PREPARATION AND CHARACTERIZATION OF 3 PURE MAGNESIUM VANADATE PHASES AS CATALYSTS FOR SELECTIVE OXIDATION OF PROPANE TO PROPENE

Three magnesium vanadate phases, i.e., MgV2O6 (metavanadate), alpha-Mg2V2O7 (pyrovanadate) and Mg3V2O8 (orthovanadate), have been successfully prepared with high purity by the citrate method at a relatively low temperature (550-degrees-C). FT-IR, LRS, XRD and SEM techniques have been used to characterize these vanadate phases. The effect of calcination temperature has also been investigated. It was found that the particle size and morphology of the MgV2O6 phase, which is a function of calcination temperature, appear to have a strong effect on the infrared spectra. Furthermore, the catalytic properties of the three phases were examined in the oxidative dehydrogenation of propane. The propene selectivity follows the order: alpha-Mg2V2O7 > Mg3V2O8 > MgV2O6, which is consistent with their redox properties. This fact suggests that there is some correlation between the catalytic and redox properties of these magnesium vanadate phases.