Synthesis Method and Principle of Octahedral Hierarchical LTA Zeolite and Its Application to Enhance Catalytic Activity in Styrene Epoxidation.

Abstract

A 4 Å zeolite prepared under the synergistic effect of intense ultrasound and a high-voltage electrostatic field had an octahedral structure rather than a conventional hexahedral structure. XPS and XRD analyses showed that the ratio of silicon to aluminum, 2θ peak position, and the corresponding crystal planes were the same as those in traditional hexahedral 4 Å zeolite, but some crystal planes were more prominent. SEM imaging showed that the octahedral zeolites had a larger particle size. Porosimetry (BET surface area and BJH analysis) showed that the octahedral zeolite had become a mesoporous zeolite, and its specific surface area increased and its pore size expanded, which was conducive to loading catalytically active materials and thus improving its catalytic performance. In this paper, the mechanism of formation of hierarchical LTA zeolite is discussed, and the octahedral hierarchical LTA zeolite is used to catalyze the epoxidation of styrene, giving very good results. It is concluded that the (600), (622), (642), and (644) crystal planes played a decisive role in the styrene epoxidation reaction, providing a realistic basis for explaining the crystal plane catalysis effect of the 4 Å zeolite. This new zeolite prepared under the synergistic effect of intense ultrasound and a high-voltage electrostatic field, being the first time to prepare the octahedral hierarchical LTA zeolite, is simple to produce, green, and environmentally friendly and has good economic development prospects compared to the use of templating agents, which not only provides ideas and simpler methods for optimizing the performance of traditional zeolites and developing new zeolites with better performance but also enhances the theoretical basis for preparing new zeolites.