Thermodynamics and Reaction Kinetics of the Sorbitol Dehydration to Isosorbide Using NbOPO₄ as the Catalyst

Isosorbide is a bio-based platform compound, and the solid acid-catalyzed conversion of sorbitol to isosorbide is an environment-friendly process. The thermodynamic calculations and reaction kinetics of the sorbitol dehydration to isosorbide catalyzed by NbOPO₄ were studied in this work. The thermodynamic analysis shows that the two-step dehydration of sorbitol is an endothermic process, in which the first one is an irreversible reaction while the second is a reversible one. Based on the reaction mechanism and thermodynamics, a first-order pseudo-homogeneous kinetic model for the sorbitol dehydration was proposed. The modeling fitting results show that the kinetic model established in this work can well fit the experiments in the range of 493.15–523.15 K. The kinetic investigation and thermodynamic analysis indicate that low temperatures would decrease the generation of byproducts in the first step while high temperatures promote the reaction equilibrium forward in the second step. Therefore, a two-stage temperature gradient way with high temperatures followed by low temperatures would be favorable in the conversion of sorbitol to isosorbide catalyzed by NbOPO₄. Hopefully, the thermodynamics and kinetic modeling results obtained in this work would guide the design of solid acid catalysts and reactors for the sorbitol dehydration process.