Iron-based spinel for H2 production and CO2 separation from plastics via chemical looping

Abstract

The integration of chemical looping combustion and hydrogen production using waste plastics as fuel presents a promising strategy for simultaneous CO₂ separation and high-purity H₂ generation. Iron-based spinel oxides (MFe₂O₄, M = Co, Mn, Cu, Ni) have emerged as robust oxygen carriers, yet their energy-material flow dynamics during redox cycles remain underexplored. Herein, a comprehensive methodology, combining Aspen Plus simulation with fixed-bed experiment was adopted to systematically assess the performance of four spinel systems. The results indicated that the system exergy efficiencies of MnFe₂O₄ and NiFe₂O₄ exceeded 78 %. Improving overall system exergy efficiency depended on the thermal integration of high-temperature gas/steam due to the low exergy utilization efficiency of the coolers. CuFe₂O₄ and NiFe₂O₄ were identified as suitable oxygen carriers for CO₂ separation in fuel reactor (83.72–99.98 %), whereas CoFe₂O₄ and MnFe₂O₄ showed enhanced H₂ yields in steam reactor (1.2–3.96 mmol/g OC). Challenges in FeO/Fe regeneration during carrier recycling highlighted the need for redox stability optimization. Notably, NiFe₂O₄ demonstrated the potential of CO₂ separation and H₂ co-production, positioning it as a benchmark material for scalable chemical looping systems. These findings provide mechanistic insights into gas quality control and process intensification for sustainable plastic-to-energy conversion.