(154b) Separation of CO2 From Biogas, Natural Gas and Flue Gas Mixtures With Elastic Layered Metal-Organic Framework (ELM) Adsorbents

The suitability of elastic layered Metal-organic framework (ELM) as gas separators for CO₂-CH₄ and CO₂-N₂ mixtures from biogas, natural gas and flue gas was evaluated. Simulated CO₂ adsorption capacities on ELM-11 [Cu(BF4)2(bpy)2] and ELM-12 [Cu(OTf)2(bpy)2] above the gating pressure and CO₂ isosteric heat of adsorption agree well with experimental data. Calculated CO₂ selectivities from those mixtures based on pure-component adsorption isotherms generally agree with the Grand Canonical Monte Carlo (GCMC) simulations.  GCMC simulated CO₂ selectivity from biogas mixture ranges from 10-45 and CO₂ selectivity from flue gas mixture ranges from 30-85 show that ELM materials are good candidates for gas separation.  

Despite these promising results, only pure component data has been studied and no attempts for a real separation experiment in a fixed adsorbent bed have been made.  In this presentation, the result of the first fixed bed packed with ELM-adsorbent for the separation of biogas mixture will be discussed. We also present density functional theory (DFT) results on the nature of the CO₂ and CH₄ separation in ELM-11 and ELM-12 framework. With the adsorption of CO₂ on framework the metal-anion bond in ELM framework was extended while that bond is virtually unchanged with CH₄ adsorption. Differences in the binding motif and energy of CO₂ and CH₄ with ELM frameworks using density functional theory calculation will also be discussed.