Dehydration of glucose to 5-hydroxymethylfurfural over sn-containing dendritic mesoporous silica

Abstract

5-Hydroxymethylfurfural (HMF) is a vital platform molecule for the synthesis of a wide variety of lignocellulosic-based biochemicals and biofuels. However, it is hard to prepare HMF from glucose, and a good match between the acid properties of the catalyst and the reaction requirements is necessary. Herein, sn-doped dendritic mesoporous silica nanoparticles (sn-xDMS) were synthesized through a simple in-situ co-assembly method. The uniform incorporation of Sn species onto the silica matrix created effective Lewis acid sites for the isomerization of glucose to fructose. Moreover, appropriately increasing the Sn loading amount was conducive to increasing the densities of Lewis acid sites. In the monophasic DMSO medium, the combination of sn-20DMS and HCl could selectively catalyze the tandem reactions of the isomerization of glucose to fructose intermediate and the dehydration of fructose to HMF. Besides, acceptable HMF yields were also achieved when sn-20DMS was used together with diluted H2SO4, sulfonated polymer, or sulfonated activated carbon. Due to the lack of suitable Brønsted acid sites, the catalytic performance of sole sn-20DMS was much inferior to those of Brønsted acid catalyst-sn-20DMS combinations. Therefore, the sulfonated sn-20DMS (sn-20DMS-SO3H) with enhanced Brønsted acidity was successfully prepared. sn-20DMS-SO3H exhibited much higher catalytic selectivity toward HMF than sn-20DMS. More importantly, the catalyst reuse experiment confirmed the good recyclability of sn-20DMS-SO3H.