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Download fileAmmoxidation of Ethane to Acetonitrile and Ethylene: Reaction Transient Analysis for the Co/HZSM‑5 Catalyst
journal contribution
posted on 2020-01-13, 09:29 authored by Xia Liu, Tingyu Liang, Roland Barbosa, Genwei Chen, Hossein Toghiani, Yizhi XiangEthane
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 Co2+ 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 CO2 formation. Excess Brønsted acid
sites of the zeolites may act as a reservoir for NH3, which
inhibits the CO2 formation through the NH3-mediated
oxidative dehydrogenation mechanism. According to the transient kinetic
analysis, the time constants τ from the back-transient decay
for NH3 and CO2 are both 7.7 min, which decreased
to 2.7 min for acetonitrile and further decreased to 3–4 s
for ethane, ethylene, and O2. Assuming first-order reaction
kinetics, the rate constants for the formation of acetonitrile and
CO2 are 0.37 and 0.13 min–1, respectively,
from their corresponding reactive intermediates.