# Experimental Setup and Graphical User Interface for Zero-Length Column Chromatography
## 7 Case Study II: Methane and Ethane Diffusion in Zeolite 5A and Basolite(r) C300
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**adsorbent** & **adsorbate** & **T[K]** & **L** & \(D\) **[m2/s]** & **Reference** \\ \hline \multirow{8}{*}{5A} & & 298 & & \(9.8\times 10^{-10}\) & [40] \\  & & 298 & & \(2.4\times 10^{-11}\) & [41] \\  & & 298 & 18.8 & \(1.5\times 10^{-12}\) & In this work \\  & & 298 & – & \(3.1\times 10^{-13}\) & [42] \\  & & 298 & & \(4.7\times 10^{-14}\) & [26; 43] \\  & & 308 & 15.1 & \(1.6\times 10^{-12}\) & In this work \\ \cline{2-6}  & & 298 & 16.6 & \(1.7\times 10^{-13}\) & In this work \\  & & 298 & – & \(7.1\times 10^{-14}\) & [42] \\  & & 298 & – & \(7.8\times 10^{-15}\) & [26] \\  & & 308 & 14.12 & \(1.8\times 10^{-13}\) & In this work \\ \hline \multirow{8}{*}{Basolite} & & 298 & 20.74 & \(1.8\times 10^{-8}\) & In this work \\  & & 298 & – & \(5.5\times 10^{-9}\) & \(1.7\times 10^{-8}\) & [44] \\  & & 300 & – & \(\approx\)\(1.8\times 10^{-8}\) & [45; 46] \\  & & 308 & 11.76 & \(1.9\times 10^{-8}\) & In this work \\ \cline{1-1} \cline{2-6}  & & 298 & 65.6 & \(1.5\times 10^{-9}\) & In this work \\ \cline{1-1}  & & 300 & – & \(6.7\times 10^{-9}\) to \(8.5\times 10^{-9}\) & [47] \\ \cline{1-1}  & & 308 & 58.82 & \(2.46\times 10^{-9}\) & In this work \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Diffusivity of methane and ethane in zeolite 5A and Basolite® C300 under kinetic conditions. Figure 8: Experimental ZLC desorption curves of ethane on zeolite 5A at 298 K, and a desorption rate of 5 sccm and 20 sccm, respectively. The crystal structures of zeolite 5A and Basolite(r) C300 are similar. However, maximum diameter of a sphere that can diffuse along the main channel of zeolite 5A framework is 4.1 A [48], while the main channel diameter of Basolite(r) C300 has around 9 A [49]. This difference in channel diameter explains why both adsorbates diffuse faster in Basolite(r) C300 than in zeolite 5A (Table 2). Diffusion in zeolite 5A is driven by the probability of the occurrence of adsorbate molecule hopping between cavities. Only one molecule of methane or ethane can hop between cages at any given time in the zeolite 5A [50]. The adsorbate-adsorbent interaction is more intense for ethane and the potential barrier between the hopping is higher. Consequently, there is a reduction in the diffusivity of this molecule relative to methane as observed experimentally in this work (Table 2). The diffusion process in Basolite(r) C300 is more complex than in zeolite 5A. The Basolite(r) C300 framework contains cavities like those of zeolite 5A but larger and pockets [31]. Diffusivity and volumetric filling have a positive correlation when the latter is small due to the reduction in the energy barriers to inter-cavity hopping, caused by repulsive interactions between adsorbate molecules. When the volumetric filling tends to one, the probability of hopping decreases, and the diffusivity tends to zero. That is why the data taken from the literature in Table 2 is a range and not a value. However, experimentally it was only possible to measure one of these values. Apparently, the lower polarity of the Basolite surface, the larger size of its pores, and the greater complexity of its lattice prevent observing a significant difference between diffusivities. It is noteworthy that the estimated values of the diffusion coefficients, using the system developed in this work, are very similar to those reported in previous works (Table 2). This demonstrates the effectiveness of the system and GUI implemented to perform this type of measurement.