在Haber-Bosch过程中进行表面化学探测
Christopher M Goodwin1,2, Patrick Lömker3, David Degerman3
1Department of Physics, Stockholm University, AlbaNova University Center, Stockholm, Sweden. cgoodwin@cells.es.
Nature
|January 10, 2024
概括
哈伯-博斯工艺使用铁 (Fe) 和 (Ru) 催化剂进行氨合成. 研究人员发现,在Fe催化剂上,化成为较低温度的速度限制步骤,与N2解离总是限制的Ru催化剂不同.
科学领域:
- 催化科学
- 表面化学
- 化学工程
背景情况:
- 哈伯-博斯工艺对于氨 (NH3) 合成至关重要,对于肥料生产至关重要.
- 由于恶劣的操作条件,Fe和Ru催化剂的确切催化机制和速度限制步骤仍在争论中.
- 之前的机械研究通常仅限于理论计算或真空表面分析.
研究的目的:
- 在操作条件下的氨合成过程中研究Fe和Ru催化剂的表面组成和化学状态.
- 阐明Fe和Ru催化剂的Haber-Bosch过程中的速度限制步骤.
- 将实验观测与有关催化机制的理论预测相协调.
主要方法:
- 使用适用于操作的X射线光电子光谱 (XPS).
- 在高达1bar的压力和高达723K的温度下研究Fe和Ru催化剂.
- 分析了表面成分,化学状态和吸附物覆盖.
主要成果:
- 在反应条件下,Fe和Ru都保持金属性.
- 催化剂的吸附度极小,表明N2解离是稳定的速度限制步骤.
- 在较低的温度下,Fe催化剂保留了吸附的,并产生了显著的氨基 (NHx) 覆盖,这表明速度限制步骤的切换.
结论:
- 氨合成的速度限制步骤在Fe和Ru催化剂之间有所不同.
- 在Ru上,N2分离始终是限制速度的步骤.
- 在Fe上,限制速度的步骤从N2解离转向低温表面物种的化,与理论预测保持一致.
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