Adsorption of carbon dioxide, methane and nitrogen:: pure and binary mixture adsorption for ZSM-5 with SiO2/Al2O3 ratio of 280

The adsorption of binary gas mixtures Of CO2-N-2, CO2-CH4 and CH4-N-2 were studied by using H-ZSM-5 as the adsorbent with a SiO2/Al2O3 ratio of 280. Pure isotherms for N-2 and CH4 at 40 degreesC and CH4-N-2 binary isotherms at 40 degreesC and 1.0 atm total pressure have been determined using concentration pulse chromatography. For CO2-N-2 and CO2-CH4 pure and binary systems, previously published data were used. The applicability of the binary adsorption prediction models, Extended Langmuir (EL), ideal adsorbed solution theory (IAST), and the Flory-Huggins form of the vacancy solution theory (FH-VST) have been studied. The CH4-N-2 binary isotherms exhibit behavior similar to the pure component isotherms, with CH4 as the dominant adsorbate. The CH4 binary isotherm did not change from the pure component isotherm. The N-2 binary isotherm decreased relative to the pure component N-2 isotherm. The theoretical models reasonably predict the binary behavior for the strongly adsorbed component in the binary system, whereas the weakly adsorbed component was not predicted well. The models are able to predict systems where the adsorption capacities of each component are relatively similar. However, none of the models were able to predict the behavior resulting from the initial competing or dominant electrostatic interaction of the adsorbates with the heterogeneous nature of the adsorbent surface. (C) 2003 Published by Elsevier B.V.