An insight into the role of the surfactant CTAB in the formation of microporous molecular sieves

Abstract

Quaternary ammonium salts are well-known zeolite structure-directing agents. However, cationic surfactants with quaternary ammonium head groups are known to fail to function as SDAs of zeolites because their long surfactant chains disrupt the ordered growth of the zeolite crystals. In this study, we found that ZSM-5 and silicalite-1 can be formed very easily with appropriate synthesis compositions over a large temperature range of 100–200 °C. The ¹³C CP/MAS data for surfactants in ZSM-5 combined with elemental analysis indicated that the surfactants were in more rigid, isolated environments and did not undergo decomposition. The surfactant head groups can serve as structure-directing agents for zeolites, and the long chains become isolated and occupy the micropores. Our findings provide a new insight into the molecular factors governing the formation of inorganic–organic microporous materials, which opens up new possibilities for the elaborate fabrication of mesoporous zeolites.