Anaerobic Ammodehydrogenation of Ethane to Acetonitrile over Ga-Loaded H‑FER Zeolite Catalysts

A reaction of ethane (C2H6) with ammonia (NH3) over metal-loaded zeolites to yield acetonitrile (CH3CN) under the O2-free conditions was studied. Among the various metal-loaded zeolites, Ga/HFER with a Ga/Al ratio of 1.0 afforded the highest CH3CN yield. A Ga-free HFER and a Ga-loaded K-exchanged FER (Ga/KFER) were nearly inactive for the ammodehydrogenation of C2H6, indicating that both Ga and Brønsted acid sites are indispensable. Extended X-ray absorption fine structure (EXAFS) results show that the Ga2O3 species in the as-prepared Ga/HFER catalyst are converted to isolated Ga cations after C2H6 ammodehydrogenation at 650 °C, while the Ga2O3 species in Ga/KFER remained unchanged after the reaction. The results indicate that the Brønsted acid sites (exchangeable H+ sites) of HFER act as the anchoring site of the isolated Ga cations, possibly formed by reductive solid-state ion exchange during the reaction, and the isolated Ga sites act as active sites for C2H6 ammodehydrogenation. Kinetic analysis suggests that CH3CN is produced via a consecutive reaction pathway: the dehydrogenation of C2H6 to ethylene (C2H4), which reacts with NH3 to give CH3CN. The co-feeding of O2 to C2H6 + NH3 significantly decreased the CH3CN yield and formation of CO2 and CO as the main products, suggesting the importance of reductive conditions in the current catalytic system.