Characterization and Performance of Sr and Co Doped Fe₂O₃-LaFeO₃ Quaternary Perovskite Composite Oxides for Efficient Realization of CH₄ Chemical Looping Conversion

The chemical looping conversion of CH4 has been one of the most promising technologies for achieving the "two-carbon" strategy. Fe2O3 oxygen carrier cannot maintain the excellent release performance of lattice oxygen at high temperature due to the sintering and carbon deposition. Therefore, quaternary La1-xSrxFe1-y CoyO3 perovskite was selected as the transfer support of oxygen ions. By using the MOF precursor method, ternary La0.8Sr0.2FeO3 was prepared via the introduction of metal Sr into the binary LaFeO3. The adsorption energy of CH4 on the La0.8Sr0.2FeO3 was the lowest (-0.054 eV), compared with separate Fe2O3 and LaFeO3, and the adsorption energy of free H at the adjacent Fe site was the lowest (1.650 eV). Furthermore, the La1-xSrxFe1-yCoyO3 perovskite was successfully synthesized by the doping of Co into the ternary La0.8Sr0.2FeO3. La0.8Sr0.2Fe0.8Co0.2O3 was chosen to composite Fe2O3 oxygen carrier. As m(Fe2O3):m(La0.8Sr0.2Fe0.8Co0.2O3) = 1:1, the lattice oxygen conversion rate was less than 47% and the selectivity of CO2 reached 99.5% through the synergistic effect of lattice oxygen and oxygen vacancies. Fe2O3-La0.8Sr0.2Fe0.8Co0.2O3 increased the lattice oxygen conversion by 17.6%, compared with Fe2O3-La0.8Sr0.2FeO3. After the CH4 chemical looping conversion cycles five times, Fe2O3-La0.8Sr0.2Fe0.8Co0.2O3 still had favorable structural stability and oxidation performance, and the lattice oxygen conversion rate still reached >95%.