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, Fe₂O₃[104]氧化CO的反应活性远高于Fe₂O₃[001], Fe₂O₃[104]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Fe₂O₃[104]可被CO彻底还原成Fe单质, Fe₂O₃[104]释放氧能力强, 反应活性高; 而Fe₂O₃[001]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Fe₂O₃[104]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 Fe₂O₃[104] for oxidizing CO is greater than that of Fe₂O₃[001]. Fe₂O₃[104] 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 Fe₂O₃[104] can be completely reduced into Fe, and Fe₂O₃[104] exhibits high oxygen transfer ability. However, Fe₂O₃[001] 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 Fe₂O₃[104].