This study presents a method for the economical production of fructose and allulose (a valuable byproduct) directly from glucose over a MgO/CaO nanocomposite under an aqueous condition. The catalyst containing MgO and CaO at equal proportions helped manipulate the inherent characteristics of CaO, particularly strong basicity and surface properties. The analytical characterizations revealed that the structural assembly is such that MgO settles at the surface to initiate the isomerization reaction by providing a higher number of weak/medium base sites. The CaO present beneath undertakes the sequential conversion of the enolintermediate to ultimate fructose and byproducts (mannose and allulose). Thus, the catalyst accelerated the glucose interconversion to obtain a fructose yield as high as 33 wt % with 80% selectivity within 15 min. At the same time, it also initiated the C-3 fructose epimerization to yield allulose (a low-calorie sugar molecule). Moreover, the adopted deep neural network modeling well predicted the catalytic response with the MAE <5%. The technoeconomic analysis estimated the minimum selling price of different products to be US $ ∼4/kg (fructose), $ ∼4/kg (mannose), and $ ∼10/kg (allulose).

Here, we describe the maximum production of 5‐HMF using glucose over Sn doped Ta2O5 in a binary solvent system. The analytical characterizations established that Sn4+ in the catalyst interacts with Ta2O5 and offers the Lewis acid sites favorable for glucose isomerization to fructose. Similarly, the Ta2O5 support offers both the Lewis and Brønsted acid sites to promote fructose dehydration to 5‐HMF. The catalyst provided favorable conditions for the sequential sugar(s) transformation, i. e., glucose isomerization followed by fructose dehydration, which resulted in a 5‐HMF yield as high as 57 % wt. and 80 % selectivity under modest reaction conditions in a water‐DMSO system using ST1 (1 % Sn on Ta2O5). The separate fructose to 5‐HMF conversion study verified the negligible influence of Sn on the dehydration reaction. Moreover, the catalyst's systematic sugar conversion enabled a >65 % fructose formation, which accounts for the enriched 5‐HMF synthesis. The neural network model best represented the 5‐HMF data (<4 % MAE for glucose and fructose conversions).

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While many reports on the kinetics and mechanism of glucose isomerization to fructose via a chemical pathway have been published, thermodynamic insights into the interconversion reaction are rarely reported. Here, we report the temperature-dependent characteristics of the cation- and anion-mediated glucose conversion to fructose. The counter ions of MgBr2 enabled the reaction via different pathways in water; e.g., Mg2+ influenced the reaction by undertaking the 1,2-hydride shift mechanism and accounted for up to 50% of the conversion. However, the counter ion (Br–) promoted the conversion via the proton transfer mechanism, which contributed to the remaining 50%, based on the results of the isotopic labeling experiments. This selective transformation (32% wt fructose yield and 76% selectivity) aided by MgBr2 is attributed to the formation of a weak water shell around Mg2+ (due to a lower ratio of MgBr2 to water), which permitted the cation to expose its catalytic activity and affected the administering activity by Br–, which induces maximum side reactions. By applying the principles of transition-state Eyring and Marcus theories to the elementary steps involving a proton transfer and electron transfer, respectively, the temperature-dependent characteristics of the corresponding pathways were determined. The Eyring model exhibited a linear trend in the ln(k/T) vs 1/T plot with an activation energy barrier of 70.25 kJ/mol (comparable to the value of the collision-based Arrhenius model). The semi-classical Marcus model disclosed that the hydride shift is a normal electron transfer rate based on the localization of k ET in the λ< -ΔG o >0 region.

Fructose serves as an important intermediate in the preparation of liquid fuel compounds. Herein, we report its selective production via a chemical catalysis method over ZnO/MgO nanocomposite. The blending of...