Hydrothermal synthesis of giant single crystals of MFI type zeolite: Modified bulk material dissolution method

In the present study, we aimed at the development of an easy and reproducible synthesis method of giant MFI zeolite crystals. We used a new synthesis method, modified bulk material dissolution (M-BMD) method, in which a piece of quartz glass tube was inserted as a silica source in a small PTFE sleeve together with ZSM-5 powder as seed crystals. We adopted a higher HF concentration (25 mmol/25 ml) of the synthesis solution than that usually used. By using this method, only a few crystal nuclei were formed separately from each other on the surface of the quartz glass tube in the PTFE sleeve and giant zeolite crystals were reproducibly synthesized on it. Giant single crystals of MFI as large as 5.0 mm were successfully synthesized at 453 K for 90 days by using the M-BMD method.