NICKEL COBALT PEROVSKITES APPLIED IN THE CHEMICAL LOOPING COMBUSTION

Perovskites with composition LaNi1-xCoxO3 (x = 0.0, 0.2, 0.5, 1.0) were evaluated on chemical looping combustion (CLC). In situ XRDs under methane flow with LaNi0.5Co0.5O3 and LaNi0.8Co0.2O3 samples indicates that the reduction mechanism is distinct for each oxide. Phase changes with LaNi0.5Co0.5O3 involve the intermediate phases, LaNi0.5Co0.5O2.5 and Co3O4. With the LaNi0.8Co0.2O3 sample, the mechanism includes oxygen-deficient perovskite structures as well as spinel and NiO phases. With increasing temperature, in both cases, the phases evidenced were Ni0 , Co0 and La2O3. The addition of cobalt contributed to the decrease in the amount of active oxygen for the reaction, making the catalysts less active. The insertion of cobalt also improved the regeneration capability of the catalysts, as it favored obtaining more deactivation resistant materials due to coke deposits. All samples tended to decrease coke formation as the cycles progressed. Among the samples most resistant to coke formation, x = 0.5 led to complete reduction in a shorter time is considered the best catalytic performance to CLC.