Efficient conversion of fructose to 5-hydroxymethylfurfural by hydrophobic modified SAPO-34 molecular sieve

Abstract

To address the issue of the accumulation of water around Brønsted acid sites during the fructose dehydration towards 5-hydroxymethylfurfural (HMF), in this work, hydrophobic SAPO-34 is prepared by post-treatment silanization by grafting alkyl hydrophobic groups on its surface. The SAPO-34 catalyst modified with dodecyl trimethoxysilane exhibits a significantly enhanced yield of 5-hydroxymethylfurfural (HMF), reaching 95.05 %. It is determined that long-chain hydrophobic groups facilitate the forward reaction of fructose dehydration by creating a microenvironment favorable for water removal and fructose enrichment. Furthermore, it releases Brønsted acid sites from water molecules, and enhance fructose’s accessibility to Brønsted acid sites. Thus, the activity, selectivity and durability of SAPO-34 can be promoted simultaneously, due to the selective removal water rather than fructose. This work put insight into the role of alkyl chain length of hydrophobic groups in promoting fructose dehydration towards HMF, which may be guideline for other dehydration reactions restricted by water.