Catalytic Properties of Iron Oxides. II. Isotopic Exchange of Oxygen, Oxidation of Carbon Monoxide, and Reduction-Oxidation Mechanism

Abstract
The reactivity and mobility of the lattice oxygen of iron oxide, in particular γ-Fe2O3, has been investigated by 18O-exchange with CO2 and CO oxidation by 18O2. The low mobility of the lattice oxygen is in agreement with the reduction-oxidation mechanism of γ-Fe2O3 bulk, which proceeds by Fe ion migration without diffusion of the lattice oxygen. The rapid diffusion of the Fe ion makes the redox cycles of γ-Fe2O3 easy and explains, together with the cation deficient structure, the high reactivity and selectivity of lattice oxygen. Thus, γ-Fe2O3may be regarded as a new prototype of selective catalyst for allylic oxidation.