On the reduction of NiFe/Al2O3 oxygen carrier in high-pressure chemical looping applications

• Published in: International journal of hydrogen energy 2024-01, Vol.49, p.1304-1317
• Main Authors: Palone, Orlando, Ramezani, Rouzbeh, Navarro, Claudia, Di Felice, Luca, Borello, Domenico, Grasa, Gemma, Gallucci, Fausto
• Format: Article
• Language: English
• Subjects: Chemical looping; High pressure; Hydrogen reduction; Nickel–iron; Redox
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2023.09.235

Chemical looping represents a promising technology with various applications ranging from clean power production to alternative syngas production. In this work, two oxygen carriers with different Ni loadings (4.3% wt. and 12% wt.) and similar Fe loadings (9.9% wt. and 8.5% wt.) are synthesized through a co-precipitation/impregnation route and tested in two thermogravimetric analyzers. Firstly, the effect of temperature (700–900 °C) on the oxygen transport capacity and reduction conversion of both materials is assessed at ambient pressure (0.5 nl/min with 20% H2/N2). The influence of material loading is also studied, and it is shown that higher Ni loadings provide a significant improvement in material activity. A complete reduction conversion is achieved at 900 °C and ambient pressure. At high pressure (10–20 bar), tests are carried out in a temperature range of 700–850 °C. The effect of flow rate (2 nl/min to 6 nl/min with 50% H2/N2) is first assessed to prevent external mass transfer limitations. Higher total pressures have a negative effect on reduction kinetics, while higher Ni loadings demonstrate increased final reduction conversion also at high pressure, reaching about 75% conversion after 20 min. The long-term cyclability of the material is also investigated both at low (100 cycles) and high pressure (80 cycles) conditions and a conversion gain is observed throughout the cycles in both cases. No changes in the material microstructure are observed after 80 high-pressure cycles. •Chemical looping cycles were carried out at ambient and high-pressure conditions.•Full reduction conversion was achieved at 900 °C after 200 s of testing for a nickel ferrite with 12% wt Ni and 8.5% wt Fe.•Total pressure showed a negative effect on reaction kinetics.•No significant changes in the microstructure of the material were observed.