Carbon Dioxide Separations Using Polymer Membranes and Status of Carbon Capture Research in the United States Benny D. Freeman The University of Texas at Austin freeman@che.utexas.edu http://membrane.ces.utexas.edu Symposium for Innovative CO Membrane Separation Technology Molecular Gate Membrane Module Technology Research Association Tokyo, Japan November 4, 011 1
US Department of Energy Workshop Membrane section co-chaired by Benny Freeman and Sam Stupp. Complete report available at: science.energy.gov/~/media/bes/pdf /reports/files/ccb00_rpt.pdf
Some Challenges Identified by DOE Workshop Enormous scale of carbon capture applications x 6 ft 3 (56,633 m 3 ) of flue gas at atmospheric pressure containing < 15% CO released from 550 MW e coal-fired power plant. Current membranes are not permeable enough 6 m of membranes required to capture 90% of CO from 550 MW e coal-fired power plant. Current membranes limited by permeability/selectivity tradeoff relation, so one cannot prepare both high flux and high selectivity membranes. Current membranes may not have sufficient chemical/thermal stability for some carbon capture applications. 3
Priority Research Directions Identified by DOE Workshop Hierarchical Structures Control 3D, asymmetric structure of matter using selfassembly. Use microelectronics lithographic technologies for preparing ultra-high surface area, 3D (rather than D) membranes. Molecularly Tailored Membranes to Enhance Separation Performance Use either polymer or inorganic materials. Design structures of controlled porosity with tailored interactions with permeant (e.g., CO ) to provide both high flux and high selectivity. Alternative Driving Forces and Stimuli-Responsive Materials Is it possible to use driving forces other than pressure (e.g., light, electric or magnetic fields, etc.) to reduce energy requirements for carbon capture? 4
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Crosslinked Poly(ethylene oxide) (XLPEO) O O 14 O O polyethylene glycol diacrylate n=14 (PEGDA) O 7 OH O polyethylene glycol acrylate n=7 (PEGA7) O 8 O O polyethylene glycol methyl ether acrylate: n=8 (PEGMEA8) Lin, H., Kai, T., et al. Macromolecules 38, 8381-93 (005) Kalakkunnath, S., Kalika, D.S., et al. Macromolecules 38, 9679-87 (005)
Ethylene Oxide-Based Polymers Have High CO Solubility 1 S [cm 3 (STP)/cm 3 atm] 0-1 - H N O CH 4 CO C H 6 C 3 H 8 C 4 H -3 He 0 0 00 300 400 / k [K] Block copolymer containing 57 wt% PEO and 43 wt% Nylon-6; 35 o C, from Bondar et al., J. Polym. Sci., Part B: Polym. Phys., 37, 463-75 (1999). 11
Glass Transition of XLPEO -35 Glass Transition Temperature [ o C] -40-45 -50-55 -60-65 PEGDA PEGA7 PEGDA PEGMEA8-70 0 80 60 40 0 PEGDA Content [wt.%] 0 PEGMEA: CH CH C O O CH CH OCH 3 [ ] 8 PEGA: CH CH C [ O CH CH] 7 OH O 1
Free Volume Characterized by PALS Radius of Free Volume Elements [Å] 3.35 3.3 3.5 3. 3.15 PEGDA-co-PEGMEA PEGDA-co-PEGA PEGDA (crosslinker) CH CH C O CH CH C PEGA (monomer) CH CH C [ O CH CH ] 13 O PEGMEA (monomer) O C O CH O CH CH OCH 3 [ ] 8 O CH CH OH [ ] 7 CH 3.1 0 80 60 40 0 0 O PEGDA Content [vol.%] I 3 is approximately independent of composition. H. Lin, E. van Wagner, J.S. Swinnea, B.D. Freeman, S.J. Pas, A.J. Hill, S. Kalakkunnath, and D.S. Kalika, J. Membrane Sci., 76, 145-161 (006). 13
CO /H Pure Gas Separation Properties 600 15 Permeability [barrer] 500 400 300 00 CO PEGDA/PEGMEA8 Infinite Dilution Selectivity CO /H PEGDA PEGMEA PEGDA/H O 0 0 0 PEGDA/PEGA7 80 60 40 0 PEGDA Content [wt.%] 0 5 0 80 60 PEGDA/PEGA 40 PEGDA Content [vol.%] 0 0 CH CH C O CH CH OCH 3 [ ] 8 CH CH C O O Lin et al., Macromolecules, 38, 8381-8393 (005) and 38, 8394-8407 (005). O CH CH OH [ ] 7 14
Free Volume in PEGDA Copolymers with PEGMEA and PEGA 3 0 3 0 CO Permeabiltiy [Barrer] 9 8 7 6 5 CO /H Selectivity CO Permeabiltiy [Barrer] 9 8 7 6 5 CO /H Selectivity 4.5 3 3.5 4 00/ [ns -3 ] 4 7 8 9 1/FFV P æ B Aexp ç - 3 è t 3 I = 3 ö ø P æ B = Aexpç - è FFV ø ö 15
Mixed Gas Separation oc 1 CO /H -0oC Upper Bound 35oC 0-1 - -1 0 1 3 CO Permeability [Barrer] 4 PEGDA/PEGMEA-30 H. Lin, E. van Wagner, B.D. Freeman, L.G. Toy, and R.P. Gupta, Plasticization-Enhanced H Purification Using Polymeric Membranes, Science, 311, 639-64 (006).
Reduction to Practice http://www.mtrinc.com/co_removal_from_syngas.html 17
1,000 gpu = 0 Barrer (permeability) at 0.1 micron (thickness) 18
Monomer to Enhance Permeability TRIS-A V.A. Kusuma, B.D. Freeman, S.L. Smith, A.L. Heilman, & D.S. Kalika, Influence of Tris-based comonomer on structure and gas transport properties of crosslinked poly(ethylene oxide), J. Membrane Sci., 359, 5-36 (0).
Permeability/Selectivity Tradeoff CO/N = 60 18 CO Permeability increases about 4.5x with TRIS-A content V.A. Kusuma, B.D. Freeman, S.L. Smith, A.L. Heilman, & D.S. Kalika, Influence of Tris-based comonomer on structure and gas transport properties of crosslinked poly(ethylene oxide), J. Membrane Sci., 359, 5-36 (0).
TRIS-A Requires Toluene as Cosolvent to Form Homogeneous Solution SiGMA Does Not
SiGMA Increases Permeability CO/N = 58 0 Kusuma, V.A., G. Gunawan, Z.P. Smith, and B.D. Freeman, Gas Permeability of Cross-Linked Poly(ethylene oxide) Based on Poly(ethylene glycol) Dimethacrylate and a Miscible Siloxane Comonomer, Polymer, 51(4), 5734-5743 (0).
Summary Polar rubbery polymers exhibit interesting permeation and selectivity characteristics for acid gas separations. End groups in the network are important. They can significantly influence chain motion and free volume and, in turn, transport properties. Permeability is much higher in rubbery polymers than in conventional glassy polymers. Polar rubbery polymers have been demonstrated for post-combustion carbon capture. 9
The Upper Bound A/B A/B= A/B/PA 3 Upper Bound H /N 1 0 - Glassy Polymers Rubbery Polymers -1 0 1 3 4 H Permeability [cm3 (STP)cm/(cm s cmhg)] 33
Theoretical Prediction of A/B and A/B A/B A/B= A/B/PA PA = SA x DA : Solution-Diffusion DA = DoA exp(-eda/rt) : Activated Diffusion lndoa= a(eda/rt) - b : Linear Free Energy EDA= cda - f : Strongly Size-Sieving Results: B.D. Freeman, Macromolecules, 3(), 375 (1999). 34
Comparison of Theory with Experimental Data 35
Effect of Temperature on the Upper Bound -43 C Upper Bound 1 TBF PC data from: Moll et al., US Patent 5,35,7 (1994). O /N Selectivity TBF PC -43-145 C 145 C 0-1 0 1 O Permeability (Barrer) Rowe, B.W., L.M. Robeson, B.D. Freeman, and D.R. Paul, Influence of Temperature on the Upper Bound: Theoretical Considerations and Comparison with Experimental Results, Journal of Membrane Science, 360, 58-69 (0).
Effect of Temperature on Solubility Results: From D.W. Van Krevelen, Properties of Polymers, 3rd Edition (1997).
Predicted Effect of Temperature on the Upper Bound 4 Diffusion selectivity decreases with increasing temperature. 3 00 K More soluble gas (CO) is the more permeable gas. 50 K CO /N Selectivity CO solubility decreases more with increasing temperature than N solubility. 300 K 350 K 400 K 1 0-1 0 1 CO Permeability (Barrer) 3 4 Therefore, permeability selectivity decreases as temperature increases. Rowe, B.W., L.M. Robeson, B.D. Freeman, and D.R. Paul, Influence of Temperature on the Upper Bound: Theoretical Considerations and Comparison with Experimental Results, Journal of Membrane Science, 360, 58-69 (0).
Predicted Effect of Temperature on the Upper Bound Diffusion selectivity decreases with increasing temperature. 1 More soluble gas (CO) is the less permeable gas. 0 400 K 350 K 300 K 50 K 00 K H /CO Selectivity -1 CO solubility decreases more with increasing temperature than H solubility. - - -1 0 1 H Permeability (Barrer) 3 Therefore, permeability selectivity increases as temperature increases, reflecting the competing effects of solubility and diffusion selectivity. 39
Comparison of Theory with Experimental Data 3 TBF PC 30-418 K O 1 Predicted permeability (Barrer) Predicted permeability (Barrer) N 0-1 -1 0 1 Experimental permeability (Barrer) PBO A 19-373 K CO He 1 O CH 4 0 N -1 - - -1 0 1 Experimental permeability (Barrer) PBO A 3
Summary Upper bound model can be extended to account for effect of temperature. Reasonable agreement with experimental data obtained with few additional parameters. Model provides a systematic mechanism to estimate data at, for example, high temperature based on data obtained at room temperature.
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