Proper Experimental Parameters in N-2 Adsorption: The Effects of Data Points and Equilibrium Interval Time

Evaluating pore structures of shale samples can be done with high accuracy with adsorption experiments. However, in order to obtain reliable results, proper guidelines of experimental parameters should be followed, including the number of test points and allocated time for equilibrium at each test interval. These parameters are somehow ignored, and researchers simply use default parameters that are in the manuals or suggested by the developer of these apparatus without being aware of how they can impact the results. Hence, to understand the effects of these two mentioned parameters on the N₂ adsorption results, in this study, the number of test points and the equilibrium interval time were examined in two separate experimental approaches. Experiments were conducted on Antrim Shale where two separate groups of samples were subjected to N₂ adsorption: in the first one, we changed the number of test points and in the second one, the equilibrium interval time. The results showed that if the experimental time is shorter due to either the smaller number of test points or limit in the equilibrium interval time, then the pore structures such as the surface area, pore volume, and pore complexity (derived from fractal analysis) might not be accurately obtained. Ultimately, the number of test points and/or the equilibrium interval time should be larger than a critical value, and then the pore information that is acquired from the adsorption data stays unchanged. Collectively, we emphasize the importance of choosing appropriate experimental parameters rather than following default values in the instrument settings in gas adsorption protocols for more meaningful pore structure analysis.