Catalytic Oxidation of CO by N₂O Enabled by Al₂O_2/3⁺: Temperature Dependent Kinetics and Statistical Modeling

The reactions of Al₂O₂⁺ + N₂O and Al₂O₃⁺ + CO, forming a catalytic cycle oxidizing CO by N₂O, have been investigated from 300 to 600 K in a variable ion source, temperature adjustable, selected-ion flow tube (VISTA-SIFT). Reaction coordinates have been calculated using density functional theory and statistical modeling of those surfaces compared to experimental kinetics data for mechanistic insight. The reaction of Al₂O₂⁺ + N₂O proceeds at the Su-Chesnavich collisional limit at all temperatures studied, yielding only Al₂O₃⁺, with the exception of a small (<5%) amount of association product, Al₂O₂(N₂O)⁺ at 300 K. The reaction of Al₂O₃⁺ with CO produces Al₂O₂⁺ with a rate constant of 4.7 ± 1.2 × 10^-10 cm³ s^-1 at 300 K, decreasing with temperature as T^-0.5±0.2. In addition, a significant amount of association product, Al₂O₃(CO)⁺, was observed with rate constants for formation ranging from 10^-11 to 10^-10 cm³ s^-1 dependent upon He buffer gas concentration and temperature. Implications of these kinetic measurements with regard to the reactive surface are discussed.