Separation of CO2 and N2 by Adsorption in C168 Schwarzite: A Combination of Quantum Mechanics and Molecular Simulation Study

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• 作者：Jianwen Jiang and Stanley I. Sandler
• 刊名：Journal of the American Chemical Society
• 出版年：2005
• 出版时间：August 31, 2005
• 年：2005
• 卷：127
• 期：34
• 页码：11989 - 11997
• 全文大小：285K
• 年卷期：v.127,no.34(August 31, 2005)
• ISSN：1520-5126

文摘

Using a hierarchical multiscale approach combining quantum mechanics and molecular simulation,we have investigated the adsorption of pure CO₂ and N₂ and their mixture at room temperature in C₁₆₈schwarzite, as a model for nanoporous carbons. First, the adsorbate-adsorbent interaction potential isdetermined using ab initio quantum mechanics computations, and then the adsorption is predicted usingfull atomistic Monte Carlo simulations. The extents of adsorption, adsorption energies, and isosteric heatsof pure CO₂ and N₂ simulated with the ab initio potential are found to be higher than those with the empiricalSteele potential that had been developed from gas adsorption on planar graphite. The inclusion of theelectric quadrupole moment of adsorbate in simulation has no discernible effect on N₂ adsorption but resultsin a larger extent of CO₂ adsorption at high coverages. The selectivity of CO₂ over N₂ in the C₁₆₈ schwarzitefrom a model flue gas is predicted to be significantly larger with the ab initio potential than with the Steelepotential. This illustrates the importance of an accurate adsorbate-adsorbent interaction potential indetermining gas adsorption and suggests that nanoporous carbons might be useful for the separation offlue gases. As a comparison, the adsorption and selectivity of CO₂ and N₂ in ZSM-5 zeolites are alsosimulated with the experimentally validated potential parameters. The selectivity in the C₁₆₈ schwarzitepredicted with the ab initio or Steele potential is found to be larger than the selectivity in all-silica ZSM-5,but less than that in Na-exchanged ZSM-5 zeolites.