Iron cation catalyzed reduction of N2O by CO: gas-phase temperature dependent kinetics

Abstract

The ion-molecule reactions F-e+ + N2O -> FeO+ + N-2 and FeO+ + CO -> Fe+ + CO2, which catalyze the reaction CO + N2O -> CO2 + N-2, have been studied over the temperature range 120-700 K using a variable temperature selected ion flow tube apparatus. Values of the rate constants for the former two reactions were experimentally derived as k(2) (10(-11) cm(3) s(-1)) = 2.0(+/- 0.3) (T/300)(-1.5(+/- 0.2)) + 6.3(+/- 0.9) exp(-515(+/- 77)/T) and k(3) (10(-10) cm(3) s(-1)) = 3.1(+/- 0.1) (T/300)(-0.9(+/- 0.1)). Characterizing the energy parameters of the reactions by density functional theory at the B3LYP/TZVP level, the rate constants are modeled, accounting for the intermediate formation of complexes. The reactions are characterized by nonstatistical intrinsic dynamics and rotation-dependent competition between forward and backward fluxes. For Fe+ + N2O, sextet-quartet switching of the potential energy surfaces is quantified. The rate constant for the clustering reaction FeO+ + N2O + He -> FeO(N2O)(+) + He was also measured, being k(4) (10(-27) cm(6) s(-1)) = 1.1(+/- 0.1) (T/300)(-2.5(+/- 0.1)) in the low pressure limit, and analyzed in terms of unimolecular rate theory.