Research ArticleMATERIALS SCIENCE

Ultraselective glassy polymer membranes with unprecedented performance for energy-efficient sour gas separation

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Science Advances  24 May 2019:
Vol. 5, no. 5, eaaw5459
DOI: 10.1126/sciadv.aaw5459
  • Fig. 1 Polymer structure, void morphologies, and gas permeation properties of AO-PIM-1 films at 35°C.

    (A) Structures of PIM-1 and amidoxime-functionalized PIM-1 (AO-PIM-1). (B) Void morphology in AO-PIM-1. The Connolly surface of the AO-PIM-1 framework is shown in blue regions (outer pore surface) and gray regions (inner pore surface) as outlined geometrically by an N2-sized probe (3.64 Å). (C) Pure-gas permeability/selectivity (CO2/CH4) trade-off curve comparison of PIM-1 and AO-PIM-1 to other polymeric materials [1 = cellulose acetate; 2 = 6FDA-PAI; 3 = 6FDA-mPDA:6FDA-durene; 4 = poly(ethylene glycol) (PEG) cross-linked polymer (PEGMC); 5 = 6FDA-DAM-DABA; 6 = PIM-6FDA-OH; 7 = PIM-PI-3]. The CO2 and CH4 permeabilities were measured at feed pressure of 2 bar at 35°C. (D) Pure-gas permeability/selectivity (H2S/CH4) trade-off curve comparison of PIM-1 and AO-PIM-1 to other polymeric. H2S was measured under 1-bar feed pressure at 35°C to avoid plasticization effects. The dashed black line is a guide to the eye used only to indicate the general trade-off between H2S permeability and H2S/CH4 selectivity in typical glassy polymers. (E) CO2/CH4 performance of AO-PIM-1 for long-term continuous active feed of 20 mol % H2S/20 mol % CO2 and 60 mol % CH4 at feed pressure of 8.6 bar at 35°C. (F) H2S/CH4 performance of AO-PIM-1 for long-term continuous active feed of 20 mol % H2S/20 mol % CO2 and 60 mol % CH4 at feed pressure of 8.6 bar at 35°C.

  • Fig. 2 Mixed-gas permeation properties of AO-PIM-1 and PIM-1 membranes in a ternary mixture (20 mol % H2S, 20 mol % CO2, and 60 mol % CH4) at 35°C under feed pressures up to 77 bar.

    (A) CO2 permeability. (B) H2S permeability. (C) CO2/CH4 selectivity. (D) H2S/CH4 selectivity. (E) Combined (H2S + CO2) permeability. (F) Combined (H2S + CO2)/CH4 selectivity.

  • Fig. 3 Combined ternary acid gas (CO2+ H2S)/CH4 performance demonstrated by productivity-efficiency trade-off for typical polymer membranes and AO-PIM-1 in sour gas separations.

    Ternary mixed-gas permeabilities and selectivities are listed in table S3. Experimental upper bound lines are drawn to guide the eye: the solid black ones reveal the trade-off between H2S or combined acid gas (CO2 + H2S) permeabilities and selectivities in typical glassy polymers; the dashed black ones show the case of hydrophilic rubbery membranes. AO-PIM-1 films (this work) were measured with ternary sour gas mixtures containing H2S as high as 20 mol % at exceedingly aggressive feed pressures higher than 55 bar and up to 77 bar; typical rubbery materials were tested at low feed pressures of ~10 bar; mixed-matrix membranes were measured at 6.9 bar (36, 37); typical glassy polymers including cellulose acetate, 6FDA-based polyimides, cross-linkable polyimides (PEGMC), fluorinated PAIs (6F-PAIs), and intrinsically microporous polyimides (PIM-6FDA-OH) were measured with ternary gas mixtures containing H2S ranging from 10 to 20 mol % at aggressive feed pressures of greater than 34.5 bar but generally less than 60 bar (5, 79, 12, 18, 19, 27).

  • Fig. 4 Mixed-gas permeation properties of AO-PIM (AO-PIM-1) membranes in a ternary mixture (20 mol % H2S, 20 mol % CO2, and 60 mol % CH4) at 35°C under feed pressures up to 77 bar: A comparison of the freshly made film before and after long-term continuous active feed of 20 mol % H2S/20 mol % CO2/60 mol % CH4 at feed pressure of 8.6 bar at 35°C.

    (A) H2S permeability as a function of total mixed-gas feed pressure. (B) Combined acid gas selectivity as a function of total mixed-gas feed pressure. (C) CO2/CH4 selectivity as a function of total mixed-gas feed pressure. (D) H2S/CH4 selectivity as a function of total mixed-gas feed pressure.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/5/eaaw5459/DC1

    Fig. S1. Synthetic scheme for AO-PIM-1.

    Fig. S2. Three-dimensional view of AO-PIM-1 (16 repeat units) in an amorphous periodic cell.

    Fig. S3. Constant volume/variable pressure permeation apparatus for pure and mixed gases.

    Fig. S4. Pure-gas H2S permeability of AO-PIM-1 and PIM-1 as a function of upstream pressure at 35°C.

    Fig. S5. Pure H2S dual-mode model fit at 35°C for AO-PIM-1 and PIM-1 dense films.

    Fig. S6. Pure CO2 dual-mode sorption model fit at 35°C for AO-PIM-1 and PIM-1 dense films.

    Fig. S7. Pure CH4 dual-mode sorption model fit at 35°C for AO-PIM-1 and PIM-1 dense films.

    Fig. S8. H2S sorption isotherm at 35°C for AO-PIM-1 dense films.

    Fig. S9. CO2 sorption isotherm at 35°C for AO-PIM-1 dense films.

    Fig. S10. CH4 sorption isotherm at 35°C for AO-PIM-1 dense films.

    Fig. S11. H2S sorption isotherm at 35°C for PIM-1 dense films.

    Fig. S12. CO2 sorption isotherm at 35°C for PIM-1 dense films.

    Fig. S13. CH4 sorption isotherm at 35°C for PIM-1 dense films.

    Fig. S14. DFT optimized structure of a single chain of AO-PIM-1.

    Fig. S15. Electrostatic potential in the AO-PIM-1 network.

    Fig. S16. Electrostatic potential of gas molecules.

    Fig. S17. DFT optimized structures of the polymer-penetrant complex and the corresponding BEs on the AO-PIM-1 network (parallel 1).

    Fig. S18. Pressure-decay sorption apparatus for gas sorption experiments.

    Table S1. Diffusion coefficients (D), sorption coefficients (S), diffusion selectivities (αD), and sorption selectivities (αS) of AO-PIM-1 and other glassy polymers at 35°C.

    Table S2. Dual-mode sorption parameters for pure H2S, CO2, and CH4.

    Table S3. Comparison of AO-PIM-1 with other polymers in mixed-gas feed streams at 35°C.

    Reference (50)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Synthetic scheme for AO-PIM-1.
    • Fig. S2. Three-dimensional view of AO-PIM-1 (16 repeat units) in an amorphous periodic cell.
    • Fig. S3. Constant volume/variable pressure permeation apparatus for pure and mixed gases.
    • Fig. S4. Pure-gas H2S permeability of AO-PIM-1 and PIM-1 as a function of upstream pressure at 35°C.
    • Fig. S5. Pure H2S dual-mode model fit at 35°C for AO-PIM-1 and PIM-1 dense films.
    • Fig. S6. Pure CO2 dual-mode sorption model fit at 35°C for AO-PIM-1 and PIM-1 dense films.
    • Fig. S7. Pure CH4 dual-mode sorption model fit at 35°C for AO-PIM-1 and PIM-1 dense films.
    • Fig. S8. H2S sorption isotherm at 35°C for AO-PIM-1 dense films.
    • Fig. S9. CO2 sorption isotherm at 35°C for AO-PIM-1 dense films.
    • Fig. S10. CH4 sorption isotherm at 35°C for AO-PIM-1 dense films.
    • Fig. S11. H2S sorption isotherm at 35°C for PIM-1 dense films.
    • Fig. S12. CO2 sorption isotherm at 35°C for PIM-1 dense films.
    • Fig. S13. CH4 sorption isotherm at 35°C for PIM-1 dense films.
    • Fig. S14. DFT optimized structure of a single chain of AO-PIM-1.
    • Fig. S15. Electrostatic potential in the AO-PIM-1 network.
    • Fig. S16. Electrostatic potential of gas molecules.
    • Fig. S17. DFT optimized structures of the polymer-penetrant complex and the corresponding BEs on the AO-PIM-1 network (parallel 1).
    • Fig. S18. Pressure-decay sorption apparatus for gas sorption experiments.
    • Table S1. Diffusion coefficients (D), sorption coefficients (S), diffusion selectivities (αD), and sorption selectivities (αS) of AO-PIM-1 and other glassy polymers at 35°C.
    • Table S2. Dual-mode sorption parameters for pure H2S, CO2, and CH4.
    • Table S3. Comparison of AO-PIM-1 with other polymers in mixed-gas feed streams at 35°C.
    • Reference (50)

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