Synergistic effect between organic structure-directing agent and crystal seed toward controlled morphology, and bimodal pore structure of aggregated nanosized ZSM-5

Hierarchical ZSM-5 zeolite has been a growing interest due to their wide applications in petrochemical process. Developing a facile and low cost strategy to synthesize hierarchical ZSM-5 is still a challenge. In this work, aggregated nanosized ZSM-5 with bimodal pore structure was synthesized via the synergistic effect of n-Butylamin (NBA) and ZSM-5 crystal seeds. In the synthesis process, The NBA molecules were transformed into RNFD3+ that would adsorbed on the surface of nuclei by electrostatic interaction in aging process. The RNFD3+ was subsequently transformed into tetrahedron configuration BuNH+ in crystallization process working as structure directing agent and promoting the aggregation of primary crystals. At low content of NBA, only microscale single crystals tended to aggregate together to form large particles. Crystal seeds were decomposed into small species, which can act as nuclei to direct the formation of primary ZSM-5 crystals and support the surface for the adsorption of RNW3+ assisting the formation of aggregated nanosized ZSM-5. With no addition of seed, the obtained sample had poor structural properties, such as small specific and external surface area. By simply adjusting the content of seed and NBA, aggregated nanosized ZSM-5 zeolite with large surface area, external surface area was obtained.