Synthesis and characterization of zeolite beta containing oxide clusters of antimony and vanadium

Individual and mixed metal oxide clusters of antimony and vanadium are synt hesized within the pore space of zeolite beta and investigated by powder X- ray diffraction, Nz physisorption, electron spin resonance spectroscopy, te mperature-programmed reduction and X-ray adsorption fine structure. Vanadiu m species (VO2+) are highly dispersed in zeolite beta by ion exchange of th e hydrogen form with VOSO4. Upon calcination in air and subsequent reductio n at 550 degrees C in hydrogen, the vanadium species do not aggregate into large oxide clusters. On the contrary, intrazeolitic antimony species obtai ned via the impregnation of antimony acetate into zeolite beta do aggregate during calcination in air. However, if antimony acetate is impregnated int o a zeolite beta containing vanadium at an Sb/V ratio near unity, mixed met al oxide clusters are formed with physicochemical properties different from either intrazeolitic vanadium or antimony or bulk SbVO4. At Sb/V ratios ab ove unity, phase-separated antimony oxide is obtained in addition to the in trazeolitic mixed metal oxide clusters. (C) 2000 Elsevier Science B.V. All rights reserved.