Titanium Silicate-1 Coupled with Sn and Er as Effective Catalysts for the Production of Lactic Acid from Saccharides

Biomass-based saccharide valorization to produce lactic acid (LaA) via chemocatalysis has emerged as a promising approach to meet the substantial demand of global LaA market, whereas the manufacture of prominent heterogeneous catalyst is still challenging. Herein, we fabricate a series of heterogeneous rare earth catalysts, and indicate that Er supported onto titanium silicate-1 (TS-1) exhibits better activity than other rare earth catalysts for glucose transformation towards LaA. Remarkably, coupling Sn with Er onto TS-1 enabled the sharp increment of LaA yield, and 3Sn15Er/TS-1 catalyst outperformed other heterogeneous rare earth catalysts as reported to date, giving as high as 82.2 % and 76.2% yields of LaA from sorbose and glucose, respectively. The catalyst characterization demonstrated the coexistence of Er2O3 and Sn2Er2O7 on 3Sn15Er/TS-1 catalyst, both of which contributed to LaA production. Sn doping favored the formation of active particles in smaller size and increased the Lewis acidic sites when compared to single 15Er/TS-1, thereby promoting the isomerization and retro-aldol reaction of glucose to C3 intermediates. 3Sn15Er/TS-1 catalyst also showed universal activity for diverse biomass-based saccharides. This work might give useful insights to explore heterogeneous rare earth catalysts with superior activity in biomass valorization.