Mechanistic Insights into the Brønsted Acid-Catalyzed Dehydration of β-d-Glucose to 5-Hydroxymethylfurfural under Ambient and Subcritical Conditions

Abstract

Conversion of biomass to fuels and other useful chemicals is one of the most active fields of research today. In this respect, dehydration of glucose to 5-hydroxymethylfurfural (HMF) has gained much attention recently. Carrying out this reaction with high efficiency in green solvents, especially in water, is a major challenge to overcome. In spite of several years of experimental and computational studies, the detailed mechanism of the conversion of glucose to HMF remains elusive. Detailed mechanistic understanding of this reaction can aid in the development of novel catalysts for carrying out the reaction in water. In addition, understanding the effects of reaction conditions such as temperature and pressure on the mechanism and kinetics of this reaction could provide additional information to optimize thermodynamic conditions for HMF production on an industrial scale, and thus, we study that here in detail. Our study is based on computational modeling of this chemical reaction in explicit water under different thermodynamic conditions using molecular dynamics simulations at the level of density functional theory. This work addresses the long-standing open questions on the mechanism and the effects of the thermodynamic conditions. Our simulations shed light on the critical steps for which a catalyst could be designed to improve the efficiency.

Discovery and Exploration of the Efficient Acyclic Dehydration of Hexoses in Dimethyl Sulfoxide/Water

“…Kinetic data were consistent with a sequential reaction of trans ‐3,4‐DGE to THA and of cis ‐3,4‐DGE to HMF, with another (presumably cyclic) pathway contributing to HMF formation from fructose. Acyclic pathways to HMF through 3‐deoxyglucosone and cis ‐3,4‐DGE have previously been suggested based on computational studies and on the experimental observation of cis ‐3,4‐DGE in carbohydrate‐ and HMF‐containing solutions . DMSO is an attractive solvent for the reaction, given its ability to solubilize carbohydrates and to reduce humin formation in comparison to aqueous solvents.…”

Controlling the Reaction Networks for Efficient Conversion of Glucose into 5‐Hydroxymethylfurfural

“…As such, the glucose‐to‐fructose isomerization and fructose‐to‐HMF dehydration can be catalyzed by OH − and H + ions, respectively. Moreover, water molecules directly participate in glucose dehydration by influencing the hydrogen‐bonding pattern . However, the selectivity to HMF in neat water is very low regardless of the catalyst type, owing to the occurrence of multiple side reactions that lead to formation of several small‐molecular or polymerized side products.…”

Identification of Crucial Intermediates in the Formation of Humins from Cellulose‐Derived Platform Chemicals Under Brønsted Acid Catalyzed Reaction Conditions

“…This can be ascribed to the presence of multiple hydroxyl groups which causes undesired side reactions during the dehydration of these molecules. [2,6,13,[17][18][19] Thus, fuel production from furanic compounds that have a fewer number of hydroxyl groups are more desired. [6,17,20,21] Among various furan compounds that can be synthesized from glucose and fructose, 5-hydroxymethylfurfural (HMF) is known for its potential in fuel production applications.…”