Enhanced Cyclic Stability of Composite-Modified Iron-Based Oxygen Carriers in Methane Chemical Looping Combustion: Mechanistic Insights from Chemical Calculations

Chemical Looping Combustion (CLC) technology has emerged as a promising approach for carbon capture owing to its CO₂ separation capability, which addresses the pressing challenge of global climate change. Although iron-based oxygen carriers offer economic advantages owing to their abundance and low cost, their limited cyclic stability restricts their industrial deployment. This study focused on optimizing the performance of iron-based oxygen carriers through composite modification with Al₂O₃ and TiO₂. Using Cantera (2.5.0) software and the minimum Gibbs free energy principle, conversion rates and product distributions of Fe₂O₃, Fe₂O₃/Al₂O₃, and Fe₂O₃/TiO₂ were systematically analyzed under varying temperatures (800–950 °C), oxygen carrier-to-fuel molar ratios (O/C = 1–15), and pressures (0.1–1.0 MPa). The optimal conditions were identified as 900 °C, O/C = 8, and 0.1 MPa. After 50 simulation cycles, Fe₂O₃/Al₂O₃ and Fe₂O₃/TiO₂ achieved average total reaction counts of 503 and 543, respectively, substantially exceeding 296 cycles for Fe₂O₃. The results indicated that Al₂O₃ and TiO₂ improved cyclic stability via physical support and structural regulation mechanisms, thereby offering a practical carrier composite modification strategy. This study provides a theoretical basis for the development of high-performance oxygen carriers and supports the industrial application of CLC technology for efficient carbon capture and emission mitigation.