The thermodynamic evaluation and process simulation of the chemical looping steam methane reforming of mixed iron oxides

Steam reforming chemical looping (CL-SMR) using mixed iron oxides has the potential as an alternative to the current partial oxidation (POX) and steam reforming (SMR) processes. In this study, the use of FeMoO₄, Fe₂ZnO₄ and Fe₂MnO₄ as oxygen carriers (OC) under the CL-SMR reaction scheme was proposed to overcome the current disadvantages of methane POX and SMR processes. This research is aimed at finding potential iron-based metal oxides for the production of syngas, which can be regenerated under favorable conditions in steam, while producing H₂. Thermodynamic evaluation and process simulation of the CL-SMR reaction scheme using mixed iron-oxides was performed. Results indicate that FeMoO₄, Fe₂ZnO₄ and Fe₂MnO₄ generated syngas at 750 °C, 730 °C and 600 °C, respectively. However, FeMoO₄ was not fully regenerated under favorable conditions, whereas Fe₂ZnO₄ and Fe₂MnO₄ were completely regenerated at 440 °C and 640 °C, respectively. Fe₂MnO₄ showed the most favorable operating conditions among the studied OC towards the production of syngas. Preliminary experimental studies involved the synthesis of Fe₂MnO₄ through a solid-state method using Fe₂O₃ and MnO as precursors, which was characterized via XRD, while its redox performance was evaluated in a TGA CH₄-H₂O redox cycle, with reduction using CH₄ followed by the steam oxidation of OC. Results indicate that both reduction with methane and oxidation with water vapor using Fe₂MnO₄ present reasonable reduction-oxidation rates to be used in the CL-SMR reaction scheme, verifying the feasibility of the theoretical study performed in the present investigation.