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Highly Selective Adsorption for Ethylene, Propylene, and Carbon Dioxide in Silver-Ionized Microporous Polyimide

Yan, Jun, Zhang, Biao, Guo, Lingxiao, Wang, Zhonggang
Journal of physical chemistry 2018 v.123 no.1 pp. 575-583
Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, adsorption, carbon dioxide, chemical structure, elemental composition, energy-dispersive X-ray analysis, enthalpy, ethane, ethylene, ions, landfills, methane, natural gas, polymers, porosity, porous media, propylene, silver
This paper presents the sulfonation and silver-ionization modifications using aromatic microporous polyimide (MPI) as precursor to obtain a new Ag⁺-decorated porous polyimide material (MPI-Ag). FTIR, XPS, and EDX spectra demonstrate the chemical structure of the resultant MPI-Ag and the homogeneously distribution of silver ions within the porous network. The evolution of porosity parameters and elemental compositions of the postmodified polymers and their effects on adsorption/separations of C₁–C₃ hydrocarbons and CO₂ gas are studied in detail. The results show that the modified MPI-Ag exhibits the enhanced affinity for CO₂ and the unsaturated hydrocarbons like C₂H₄ and C₃H₆ as evidenced by the significantly increased enthalpies of adsorption, Henry’s constants and first virial coefficients. Consequently, at 273 K, the adsorption selectivities of C₂H₄/C₂H₆ (0.9) and C₃H₆/C₃H₈ (2.0) for MPI dramatically rise to 3.5 and 16.5 for MPI-Ag, respectively. Moreover, the selectivities of C₃H₆/CH₄ (3785) and CO₂/CH₄ (65.3) are achieved for MPI-Ag, which are among the highest values reported to date for porous materials. The excellent selective adsorptions for unsaturated alkenes and CO₂ gas endow MPI-Ag with potential applications in stripping CO₂ from natural gas and landfill gas as well as the purification of C₂H₄ and C₃H₆ from their mixtures with CH₄, C₂H₆, and C₃H₆ impurities.