Time distribution of adsorption entropy of gases on heterogeneous surfaces by reversed-flow gas chromatography.
Time distribution of adsorption entropy of gases on heterogeneous surfaces by reversed-flow gas chromatography.
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DOI：
10.1016/j.chroma.2006.05.067
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发表时间：
2006-09
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影响因子：
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通讯作者：
N. Katsanos;J. Kapolos;D. Gavril;N. Bakaoukas;V. Loukopoulos;A. Koliadima;G. Karaiskakis
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文献类型：
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作者：
N. Katsanos;J. Kapolos;D. Gavril;N. Bakaoukas;V. Loukopoulos;A. Koliadima;G. Karaiskakis
用反流气相色谱(RF-GC)技术测定了在393.15 K和413.15 K时，气态戊烷在两种固体(γ-氧化铝和二氧化硅负载的Rh催化剂)表面吸附时的吸附熵随时间的变化。利用实验层析数据，该方法还可以以时间分辨的方式同时测量局部吸附能ɛ、局部平衡吸附浓度cs*和局部吸附等温线θ(p，T，ɛ)。与其他反相色谱方法在零表面覆盖度下测定标准熵的方法不同，本方法在较宽的表面覆盖度范围内操作，不仅考虑了吸附-吸附剂相互作用，而且还考虑了吸附-吸附相互作用。本工作最有趣的观察结果之一是，与在γ-Al_2O_3催化剂上相比，正戊烷在Rh/SiO_2催化剂上的相互作用是自发的，时间间隔很短。这可以解释每个特定气固体系不同的动力学行为，这可以归因于如下事实：与γ-Al_2O_3催化剂相比，Rh/SiO_2催化剂的活性中心上存在大量的n-C_5H_(12)，如局部平衡吸附浓度值cs*所示。
The reversed-flow gas chromatography (RF-GC) technique has been applied to measure the adsorption entropy over time, when gaseous pentane is adsorbed on the surface of two solids (γ-alumina and a silica supported rhodium catalyst) at 393.15 and 413.15K, respectively. Utilizing experimental chromatographic data, this novel methodology also permits the simultaneous measurement of the local adsorption energy, ɛ, local equilibrium adsorbed concentration, cs*, and local adsorption isotherm, θ(p, T, ɛ) in a time resolved way. In contrast with other inverse gas chromatographic methods, which determine the standard entropy at zero surface coverage, the present method operates over a wide range of surface coverage taking into account not only the adsorbate–adsorbent interaction, but also the adsorbate–adsorbate interaction. One of the most interesting observations of the present work is the fact that the interaction of n-pentane is spontaneous on the Rh/SiO2catalyst for a very short time interval compared to that on γ-Al2O3. This can explain the different kinetic behavior of each particular gas–solid system, and it can be attributed to the fact that large amounts of n-C5H12are present on the active sites of the Rh/SiO2catalyst compared to those on γ-Al2O3, as the local equilibrium adsorbed concentration values, cs*, indicate.