LaNi1-xCoxO3 perovskites for methane combustion by chemical looping

Perovskite oxides with composition LaNi1-xCoxO3 (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 LaNi0.5Co0.5O3 and LaNi0.8Co0.2O3 samples, suggest that a different reduction mechanism is activated depending on the composition of the starting material: LaNi0.5Co0.5O3 reduction involved the formation of LaNi0.5Co0.5O2.5 and Co3O4 as intermediate phases, whereas LaNi0.8Co0.2O3 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 Ni0, Co0 and La2O3. 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 LaNi1-xCoxO3 samples resistant to coke formation (x = 0.5 and 1.0), LaNi0.5Co0.5O3 lead to a complete reduction in less time and is therefore considered the best CLC sample of the series.

Automated summary

Perovskite oxides LaNi1-xCoxO3 (x = 0.0; 0.2; 0.5; 1.0) were studied in chemical looping combustion of methane. Nickel substitution for cobalt decreased active oxygen, while cobalt insertion improved re-oxidation rates and reduced coke deposits. The best CLC sample in the series was found to be LaNi0.5Co0.5O3 due to its faster complete reduction and resistance to coke formation.