CATALYTIC PROPERTIES OF IRON-OXIDES .2. ISOTOPIC EXCHANGE OF OXYGEN, OXIDATION OF CARBON-MONOXIDE, AND REDUCTION-OXIDATION MECHANISM

The reactivity and mobility of the lattice oxygen of iron oxide, in particular gamma -Fe//2O//3, has been investigated by **1**8O-exchange with CO//2 and CO oxidation by **1**8O//2. The low mobility of the lattice oxygen is in agreement with the reduction-oxidation mechanism of gamma -Fe//2O//3 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 gamma -Fe//2O//3 easy and explains, together with the cation deficient structure, the high reactivity and selectivity of lattice oxygen. Thus, gamma -Fe//2O//3 may be regarded as a new prototype of selective catalyst for allylic oxidation.