Kinetic study of the double dehydration of sorbitol into isosorbide over commercial sulfonic acid resin

Abstract

Biomass-derived chemicals show great promise as an alternative resource for the replacement of fossil fuel-derived chemicals. The double dehydration of sorbitol produces isosorbide, which is an important chemical building platform and a component in food, pharmaceuticals, and plasticizers. Homogeneous catalysts are used to perform this reaction due to their good performance, but they also exhibit some drawbacks. Therefore, in this study, the sulfonic acid resin Purolite CT269 was used as a heterogeneous catalyst to study isosorbide production. The reaction was carried out with a 4.43 wt.% catalyst loading, reaction temperature of 151 °C, and reaction time of 4 h under a vacuum. 100 % conversion of sorbitol was observed within 2 h, and an isosorbide yield of about 78 % was achieved after 4 h. The kinetics of the reaction were evaluated, the rate law followed a first-order reaction model, and the reaction rate depended on the concentration of reactant. The Langmuir–Hinshelwood–Hougen–Watson (LHHW) model was used to determine that the first dehydration was the rate-determining step of this reaction. The study also examined the deactivation of the catalyst using FE-SEM, N₂ adsorption/desorption, DSC, TGA, and XPS, confirming that changes to the catalytic properties after the reaction negatively impacted the performance of the sorbitol dehydration reaction. The catalytic performance and kinetic analysis were used to explain the mechanism of the double dehydration of sorbitol into isosorbide, providing essential information for catalyst and isosorbide production process design.