A definitive assessment of the CO oxidation pattern of a nanocomposite MnCeOx catalyst

Abstract

The CO oxidation pattern of a nanocomposite MnCeO_x catalyst (M5C1; Mn_at/Ce_at, 5) in the range of 293–533 K (P, 1 atm) has been probed under a kinetic regime, varying reagent pressure (p⁰_CO, 0.01–0.025 atm; λ₀, 1), ratio (λ₀, 0.25–4.0) and CO₂ co-feeding (0.05–0.10 atm). Activity data indicate fractional orders on p_CO (0.6 ± 0.1) and p_O2 (0.4 ± 0.1), with an activation energy of 40 ± 3 kJ mol⁻¹, and a negative kinetic effect of CO₂ co-feeding due to competitive adsorption processes. Coupled with systematic evidence on the reactivity and mobility of catalyst oxygen and surface intermediates, kinetic data disclose a concerted redox mechanism of Langmuir–Hinshelwood type, which starts by abstraction of O-atoms from surface active Mn^IV centres (r.d.s.), and is sustained by adsorption of diatomic oxygen species on O-vacancies. The derivative and integral forms of the formal rate equation explain the empirical kinetics, predicting the activity pattern of the MnCeO_x catalyst in the range of 293–533 K.