Reaction kinetics study and the estimation of thermodynamic parameters for the conversion of glucose to 5-hydroxymethylfurfural (5-HMF) in a dimethyl sulfoxide (DMSO) medium in the presence of a mesoporous TiO2 catalyst

Abstract

BackgroundsGlucose is a potential feedstock for the production of 5-HMF, a top ten platform chemical. The kinetics of glucose conversion to 5-HMF in organic dimethylsulfoxide (DMSO) medium is not known. In this study, glucose dehydration kinetics is performed over TiO2 catalyst in the DMSO medium. MethodsThe kinetic experiments were performed in a 15 mL screw tight glass vial at 100-180 °C. A first-order kinetic model was developed by assuming a four steps process including (1) glucose conversion to 5-HMF via dehydration, (2) direct glucose decomposition to FA and polymerization to humin or polymeric products, (3) 5-HMF conversion to LA and FA via rehydration and (4) 5-HMF decomposition to humin and FA. The obtained models were solved by non-linear regression techniques by minimizing the sum of the square using Polymath. Further, the thermodynamic parameters (∆H‡, ∆S‡, and ∆G‡) of activation for all the probable reaction steps were calculated. Significant findingsThe model was fitted very well with the experimental data with an R2 value of > 0.97. The calculated activation energy for glucose dehydration to 5-HMF was 66.2 kJ mol−1 and for 5-HMF rehydration to LA and FA was (51 kJ mol−1), respectively. The higher value (∼63 kJ mol−1) of the enthalpy of activation (∆H‡) for glucose conversion to 5-HMF depicted the higher energy required to break the stable pyranose glucose ring, and the obtained positive ∆G‡ value suggested that the reactions were non-spontaneous.