Structure and catalytic activity of iron oxide and magnesium oxide solid solutions. Part 2.—Catalytic activity for N2O decomposition

Abstract

The catalytic activity of magnesium oxide-iron oxide and magnesium oxide-iron oxide-lithium oxide systems has been investigated for N2O decomposition. The magnesium oxide-iron oxide samples, fired in air and containing MgFe2O4, have low activity. Similar samples, fired under reducing atmospheres and containing Fe2+ in solid solution, are active. The ions Fe2+ are oxidized during the catalytic experiments to Fe3+. The latter ions are reduced to Fe2+, during outgassing, thus restoring the active sites on the surface via a mechanism of electron migration which eventually yields the phase MgFe2O4 in the bulk of the particles.The samples containing lithium oxide are active only when [Li]/[Fe] < 1. The nature of the active sites in these samples is discussed taking into account the role of lithium oxide.