Nanoporous Sn-Substituted ZSM-48 Nanostructures for Glucose Isomerization

The hierarchical Sn-substituted ZSM-48 nanostructures (Sn-Si/ZSM-48) have been successfully fabricated via a one-pot hydrothermal process with the aid of cyclic diquaternary ammonium (CDM) as structure-directing agent (SDA) and amorphous Sn-Si nanobeads as starting materials. The physicochemical properties of all the prepared materials were characterized by means of X-ray diffraction (XRD), energy dispersive X-ray (EDS) elemental analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), N-2 adsorption/desorption, X-ray photoelectron spectroscopy (XPS), and UV-vis spectroscopy. Compared with using a traditional synthesis method, by using the simultaneous presence of Sn and Si species in nanobeads, the homogeneous distribution of Sn along the ZSM-48 crystals could be observed with the high fraction of tetrahedral Sn located in the zeolite framework. The Sn-Si/ZSM-48 demonstrates that the use of Sn-Si nanobeads is advantageous in terms of improving the crystallization and dissolution rate of zeolites and providing uniform spherical morphology and high fraction of tetrahedral Sn in the framework. To illustrate the beneficial effect of synthesized materials, the Sn-Si/ZSM-48 remarkably enhances the catalytic performance in glucose conversion to fructose in terms of conversion (32.7%) and fructose selectivity (95.5%) in the mixed DMSO and water system. These findings open up the concept of preparation of hierarchical ZSM-48 with a one-dimensional porous system homogeneously incorporated with Sn as Lewis acid sites by using amorphous Sn-Si nanobeads for glucose upgrading applications.