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.