催化多孔体中表面访问限制：基于孔隙解析CFD的性能诊断
Surface-access limitation in catalytic porous monoliths: Performance diagnosis using pore-resolved CFD
AI总结：
研究通过孔隙解析CFD分析催化多孔体中表面访问限制问题，揭示结构依赖的表面可及性对反应性能的影响，验证了反应性CFD在真实操作条件下的应用价值。
摘要：
多孔体因其高比表面积、连通通道、热稳定性和机械强度而成为有前途的催化剂支持材料。然而，其可调拓扑结构使设计复杂化：转换率与压降之间的权衡无法可靠地通过宏观描述符如孔隙率、比表面积或曲折度来捕捉。孔隙解析计算流体动力学（PRCFD）通过解析孔隙尺度的流动和传输，填补了这一空白，能够对宏观上相似的结构进行诊断和区分。我们研究了表面访问受限性：一种在低达摩克利数（Da<1）时，转换率受限于流动分布不均和催化表面未完全利用的情况。使用钯纳米颗粒涂层的硅凝胶多孔体进行对硝基苯酚还原反应，通过微焦点计算机断层扫描基于的几何结构进行反应性PRCFD模拟，校准了伪异质蛋壳反应模型，并验证了其在不同样本和流量率下的可转移性。然后通过扩散性和反应动力学对转换率影响有限来诊断表面访问受限性。此外，我们比较了在匹配孔隙率和表面积下合成的随机多孔体与三重周期最小表面结构。显著的是，对于相同的摩尔产量率，所需泵送功率可减少一个数量级，取决于拓扑结构。这些结果表明，在受表面访问限制的非均质系统中，反应器性能由结构依赖的表面可及性而非内在动力学或分子扩散单独决定，并且经过验证的反应性PRCFD提供了一个实用框架，用于在真实操作条件下诊断和比较多孔反应器几何结构。
英文摘要：
Porous monoliths are promising catalyst supports due to their high surface area, interconnected channels, thermal stability and mechanical robustness. However, their tunable topology complicates design: trade-offs between conversion and pressure drop are not reliably captured by macroscopic descriptors, such as porosity, specific surface area, or tortuosity. Pore-resolved computational fluid dynamics~(PRCFD) addresses this gap by resolving pore-scale flow and transport, enabling diagnostics and discrimination between macroscopically similar structures. We investigate surface-access-boundedness: a case where conversion is limited by flow maldistribution and incomplete utilisation of the catalytic surface, even at low Damköhler numbers (Da<1). Using palladium-nanoparticle-coated silicone monoliths for p-nitrophenol reduction, we perform reactive PRCFD in microcomputed-tomography-based geometries, calibrate a pseudo-heterogeneous eggshell reaction model, and validate transferability across samples and flow rates. We then diagnose surface-access-boundedness via the limited influence of diffusivity and reaction kinetics on conversion. Furthermore, we compare synthesised random monoliths with triply periodic minimal surface structures under matched porosity and surface area. Significantly, the required pumping power can decrease by up to an order of magnitude for the same molar production rate, depending on topology. These results show that, in heterogeneous systems affected by surface-access limitations, reactor performance is governed by structure-dependent surface accessibility rather than intrinsic kinetics or molecular diffusion alone, and that validated reactive PRCFD provides a practical framework to diagnose and compare porous reactor geometries under realistic operating conditions.
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