One-step synthesis of hierarchical aluminosilicates using alkoxy-functionalized ionic liquid as a novel template

Abstract

Hierarchical zeolites have bridged the gap between conventional zeolite and mesoporous materials, which not only maintain the excellent advantages of microporous sieves, but also effectively resolve the diffusion limitations. Herein, a novel alkoxy-functionalized ionic liquid was employed as a mesoporous structure-directing agent to synthesize hierarchical aluminosilicates with dual micro–mesoporous channels. X-ray diffraction (XRD), N₂ adsorption–desorption isotherms (BET), scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature-programmed desorption (TPD), thermogravimetric analysis (TGA) and ²⁷Al magic-angle spinning nuclear magnetic resonance (²⁷Al MAS NMR) were used to characterize the structural and textural features of the hierarchical aluminosilicates. The results showed that the ionic liquid (MTPI) employed played the role of a mesoporous structure-directing agent which was trapped within the pores of a faujasite structure through –Si–O–Al– and –Si–O–Si– linkages. The mesoporous diameters and structures of the final hierarchical materials could be uniformly tailored by tuning the added amount of template. Hierarchical aluminosilicates with the combined advantages of both mesoporous properties and the microporous crystalline structure of zeolites exhibited high catalytic activity and resistance to deactivation in the alkylation of o-xylene with styrene, as compared to the conventional zeolite with the sole presence of micropores. The distinct catalytic performance of hierarchical aluminosilicates could be attributed to the short diffusion routes and abundant exposed acidic sites on the external surface.