Selective oxidation of ethane. Developing an orthorhombic phase in Mo-V-X (X=Nb, Sb, Te) mixed oxides

P. BOTELLA; A. DEJOZ; M.C. ABELLO; M.I. VAZQUEZ; L. ARRUA; J. M. LOPEZ NIETO

CATALYSIS TODAY

Elsevier

Año: 2009 vol. 142 p. 272 - 277

0920-5861

Mo-V-X (X= Nb, Sb and/or Te) mixed oxides have been prepared by hydrothermal synthesis and heat-treated in N2 at 450 ºC or 600 ºC for 2h. The calcination temperature and the presence or absence of Nb determines the nature of crystalline phases in the catalyst. Nb-containing catalysts calcined at 450 ºC are mostly amorphous solids, while Nb-free catalysts calcined at 450ºC and samples treated at 600 ºC present clearly indicate the presence crystalline phases.  TPR-H2 experiments show higher H2 consumption on catalysts with amorphous phases. Catalytic results in the oxidative dehydrogenation of ethane indicate that the selective production of the olefin depends on the development of an orthorhombic phase (the so-called M1 phase), Te2M20O57 or (SbO)2M20O56 (depending on the catalyst composition), which is formed at 600 ºC. This active and selective crystalline phase shows moderate reducibility and active centers enough for alkane activation on surface with the minimum quantity possible of active centers for olefin activation. In this sense, the best yield to ethylene has been achieved on a Mo-V-Te-Nb mixed oxide.