Low-Temperature Hydrogen Reduction of Iron Oxide (Fe2O3) with SiO2 (Lunar Regolith) Mixture: An Experimental Approach to Hydrogen Spillover

초록

The low-temperature hydrogen reduction of iron oxide is essential for transforming the steel industry sustainably with zero carbon emissions. Previous studies have shown that physically mixed reducible supports (Na-MOR and Na-ZSM-5) with Fe<inf>2</inf>O<inf>3</inf> can lower the reduction temperature. However, the effect of mixing Fe<inf>2</inf>O<inf>3</inf> with non-reducible support of SiO2 has not been explored. Therefore, this study aims to validate the effectiveness of SiO<inf>2</inf> in lowering the reduction temperature of Fe<inf>2</inf>O<inf>3</inf>, potentially simplifying the iron smelting process with high effectiveness. We conducted XRD, SEM/EDS, H2-TPR, and XPS analyses to investigate the reduction characteristics. H<inf>2</inf>-TPR results revealed that the final reduction peak of Fe<inf>2</inf>O<inf>3</inf>, corresponding to the FeO → Fe step, decreased from 783.7 °C (pure Fe<inf>2</inf>O<inf>3</inf>) to 731.2 °C (Fe<inf>2</inf>O<inf>3</inf>/SiO<inf>2</inf>) and 458.6 °C (Fe<inf>2</inf>O<inf>3</inf> + SiO<inf>2</inf>). After reduction at 500 °C, XRD and XPS analyses showed that the majority of Fe2O3 in the Fe2O3 + SiO2 was reduced to metallic iron, while Fe<inf>2</inf>O<inf>3</inf>/SiO<inf>2</inf> still contained iron oxides (Fe<inf>2</inf>O<inf>3</inf>, Fe<inf>3</inf>O<inf>4</inf>, and FeO) and fayalite (Fe<inf>2</inf>SiO<inf>4</inf>), indicating incomplete reduction and thermal agglomeration, respectively. These findings confirm that physically mixed SiO<inf>2</inf> enhances the reduction rate significantly. The formation of Si-OH bonds after reduction suggests that hydrogen was adsorbed on the SiO<inf>2</inf> surface, which has lower adsorption energy than the Fe<inf>3</inf>O<inf>4</inf> → FeO and FeO → Fe reduction energy. Consequently, hydrogen was adsorbed on the SiO2, diffused through the long-distance hydrogen spillover mechanism to Fe<inf>2</inf>O<inf>3</inf>, and reduced the Fe<inf>2</inf>O<inf>3</inf> to metallic iron. © 2025, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

키워드