microscopy revealed that the use of modifiers has a limited impact on the size of crystals, but has a significant effect on crystal morphology. Conventional ZSM-5 crystals have twinned boat morphology with an average size of ~1.5 μm. ZSM-5 synthesized in presence of charged modifiers resulted in varying crystal sizes (1-2 µm) and morphological attributes depicting enhanced basal plane (higher c-axis growth), appearance of facets relevant to reaction studies, and higher b-axis growth. AFM studies on the as-synthesized zeolite helped explore the underlying growth mechanisms in presence of different modifiers. Further, modifiers were able to significantly increase Bronsted acid sites (IR band at 1548 cm-1) from 104 μmol gm-1 (control) to 198 μmol gm-1 (modified) in ZSM-5. A careful selection of modifiers also helped us to modulate extra-framework Aluminum sites, increase Lewis acidic character and reduce the H-bonded acid sites by half.
Overall, these observations provided unprecedented insights into the critical role of growth modifiers on crystal morphology and acid characteristics (effected by Aluminum speciation in growth solution) and thereby the catalytic potential of these as-synthesized zeolite.