A few reaction steps were proposed for ICCU-DRM using Fe2O3/Al2O3 and CaCO3 combined functional materials (https://doi.org/10.1021/acs.iecr.9b05783). At the initial stage, the catalyst and the sorbent work separately. At the 2nd stage, the interaction between sorbent and catalyst (having oxygen storage capacity) happens. This is reflected by the remaining iron oxides, while CaCO3 disappears. In addition, FeO acts as a catalyst to promote the reaction between CaCO3 and CH4. At the 3rd stage, FeO is present other than Fe, indicating that oxygen sources (e.g. CO2) contributes to the presence of iron oxides and prohibit the reduction of FeO. This 3rd stage phenomena are not observed for the single Fe2O3-CH4 reforming. Therefore, the introduction of oxygen sources (from CaCO3) promotes syngas production from Fe2O3-CH4 reforming. At the last stage, it is interesting to see the reappearance of CaCO3, indicating that CO2 is recaptured by CaO. The interaction between CaCO3 and Fe2O3 during methane reforming results in the production of stable syngas.
