Hydrothermal Reactions of Biomass-Derived Platform Molecules: Distinct Effect of Aprotic and Protic Solvents on Primary Decomposition of Glucose and Fructose in Hot-Compressed Solvent/Water Mixtures

Abstract

The study compares the effects of aprotic (i.e., gamma-valerolactone, acetone, and 1,4-dioxane) and protic (i.e., methanol and ethanol) solvents on the primary decomposition reactions of glucose and fructose, which are key biomass-derived platform molecules, in hot-compressed solvent/water mixtures (10 vol %) at various temperatures. Aprotic solvents enhance dehydration reactions and suppress isomerization reactions during glucose and fructose decomposition. Particularly, 5-hydroxymethyl-furfural (5-HMF) that is a secondary product for both glucose and fructose decomposition in protic solvent/water mixtures becomes a primary product for their decomposition in aprotic solvent/water mixtures, contributing to ∼25–27% and ∼19–22% of the primary decomposition reactions for glucose and fructose, respectively. In contrast, the protic solvent has little effect on the primary decomposition of sugars in hot-compressed solvent/water mixtures. The addition of the aprotic solvent reduces the activation energy of sugar decomposition in the solvent/water mixture, but the reaction rate constant in the aprotic solvent/water mixture is still lower than that in the protic solvent/water mixture.

Isomerization of glucose to fructose catalyzed by metal–organic frameworks

“…Apart from catalyst selection, another decisive factor in glucoseto-fructose isomerization is the solvent employed. Here, the first option is water 2,[7][8][9]18,40 due to the good solubility of sugars in water, although various other solvents have been tested to improve the reaction rate and minimize secondary products, such as alcohols 5,11,41 , ionic liquids 42 , and polar aprotic organic solvents including N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), dimethylacetamide (DMA), sulfolane, γvalerolactone, acetone, and 1,4-dioxane 4,43 . This work presents a novel study on the isomerization of glucose to fructose by using five selected MOF catalysts (three MOFs synthesized, MIL-53(Cr), CuBTC, and MIL-101(Cr)), and two other commercial catalysts, FeBTC, and MIL-53(Al)).…”

Effect of the Solvent on the Basic Properties of Mg–Al Hydrotalcite Catalysts for Glucose Isomerization

“…Subsequently, a proton is transferred from O2 to O1, and fructose is produced due to the protonation of C1. In some studies, the ring-opening of glucose has been influenced by the solvent [30,31]. In addition, the basic properties of the catalyst used in the reaction have been reported to play an important role in the glucose isomerization [32,33].…”

Furfural manufacture from xylose : routes towards high selectivity and novel processes

“…29,32,33 This results in differences in the solvent-solute interaction, which also reflects on the reaction parameters, mechanism, and kinetics, with no possibility of forming glucosides. [76][77][78][79] Specifically, the presence of aprotic solvents in the mixture has been reported to promote the glucose-to-fructose isomerization (Scheme 2.2) and the formation of furanose-aldehyde intermediates (Schemes 2.1a and 2.2a). 76 The product/by-product distribution is also affected, largely increasing the selectivity of the dehydration towards HMF.…”

“…[76][77][78][79] Specifically, the presence of aprotic solvents in the mixture has been reported to promote the glucose-to-fructose isomerization (Scheme 2.2) and the formation of furanose-aldehyde intermediates (Schemes 2.1a and 2.2a). 76 The product/by-product distribution is also affected, largely increasing the selectivity of the dehydration towards HMF. 76 This specific behavior of aprotic solvents can be generalized to all dehydration reactions, with a direct effect on its mechanism, owing to competition between water and the polar organic solvent in the interaction with the hydroxyl groups, analyzed through DFT simulations of the spatial distribution of the solvents.…”

“…76 The product/by-product distribution is also affected, largely increasing the selectivity of the dehydration towards HMF. 76 This specific behavior of aprotic solvents can be generalized to all dehydration reactions, with a direct effect on its mechanism, owing to competition between water and the polar organic solvent in the interaction with the hydroxyl groups, analyzed through DFT simulations of the spatial distribution of the solvents. 77 Aprotic solvents alter the relative stability of initial and transition states in the dehydration reactions.…”