Synthesis and structure-directing effect of piperazinium hydroxides derived from piperazines for the formation of porous zeolites

A series of organic structure-directing agents (SDAs) derived from N-methyl piperazine are synthesized and first used in the zeolite synthesis. When the hydrothermal synthesis route is applied, SDA1, SDA3 and SDA4 are beneficial to the formation of ZSM-12 lattice, but SDA2 and SDA5 readily induce the nucleation and crystallization of ZSM-5 phase. When using the dry gel conversion route, only SDA5 yields a porous material similar to the ZSM-11 topology. Thus, synthesized zeolites have been confirmed by XRD and IR characterizations to possess characteristics of MFI, MEL and MTW lattices, respectively. The crystal size (1.0 × 9.3 μm) of ZSM-5 synthesized is measured to be much larger than those of ZSM-11 (0.10∼0.50 μm) and ZSM-12 (0.80∼2.0 μm). The TG curve of ZSM-12 shows a two-stage weight loss in the flow of air, while those of ZSM-5 and ZSM-11 contain three-stage weight losses in air. 13C CP MAS NMR spectra confirm the encapsulation of SDAs in the pore channels of as-synthesized ZSM-5, ZSM-11 and ZSM-12.