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Movie of CO 2 and H 2 Permeation. Movie courtesy of Josh Chamot, NSF: http://www.nsf.gov/news/news_summ.jsp?cntn_id=105797&org=NSF. Membrane Hydrogen Purification: Classic. H 2 /hydrocarbon separation H 2 /CO ratio adjustment NH 3 purge gas recovery. Photo from Air Liquide.
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Movie of CO2 and H2 Permeation Movie courtesy of Josh Chamot, NSF: http://www.nsf.gov/news/news_summ.jsp?cntn_id=105797&org=NSF
Membrane Hydrogen Purification: Classic • H2/hydrocarbon separation • H2/CO ratio adjustment • NH3 purge gas recovery Photo from Air Liquide
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): 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
Air Liquide Slides courtesy of Dr. Greg Fleming, UT Ph.D. ‘87
Fuel Cell OperationFrom Jim McGrath, Virginia Tech Source: H Power
Just what the environment needs from a car. Water. Hydrogen powered Fuel Cell vehicles only emit water. From Jim McGrath, Virginia Tech
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.
Cost Estimates for H2 Production http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/vision_doc.pdf
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
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.)
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
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.
Natural Gas Purification U.S. Pipeline Specifications1: Amine Scrubber • Potential membrane applications: • Acid gas removal • N2 removal • Higher hydrocarbon removal • Dehydration Membrane Unit 1R.W. Baker, I.&E.C. Res., 41, 1393 (2002).
Gas Transport in Polymers: Solution-Diffusion Model J. Membr. Sci., 107, 1-21 (1995)
Characteristic Polymer Permeation Properties PDMS: PSF:
Solubility and Diffusivity Characteristics 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).
Materials Design Approach • Traditional membrane materials • 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)
Effect of Polar Groups in Liquid Solvents on CO2 Solubility and CO2/N2 Solubility Selectivity THF ACN Lin and Freeman, J. Molecular Structure, 739(1-3), 57-74 (2005).
Crosslinked Poly(ethylene oxide) [XLPEGDA] OR PEO O C C C C C C C C O [ ] O C CH C O CH CH CH OR O O 2 2 C 2 C PEO O PEO O PEO O OR PEO O O C O C O C C C C C C C [ ] CH CH C O CH CH O C CH CH 2 2 2 2 14 O O Poly(ethylene oxide) diacrylate (PEGDA: Crosslinker) n UV R=CH3; poly(ethylene glycol) methyl ether acrylate (PEGMEA); n=8 R=H; poly(ethylene glycol) acrylate (PEGA); n=7
Mixed Gas Separation Lin, Haiqing, E. van Wagner, B.D. Freeman, L.G. Toy, and R.P. Gupta, “Plasticization-Enhanced H2 Purification Using Polymeric Membranes,” Science, 311(5761), 639-642 (2006).
Mixed Gas CO2/CH4 Separation [ ]13 CH CH C O CH CH CH CH O C 2 2 2 2 O O [ ]8 CH C O CH CH CH OCH3 2 2 2 O PEGDA (crosslinker; 30wt %) PEGMEA (monomer: 70 wt%) 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).