Insight in kinetics from pre‐edge features using time resolved in situ XAS
Insight in kinetics from pre‐edge features using time resolved in situ XAS
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DOI：
10.1002/aic.16017
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发表时间：
2018-04
期刊：
影响因子：
3.7
通讯作者：
N. A. Dharanipragada;V. Galvita;H. Poelman;L. Buelens;G. Marin;A. Longo
中科院分区：
文献类型：
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作者：
N. A. Dharanipragada;V. Galvita;H. Poelman;L. Buelens;G. Marin;A. Longo
使用 XRD 和时间分辨 Fe-K QXANES 研究了 10 wt% Fe2O3-MgAl2O4 尖晶石的还原动力学。 XRD 图案的 Rietveld 精修显示尖晶石结构中 Al 被 Fe 取代，并形成 MgFeAlOx。 XANES 预边缘功能用于研究 H2-TPR（程序升温还原）期间高达 730°C 的还原动力学。 MgFeAlOx 中约 55% 的 Fe3+ 被还原为 Fe2+。应用了收缩核心模型，该模型通过氧扩散系数考虑固态扩散，并通过反应速率系数考虑气固反应。化学反应的活化能与转化率呈线性相关，在材料还原过程中从 104 kJ/mol 增加到 126 kJ/mol。收缩核心模型描述与实验数据之间的良好一致性表明，XANES 前边缘特征可用于关联材料结构和反应动力学的变化。 © 2017 美国化学工程师学会 AIChE J, 64: 1339–1349, 2018
The kinetics of reduction of a 10 wt %Fe2O3-MgAl2O4 spinel were investigated using XRD and time resolved Fe-K QXANES. The Rietveld refinement of the XRD pattern showed the replacement of Al with Fe in the spinel structure and the formation of MgFeAlOx. The XANES pre-edge feature was employed to study the reduction kinetics during H2-TPR (Temperature Programmed Reduction) up to 730°C. About 55% of the Fe3+ in MgFeAlOx was reduced to Fe2+. A shrinking core model, which takes into account both solid-state diffusion via an oxygen diffusion coefficient, and gas-solid reaction through a reaction rate coefficient, was applied. The activation energy for chemical reaction showed a linear dependence on the conversion, increasing from 104 to 126 kJ/mol over the course of material reduction. The good accordance between the shrinking core model description and the experimental data indicates that XANES pre-edge features can be used to correlate changes in material structure and reaction kinetics. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1339–1349, 2018