Insights into the Role of Deep Eutectic Solvents in Sorbitol Dehydration: A Combined Experimental and Molecular Dynamics Study

Dehydration of sorbitol catalyzed by inorganic acids has been regarded as an efficient way to produce isosorbide, which shows application in the manufacture of various high value-added compounds. However, these catalysts can cause equipment corrosion and are not recyclable. As a cheap and environmentally friendly catalyst with special tunability and stability, a deep eutectic solvent (DES) composed of p-toluenesulfonic acid (p-TSA) and choline chloride (ChCl) has emerged to meet the demand for “green production” of isosorbide. The conditions for the dehydration of sorbitol catalyzed by DESs were systematically investigated. The differences in catalytic efficiency stemming from the structural diversity of DESs were explored by FT-IR characterization and molecular dynamics simulation. The results showed that isosorbide exhibited notable selectivity (88%) within the DESs (p-TSA:ChCl = 1.2), and achieved a high extraction rate (83%) under the synergistic effect of ethyl acetate and acetone (4:1). MD simulations indicated that hydrogen bonding was the dominant factor influencing the catalytic activity. The theoretical understanding of the p-TSA/ChCl structure may provide a reference for the tunability of novel DESs to meet the requirements of catalysis, absorption, and extraction.