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Reaction mechanism of spinel CuFe2O4 with CO during chemical-looping combustion: An experimental and theoretical study
Proceedings of the Combustion Institute ( IF 3.4 ) Pub Date : 2018-07-17 , DOI: 10.1016/j.proci.2018.06.222
Feng Liu , Jing Liu , Yingju Yang , Zhen Wang , Chuguang Zheng

Spinel CuFe2O4 is a promising oxygen carrier due to its synergistic enhanced performance. A fundamental understanding of the reaction mechanism between oxygen carrier and fuels is important for a rational design of highly efficient oxygen carrier. The reaction mechanism of spinel CuFe2O4 with CO during chemical-looping combustion (CLC) was studied based on thermogravimetric analyses (TGA) and density functional theory (DFT) calculations. Two distinct reaction stages were clearly observed. CuFe2O4 was mainly transformed into Cu and Fe3O4 with a rapid reaction rate in the initial stage, and then product Fe3O4 was slowly reduced to FeO or even to Fe. The reactivity of CuFe2O4 is much higher than that of Fe2O3, which is ascribed to the existence of Cu. The enhanced oxygen evolution activity of CuFe2O4 at low temperature is validated by both the experimental and theoretical methods. Three types of surface oxygen coordinated with different metal atoms show different reactivity. Two kinds of reaction pathways are involved in CO oxidation over CuFe2O4. In the one-step reaction pathway, CO directly reacts with the oxygen bonding to two octahedral Cu and one octahedral Fe atoms to form a CO2 molecule without an energy barrier, which corresponds to the surface oxygen consumption observed in TGA experiments. In the possible two-step reaction pathway, CO first adsorbs on the surface, and then reacts with the oxygen bound to one octahedral Cu and two octahedral Fe atoms to generate CO2 by surmounting an energy barrier of 10.84 kJ/mol, which is the most kinetically and thermodynamically favorable pathway.



中文翻译:

尖晶石CuFe 2 O 4与CO在化学循环燃烧中的反应机理:实验和理论研究。

尖晶石CuFe 2 O 4具有协同增效的性能,是一种很有前途的氧气载体。氧气载体与燃料之间反应机理的基本理解对于合理设计高效氧气载体至关重要。基于热重分析(TGA)和密度泛函理论(DFT)计算,研究了尖晶石CuFe 2 O 4与CO在化学循环燃烧(CLC)过程中的反应机理。清楚地观察到两个不同的反应阶段。在初始阶段,CuFe 2 O 4主要以快速的反应速率转变为Cu和Fe 3 O 4,然后生成Fe 3 O4逐渐还原为FeO甚至是Fe。CuFe 2 O 4的反应性比Fe 2 O 3的反应性高得多,这归因于Cu的存在。通过实验和理论方法验证了CuFe 2 O 4在低温下增强的析氧活性。与不同金属原子配位的三种类型的表面氧表现出不同的反应性。CuFe 2 O 4上的CO氧化涉及两种反应途径。在一步式反应路径中,CO与与两个八面体Cu和一个八面体Fe原子键合的氧直接反应形成CO 2分子没有能垒,相当于在TGA实验中观察到的表面氧消耗。在可能的两步反应路径中,CO首先吸附在表面上,然后与键合到一个八面体Cu和两个八面体Fe原子上的氧发生反应,从而克服了10.84 kJ / mol的能垒,从而产生了CO 2。在动力学和热力学上最有利的途径。

更新日期:2018-07-17
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