Effects of the enhancement of the abstraction of lattice oxygen from magnesium vanadates incorporated with copper(II) cations on the oxidative dehydrogenation of propane

Abstract

The influences of the incorporation of copper(II) cations into MgV 2O 6, Mg 2V 2O 7 and Mg 3V 2O 8 on the catalytic activities and the mobility of lattice oxygen in those catalysts have been investigated to observe the contribution of lattice oxygen in magnesium vanadates to the oxidative dehydrogenation of propane. The incorporation of Cu 2+ into those magnesium vanadates resulted in the decrease of the selectivity to propylene, while the evident enhancement of the reaction rate per unit of the surface area was observed. In order to examine the mobility of lattice oxygen in those Cu 2+ incorporated catalysts, those magnesium vanadates incorporated with Cu 2+ at the atomic ratios of Cu/[Mg + Cu] = 0 and 0.10 were employed for the oxidative dehydrogenation in the absence of oxygen for 2.25 h, followed by the addition of gaseous oxygen into the feed-stream. After the addition of gaseous oxygen under the present conditions, oxygen in the effluent gas was detected at approximately 36, 7 and 2 min with MgV 2O 6, Mg 2V 2O 7 and Mg 3V 2O 8 while no oxygen was detected from those catalysts incorporated with Cu 2+ even 60 min after the addition of gaseous oxygen. Therefore, the incorporation of Cu 2+ into those magnesium vanadates results in the enhancement of the abstraction of lattice oxygen from the catalysts. 51V MAS NMR and XPS revealed that redox of vanadium and copper species in those catalysts contributed to the abstraction of the lattice oxygen from the corresponding catalysts.