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

摘要

Gamma-alumina-supported MoO_x, MoVO_x (Mo/V = 11) and MoVPO_x (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 MoO_x < MoVO_x < MoVPO_x series. Analyses of MoVPO_x show that part of Mo is stabilised as Al2(MoO4)_3 and that the surface is made up from single or mixed Mo and Voxospecies. 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 MoVPO_x, which are also related to the coordination of Mo active species.