Ni-Nb mixed oxides: One-pot synthesis and catalytic activity for oxidative dehydrogenation of ethane

Abstract

Ni–Nb mixed oxides were prepared by two methods, conventional evaporation method and combustion synthesis. With the latter technique, the mixed oxide can be quickly prepared from an aqueous solution of metal precursors (oxidizers) and sucrose (fuel). The solids with a 0.15/0.85 Nb/Ni atomic ratio were characterized by different techniques including X-ray diffraction, scanning electron microscopy, XPS and Raman spectroscopy, and N2 adsorption–desorption measurements. Ni–Nb mixed oxides were tested in the oxidative dehydrogenation (ODH) of ethane to ethylene. The catalyst prepared by combustion synthesis (a technique that is simpler than evaporation method) showed a good performance in terms of activity and stability levels when compared to the catalyst synthesized by the evaporation method, even for long-term runs. Regarding the effect of the metal precursor, nickel nitrate and ammonium niobate oxalate generated the better catalyst in both synthesis routes. Surface activity for ethane consumption and ethylene formation was higher than that observed for the sample prepared by the evaporation method with the same metal precursors. Both prepared catalysts presented almost constant ethylene yields for 120 h in stream at 400 C and W/ F = 0.06 g s/cm3 (8% and 15% for combustion and evaporation synthesis, respectively) with a slight decrease over time on stream (13% and 11%).