One-Step Synthesis of Open Hierarchical ZSM-5: Influence of the Temperature Ramping Rate on Morphology

Exploration of zeolites with various morphologies has received significant attention as a strategy to enhance their catalytic performance and elongate their lifetime. This study presents open hierarchical ZSM-5 which consists of micropores and mesopores, with a further extension to macropores owing to the presence of open structures. A one-step facile synthetic strategy features utilization of tubular reactors for precise and rapid temperature control, where faster ramping rates play a critical role in formation of open structures by enhancing gel aggregation. Further characterization of atomic composition and modification in synthesis environments (e.g., synthesis temperature, batch Si/Al) revealed that formation of open hierarchical ZSM-5 is based on the intricate interplay among three key steps: aggregation, crystallization, and dissolution. Fast aggregation and comparable crystallization to dissolution play a critical role in formation of open structures, while modification in individual steps leads to the absence of open structures and different polycrystalline features. This study sheds light on the parameter of ramping rate, which is often overlooked in zeolite synthesis, further providing insight into optimizing zeolite synthesis.