Synthesis of a Zr/Sn/Al-SBA-15 catalyst for the conversion of glucose to lactic acid

Abstract

This work reports the synthesis and catalytic evaluation of mono- and bimetallic Zr/Sn/Al-SBA-15 catalysts for the chemo-catalytic conversion of glucose to lactic acid. SBA-15 was modified via alumination to enhance Brønsted acidity and subsequently impregnated with varying loadings of zirconium and tin to introduce Lewis acid sites. Comprehensive characterization using BET, XRD, and NH₃-TPD confirmed that metal loading significantly influenced the textural and acidic properties of the catalysts. Among the monometallic variants, 2% Sn/Al-SBA-15 exhibited the highest lactic acid yield (4.1%) and glucose conversion (47.5%) under the screening conditions (200 °C, 5 bar N₂, and 3 h). Bimetallic catalysts achieved higher glucose conversions (up to 72.5%) but slightly lower lactic acid yields, likely due to side reactions and catalyst deactivation. Optimization studies identified 210 °C and 50 bar N₂ as the optimal conditions, achieving a lactic acid yield of 25.2% with 99.6% glucose conversion. The results highlight the synergistic role of Lewis and Brønsted acid sites in enhancing catalytic performance and demonstrate the potential of Zr/Sn/Al-SBA-15 catalysts for sustainable lactic acid production from biomass-derived glucose.