LaNi1-xCoxO3 perovskites for methane combustion by chemical looping

Perovskite oxides with composition LaNiCoO (x = 0.0; 0.2; 0.5; 1.0) were studied in the chemical looping combustion (CLC) of methane. In situ XRDs under methane flow at different temperatures of LaNiCoO and LaNiCoO samples, suggest that a different reduction mechanism is activated depending on the composition of the starting material: LaNiCoO reduction involved the formation of LaNiCoO and CoO as intermediate phases, whereas LaNiCoO showed an oxygen-deficient perovskite structure as well as spinel and NiO phases. At temperatures higher than 700 °C, in both samples, the final phases evidenced under methane flow were Ni, Co and LaO. The substitution of nickel for cobalt contributed to a decrease in the quantity of active oxygen for the methane combustion reaction, making the catalysts less active. However, the insertion of cobalt improved the re-oxidation rate of the catalysts and lead to materials that were less contaminated by coke deposits. During methane CLC, the formation of coke tended to decrease for all samples with the progress of the reaction. After CLC process, the catalysts external morphology was appeared much more uniform. Among the LaNiCoO samples resistant to coke formation (x = 0.5 and 1.0), LaNiCoO lead to a complete reduction in less time and is therefore considered the best CLC sample of the series.