The oxidation of carbon monoxide on a catalyst with a spinel structure containing Mg ferrite

The oxidation of carbon monoxide on xMgO · yFe2O3 catalysts was studied over the temperature range 440–660 K. The catalysts contained 5, 40, and 75 at % Fe and the spinel MgFe2O4 and MgO phases. Complete CO conversion on compact and deposited (on γ-Al2O3) catalysts containing 75 at. % Fe occurred at 650–660 K. The kinetics of interaction of CO with adsorbed oxygen was studied on catalysts with 5 and 40 at % Fe below and above the Curie point (Tc = 593 ± 10 K). The differences in the reaction orders with respect to gaseous CO and adsorbed oxygen below and above Tc were explained as follows. In the ferromagnetic state of the active MgFe2O4 phase, oxidation involved adsorbed oxygen localized at oxygen vacancies in the environment of Fe3+ ions, whereas, in the paramagnetic state, superexchange interactions were absent in spinel structure fragments.