Incorporation of mixed valence vanadium in the microporous titanosilicate AM-2

Titanium and silicon have been partly substituted by vanadium in the microporous titanosilicate AM-2 to produce V-AM-2 via direct hydrothermal method. The presence of vanadium was confirmed by energy dispersive X-ray spectrometry (EDS) analysis. Its structural incorporation leads to slight extension of the unit cell volume. This fact suggests an isomorphous substitution of tetrahedral silicon by vanadium, which is bigger than the former one. Over 500 °C the TG curve of V-AM-2 indicates increasing mass due to the oxidation of V4+–V5+. The presence of vanadium and its oxidation state are also investigated by diffuse reflectance ultraviolet–visible (DR UV–Vis) spectroscopy, 51V and 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy.