Abstract: To investigate the influence mechanism of metal doping contenton the reduction kinetics of iron-based oxygen carriers,a series of iron-based oxygen carriers with low concentration lanthanum doping (molar fraction of lanthanum : 0 - 3%) were synthesized, the structureof iron-based oxygen carriers with different lanthanum doping loadings were examined by X-ray diffraction, N₂ adsorption-desorption, scanning electron microscopy, etc., and the variation trends of methane reduction reaction kinetics were evaluated through a coupled approach of modelling calculations and experiments. Results indicate that the doped lanthanum enters the lattice of iron-based oxygen carrier, causing leftward shifts in the XRD diffraction peaks of Fe₂O₃ and ZrO₂. Moreover, the degree of shift increases with increasing lanthanum doping concentration. At a lanthanum molar fraction of 3%, a distinctive perovskite-structured LaFeO₃ crystalline phase forms, leading to a decrease in the specific surface area of oxygen carrier. The methane reduction reaction over iron-based oxygen carriers comprises three steps: Fe₂O₃ → Fe₃O₄ (R₁), Fe₃O₄ → Fe_1-xO (R₂), and Fe_1-xO → Fe (R₃). Steps R₁ and R₂ conform to first-order reaction models, while R₃ follows a nucleation model. Lanthanum doping does not alter the methane reduction reaction pathway or its kinetic model of oxygen carrier. The 1% La-doped oxygen carrier exhibits an optimal reduction performance, significantly enhancing the overall reaction rate and simultaneously lowering the activation energies of each reaction step.

Key words: chemical looping, lanthanum metal doping, iron-based oxygen carrier, reaction kinetics, activation energy