Movie of CO2 and H2 Permeation
QuickTime™ and a
Sorenson Video 3 decompressor
are needed to see this picture.
Movie courtesy of Josh Chamot, NSF:
http://www.nsf.gov/news/news_summ.jsp?cntn_id=105797&org=NSF
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Membrane Hydrogen Purification: Classic
(2) Recovered H2
H2
Oil
Membrane
(3) Fuel
Gas
Hydrotreater
(1) Inerts
Purge
Oil/Gas
Separator
Treated
Oil
• H2/hydrocarbon separation
• H2/CO ratio adjustment
• NH3 purge gas recovery
Photo from Air Liquide
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Interest in Hydrogen
• U.S. H2 production was 810 million kg/yr in 2003. (DOE)
– Growth due to:
• Low grade crude in refineries
• Power source for fuel cells
• Steam reforming of hydrocarbons
accounts for 95% of the hydrogen
produced in the U.S. (DOE 2003):
CH 4  2H 2O  CO2  4H 2
Fuel Cell Facility (PLUG)
• Membranes may be useful for purifying H2:
- Low capital costs
- Compact size
- Ease of operation
DOE = http://www.eere.energy.gov/hydrogenandfuelcells/
PLUG = http://www.plugpower.com/technology/overview.cfm
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Air Liquide Slides courtesy of Dr. Greg Fleming, UT Ph.D. ‘87
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Fuel Cell Operation
From Jim McGrath, Virginia Tech
Source: H Power
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Just what the environment
needs from a car. Water.
Hydrogen
powered Fuel
Cell vehicles
only emit
water.
From Jim McGrath, Virginia Tech
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H2 Purity Requirements for Fuel Cells
A National Vision of America’s Transition to a Hydrogen Economy 2030 and Beyond, U.S. DOE, 2/2002.
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Cost Estimates for H2 Production
http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/vision_doc.pdf
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FutureGen
"Today I am pleased to announce that the United
States will sponsor a $1 billion, 10-year
demonstration project to create the world's first
coal-based, zero-emissions electricity and
hydrogen power plant..."
President George W. Bush
February 27, 2003
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FutureGen Concept
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Gas Separations Using Membranes
Current applications:
• Air separation - mainly N2 enriched air
• Natural gas treatment - acid gas removal
• H2 separation - H2 from hydrocarbons, ammonia purge, syngas
• Removal of vapors from mixtures with light gases (vapor separation)
Advantages:
• Low energy separation (no phase change)
• Reliable (no moving parts)
• Small footprint
Drawbacks:
• Incomplete separation (need higher selectivity)
• Low chemical/thermal stability (need more resistant matls.)
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Ideal Membrane Characteristics
• High flux (high permeability, thin)
• High selectivity
• Tolerance to all feed components
• Mechanical stability
• Ability to be packaged in high surface area modules
• Excellent manufacturing reproducibility, low cost
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Hollow Fiber Module
Contaminated Natural Gas
(High Pressure)
CO2- rich permeate
(Low pressure)
~5,000 m2/m3
Upgraded Natural gas
(High Pressure)
D. Wang, et al., ACS Symp. Ser., v. 744, p. 107, 1999.
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Natural Gas Purification
U.S. Pipeline Specifications1:
Amine Scrubber
Component
Specification
CO2
<2%
H 2O
<120 ppm
H 2S
<4 ppm
C3+ hydrocarbons
950-1050
Btu/ft3(STP)
Dew Point -20C
Inerts (N2, CO2, He, etc.)
<4%
Potential membrane applications:
• Acid gas removal
• N2 removal
• Higher hydrocarbon removal
• Dehydration
Membrane Unit
1R.W.
Baker, I.&E.C. Res., 41, 1393 (2002).
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Gas Transport in Polymers:
Solution-Diffusion Model
J. Membr. Sci., 107, 1-21 (1995)
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10 -6
CO
10 -7
H
Permeability [cm
C H
2 6
2
O
10
10
2
-8
He
H
2
NH
-9
10 -10
O
N
3
10
10
-12
C H
PDMS:
3 8
4
CH3
CO
2
n
2
2
N
Si O
2
CH
-11
CH3
PDMS, 35°C
2
CH
3
(STP)  cm/(cm 2 s cmHg)]
Characteristic Polymer Permeation Properties
PSF:
4
PSF, 23°C
SF
CH 3
SO 2
6
CCl F
2 2
C Cl F
2
2 4
O
C
CH 3
O
n
10 -13
50
100
150
200
3
V c [cm /mole]
250
300
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Solubility and Diffusivity Characteristics
PSF
(STP)/(cm
PDMS
C2 H6
10
-2
10 -3
Diffusion Coefficient [cm
10
-1
3
Solubility [cm
H
10 -5
N
2
O
2
/s]
10 -4
3
 cmHg)]
10 0
2
CO
He
10
10
C H
2 6
2
CF
-6
4
3 8
10 -4
0
N2 O CH4
2
100
200
CO 2
300
T c [K]
O
2
CO
-8
N
2
2
CH
4
-9
PSF
10 -10
C H
4 10
C3 H8n-C4 H10
400
500
PDMS
C F
10 -11
H2
C H
2 6C F
3 8
10 -7
10
2 CH 4
10 -12
10
100
V c [cm 3 /mole]
1000
B.D. Freeman and I. Pinnau, "Polymeric Materials for Gas Separations," in Polymeric Membranes for
Gas and Vapor Separations: Chemistry and Materials Science, Edited by B.D. Freeman and I. Pinnau,
ACS Symp. Ser. 733, pp. 1-27 (1999).
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Materials Design Approach
PA  SA DA
 A/B
• Traditional membrane materials
S A DA

S B DB
• Glassy polymers
• Designed to be strongly size-sieving
• Low permeability
• High selectivity due to high diffusion selectivity
• Upon plasticization, selectivity decreases, sometimes strongly
• H2 selective in H2/CO2 separations
• Our approach
• Rubbery polymers
• Designed to be strongly solubility-selective
• High permeability
• Selectivity derives primarily from high solubility selectivity
• Upon plasticization, separation properties can increase in
some cases (CO2/H2)
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Effect of Polar Groups in Liquid Solvents on
CO2 Solubility and CO2/N2 Solubility Selectivity
AN
DMF
DMS MeOH
THF
MAc
PC
TCM
ACN
THF
10
ACN
2
10
THF
2
CO 2 Solubility [cm
100
ACN
CO /N Solubility Selectivity
C6
100
3
(STP)/(cm 3 atm)]
25o C
1
1
10
15
20
25
30
Solvent Solubility Parameter [MPa
35
0.5
]
Lin and Freeman, J. Molecular Structure, 739(1-3), 57-74 (2005).
O
H3C C N
Crosslinked Poly(ethylene oxide) [XLPEGDA]
CH 2
CH
C
[O
CH 2
CH 2 ] O
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O
C
CH
CH 2
OR
O
PEO
Poly(ethylene oxide) diacrylate (PEGDA: Crosslinker)
O
CH 2
CH
C
[O
C
CH 2 CH 2 ] OR
n
O
O
R=CH3; poly(ethylene glycol) methyl
ether acrylate (PEGMEA); n=8
R=H; poly(ethylene glycol) acrylate
(PEGA); n=7
UV
O
C
C
C
C
C O
C
O
PEO
PEO
PEO
OR
O
C
C
C
PEO
O
O
C
C
C
C
O
C
O
C
C
C
C
C
O
Mixed Gas Separation
102
10oC
1
10
2
CO /H
2
-20oC

Upper Bound
35oC
100
10-1
10-2
10-1
100
101
102
103
CO Permeability [Barrer]
104
2
Lin, Haiqing, E. van Wagner, B.D. Freeman, L.G. Toy, and R.P. Gupta, “PlasticizationEnhanced H2 Purification Using Polymeric Membranes,” Science, 311(5761), 639-642 (2006).
Mixed Gas CO2/CH4 Separation
50
35oC
upper bound
6FDA-mPD
102
-20oC
4
30
PEGDA/PEGMEA-30
20
Pure
10
mixed
0
0
5
10
15
20
101
35oC
100
100
CO2 Partial Pressure [atm]
PEGDA (crosslinker; 30wt %)
CH2
CH C [ O CH2 CH2]13O C CH CH2
O
O
10oC
CA
2
 CO /CH

CO2/CH4
40
101
102
103
104
105
CO2 Permeability [Barrer]
PEGMEA (monomer: 70 wt%)
CH 2
CH
C
[O
CH 2 CH 2 ]8OCH3
O
Lin, Haiqing, E. van Wagner, B.D. Freeman, and I. Roman, “High Performance Polymer
Membranes for Natural Gas Sweetening,” Advanced Materials, 18, 39-44 (2006).
THANK YOU!
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