Phenomenological Study of Confined Criticality: Insights from the Capillary Condensation of Propane, n-Butane, and n-Pentane in Nanopores
Phenomenological Study of Confined Criticality: Insights from the Capillary Condensation of Propane, n-Butane, and n-Pentane in Nanopores
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DOI：
10.1021/acs.langmuir.8b00125
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发表时间：
2018-04-17
期刊：
影响因子：
3.9
通讯作者：
Chen, Jin-Hong
中科院分区：
文献类型：
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作者：
Barsotti, Elizabeth;Tan, Sugata P.;Chen, Jin-Hong
我们使用实验测量的丙烷、正丁烷和正戊烷在2.90、4.19和8.08 nm MCM-41中的等温线的比较来表明，当前的毛细管缩合过程模型可能不适用于链分子，如正构烷烃。到目前为止，气体在没有连通的、大小一致和形状相同的纳米孔中的毛细凝聚被证明在结束受限流体的超临界之前经历了两个截然不同的阶段。首先，在等温测量中，在相对较低的温度下，相变伴随着吸附和解吸的滞后。第二，随着温度的升高，磁滞临界温度被超过，相变发生可逆变化。尽管丙烷遵循了这一进程，但我们观察到了正丁烷和正戊烷的新进程，在该进程中，滞后继续进入受限流体的超临界区域。我们将这种行为归因于吸附物的分子链长。通过对吸附、脱附和临界性质的进一步比较，我们发现了受限超临界流体的新的压力现象。
We use the comparison of experimentally measured isotherms for propane, n-butane, and n-pentane in 2.90, 4.19, and 8.08 nm MCM-41 to show that the current model for the progression of capillary condensation may not hold true for chain molecules, such as normal alkanes. Until now, the capillary condensation of gases in unconnected, uniformly sized and shaped nanopores has been shown to progress in two distinct stages before ending in supercriticality of the confined fluid. First, at relatively low temperatures in isothermal measurements, the phase change is accompanied by hysteresis of adsorption and desorption. Second, as temperature increases, the hysteresis critical temperature is surpassed, and the phase change occurs reversibly. Although propane followed this progression, we observed a new progression for n-butane and n-pentane, in which hysteresis continues into the supercritical region of the confined fluid. We attribute this behavior to the molecular chain lengths of the adsorbates. Through further comparison of the adsorption, desorption, and critical properties of the adsorbates, we discovered new pressure phenomena of the confined supercritical fluids.