The activation of NO molecule by Co2+ in CoZSM-5 in the presence of ammonia and pyridine molecules - IR studies

The effect of interaction of electron donor ammonia and pyridine molecules with Co2+ sites on the properties of these Co2+ ions, as well as the effect of adsorbed NO on the properties of NH3 interacting with Co2+ has been followed in the present study. It has been shown that the molecules NO interacting with Co2+ which bonds pyridine or ammonia molecules were strongly activated (NO stretching band was shifted to lower frequency by 60-110cm(-1)). This activation could be realized by the transfer of electrons from basic molecules via Co2+ to antibonding pi* orbitals of NO. The significant NO activation took place when NO interacted with Co2+ cations, which coordinated maximum possible number of NH3 molecules (NH3/Co = 6). For this case the formation of [Co(NH3)(6)NO](2+) complexes in which the transfer of full electrons from Co2+ to antibonding pi* orbitals of NO occurred. Such strong activation of NO molecules by ammonia and pyridine molecules makes available the formation of N2O. The fact that NO accepts electron forming NO- and finally N2O indicates that NO acts as oxidant in the presence of [Co(py)](2+) or [Co(NH3)(6)](2+). On the other hand, earlier IR study showed that without preadsorbed basic molecules NO acted as reducer: Co3+ was reduced to Co2+ whereas NO oxidized to NO+. (C) 2010 Elsevier B.V. All rights reserved.