One-pot synthesis of nano-hierarchical SSZ-13 with superior catalytic performance in methanol-to-olefins reaction

Nano-sized SSZ-13 with hierarchical structure were fast synthesized by combining ultrasonic pretreatment and seed induced crystallization. The physicochemical properties of the synthesized catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption–desorption, X-ray fluorescence (XRF), Transmission electron microscopy (TEM), and temperature programmed desorption of ammonia (NH3-TPD) analysis. As verified by XRD and SEM, ultrasonic pretreatment not only remarkably reduced the crystallization time to 7 h but also evidently decreased the zeolite crystals to nano size (ca. 650 nm). The N2 adsorption–desorption and TEM resulted revealed that ultrasonic pretreatment created abundant intracrystalline mesopores in the zeolite structures. In comparison to the conventional SM-24 catalyst, both improved catalytic lifetime and selectivity of ethylene and propylene were obtained over the hierarchical nano-sized SN-17 catalyst due to the greatly enhanced mass transport efficiency and decreased coking rate.