Incorporation of germanium into the framework of nanocrystalline faujasite

• Germanium was substituted into nanocrystalline FAU zeolites.
• Recycling method was an effective method for increasing zeolite yield.
• NaOH and GeO2 replaced in subsequent recycling batches to keep Si/Ge constant.
• Same synthesis conditions yielded nanocrystalline LTA zeolite in the absence of germanium.

Due to their large surface area and accessible pore network, research on nanocrystalline zeolites is a rapidly developing area. Incorporation of tetravalent elements into the zeolite framework beyond the traditional silicon and aluminum is one facet of this research and development. Another important facet of nanocrystalline zeolite research is minimizing waste and improving product yield towards greener chemistry synthesis. The study reported here incorporates both of these facets as germanium containing FAU type zeolites with Si/Al ratios below 1.5 were synthesized with recycling methods in order to increase zeolite yield. Sub 40 nm nanocrystalline FAU type zeolites with germanium incorporated into the framework were synthesized from clear reaction mixtures with systematically varied synthesis conditions. The zeolite products were characterized with transmission electron microscopy (TEM) for crystal size and morphology, inductively coupled plasma optical emission spectroscopy (ICP-OES) for elemental ratios, powder XRD for crystallinity and framework type, nitrogen adsorption for BET surface area, and both 29Si and 27Al NMR to study framework coordination.

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