Adsorption of carbon dioxide,methane and nitrogen:pure and binary mixture adsorption for ZSM-5 with SiO_2/Al_2O_3 ratio of 280

摘要

The adsorption of binary gas mixtures of CO_2-N_2,CO_2-CH_4 and CH_4-N_2 were studied by using H-ZSM-5 as the adsorbent with a SiO_2/Al_2O_3 ratio of 280.Pure isotherms for N_2 and CH_4 at 40 degC and CH_4-N_2 binary isotherms at 40 degC and 1.0 atm total pressure have been determined using concentration pulse chromatography.For CO_2-N_2 and CO_2-CH_4 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 vacany solution theory (FH-VST) have been studied.The CH_4-N_2 binary isotherms exhibit behavior similar to the pure component isotherms,with CH_4 as the dominant adsorbate.The CH_4 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 reasonbly 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.