高指数晶面结构氧化铁化学链燃烧反应活性及深层还原反应机理

采用密度泛函理论计算和实验研究形貌可控制备氧化铁作为高效载氧体用于化学链燃烧的可行性. 首先从理论上对比分析Fe₂O₃高指数晶面104]和低指数晶面001]的反应活性及深层还原反应机理. 表面反应结果显示, Fe₂O₃104]氧化CO的反应活性远高于Fe₂O₃001], Fe₂O₃104]被还原成为低价的铁氧化物或单质, 这些低价的铁氧化物或单质可被O₂氧化再生. 载氧体和CO深层反应结果显示Fe₂O₃104]可被CO彻底还原成Fe单质, Fe₂O₃104]释放氧能力强, 反应活性高; 而Fe₂O₃001]还原到一定程度后反应能垒高, 抑制表面进一步还原, 释放氧能力有限. 最后, 实验结果进一步证明了Fe₂O₃104]作为载氧体用于化学链燃烧的高反应活性及稳定性.

Reaction Activity and Deep Reduction Reaction Mechanism of a High Index Iron Oxide Surface in Chemical Looping Combustion

The possibility of morphological control of iron oxide as an oxygen carrier for chemical looping combustion was investigated using density functional theory and experiment. First, we calculated the reactivity of Fe₂O₃ with high- index facets 104] and low- index facets 001], as well as the deep reduction reaction mechanism of these two facets. Surface reaction results show that the activity of Fe₂O₃104] for oxidizing CO is greater than that of Fe₂O₃001]. Fe₂O₃104] was reduced into iron oxide at lower oxidation state or into iron, which could then be regenerated after being oxidized by O₂. The deep reduction reaction mechanism between oxygen carrier and CO shows that Fe₂O₃104] can be completely reduced into Fe, and Fe₂O₃104] exhibits high oxygen transfer ability. However, Fe₂O₃001] can only be reduced to a limited extent, with a high energy barrier preventing further reduction, while it also exhibits limited oxygen transfer capacity. Results of experiments further verify the high reactivity and stability of Fe₂O₃104].