Oxidative dehydrogenation of ethane to ethene on alumina-supported molybdenum-based catalysts modified by vanadium and phosphorus

Gamma-alumina-supported MoOx, MoVOx (Mo/V = 11) and MoVPOx (Mo/V = 11, V/P = 1) catalysts were prepared and their properties studied by several techniques (EDX-SEM, XRD, XPS, LRS, TPR). Acid–base and catalytic properties were determined by carrying out 2-propanol decomposition and oxidative dehydrogenation of ethane to ethene, respectively. In situ X-ray diffraction and X-ray photoelectron spectroscopy after pre-treatment were carried out in redox conditions (with H2/N2, C2H6/N2 as reducing and O2/N2 as oxidant). The catalytic performance increases along MoOx < MoVOx < MoVPOx series. Analyses of MoVPOx show that part of Mo is stabilised as Al2(MoO4)3 and that the surface is made up from single or mixed Mo and V oxospecies. Vanadium increases the reducibility of the catalyst as shown by TPD and XPS. Both the acid–base and redox properties are responsible for the catalytic properties of MoVPOx, which are also related to the coordination of Mo active species.