Al-containing Ge-rich IWV: rapid synthesis via interzeolite transformation and application in Baeyer-Villiger oxidation

Abstract

Ge-containing Lewis acidic zeolites are typically synthesized using a conventional hydrothermal strategy from amorphous silica sources, through a long time- and energy-consuming approach limiting their wide applications. This study reports a rapid synthesis strategy for a series of IWV aluminogermanosilicate zeolites (T-x-Al) with a wide range of Si/Ge molar ratios (5–15) by interzeolite transformation of dealuminated FAU (DA-FAU). Notably, Ge-rich IWV could be obtained with crystallization time as short as one day by the equimolecular Si/Ge ratio gel. The effect of synthetic parameters was investigated and the obtained T-x-Al samples were characterized by XRD, SEM, EDS, ICP, ²⁹Si and ²⁷Al MAS NMR, FTIR, and N₂ physisorption analyses. Compared with a previously reported IWV germanosilicate (H-3), T-x-Al displayed a better catalytic activity in Baeyer-Villiger (BV) oxidation, attributed to the presence of the active framework Ge sites with the assistance of the extra-framework Al species. The cyclic catalysis tests revealed that the presence of framework Al species contributed to the stability of the T-x-Al. Specifically, T-x-Al, with 14-membered ring (MR) supercages, outperformed the typical 12-MR Sn-beta catalyst in the BV oxidation of large ketone-like 2-admantanone, indicating a promising potential application in the macromolecular catalytic process.