Enhanced Catalytic Ring-Opening of Propylene Oxide Using a Germanium-Containing MFI Zeolite Catalyst with High Selectivity

Germanium-containing zeolites (Ge-MFI) offer significant potential for catalytic applications, owing to their unique structural properties such as extra-large porosity, facilitated by a broader range of Ge–O–Si angles and Ge–O bonds compared to the Al–O–Si, Al–O, and Si–O found in conventional aluminosilicate zeolites. This study highlights the catalytic performance of the Ge-MFI catalyst in the ring-opening reaction of propylene oxide, an essential step in synthesizing value-added chemicals. Employing in situ and operando FTIR spectroscopy, we investigated the reaction mechanism and product distribution, uncovering how propylene oxide interacts with Ge-based Lewis acid sites and induces group migration that facilitates molecular reorganization. This work demonstrates that incorporating germanium into the MFI framework produces a highly stable and selective catalyst with discrete Lewis acid sites, activated at 450 °C. The catalyst achieved a conversion of 37% at 400 °C, markedly outperforming its siliceous counterpart (Si-MFI catalyst), which reached only 16%. Furthermore, the Ge-MFI catalyst exhibited superior selectivity toward propionaldehyde, attaining 85% at 350 °C compared to 35% for Si-MFI under identical conditions.