Adsorption equilibrium of binary mixtures of carbon dioxide and nitrogen on zeolites ZSM-5 and 13X

An investigation of the adsorption equilibrium of carbon dioxide (CO2) and nitrogen (N-2) and their mixtures on zeolites ZSM-5 and 13X is presented. Pure component isotherms are measured at five different temperatures in the range of 25 degrees C and pressures up to 10 bar, and the resulting data are described with an appropriate isotherm equation. Adsorption equilibrium of CO2/N-2 mixtures was measured at two temperatures (25 degrees C and 45 degrees C) and three pressure levels (1.2 bar, 3 bar and 10 bar) using three feed gas compositions on both materials tested. The isotherms obtained from the pure component measurements are used to predict the binary data using two approaches: An empirical extension of the Sips isotherm and the application of ideal adsorbed solution theory (IAST). In the context of the binary CO2/N-2 adsorption, it was found that for ZSM-5 the system behaves close to ideal over the whole range of pressure and temperature investigated here and thus is well described by the IAST prediction. On the other hand, our results demonstrate non-ideal behavior in the adsorbed phase with increasing pressure for zeolite 13X, thus motivating the use of real adsorbed solution theory (RAST) to accurately deScribe the binary adsorption data. (C) 2015 Elsevier Inc. All rights reserved.