Evaluation of the Reactivity of Hematite Oxygen Carriers Modified Using Alkaline (Earth) Metals and Transition Metals for the Chemical Looping Conversion of Lignite

Chemical looping (CL) technology is a novel for the clean and efficient use of energy. Oxygen carriers (OCs) are cornerstone CL technology. The development low–cost, high–performance OCs crucial application conversion. Hematite, one natural Fe–based OCs, has several advantages (e.g., low cost environmental friendliness), but its reactivity limits in CL. performance hematite can be effectively improved by modifying some active components. This study explored improvement adding alkaline (earth) metals (K, Na, Ca) transition (Ni, Cu, Mn). crystal phases were characterized using X-ray diffraction (XRD), results revealed that addition significantly changed phase original hematite. solid solution K–Fe–O Na–Fe–O species exhibited strong catalytic activity to facilitate lignite char CaO promoted devolatilization lignite, while formation CaFe2O4 with inhibited lattice oxygen release. presence CuO/CuFe2O4 Cu–modified sample could release small amount free O2 promote volatile high NiO NiFe2O4 Ni–modified improve reaction However, MnFeO3 was generated Mn–modified OC, decreasing rate OC char.