Cellulosic biomass represents an abundant renewable resource for the production of bio-based products and biofuels. 5-hydroxymethylfurfural (HMF) is a critical and versatile intermediate for converting biomass to liquid alkanes and many other value-added products. However, cost effective conversion of glucose, the dominant biomass monomer sugar, to HMF remains a critical issue. Experimentally, it was found that glucose conversion and selectivity are especially sensitive to the type of catalysts present and the solvent media. During brønsted acid-catalyzed glucose reactions including mutarotation, condensation, dehyration and isomerization reactions , our simulation results show that protonation of one of the hydroxyl groups on the glucose ring or the ring O and the subsequent breakage of the C-O bond is the critical step. Our results demonstrate that the barriers for acid-catalyzed glucose reactions are largely solvent induced due to the competition for proton between the hydroxyl groups on glucose and the solvent molecules. The barriers and reaction free energies were calculated for glucose dehydration to HMF in various DMSO-H2O mixtures using ab initio molecular dynamics simulations (CPMD) coupled with metadynamics simulations. The effects of solvent on the reaction barrier for glucose to HMF conversion in various DMSO-H2O mixtures were determined and presented here.
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