Hierarchical ZSM-5 zeolites as catalysts for biomass valorization reactions

ZSM-5 zeolites are widely used in the petrochemical industry because of their acidity, shape selectivity, thermal stability, and tunable hydrophobicity. These properties also make them promising catalysts for biomass valorization. Hierarchical ZSM-5 zeolites, containing both micro- and mesopores, improve diffusion and enhance the formation of larger products. Mesoporosity can be introduced through alkaline NaOH treatment, which partially removes silicon and increases Lewis acidity. In this work, hierarchical ZSM-5 zeolites with Si/Al ratios of 23, 38, and 48 were evaluated for the conversion of furfural into isopropyl levulinate, a valuable biofuel additive precursor. The reaction employed isopropanol as both solvent and hydrogen donor through a Meerwein–Ponndorf–Verley transfer hydrogenation mechanism, avoiding the use of molecular hydrogen and enabling safer, lower-cost operating conditions. Catalyst properties were characterized by XRD, XRF, N₂ physisorption, TPD-NH₃, and FTIR-Py. Treated catalysts achieved 95% furfural conversion, 98% selectivity, and maintained excellent performance after three recycling cycles.