Effect of V in La 2Ni xV 1− xO 4+ δ on selective oxidative dehydrogenation of propane

Abstract

In this study, non-stoichiometric redox compounds such as La 2NiO 4+ δ , La 2Ni 0.95V 0.05O 4.07+ δ and La 2Ni 0.9V 0.1O 4.15+ 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 H 2/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 CO 2 and H 2O 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 CO 2 stopped without changing the amount of C 3H 6 produced. At this stage, also CH 4 and C 2H 4 are being formed. V-doped catalysts have shown a constant level of C 3H 6 production within a broad window of oxidation degree, while the performance of La 2NiO 4+ δ , catalyst deteriorated drastically after just a few pulses. CO, CH 4 and coke deposits are formed with La 2NiO 4+ 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.