Synthesis and characterization of an unusual snowflake-shaped ZSM-5 zeolite with high catalytic performance in the methanol to olefin reaction

Abstract

The ZSM-5 zeolite with an unusual snowflake-shaped morphology was hydrothermally synthesized for the first time, and compared with common ellipsoidal and boat-like shaped samples. These samples were characterized by N2 adsorption-desorption, X-ray fluorescence spectroscopy, scanning electron microscopy, X-ray diffraction, magic angle spinning nuclear magnetic resonance, temperature-programmed desorption of ammonia, and infrared spectroscopy of pyridine adsorption. The results suggest that the BET surface area and SiO2/Al2O3 ratio of these samples are similar, while the snowflake-shaped ZSM-5 zeolite possesses more of the (101) face, and distortion, dislocation, and asymmetry in the framework, resulting in a larger number of acid sites than the conventional samples. Catalysts for the methanol to olefin (MTO) reaction were prepared by loading Ca on the samples. The snowflake-shaped Ca/ZSM-5 zeolite exhibited excellent selectivity for total light olefin (72%) and propene (39%) in MTO. The catalytic performance influenced by the morphology can be mainly attributed to the snowflake-shaped ZSM-5 zeolite possessing distortion, dislocation, and asymmetry in the framework, and lower diffusion limitation than the conventional samples.