Hydrogen and Carbon Monoxide Production by Chemical Looping over Iron-Aluminium Oxides

• Published in: Energy technology (Weinheim, Germany) Germany), 2016-02, Vol.4 (2), p.304-313
• Main Authors: Rihko-Struckmann, Liisa K., Datta, Pradyot, Wenzel, Marcus, Sundmacher, Kai, Dharanipragada, N. V. R. A., Poelman, Hilde, Galvita, Vladimir V., Marin, Guy B.
• Format: Article
• Language: English
• Subjects: Aluminum; Aluminum oxide; Carbon dioxide; Carbon monoxide; Deactivation; energy conversion; Exothermic reactions; Formations; hydrogen; iron; Iron oxides; Mixed oxides; Sintering; Spinel; Splitting; Storage capacity; water splitting
• ISSN: 2194-4288; 2194-4296
• DOI: 10.1002/ente.201500231

H2 and CO production from H2O and CO2 is investigated experimentally using a two‐step chemical looping process based on the redox cycles of iron‐alumina mixed oxides. The reduction of Fe3O4 in the first endothermic step is followed by the splitting of CO2 or H2O in a second exothermic step. The iron‐aluminum oxides are more reactive with H2O than with CO2 in the range 650–750 °C. In situ XRD shows that deactivation results from different processes: iron oxide sintering and the formation of spinel (FeAl2O4) with a lower oxygen‐storage capacity. However, FeAl2O4 assumes the role of Al2O3 and mitigates the iron oxide sintering. Deactivation at 650 °C is governed predominantly by sintering, and the further loss of activity is caused by combined sintering and spinel formation. Spinel formation is more dominant at 750 °C. A mixed oxide of Fe2O3 and Al2O3 with a mass ratio of 70:30 was the most active and stable for H2O and CO2 splitting in chemical looping. In the mix: Iron‐alumina mixed oxides are able to split either CO2 or H2O to generate CO and H2, respectively, in a cyclic redox process. The inclusion of alumina in the iron oxide reduces the amount of oxygen available and the yield of the cyclic H2 or CO production process but prevents the iron oxide from intensive sintering