1
Carbon Dioxide Separations Using PolymerMembranes and Status of Carbon Capture
Research in the United StatesBenny D. Freeman
The University of Texas at [email protected]
http://membrane.ces.utexas.edu
Symposium for Innovative CO2 MembraneSeparation Technology
Molecular Gate Membrane Module TechnologyResearch Association
Tokyo, JapanNovember 4, 2011
2
US Department of Energy Workshop
• Membrane section co-chaired byBenny Freeman and Sam Stupp.
• Complete report available at:
science.energy.gov/~/media/bes/pdf/reports/files/CCB2020_rpt.pdf
33
Some Challenges Identified by DOE Workshop
• Enormous scale of carbon capture applications• 2x106 ft3 (56,633 m3) of flue gas at atmospheric pressure containing
< 15% CO2 released from 550 MWe coal-fired power plant.
• Current membranes are not permeable enough• 106 m2 of membranes required to capture 90% of CO2 from 550 MWe
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 stabilityfor some carbon capture applications.
4
Priority Research Directions Identified by DOE Workshop
• Hierarchical Structures• Control 3D, asymmetric structure of matter using self-
assembly.• Use microelectronics lithographic technologies for preparing
ultra-high surface area, 3D (rather than 2D) membranes.
• Molecularly Tailored Membranes to Enhance SeparationPerformance
• Use either polymer or inorganic materials.• Design structures of controlled porosity with tailored
interactions with permeant (e.g., CO2) to provide both high fluxand 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 energyrequirements for carbon capture?
5
6
7
8
9
O
O
O8
O
O
OH7
polyethylene glycol diacrylate n=14 (PEGDA)
polyethylene glycol acrylate n=7 (PEGA7)
polyethylene glycol methyl ether acrylate: n=8 (PEGMEA8)Lin, H., Kai, T., et al. Macromolecules 38, 8381-93 (2005)Kalakkunnath, S., Kalika, D.S., et al. Macromolecules 38, 9679-87 (2005)
O
O
O14
O
Crosslinked Poly(ethylene oxide) (XLPEO)
10
10-3
10-2
10-1
100
101
0 100 200 300 400
S[c
m3
(ST
P)/
cm3
atm
]
/ k [K]
He
H2
N2
O2
CH4
CO2
C2H
6
C3H
8
C4H
10
Block copolymer containing 57 wt% PEO and 43 wt% Nylon-6; 35oC, fromBondar et al., J. Polym. Sci., Part B: Polym. Phys., 37, 2463-75 (1999). 11
Ethylene Oxide-Based PolymersHave High CO2 Solubility
Glass Transition of XLPEO
CH2 CH C
O
O CH2 CH2 OH[ ]7CH2 CH C
O
O CH2 CH2 OCH3[ ]8
PEGMEA: PEGA:
-70
-65
-60
-55
-50
-45
-40
-35
020406080100
Gla
ssT
ran
siti
on
Tem
per
atu
re[
oC
]
PEGDA Content [wt.%]
PEGDAPEGA7
PEGDAPEGMEA8
12
CH2 CH C
O
O CH2 CH2 OH[ ]7
PEGA (monomer)
]13[ OCH2CH2O
O
CCHCH2 C
O
CH CH2
PEGDA (crosslinker)
CH2 CH C
O
O CH2 CH2 OCH3[ ]8
PEGMEA (monomer)
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., 276, 145-161 (2006).
Free Volume Characterized by PALS
3.1
3.15
3.2
3.25
3.3
3.35
020406080100
Rad
ius
of
Fre
eV
olu
me
Ele
men
ts[Å
]
PEGDA Content [vol.%]
PEGDA-co-PEGMEA
PEGDA-co-PEGA
13
I3 is approximately independent of composition.
CO2/H2 Pure Gas Separation Properties
CH2 CH C
O
O CH2 CH2 OH[ ]7CH2 CH C
O
O CH2 CH2 OCH3[ ]8
5
10
15
020406080100In
fin
ite
Dilu
tio
nS
elec
tivi
ty
PEGDA Content [vol.%]
PEGDA/PEGA
PEGDAPEGMEA
PEGDA/H2O
CO2/H
2
Lin et al., Macromolecules, 38, 8381-8393 (2005) and 38, 8394-8407 (2005).
0
100
200
300
400
500
600
020406080100
Per
mea
bili
ty[b
arre
r]
PEGDA Content [wt.%]
PEGDA/PEGA7
PEGDA/PEGMEA8CO
2
14
÷÷ø
öççè
æ-=
333
expI
BAP
t ÷øö
çèæ -=
FFVB
AP exp
Free Volume in PEGDA Copolymerswith PEGMEA and PEGA
4
5
6
7
8910
20
2 2.5 3 3.5 4
102
103
1000/
CO
2P
erm
eab
iltiy
[Bar
rer]
CO
2/H2
Sel
ecti
vity
[ns-3]
102
103
4
5
6
7
8910
20
7 8 9 10
1/FFVC
O2P
erm
eab
iltiy
[Bar
rer]
CO
2/H2
Sel
ecti
vity
15
Mixed Gas Separation
10-1
100
101
102
10-2 10-1 100 101 102 103 104
CO
2/H2
CO2
Permeability [Barrer]
Upper Bound35oC
10oC
-20oC
PEGDA/PEGMEA-30H. Lin, E. van Wagner, B.D. Freeman, L.G. Toy, and R.P. Gupta, “Plasticization-Enhanced H2 Purification UsingPolymeric Membranes,” Science, 311, 639-642 (2006).
17
Reduction to Practice
http://www.mtrinc.com/co2_removal_from_syngas.html
1,000 gpu =100 Barrer (permeability)at 0.1 micron (thickness)
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Monomer to Enhance Permeability
V.A. Kusuma, B.D. Freeman, S.L. Smith, A.L. Heilman, & D.S. Kalika, “Influenceof Tris-based comonomer on structure and gas transport properties ofcrosslinked poly(ethylene oxide),” J. Membrane Sci., 359, 25-36 (2010).
TRIS-A
V.A. Kusuma, B.D. Freeman, S.L. Smith, A.L. Heilman, & D.S. Kalika, “Influenceof Tris-based comonomer on structure and gas transport properties ofcrosslinked poly(ethylene oxide),” J. Membrane Sci., 359, 25-36 (2010).
CO2/N2 = 60 18
CO2 Permeability increasesabout 4.5x with TRIS-A content
Permeability/Selectivity Tradeoff
TRIS-A Requires Toluene asCosolvent to Form Homogeneous
Solution – SiGMA Does Not
CO2/N2 = 58 20
SiGMA Increases Permeability
Kusuma, V.A., G. Gunawan, Z.P. Smith, and B.D. Freeman, “Gas Permeability ofCross-Linked Poly(ethylene oxide) Based on Poly(ethylene glycol) Dimethacrylateand a Miscible Siloxane Comonomer,” Polymer, 51(24), 5734-5743 (2010).
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Summary
• Polar rubbery polymers exhibit interestingpermeation and selectivity characteristics for acidgas separations.
• End groups in the network are important. They cansignificantly influence chain motion and free volumeand, in turn, transport properties.
• Permeability is much higher in rubbery polymers thanin conventional glassy polymers.
• Polar rubbery polymers have been demonstrated forpost-combustion carbon capture.
100
101
102
103
10-2 10-1 100 101 102 103 104
Glassy PolymersRubbery Polymers
H2 Permeability 1010 [cm3 (STP)cm/(cm 2 s cmHg)]
Upper Bound
H
2/N
2
The Upper BoundA/B=A/B/PA
A/B
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34
PA = SA x DA : Solution-Diffusion
DA = DoAexp(-EDA
/RT) : Activated Diffusion
lnDoA= a(EDA
/RT) - b : Linear Free Energy
EDA= cdA
2 - f : Strongly Size-Sieving
Results:
Theoretical Prediction of A/B and A/B
A/B=A/B/PAA/B
B.D. Freeman, Macromolecules, 32(2), 375 (1999).
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Comparison of Theory with Experimental Data
Effect of Temperature on the Upper Bound
100
101
10-1 100 101 102
O2/N
2S
elec
tivi
ty
O2
Permeability (Barrer)
TBF PC-43-145 °C
-43°C
145 °C
UpperBound
TBF PC data from: Mollet al., US Patent5,352,272 (1994).
Rowe, B.W., L.M. Robeson, B.D. Freeman, and D.R. Paul, “Influence of Temperatureon the Upper Bound: Theoretical Considerations and Comparison with ExperimentalResults,” Journal of Membrane Science, 360, 58-69 (2010).
Effect of Temperature on Solubility
From D.W. Van Krevelen, Properties ofPolymers, 3rd Edition (1997).
Results:
100
101
102
103
104
10-1 100 101 102 103 104
CO
2/N2
Sel
ecti
vity
CO2
Permeability (Barrer)
200 K
250 K
300 K
350 K400 K
Predicted Effect of Temperature on the Upper Bound
Rowe, B.W., L.M. Robeson, B.D. Freeman, and D.R. Paul, “Influence of Temperatureon the Upper Bound: Theoretical Considerations and Comparison with ExperimentalResults,” Journal of Membrane Science, 360, 58-69 (2010).
• Diffusion selectivity decreaseswith increasing temperature.
• More soluble gas (CO2) is themore permeable gas.
• CO2 solubility decreases morewith increasing temperaturethan N2 solubility.
• Therefore, permeabilityselectivity decreases astemperature increases.
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10-2
10-1
100
101
102
10-2 10-1 100 101 102 103
H2/C
O2
Sel
ecti
vity
H2
Permeability (Barrer)
200 K250 K300 K350 K400 K
Predicted Effect of Temperature on the Upper Bound
• Diffusion selectivity decreaseswith increasing temperature.
• More soluble gas (CO2) is theless permeable gas.
• CO2 solubility decreases morewith increasing temperaturethan H2 solubility.
• Therefore, permeabilityselectivity increases astemperature increases,reflecting the competing effectsof solubility and diffusionselectivity.
Comparison of Theory with Experimental Data
10-1
100
101
102
10-1 100 101 102
TBF PC230-418 K
O2
N2
Pre
dic
ted
per
mea
bili
ty(B
arre
r)
Experimental permeability (Barrer)
10-2
10-1
100
101
102
103
10-2 10-1 100 101 102 103
PBO A192-373 K
CO2
He
O2
N2
CH4
Pre
dic
ted
per
mea
bili
ty(B
arre
r)Experimental permeability (Barrer)
PBO A
Summary
• Upper bound model can be extended to account foreffect of temperature.
• Reasonable agreement with experimental dataobtained with few additional parameters.
• Model provides a systematic mechanism to estimatedata at, for example, high temperature based on dataobtained at room temperature.
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