Effect of V in La2NixV1−xO4+δ on selective oxidative dehydrogenation of propane

In this study, non-stoichiometric redox compounds such as La2NiO4+δ, La2Ni0.95V0.05O4.07+δ and La2Ni0.9V0.1O4.15+δ have been tested as oxidants in selective oxidation of propane, in order to judge the suitability of these materials for a dense membrane reactor for selective propane oxidation. Reducibility of the samples has been investigated using temperature programmed reduction in H2/Ar flow. The catalysts’ activity and selectivity at 550 °C have been investigated employing sequential pulses of diluted propane over the oxides. Pulsing with propane induces step-by-step reduction of the oxide; consequently, the activity of remaining oxygen decreases with the number of pulses, affecting the products distribution. It is observed that at 550 °C on oxidized catalysts CO2 and H2O are the main products and the selectivity towards propylene is very low. At a certain reduction level, obtained after pulse 8 in our experiments, the production of CO2 stopped without changing the amount of C3H6 produced. At this stage, also CH4 and C2H4 are being formed. V-doped catalysts have shown a constant level of C3H6 production within a broad window of oxidation degree, while the performance of La2NiO4+δ, catalyst deteriorated drastically after just a few pulses. CO, CH4 and coke deposits are formed with La2NiO4+δ, caused by the formation of metallic Ni. Vanadium is able to prevent this phenomenon, thus drastically broadening the window of selective oxidation of propane.