在微孔和中孔的相互透网络中,客体扩散
Filipe Furtado1, Petrik Galvosas, Maraisa Gonçalves
1Department of Environmental Engineering, UFZ-Helmholtz Centre for Environmental Research, Leipzig, Germany.
Journal of the American Chemical Society
|February 9, 2011
概括
脉冲场梯度NMR揭示了客分子在等级孔中的扩散取决于样本历史. 在压力下降 (脱吸) 后的扩散性比在压力增加 (吸附) 后更高.
科学领域:
- 材料科学 材料科学 材料科学
- 物理化学 物理化学
- 化学工程是化学工程的重要组成部分.
背景情况:
- 层次性多孔材料结合了微孔和中孔,影响了客分子扩散.
- 了解这些复杂系统中的扩散对于催化,分离和储存中的应用至关重要.
- 之前的研究集中在纯粹的中孔固体上,使混合系统中的扩散变得不那么被探索.
研究的目的:
- 在不同的外部压力下,研究客分子在层次性多孔材料 (活性碳MA2) 中的扩散特性.
- 为了确定吸附-脱吸史对分子扩散性的影响.
- 为了比较混合微/中孔系统中的扩散行为与纯中孔系统.
主要方法:
- 使用脉冲场梯度核磁共振 (PFG-NMR) 来监测扩散.
- 在外部大气中应用受控的压力变化.
- 使用环素作为客分子和活性碳MA2作为多孔材料.
主要成果:
- 环素在活性炭MA2中的扩散性受到样品压力史的显著影响.
- 与吸附分支 (压力增加后) 相比,在脱吸分支 (压力下降后) 始终观察到更高的扩散性,在同等压力下.
- 一个简单的模型质量地复制了观察到的扩散率及其度依赖性.
结论:
- "历史效应"在确定层次性多孔材料中的客分子扩散方面发挥着主导作用.
- PFG-NMR是阐明复杂孔隙结构中的扩散机制的强大工具.
- 结果提供了有关气体储存和分离技术的活性炭分子运输的见解.
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