Adsorption of n-alkanes by carbon adsorbents at sub- and supercritical temperatures

The adsorption of methane, ethane, and propane on the microporous carbon adsorbents MPU-007 and FAS-3 was studied at temperatures of 303, 313, 323, and 333 K over a pressure range of 0.1-40, 0.001-4.5, and 0.001-0.9 MPa for methane, ethane, and propane, respectively. The structural parameters of the adsorbents (adsorption volume and effective pore size) were determined using the theory of volume filling of micropores. The adsorption isotherms were measured for the studied adsorption systems and were used for the calculation of isotherms of excess adsorption and those of total content. The adsorption isosteres were constructed and the initial and isostereic heats of adsorption were calculated taking into account the adsorption isotherms of total content. Ethane and propane are adsorbed with higher heats than methane, which indicates that the studied adsorbents would be promising in the designed systems of selective extraction of ethane and propane from the natural gas flow. The initial heats of adsorption are well consistent with the polarizability of molecules of saturated hydrocarbons and, therefore, the polarizabilities of these molecules and adsorbent atoms can be used for the calculation of heats of adsorption.