The reaction of oxygen with the surface of γFe2O3 has been studied by infrared spectroscopy method. It has been shown that a variety of forms of adsorbed oxygen is produced. The adsorption bands corresponding to the different forms of adsorbed oxygen lie in the 1600 - 800 cm-1 spectral range. Two species are clearly distinguished: one neutral molecular specie highly polarised which absorbs in the 1500-1540 cm-1 region and one charged specie O2n- with 0 < n < 1 which absorbs in the 1500 - 1200 cm-1 region. Their thermodesorption in vacum at 250°C is accompanied by sample reduction to Fe3O4 state. Hydrogen reacts selectively (according to temperature) with adsorbed molecular oxygen then lattice oxygen. With molecule interacts physically among hydrogen bonds with some O2n- species, however dipole-dipole interaction with polarized species is pointed out. At room temperature, propen adsorption leads to chemisorbed species obtained by a reaction with adsorbed oxygen.
Pages 13- 23