Electron paramagnetic resonance study of the reactivity toward carbon monoxide and oxygen of O– ions adsorbed on silica-supported molybdenum catalysts

Abstract

Using the e.p.r. technique, the reaction at 77 K of an O– radical, formed by N2O adsorption on reduced MoO3/SiO2 samples, with CO or 13CO was followed, and it was possible to detect a CO–2 radical (g1= 2.0029, g2= 2.0016, g3= 1.9974, A1= 199 G, A2= 240 G, A3= 207 G) which was stable at room temperature. This species reacted with O2 at 77 K to give rise to a radical of the type (O2COO)–(g1= 2.0486, g2= 2.0078, G3= 2.0026, A1C= OG, A2C= 4.8 G, A3C= 6 G, A3OI= 140 G, A3OII= 40 G). At 150 K, it disappeared irreversibly, generating an O–2 radical (g1= 2.0175, g2= 2.0097, g3= 2.0040, A3OI= 80 G, A3OII= 70 G) similar to that formed by direct adsorption of oxygen on reduced MoO3/SiO2.