Direct synthesis of self-assembled ZSM-5 microsphere with controllable mesoporosity and its enhanced LDPE cracking properties

Abstract

Self-assembled mesoporous ZSM-5 microspheres (∼5 μm), which are composed of inter-growthed primary nano-strips, are directly synthesized using n-hexylamine as the single template. The mesopore distribution can be facilely controlled by adjusting the size of primary particles via modulating the alkalinity of the synthesis gel. The samples obtained by varying Na₂O/SiO₂ molar ratios from 0.07 to 0.15 are denoted as ZM-X (X = 1–5). The ZM-X samples are characterized by techniques including XRD, TEM, SEM, N₂ adsorption–desorption and FTIR. It is found that ZM-3 exhibits a uniform mesopore distribution around 10 nm and possesses the largest amount of external acid sites, which lead to the remarkably enhanced catalytic performance in polyolefin cracking. A possible growth mechanism of self-assembled ZSM-5 microspheres directed by n-hexylamine is proposed.