Optimized preparation and regeneration of MFI type base catalysts for D-glucose isomerization in water

The isomerization of D-glucose to D-fructose is an important transformation in food and biomass chemistry, for which the use of robust heterogeneous catalysts instead of restrictive enzyme-based systems is desirable, although continues to be very challenging. Herein, solid base catalysts possessing a relatively robust hierarchical MFI structure and (non-toxic) alkali (M = Na, K) and alkaline-earth (Me = Ca, Mg) metals were prepared via top-down strategies and characterized via complementary techniques. The catalyst preparation and regeneration conditions were optimized to meet superior performances. The highest catalyst stability was reached for the Mg,K-containing hierarchical zeotype prepared via solid-state impregnation (SSI) of Mg, which led to 65 % D-fructose selectivity at 45 % conversion, 100 ⁰C, 2 h, or 99 % selectivity at 26 % conversion, 75 ⁰C. The SSI is an up scalable process which advantageously avoids the use of solvents, pre-preparation of alkaline liquid solutions and solvent evaporation stages for manufacturing eco-friendly catalysts.