PHASE COMPOSITION AND OXIDATION DEGREE OF VANADIUM IN CATALYSTS FOR OXIDATIVE DEHYDROGENATION OF PROPANE

Abstract

The phase composition of vanadium and vanadium-antimony-containing samples of γ-Al2O3 and the degree of oxidation of vanadium in them were examined by XRD and EPR methods, respectively. The data of XRD and EPR spectroscopy show the formation of highly dispersed vanadium-oxygen and vanadiumantimony-oxygen structures on the surface of the support. It is shown that the EPR spectra of the studied samples are due to "isolated" vanadium ions with an oxidation state of +4 in nonstoichiometric vanadium-oxygen and vanadium-antimony-oxygen formations with a square pyramid local environment structure with a characteristic V=O double bond. The EPR spectra of two types of paramagnetic centers of vanadium, which differ in the distortion of the square-pyramidal structure of the local environment of the vanadium ion, were identified. It was established that the number of ions with an oxidation state of +4 in V,Sb-containing samples depends on the V/Sb ratio in them.