Experiments and kinetic modeling of the sorbitol dehydration to isosorbide catalyzed by sulfuric acid under conditions of non-constant volume

Abstract

Isosorbide is a novel bio-based material, derived as a secondary dehydration product of sorbitol. This work focuses on the kinetics of sulfuric acid-catalyzed dehydration of sorbitol under conditions of non-constant volume. Herein, the effects of stirring rate, catalyst dosage, reaction temperature, and reaction time on the dehydration reaction of sorbitol were investigated. The yield of isosorbide up to 77.13% was obtained after 1.5 hours of reaction time under conditions of 2 kPa, 1.0% (mass) catalyst dosage, and 413.15 K. Based on the sorbitol dehydration reaction mechanism and a simplified reaction network, a kinetic model was developed in this work. A good agreement was accomplished between kinetic modeling and experiments between 393.15 and 423.15 K. The fitting results indicate that side reactions with higher activation energy are more affected by reaction temperatures, and the main side reaction that influences the selectivity of isosorbide is the oligomerization reaction among the primary dehydration products of sorbitol. The model fitting of the catalyst amounts effect shows that the effective concentration of sulfuric acid would be reduced with the increase of dosage due to the molecular agglomeration effect. Hopefully, the kinetic experiments and modeling results obtained in this work will be helpful to the design and optimization of the industrial sorbitol dehydration process.