Bifunctional Sn-Y zeolite triggers tandem catalytic conversion of glucose into 5-hydroxymethylfurfural

Abstract

5-Hydroxymethylfurfural (HMF) is a pivotal multifunctional platform compound. The transformation of glucose into HMF generally follows tandem catalysis, involving the isomerization of glucose to fructose and the dehydration of fructose to the targeted product HMF. Designing robust catalysts with a high diffusion performance is highly desired. Herein, Sn-containing Y zeolite with hierarchical channel systems was post-synthesized through successive acid dealumination and stannation treatments. Sn ions existed in a tetra-coordinated state in the zeolite framework. Precisely controlling the acid-treatment time was necessary to prepare a robust Sn-Y zeolite catalyst for the conversion of glucose into HMF, which was closely related to the Al and Sn contents. The structure–performance relationship revealed that the first step of glucose isomerization was triggered by the Lewis acid site, while both the Lewis and Brønsted acid sites fueled the second step of fructose dehydration. Under optimal reaction conditions (H₂O/dimethyl sulfoxide cosolvent with a volume ratio of 1 : 3; catalyst, 70 mg; temperature, 160 °C; time, 2 h), the Sn-Y zeolite catalyst exhibited extraordinary catalytic performance with a glucose conversion of 88.8% and HMF yield of 61.4%, outperforming most other reported zeolite catalysts. This impressive performance was likely due to the excellent diffusion performance contributed by opened pores and hierarchical channel systems. Finally, the reusability, deactivation mechanism, and regeneration method of the catalyst were also investigated in detail. The catalytic performance of the deactivated catalyst could be easily restored to its initial level through a simple calcination method.