Hyperpolarised xenon MRI and time-resolved X-ray computed tomography studies of structure-transport relationships in hierarchical porous media
Hyperpolarised xenon MRI and time-resolved X-ray computed tomography studies of structure-transport relationships in hierarchical porous media
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DOI：
10.1016/j.cej.2020.126750
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发表时间：
2021-02
影响因子：
15.1
通讯作者：
F. Hill-Casey;T. Hotchkiss;K. Hardstone;I. Hitchcock;V. Novák;C. Schlepütz;T. Meersmann;G. Pavlovskaya;S. Rigby
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文献类型：
--
作者：
F. Hill-Casey;T. Hotchkiss;K. Hardstone;I. Hitchcock;V. Novák;C. Schlepütz;T. Meersmann;G. Pavlovskaya;S. Rigby
催化柴油机微粒过滤器（DPF）整体是分级多孔固体，如通过压汞法所证明的。建立结构-运输关系，包括评估催化剂的一般可及性，具有挑战性，因此，需要采取全面的方法。贡献，从每个孔隙度水平，运输已建立使用超极化（hp）氙-129磁共振成像（MRI）的DPF整料内的气体分散在可变的水饱和度，因为X射线计算机断层扫描，和1H和2 H NMR方法，已经表明，孔隙度水平逐渐变干。在高饱和度下，hp 129 MRI显示整料通道之间的气体传输主要发生在具有高大孔隙率的通道壁交叉处。由于微孔/介孔载体涂料层远离交叉点分布，壁本身对穿透传输的贡献相对较小。只有在低饱和度时，当最小的孔隙打开时，hp 129的MR图像才受到弛豫的强烈影响。这一观察结果表明，只有当最小的孔打开时，气体的顺磁性（催化）中心才能进入。
Catalysed diesel particulate filter (DPF) monoliths are hierarchical porous solids, as demonstrated by mercury porosimetry. Establishing structure-transport relationships, including assessing the general accessibility of the catalyst, is challenging, and, thus, a comprehensive approach is necessary. Contributions, from each porosity level, to transport have been established using hyperpolarised (hp) xenon-129 magnetic resonance imaging (MRI) of gas dispersion within DPF monoliths at variable water saturation, since X-ray Computerised-Tomography, and1H and2H NMR methods, have shown that porosity levels dry out progressively. At high saturation, hp129Xe MRI showed gas transport between the channels of the monolith is predominantly taking place at channel wall intersections with high macroporosity. The walls themselves make a relatively small contribution to through transport due to the distribution of the micro-/meso-porous washcoat layer away from intersections. Only at low saturation, when the smallest pores are opened, do hp129Xe MR images became strongly affected by relaxation. This observation indicates accessibility of paramagnetic (catalytic) centres for gases arises only once the smallest pores are open.