A thermodynamic investigation of adsorbate-adsorbate interactions of carbon dioxide on nanostructured carbons

Abstract

A thermodynamic study of carbon dioxide adsorption on a zeolite-templated carbon (ZTC), a superactivated carbon (MSC-30), and an activated carbon (CNS-201) was carried out at temperatures from 241 to 478 K and pressures up to 5.5•106 Pa. Excess adsorption isotherms were fitted with generalized Langmuir-type equations, allowing the isosteric heats of adsorption and adsorbed-phase heat capacities to be obtained as a function of absolute adsorption. On MSC-30, a superactivated carbon, the isosteric heat of carbon dioxide adsorption increases with occupancy from 19 to 21 kJ•mol−1, before decreasing at high loading. This increase is attributed to attractive adsorbate–adsorbate intermolecular interactions as evidenced by the slope and magnitude of the increase in isosteric heat and the adsorbed-phase heat capacities. An analysis of carbon dioxide adsorption on ZTC indicates a high degree of binding-site homogeneity. A generalized Law of Corresponding States analysis indicates lower carbon dioxide adsorption than expected. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1026–1033, 2018.