Engineering of Lewis Acid Sites in Mesoporous Zeolite Achieves Record Fructose Yield of 71.5% for Glucose Isomerization in Ethanol

Lewis acid catalyzed glucose isomerization is a vital step in biorefinery, but it's restricted by the limited catalytic toolkit and reaction equilibrium. Herein, we report that engineering Lewis acid sites in a mesoporous zeolite can greatly boost productivity. Incorporating a few of Sn species into KIT-6 zeolite with the assistance of phosphorylation delivered SnPO/KIT(x) materials with abundant Lewis acid sites and a few of Brønsted acid sites, while conserving the ordered mesoporous structure. Moreover, the Lewis acidic Sn sites have a coordination environment distinct from those in traditional zeolites and metal phosphates, as is crucial to facilitate isomerization and to control side-reactions. Rigorous experiments showed that the use of SnPO/KIT(80) catalyst in two-step isomerization process combined with adequate hydrolysis of ethyl fructoside attains a fructose yield of 71.5%, surpassing the state-of-the-art catalytic systems, along with good reusability and tolerance to high-concentration glucose. These findings highlight the great potential of precisely manipulating coordination environment of Lewis acid sites to boost catalytic performance.