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.

Keywords:

• Adsorption
• Equilibrium
• Binary adsorption isotherms
• Multi-component adsorption
• Carbon dioxide
• Nitrogen
• Methane
• ZSM-5
• HT-CPM
• Extended Langmuir
• IAST
• FH-VST

Acknowledgments

Financial support received from the Natural Sciences and Engineering Research Council (NSERC) of Canada is gratefully acknowledged. ZSM-5 samples were prepared and donated by Dr Ahmet Sirkecioglu of the Department of Chemical Engineering at Istanbul Technical University in Turkey.