Sequential dehydration of sorbitol to isosorbide over acidified niobium oxides

Isosorbide is a bio-based functional diol, which is prepared by sequential dehydration of sorbitol and widely used in plasticizers, monomers, solvents or pharmaceuticals. In this study, a variety of acidified Nb2O5 catalysts were prepared and used for the sequential dehydration of sorbitol to isosorbide. Acidification can effectively regulate the surface acidity of catalysts, which was measured by pyridine infrared spectroscopy and NH3-TPD analysis. The catalytic performance was related to the surface acidity, including the reaction temperature and the amount of catalysts. After optimization of reaction conditions, the yield of isosorbide reached 84.1% with complete sorbitol conversion during reaction at 150 degrees C for 3 h over 2 M sulfuric acid modified Nb2O5. Finally, the reaction mechanism regarding the role of Lewis acid sites was discussed. This study is of great significance for further development of an efficient catalytic system for the dehydration of carbohydrates to isosorbide.