Ammoxidation of Ethane to Acetonitrile and Ethylene: Reaction Transient Analysis for the Co/HZSM-5 Catalyst

Abstract

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.

Catalytic Light Alkanes Conversion through Anaerobic Ammodehydrogenation

“…Since the production of CH 3 CN strongly depends on the acrylonitrile capacity, an on-purpose technique for CH 3 CN production from the cheap and abundant ethane could be an important alternative. Our recent studies have shown that Co- and Sn-modified HZSM-5 catalysts are active for ethane ammoxidation for CH 3 CN. However, as depicted in Figure , the formation of CO 2 and NO x is inevitable under oxidative conditions, which was absent during the anaerobic ADeH.…”

Cu-loaded zeolites enable the selective activation of ethane to ethylene at low temperatures and pressure

“…5 Non-oxidative (EDH) and oxidative (ODH) dehydrogenation of ethane are among the most studied pathways for direct ethane conversion. 6 EDH typically requires high temperatures and low pressures to push the equilibrium toward product formation due to the endothermic nature of the reaction. However, high temperatures can lead to less controllable gas phase reactions between the reactants and products and therefore often lead to equilibrium constraints for EDH reactions.…”

Decarbonizing Petrochemical Processes: Contribution and Perspectives of the Selective Oxidation of C1–C3 Paraffins

“…The investigated processes are based upon various routes such as the catalytic reaction between acetylene and ammonia, the reaction between CO, NH 3 , and H 2 over a Mo- or Fe-based catalyst, , and the non-catalytic hydrocyanation of methane with HCN . The preferred and safer processes, however, involve the ammoxidation of ethane or ethylene with the former producing the higher yields to acetonitrile. − As shown in Table , independently of the used catalyst, the reached yields are still low (21% as maximum) to be considered for an industrial scale-up. Catalysts for ethane ammoxidation include mixed molybdates, Nb-promoted Ni oxides, Co-exchanged zeolites, MoVNbO mixed oxides containing Te or Sb, and Mo oxides supported on zeolites, with the major byproduct being ethylene.…”