Azzan Hassan, Gmyrek Killian, Danaci David, Rajagopalan Ashwin Kumar, Petit Camille, Pini Ronny
Department of Chemical Engineering, Imperial College London, London, SW7 2AZ UK.
The Sargent Centre for Process Systems Engineering, Imperial College London, London, SW7 2AZ UK.
Adsorption (Boston). 2025;31(2):39. doi: 10.1007/s10450-025-00599-3. Epub 2025 Jan 31.
The adsorption kinetics of carbon dioxide (CO) in three cationic forms of binderless pellets of Y-types zeolites (H-Y, Na-Y, and TMA exchanged Na-Y) are studied using the zero-length column (ZLC) technique. The measurements were carried out at [Formula: see text] and [Formula: see text] using different flowrates and an initial CO partial pressure of [Formula: see text]- conditions representative of post-combustion CO capture applications. The mass transport within the adsorbent pellets was described using a 1-D Fickian diffusion model accounting for intra- and inter-crystalline mass transport. For the latter, the parallel pore model formulation was used to explicitly account for the adsorbent's macropore size distribution in estimating the volume-averaged diffusivity of the gas. Experiments carried out using different carrier gases, namely helium and nitrogen, were used (i) to determine that these systems are macropore diffusion limited and (ii) to simplify the parameter estimation to a single parameter - the macropore tortuosity. The latter ([Formula: see text]) was in good agreement with independent measurements using MIP ([Formula: see text]). The associated diffusion coefficient, [Formula: see text], was found to vary due to differences in the materials' macropore size distributions and overall porosity. Upon combining the parallel pore model formulation with the temperature dependencies for the pore diffusivities derived from molecular theories of gases, we predict [Formula: see text] with [Formula: see text] depending on the macropore size distribution. Notably, for the range of temperature tested in this study, [Formula: see text] varies approximately linearly with temperature ([Formula: see text])- in contrast to the commonly reported correlation of [Formula: see text], which may be more appropriate for systems where molecular diffusion dominates and Knudsen diffusion is negligible. The binderless pellets of Y-type zeolites studied exhibit generally higher values for the effective macropore diffusivity of CO compared to previously reported results on commercial FAU zeolites.
The online version contains supplementary material available at 10.1007/s10450-025-00599-3.
采用零长度柱（ZLC）技术研究了三种阳离子形式的Y型沸石无粘结剂颗粒（H - Y、Na - Y和TMA交换的Na - Y）对二氧化碳（CO₂）的吸附动力学。测量在[公式：见原文]和[公式：见原文]下进行，使用不同的流速以及初始CO₂分压为[公式：见原文]——这些条件代表了燃烧后CO₂捕集应用。使用一维菲克扩散模型描述吸附剂颗粒内的传质，该模型考虑了晶内和晶间传质。对于后者，采用平行孔模型公式来明确考虑吸附剂大孔尺寸分布，以估计气体的体积平均扩散率。使用不同的载气（即氦气和氮气）进行实验，目的是（i）确定这些系统受大孔扩散限制，以及（ii）将参数估计简化为单个参数——大孔曲折度。后者（[公式：见原文]）与使用压汞法（MIP）（[公式：见原文]）的独立测量结果吻合良好。发现相关的扩散系数[公式：见原文]因材料大孔尺寸分布和总体孔隙率的差异而变化。将平行孔模型公式与从气体分子理论推导的孔隙扩散率的温度依赖性相结合，我们预测[公式：见原文]，其中[公式：见原文]取决于大孔尺寸分布。值得注意的是，在本研究测试的温度范围内，[公式：见原文]随温度大致呈线性变化（[公式：见原文]）——这与通常报道的[公式：见原文]的相关性不同，后者可能更适用于分子扩散占主导且克努森扩散可忽略不计的系统。与先前报道的商业FAU沸石的结果相比，所研究的Y型沸石无粘结剂颗粒对CO₂的有效大孔扩散率通常具有更高的值。
在线版本包含可在10.1007/s10450 - 025 - 00599 - 3获取的补充材料。
