Efficient production of lactic acid from biomass-derived carbohydrates under synergistic effects of indium and tin in In–Sn-Beta zeolites†
In the catalytic transformation of biomass into valuable chemicals, it is extremely important to inhibit undesirable reactions to increase the yield of target products. In this study, the introduction of indium and tin into Beta zeolites promoted the transformation of glucose into lactic acid with a high yield of 53%. Selective experiments and a developed kinetic model confirmed the sensitivity of the main reaction rate to the action of tin, including those of the isomerization and retro-aldol condensation reactions, and shielding of the side reactions by indium. An in-depth analysis of the catalyst acidity showed that weak Lewis acidity in the indium and tin species promoted the main reaction steps, whereas the decreased amount of strong Lewis acidity by introduction of indium into the Sn-Beta catalyst suppressed the side reactions. The coupling of multifunctional active sites provides a new strategy for addressing challenges in commercial lactic acid production.