Highly productive xylose dehydration using a sulfonic acid functionalized KIT-6 catalyst

Abstract

A highly efficient and selective dehydration of xylose to furfural was achieved using a sulfonic acid-functionalized, mesoporous silica KIT-6 type catalyst in a water/toluene biphasic system. The catalyst was prepared by co-condensation between tetraethoxysilane and 3-mercaptopropyl(methyl)dimethoxysilane, in the presence of poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (Pluronic, P123, Mw = 5800). The catalytic performance was then investigated with respect to the molar ratio of tetraethoxysilane and 3-mercaptopropyl(methyl)dimethoxysilane, as well as the reaction temperature and reaction time. The optimal catalyst was prepared using tetraethoxysilane and 3-mercaptopropyl(methyl)dimethoxysilane in a molar ratio of 0.8:0.2, giving both high xylose conversion and furfural selectivity (greater than 94%) at 170 °C for 2 h. In addition, the catalyst had a high turnover frequency and could be reused without treatment for up to three cycles. The high turnover frequency in the xylose dehydration reaction was attributed to the three-dimensional structure of the KIT-6 mesoporous silica that facilitates the diffusion of both the reactant and products in the xylose dehydration reaction.