Deformation of AUK Adsorbent and Adsorbate Structure upon n-Octane Adsorption

Relative linear deformation of AUK microporous carbon adsorbent with a narrow pore size distribution has been measured upon n-octane adsorption at pressures of 1 Pa to 1.6 kPa and temperatures of 273, 293, 313, 353, and 393 K. Throughout the studied temperature range, adsorption-induced deformation curves exhibit a similar behavior. At low and moderate degrees of micropore filling, the adsorbent remains almost undeformed, while it dramatically expands in the region of high degrees of filling. Adsorption of n-octane molecules in a model slitlike pore, the average effective width of which corresponds to the width of micropores in the AUK adsorbent, has been numerically simulated by the molecular dynamics method. It has been shown that, in the initial and middle regions of micropore filling, the behavior of the deformation dependences is determined by the ratio between the sizes of n-octane molecules and micropores. At high degrees of filling, the formation of adsorption associates in the micropores leads to a rise in the internal pressure and a drastic expansion of the adsorbent. The compressibility of AUK has been calculated, and the results obtained correspond to the data published previously.