Study of nickel, lanthanum and niobium-based catalysts applied in the partial oxidation of methane

Catalysts based on nickel, niobium and lanthanum were obtained from precursors such as LaNiO3, LaNi0.5Nb0.5O3 and NiO/Nb2O5 and evaluated in the partial oxidation of methane (POM). X-ray diffraction (XRD) in situ studies using synchrotron light, under H-2, indicate that after reduction the LaNiO3 perovskite precursor is transformed into Ni degrees/La2O3. On the other hand, LaNi0.5Nb0.5O3 is converted into Ni degrees/La2O3-LaNbO4 and NiO/Nb2O5 in Ni degrees/Nb2O5. Temperature programmed surface reaction (TPSR) indicates that only catalysts obtained from LaNiO3 and LaNi0.5Nb0.5O3 are active in the POM under the conditions investigated. XRD in situ studies using synchrotron light, under reaction atmosphere, show that nickel sites obtained from the precursor LaNi0.5Nb0.5O3 were less susceptible to oxidation. Long-term catalytic tests showed that the addition of niobium to LaNiO3 promotes the methane conversion per weight of nickel, a result which is associated with a larger nickel surface. This agrees with the mean crystallite size of nickel measured by XRD and with nickel particle size obtained from transmission electron microscopy (TEM). The regeneration of catalysts obtained from the precursors LaNiO3 and LaNi0.5Nb0.5O3 led to an increase in catalytic activity without a change in selectivity, and this can be attributed to a higher dispersion of the nickel particles after regeneration.