A micro-scale analysis of mass transport in ceramic foams that are used as catalyst supports in gas phase reactions is of high interest. Although the effects of flow rate and foam parameters on the radial and axial dispersion are known for liquid flows, no pore-scale experimental analysis has been yet reported to correlate the mechanical and diffusional dispersion of gas flows to the geometry of open-cell foams. Here, a spatially resolved Pulsed Field Gradient NMR method is applied to determine dispersion coefficients of thermally polarized gas along axial and transversal directions of open-cell foams. The comparative study of three commercial foam samples with different morphologies shows the effect of open porosity, window size, and flow rate on gas dispersion. Additionally, the influence of mechanical and diffusional dispersion at each flow rate is investigated for individual samples. By observing the transition from diffusional dispersion to mechanically driven dispersion of gas, it is found that diffusional dispersion plays an important role, even at higher flow rates after a transition from Darcy to Darcy-Forchheimer regime occurs. The measured values for dispersion coefficients of methane can be directly used in pseudo-heterogeneous models for the methanation reaction.

对在气相反应中用作催化剂载体的陶瓷泡沫中的传质进行微观分析非常受关注。尽管对于液体流动来说，流速和泡沫参数对径向和轴向弥散的影响是已知的，但尚未有孔尺度的实验分析将气体流动的机械弥散和扩散弥散与开孔泡沫的几何形状相关联。在此，应用空间分辨的脉冲场梯度NMR方法确定热极化气体沿开孔泡沫的轴向和横向方向的弥散系数。对三种不同形态的商业泡沫样品的比较研究表明，开孔率，窗口大小和流速对气体扩散的影响。另外，对于单个样品，研究了每种流速下机械分散和扩散分散的影响。通过观察从气体的扩散扩散到机械驱动的扩散的过渡，发现即使在从达西过渡到达西-福希海默状态之后的较高流速下，扩散分散也起着重要的作用。甲烷的弥散系数的测量值可以直接用于甲烷化反应的伪多相模型中。