一个层次结构核心@贝尔催化剂的现场多模式3D化学成像
Thomas L Sheppard1, Stephen W T Price2, Federico Benzi1
1Institute for Chemical Technology and Polymer Chemistry, Karlsruhe Institute of Technology , Engesserstraße 20, 76131 Karlsruhe, Germany.
Journal of the American Chemical Society
|May 13, 2017
概括
这项研究揭示了用于将合成气转化为二甲基以太 (DME) 的核心催化剂的现场行为. 多模X射线计算机断层扫描 (CT) 在反应过程中可视化了纳米级的铜物种及其氧化状态.
科学领域:
- 材料科学
- 催化剂
- 化学工程
背景情况:
- 对高效的合成气体转换而言,层次设计的核心/外催化剂至关重要.
- 了解反应条件下的活性位点的动态行为对于催化剂优化至关重要.
- 之前的表征方法缺乏空间分辨率以观察这些现场过程.
研究的目的:
- 在二甲基乙醇 (DME) 合成过程中研究Cu/ZnO/Al2O3@ZSM-5核心@shell催化剂的结构和化学状态.
- 展示多式现场X射线计算机断层扫描 (CT) 对于复杂的催化材料的特性.
- 提供有关催化剂活性金属物种化和结构稳定的见解.
主要方法:
- 同时在现场成像使用基于同步射线的微型X射线光 (μ-XRF),X射线衍射 (μ-XRD) 和扫描传输X射线显微镜 (STXM) 计算机断层扫描 (CT).
- 在氧化,还原和模型反应条件下对相同样本体积进行逐步成像 (H2:CO:CO2 = 16:8:1,高达250°C).
- 微米空间分辨率使催化剂的核心和外部件可视化.
主要成果:
- 在还原过程中观察到纳米化Cu物种在催化剂核心中的分散,在核心-外接口处具有转移稳定的Cu+相.
- 在DME反应条件下揭示了Cu0和部分氧化Cu物种在活性催化剂核中的共存.
- 在整个过程中证实了石外和核心外接口的稳定性, 保持了催化剂的双功能性质.
结论:
- 多模态现场X射线CT提供了前所未有的3D空间解析洞察力,超越了批量技术的局限性.
- 这项研究强调了这种先进的特征化技术在优化层次设计的催化材料方面的潜力.
- 了解纳米级的动态过程是设计更高效的催化剂转化为DME的关键.
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