Bimetallic synergy in tin-modified zeolites for highly efficient conversion of cellulose to methyl levulinate

The efficient transformation of cellulose from renewable biomass into the fuel additive methyl levulinate remains a significant challenge. Herein, the hydrothermal post-synthesis method was employed to synthesize a series of tin-based bimetallic Beta zeolites with multifunctional properties, Sn-M-Beta-SO 3 H (M = Al 3 + , In 3+ , Ti 4+ , and Zr 4+ ), for the direct conversion of cellulose to ML. The as-prepared Sn-M-Beta-SO 3 H catalysts were systematically analyzed via XRD, SEM, TEM, UV-Vis, XPS, FT-IR, NH 3 -TPD, and Py-IR techniques. The results revealed that the synergistic interaction between Sn and M influences the composition of acidic sites and the physical properties of these multifunctional zeolites. Notably, Sn-Al-Beta-SO 3 H, with an optimal balance of Lewis and Brønsted acidic sites, achieved an impressive ML yield of 69.7 % at 180 °C within 6 h—one of the highest reported values among heterogeneous catalysts to date. Furthermore, based on experimental findings, a potential reaction pathway for cellulose conversion over Sn-Al-Beta-SO 3 H was proposed, with fructose identified as a key intermediate.