Asymmetrical Gemini Surfactants Directed Synthesis Of Hierarchical ZSM-5 Zeolites and Their Immobilization of Molybdenum Complex for the Catalytic Epoxidation of Alkenes

An eco-friendly strategy for the synthesis of highly ordered meso- and microporous zeolites is required both in academia and industry. Therefore, asymmetrical anionic-nonionic gemini surfactants, polyoxyethylene laurinol ether sodium sulfoitaconate (Gemini-n), have been designed, synthesized and used in the directed synthesis of hierarchical ZSM-5 zeolites (HZSM-5) by imparting substantial mesoporosity. The hydrothermal temperature, the amount of gemini surfactants and the crystallization time strongly affected the crystallization degree and the textural properties of the HZSM-5. The tune of the porous size distribution (microporous to mesoporous) can be obtained by varying the number of the ethylene oxide units in the gemini surfactants. Besides, the use of these novel anionic-nonionic gemini surfactants is an effective strategy to avoid phase-separation. The existence of abundant hydroxyl groups on the surface of HZSM-5 was used to immobilize molybdenum compound by the stable Mo-O bond. The complex with abundant intercrystal mesopores exhibited superior catalytic performance with high yield and selectivity for the epoxidation reactions of alkenes as compared to the conventional ZSM-5. Moreover, the complex presented high catalytic ability after been reused for five times.

Automated summary

An eco-friendly strategy using asymmetrical anionic-nonionic gemini surfactants has been developed for the synthesis of hierarchical ZSM-5 zeolites with substantial mesoporosity. The gemini surfactants can effectively control the pore structure of the zeolites, resulting in improved catalytic performance and stable Mo-O bonding for immobilizing molybdenum compounds. The complex with intercrystal mesopores exhibited superior catalytic performance in epoxidation reactions, showing high yield and selectivity, even after repeated use.