Understanding the mechanism of nontraditional zeolite synthesis using in situ nuclear magnetic resonance spectroscopy and X-ray diffraction

In situ solid-state nuclear magnetic resonance (NMR) spectroscopy and in situ powder X-ray diffraction (PXRD) experiments are used to develop mechanistic insights into the disassembly and organization steps of nontraditional zeolite synthesis using the ADOR (Assembly, Disassembly, Organization, Reassembly) process. The work focuses on the reaction of the germanosilicate zeolite UTL to form two ADOR intermediates: IPC-1P on reaction with water and IPC-2P on reaction with aqueous HCl. The changes in the local structure on reaction with water can be modeled as one overall disassembly process, but the long-range changes, as measured by changes in interlayer spacing determined by XRD, indicate multiple stages of the reaction as the layer structure develops. For the reaction with aqueous acid, the local changes are modeled with two processes: a disassembly and an interlayer rearrangement (organization step). However, only one major stage of change is seen in the XRD measurements. The new details revealed by the in situ studies demonstrate that both local (probed by NMR spectroscopy) and long-range (probed by XRD) changes to the structure are required to truly understand how the reaction proceeds. The results provide new insights into the relative kinetics of the different processes involved in the reactions under different conditions and reveal new features such as staging in the layer stacking changes in the organization step.