Hydrothermal conversion of FAU and ∗BEA-type zeolites into MAZ-type zeolites in the presence of non-calcined seed crystals

• The seed-assisted and OSDA-free synthesis of MAZ from FAU and ∗BEA was successfully achieved.
• Pure MAZ could not be synthesized from MFI.
• The crystallinity of MAZ from FAU was higher than that of MAZ from ∗BEA.
• The composite building unit composed of a common 4-MR is a key for OSDA-free synthesis of MAZ.
• The structural similarity between starting and finally crystallized zeolites is a crucial factor.

To gain further insight into the interzeolite conversion, we investigated the seed-assisted synthesis of MAZ-type zeolite from various starting zeolites with different framework structures, such as FAU, ∗BEA, and MFI-type zeolites, without the use of an organic structure-directing agent (OSDA). The OSDA-free synthesis of MAZ-type zeolite from FAU and ∗BEA-zeolites was successfully achieved in the presence of non-calcined seed crystals. However, a pure MAZ-type zeolite could not be obtained from MFI-type zeolite. The crystallinity of the obtained MAZ-type zeolite strongly depended on the kind of framework structure of the initial zeolite. The crystallinity of MAZ from FAU was higher than that of MAZ from ∗BEA. It was confirmed that the structural similarity between the starting and the finally crystallized zeolites is a crucial factor for the interzeolite conversion process. The presence of composite building units composed of a common structural entity, namely a four-membered ring, is a key factor for the OSDA-free synthesis of MAZ-type zeolite.

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