Controllable synthesis of mesoporous KL zeolites via a simple one-step strategy

Abstract

A simple strategy with additional KF in the synthesis gel was developed to fabricate mesoporous KL zeolites with tunable morphology, hierarchical structure and catalytic selectivity. By modulating the molar ratio of KF/Al2O3 from 0 to 10, the morphology of resultant KL zeolites changed from cylinder, to gyro shape, and to loosen stacking nanocrystal aggregates. The value of BET surface and pore volume for synthesized KL zeolites increased with increasing the KF, indicating the hierarchical structure of mesoporous KL zeolites can be systematically tailored by tuning the concentrations of KF. The effect of KF on the crystallization process of KL zeolites was also investigated, it revealed that the K+ played a crucial role to produce a large number of nucleation centers as the structure directing agent, which not only significantly shortened the crystallization time but also generated the defective growth units by influencing the electric balance between K+ with negative aluminosilicate species, leading to the formation of mesopores. Besides, the introduction of mesopores in KL zeolites can greatly improve the selectivity of bulk products in the alkylation between phenol with tert-butyl alcohol owing to the opened mesoporosity.