Zeolite Growth in Nonionic Microemulsions: Synthesis of Hierarchically Structured Zeolite Particles

The synthesis of silicalite-1 in nonionic microemulsions is explored. The work presented here is a systematic study showing how parameters such as synthesis temperature, microemulsion composition, and surfactant identity impact the formation and growth of silicalite-1. The work demonstrates the possibility of using microemulsions to manipulate the shape and size of silicalite-1 materials, growing both spheres and high-aspect ratio platelets. In both cases, these large particles are robust aggregates of small submicron particles that are stable to calcination. The size of the primary particles is adjustable based on the synthesis temperature, whereas the size of the large aggregates is adjustable based on the silicalite-1 content of the mixture. On the basis of the results presented, a mechanism is proposed illustrating the role of both the confined space presented by the microemulsion as well as the importance of the surfactant−silicate interactions leading to the formation of the large aggregates. The results suggest this to be a versatile and useful approach for making zeolitic materials that possess unique morphological properties and hierarchical structure.