Hierarchical Zeolites Prepared Using a Surfactant-Mediated Strategy: ZSM-5 vs. Y as Catalysts for Friedel-Crafts...

Hierarchical ZSM5 and Y zeolites were prepared through a surfactant-mediated strategy with NH₄OH changing the duration of the treatment and the amount of CTAB surfactant and taking as reference multiples of the critical micellar concentration (CMC). The materials were characterized using powder X-ray diffraction, N₂ adsorption isotherms at -196 °C, and SEM and TEM microscopy. The catalytic performance was evaluated in Friedel-Crafts acylation of furan with acetic anhydride at 80 °C. The alkaline surfactant-mediated treatment had different effects on the two zeolites. For ZSM5, the CTAB molecular aggregates can hardly diffuse inside the medium-size pores, leading mainly to intercrystalline mesoporosity and increased external surface area, with no positive catalytic impact. On the other hand, for large-pore Y zeolite, the CTAB molecular aggregates can easily diffuse and promote the rearrangement of crystal units around micelles, causing the enlargement of the pores, i.e., intracrystalline porosity. The optimized Y-based sample, treated for 12 h with a CTAB amount 32 times the CMC, shows an increase in product yield and rate constant that was not observed when a higher amount of surfactant was added. The reuse of spent catalysts upon thermal treatment at 400 °C shows a regeneration efficiency around 90%, showing good potentialities for the modified catalysts.