The activation of NO molecule by Co 2+ in CoZSM-5 in the presence of ammonia and pyridine molecules – IR studies

Abstract

The effect of interaction of electron donor ammonia and pyridine molecules with Co 2+ sites on the properties of these Co 2+ ions, as well as the effect of adsorbed NO on the properties of NH 3 interacting with Co 2+ has been followed in the present study. It has been shown that the molecules NO interacting with Co 2+ which bonds pyridine or ammonia molecules were strongly activated (NO stretching band was shifted to lower frequency by 60–110 cm −1). This activation could be realized by the transfer of electrons from basic molecules via Co 2+ to antibonding π* orbitals of NO. The significant NO activation took place when NO interacted with Co 2+ cations, which coordinated maximum possible number of NH 3 molecules (NH 3/Co = 6). For this case the formation of [Co(NH 3) 6NO] 2+ complexes in which the transfer of full electrons from Co 2+ to antibonding π* orbitals of NO occurred. Such strong activation of NO molecules by ammonia and pyridine molecules makes available the formation of N 2O. The fact that NO accepts electron forming NO − and finally N 2O indicates that NO acts as oxidant in the presence of [Co(py)] 2+ or [Co(NH 3) 6] 2+. On the other hand, earlier IR study showed that without preadsorbed basic molecules NO acted as reducer: Co 3+ was reduced to Co 2+ whereas NO oxidized to NO +.