Ethane ammoxidation to acetonitrile and ethylene over the Co/HZSM-5 catalysts was revisited based on both transient and steady-state performance evaluation to elucidate the structure/reactivity relationships. We suggested that the exchanged Co 2+ cation encapsulated in the zeolite favors the formation of acetonitrile and ethylene, whereas nanosized cobalt oxide particles without close proximity with the HZSM-5 only favor CO 2 formation. Excess Brønsted acid sites of the zeolites may act as a reservoir for NH 3 , which inhibits the CO 2 formation through the NH 3 -mediated oxidative dehydrogenation mechanism. According to the transient kinetic analysis, the time constants τ from the back-transient decay for NH 3 and CO 2 are both 7.7 min, which decreased to 2.7 min for acetonitrile and further decreased to 3−4 s for ethane, ethylene, and O 2 . Assuming first-order reaction kinetics, the rate constants for the formation of acetonitrile and CO 2 are 0.37 and 0.13 min −1 , respectively, from their corresponding reactive intermediates.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.