The efficient conversion of biomass-derived glucose to fructose holds significant research value, as fructose serves as a critical intermediate in transforming cellulosic biomass into biofuels and chemicals. Currently, glucose isomerase is predominantly utilized as a catalyst in industrial processes; however, this enzymatic method faces limitations due to reaction constraints, leading to high production costs. Moreover, while chemical catalysis can achieve glucose-to-fructose isomerization, it typically requires elevated temperatures, which adds to operational complexity. This study aimed to develop an innovative method for the isomerization of glucose to fructose at room temperature (25°C) in water. The CaO-MgO base catalyst was synthesized by varying the molar ratios of CaO and MgO (denoted as CM-X, where X% represents the CaO molar content in the catalyst). Key parameters including CaO content, reaction time, and catalyst loading were optimized using response surface methodology (RSM). Verification experiments confirmed that when CM-10 catalyst was used for 40 min at 25°C, with a catalyst-to-glucose mass ratio of 0.75, the fructose yield reached 34.6 %, with a selectivity of 76.3 %. Furthermore, CM-10 can be calcined and recycled at least five times while maintaining stable catalytic activity. CaO content is the most significant factor influencing the catalytic performance at room temperature, as it dictates the quantity of medium and strong basic sites on CM-X catalyst. Specifically, the ratio of medium/strong to weak basic sites of the CM-Xs exhibits a positive linear relationship with CaO content. DFT calculations indicate that CaO, as the source of strong basicity in CM-10, is the preferred contributor to the selectivity of glucose isomerization towards fructose. Additionally, first-order kinetic modeling validated the mechanism of glucose isomerization. Therefore, this study proposes an efficient, green, and simple method for chemical isomerization of glucose into fructose at room temperature. • Glucose isomerized efficiently to fructose in water at room temperature. • RSM was employed to optimize the reaction conditions. • CaO-MgO showed high activity with 34.4 % yield and 76.3 % selectivity of fructose. • CaO (strong basicity) preferentially drives fructose selectivity in DFT analysis. • The catalyst exhibited good recyclability after facile thermal regeneration.
Long et al. (Fri,) studied this question.