在Ru催化剂上的CO化过程中,高覆盖度的CO化学吸收和解离
Brett T Loveless1, Corneliu Buda, Matthew Neurock
1Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA.
Journal of the American Chemical Society
|March 14, 2013
概括
这项研究揭示了一氧化碳 (CO) 如何在费舍-托普施合成 (FTS) 过程中与催化剂结合并激活. 辅助的CO激活,而不是无助解离,是关键,特别是在曲的集群表面.
科学领域:
- 催化剂是一种催化剂.
- 表面科学是一门学科.
- 计算化学计算化学
背景情况:
- 了解一氧化碳 (CO) 吸附和激活对于优化费舍尔-托普施合成 (FTS) 至关重要.
- 之前的研究提出了CO分离的低协调位点,但实验和理论证据仍在争论中.
研究的目的:
- 在FTS期间研究表面和集群上化学吸收的CO (CO*) 的结构,热力学和激活.
- 阐明主要的CO激活路径及其对催化剂结构和反应条件的依赖.
主要方法:
- 密度函数理论 (DFT) 计算以建模CO吸附和反应障碍物.
- 红外光谱学用于描述CO附加层结构和移动性.
- 基于机制的速率方程来分析FTS动力学和激活能量.
主要成果:
- 随着覆盖范围的增加,CO结合会减弱,在曲的Ru201星团上具有较弱的排斥性相互作用.
- Ru201星团通过双二碳基稳定了超单层覆盖面.
- 红外光谱显示Ru/SiO2上的移动CO附加层在和时形成更密集的结构.
- DFT预测H辅助的CO分离在 (111) 露台上是占主导地位的途径,无辅助分离的障碍更高.
- 辅助路径与观察到的压力,集群大小和选择性效应一致.
结论:
- 辅助的二氧化碳解离,而不是在特殊地点的无辅助解离,控制了Ru,Co和Fe催化剂上的FTS.
- 在复杂的,曲的集群表面上模拟催化时,DFT是有效的.
- 这些发现挑战了关于FTS中CO分离的活性位点的先前假设.
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