支持的氧化瓦纳物种的大小依赖的催化活性:的氧化脱
Xavier Rozanska1, Remy Fortrie, Joachim Sauer
1Institut für Chemie, Humboldt Universität zu Berlin , Unter den Linden 6, D-10099 Berlin, Germany.
Journal of the American Chemical Society
|May 16, 2014
概括
密度函数理论揭示了氧化二氧化瓦纳对的二极体在氧化脱中比单体更有效. 模态物种具有较低的能量障碍,提高了这一关键工业过程的反应速率.
科学领域:
- 不同质的催化剂.
- 表面科学是一门科学.
- 计算化学是一种计算化学.
背景情况:
- 的氧化脱是生产的关键反应,是一种重要的工业化学品.
- 支持氧化物的氧化物催化剂被广泛研究用于这种转化.
- 了解活性部位和反应机制对于催化剂优化至关重要.
研究的目的:
- 通过密度函数理论研究氧化脱的反应途径,在氧化物催化剂上进行氧化脱.
- 为了比较单体和二元氧化物物种的活性.
- 阐明V (V) /V (IV) 和V (V) /V (III) 氧还原循环在反应机制中的作用.
主要方法:
- 密度函数理论 (DFT) 的计算被用于模拟单体和二元氧化物物种.
- 用vanadyl替代的silsesquioxanes作为模型化合物被使用.
- 进行微动力学模拟以确定速度决定步骤和预测速度常数.
主要成果:
- 反应通过两个抽象步骤进行,形成一个基,然后是.
- 比起V (V) /V (III) 循环,V (V) /V (IV) 反氧循环更受青.
- 与单体物种 (124 kJ/mol) 相比,二元氧化瓦纳物种的激活能障碍较低 (114 kJ/mol在750 K),导致预测速率常数更高.
结论:
- 对于的氧化脱,二元氧化物种比单元物种更具反应性.
- 预计随着寡合体大小的增加反应性的趋势将继续下去.
- 寡合物种的统计分布和速率常数的适度增加解释了观察到的周转频率对瓦纳迪亚负载的不敏感性.
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