Adsorption of carbon dioxide, methane, and nitrogen: pure and binary mixture adsorption by ZSM-5 with SiO2/Al2O3 ratio of 30

Abstract

The adsorption of binary gas mixtures of CO2–N2, CO2–CH4, and CH4–N2 were studied by using H-ZSM-5 as the adsorbent with a SiO2/Al2O3 ratio of 30. Pure isotherms for N2 and CH4 at 40°C and CH4–N2 binary isotherms at 40°C and 1.0 atm total pressure have been determined using concentration pulse chromatography. For CO2–N2 and CO2–CH4 pure and binary systems, previously published data were used. The applicability of the binary adsorption prediction models, Extended Langmuir, Extended Nitta, Ideal Adsorbed Solution Theory, and the Flory–Huggins form of the Vacancy Solution Theory have been studied. The CH4–N2 binary isotherms exhibit behavior similar to the pure component isotherms, with CH4 as the dominant adsorbate. The separation factor steadily declines as the mole fraction of CH4 in the gas phase is increased. All the theoretical models used reasonably predict the binary systems for CH4–N2. The CO2–N2 system was not predicted well. CO2–CH4 behavior was predicted reasonably well by all the models, except by the Extended Nitta. The models appear to be able to predict systems where the adsorption capacities of each component are relatively similar.