Sequential extraction and separation of soluble humins from fructose conversion for structural and evolutional understanding

Abstract

Understanding the evolution, structure, and separation of humins (i.e., carbonaceous polymeric side-products) during the acid-catalyzed conversion of fructose, especially at high substrate loading, is of crucial importance for future inhibition...

Synthesis of 2,5-Furandicarboxylic Acid from Fructose Employing a “One-Pot and Two-Step” Approach with Biotar-Derived Functional Catalysts

“…They clearly explained the extraction and analysis results of humus, making important contributions to the study of these substances. The main focus of this study is to elucidate the reaction conditions and the two-step process of one pot and two steps in series. , At elevated temperatures, especially exceeding 150 °C, DMSO will undergo excessive decomposition into substances such as dimethyl sulfur and dimethyl thiophenol under the existing hydrogen peroxide. These substances will cause the solution to exhibit a cloudy color and emit irritating and unpleasant gases.…”

Water Removal Enables High-Efficacy Synthesis of 5-Ethoxymethylfurfural and Ethyl Levulinate as Biofuel Candidates from High-Concentration Fructose

“…In addition, the sharp increase of 100 – TCB from 11.6 to 27.5% with increasing water content from 0 to 2.0 vol % revealed the aggravation of humin formation via the etherification–dehydration–condensation path. However, a negligible effect was observed on the degradative–condensation path to humins in the presence of water because the concentration effect of the substrate was thought to play a crucial role in inhibiting such humins formation …”

“…As shown in Figure 1a, 94.8% of fructose was converted in EtOH, wherein EMF and EL were detected as the main products with a total yield of 58.1 mol %, whereas HMF (22.3 mol %), EF (10.5 mol %), and a trace amount of FF (0.5 mol %) were detected as the side-products. Our previous work showed that the stoichiometric excess formation of EF relative to EL revealed the occurrence of degradative−condensation of fructose, HMF, and/or EMF to humins, 29 wherein the corresponding carbon loss could be evaluated by the difference between the theoretical carbon balance (TCB) and actual carbon balance (ACB) (i.e., TCB − ACB). Moreover, the etherification−dehydration−condensation of fructose to humins also occurs under a high-substrate concentration condition, wherein the corresponding carbon loss could be calculated using 100 − TCB.…”

“…However, a negligible effect was observed on the degradative−condensation path to humins in the presence of water because the concentration effect of the substrate was thought to play a crucial role in inhibiting such humins formation. 29 Effect of Water Removal on Product Distribution in Fructose Conversion. Considering the negative influence of water on the reaction kinetics and humin formation via the etherification−dehydration−condensation pathway, the removal of the as-formed water from the catalytic system was attempted by adding dewatering reagents such as 3/4 Å molecular sieves (1.6−2.5 mm), silica sand (0.5−1.0 mm), or silica gel (0.4−1.0 mm).…”

“…Recent progress has revealed two-aspect considerations on performing the fructose-to-EMF/EL. On the one hand, a lower fructose concentration was thought to be necessary to reduce the formation of undesired polymerized side-products called humins because the increase of fructose concentration was thought to promote the formation of humins via a path of etherification–dehydration–condensation of fructose and/or HMF. , On the other hand, the side-product water generated in the step of fructose-to-HMF dehydration was deemed to decelerate the reaction kinetics and then lead to a relatively longer reaction time to reach reaction equilibrium. − To improve the process efficiency of fructose-to-EMF/EL conversion, the substrate concentration should be enhanced, whereas the negative influence of water should be limited as thoroughly as possible. Herein, a water-removal strategy might be promising because it has exhibited validity in fructose-to-HMF dehydration by suppressing undesired rehydration of HMF to levulinic acid and condensation of partially dehydrated intermediates to humins …”