Composite xNiFe2O4/(1-x)SrFe12O19 oxygen carriers for chemical looping reforming of bioethanol coupled with water splitting to coproduce syngas and hydrogen

Abstract

Sr–Fe oxides are suitable oxygen carriers (OCs) with excellent cyclic stability. However, the moderate redox activity causes a deficiency in H₂ yield in chemical looping reforming coupled with water splitting (CLR-WS) process. Herein, we designed and prepared the composite xNiFe₂O₄/(1-x)SrFe₁₂O₁₉ OCs by ball milling method, which exhibited both high redox activity and high cyclic stability during reactions. A series of characterizations showed that the introduction of NiFe₂O₄ promoted the oxygen vacancy formation and the release of lattice oxygen, facilitating the reforming of bioethanol in fuel reactor (FR). During CLR-WS process, a high carbon conversion of 79.20 % and a H₂ yield of 13.23 mmol/g OC were achieved by 3Ni7Sr OC at 800 °C, outperforming that of the conventional SrFe₁₂O₁₉ OC. Moreover, the severe carbon deposition and sintering issues inherent to NiFe₂O₄ were avoided due to the presence of Sr. All Sr-containing composite OCs showed H₂ purity exceeding 99.26 % and excellent cycling stability with no apparent activation of oxygen transport capacity over 3000 min redox reactions.