Hydrothermal synthesis of nanosized Sn-beta zeolites by interzeolite transformation for glucose isomerization

Abstract

As one of the state-of-the-art solid Lewis acid catalysts, the Sn-beta stannosilicate zeolite is increasingly applied in the field of biomass conversion. Due to the similar framework structures between FAU and beta topology, the efficient hydrothermal synthesis of Sn-beta zeolites from low-cost FAU zeolites should be possible via an interzeolite transformation method. In the present work, a well-crystallized Sn-beta zeolite was rapidly synthesized via a novel interzeolite transformation method without the aid of beta seeds, and its structural evolution was systematically investigated by tracking the crystallization time. These results indicated that the nanosized Sn-beta zeolite framework contained four-fold coordinated Sn species, along with abundant intercrystalline mesopores. In addition, the glucose isomerization performance of the Sn-beta zeolite catalyst was evaluated and compared with that of traditional fluoride-mediated Sn-beta-F and gas–solid isomorphous substituted Sn-beta-PS zeolites with similar Sn contents. The fructose yield results demonstrated the superior performance of the Sn-beta catalyst. Further, the reaction parameters (reaction temperature, catalyst dosage, and reaction time) were optimized, and the excellent reusability of the Sn-beta zeolite was demonstrated by almost complete regeneration and restoration of the catalytic performance via calcination. This resultant Sn-beta zeolite was an active and stable heterogeneous catalyst for the isomerization of glucose into fructose. This work provides some guidance for the design and synthesis of nanosized metallosilicate zeolites via interzeolite transformation, focusing on the promotion effects of zeolite nucleation and crystallization.