CO2 Capture Challenges and Opportunities

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CO2 Capture Challenges and Opportunities

• Joan F. Brennecke

Department of Chemical and Biomolecular
Engineering University of Notre Dame Notre Dame,
IN 46556
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U. S. Energy Consumption - 2003
Source EIA Renewable Energy Trends with
Preliminary Data for 2003, Figure 1, The Role of
Renewable Energy Consumption in the Nation's
Energy Supply, 2003.
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Role of Fossil Fuels

• Fossil fuels gt 85 of primary energy consumption
• Coal gt 50 of electricity
• Vigorous growth in renewables (wind, solar,
  cellulosic biomass) will require many decades
  before making significant contribution top
  primary needs
• U.S. (and Indiana 57 billion tons) have
  abundant reserves of coal
• Will continue to use fossil fuels
• Need to use them responsibly (SO2, NOx,
  particulate, and CO2)

Indiana Geological Survey
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Post-Combustion CaptureConventional PC Power
Plant
Atmospheric pressure 12 CO2
http//www.bellona.org/factsheets/1191913555.13
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Pre-Combustion CaptureIGCC
gt20 atmospheres gt30 CO2
http//www.bellona.org/factsheets/1191913555.13
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US Dept. of Energy CCS Targets

• Separation and Capture
• Sequestration/Storage
• Monitoring, Mitigation and Verification

Sean Plasynski NETL, 6/5/07
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US Dept. of Energy CCS Program
Sean Plasynski NETL, 6/5/07
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Adequate CO2 Storage Capacity
6 GT/yr total US emissions
Sean Plasynski NETL, 6/5/07
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Motivation

• Designing Ionic Liquids for specific and
  selective gas separations particularly CO2
  capture
• ILs as absorbent for separation of flue gas
• CO2, N2, O2, H2O, NOx, SOx, etc.
• Replace volatile and/or corrosive solvents
  currently used for acid gas capture
• Better understand the structure relationships for
  gas solubility in ILs

Brennecke and Maginn, US Patent 6579343, 2003
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Typical Ionic Liquids
X Cl NO3 CH3CO2 CF3CO2 BF4 CF3SO3 PF6
(CF3SO2)2N
1-n-butyl-3-methylimidazolium tetrafluoroborate
bmimBF4 Not all ILs created equal
(viscosity, Tm, toxicity, PF6 and BF4 anion
degradation)
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Ionic Liquids and GHG Management

• Exploit unique properties of ILs
• Very low volatility
• High thermal stability
• Properties can be varied by choice of anion,
  cation and substituents
• Application areas
• Post-combustion CO2 capture
• Pre-combustion CO2 capture
• Other (e.g., air separation for IGCC and oxyfuel)
• Other possible separations

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Typical Post-Combustion Absorption System
13.8 MPa (2000 psia)
Conventional Absorber/Stripper
Trimeric
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Key Properties for CO2 Capture

• High CO2 solubility
• High CO2 selectivity
• Ease of regeneration
• Low enthalpy of solution
• Low solubility with water
• Low heat capacity
• Stability
• Thermal
• Other gases (e.g., SO2)
• Low viscosity
• Inexpensive

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Research Equipment

• Vapor-Liquid Equilibrium
• IGA
• Low pressure (0-20 bar)
• Small sample (75 mg)

• Rubotherm
• High pressure/high temperature
• Larger sample (1.5 g)

Intelligent Gravimetric Analyzer (IGA) -Hiden
Analytical, Inc.
Rubotherm
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Pure Gas Solubility - CO2

• Gas solubility
• Important for reusability of ILs
• Absorb at low T
• Remove at high T
• Trend seen for CO2 solubility in all ILs measured

Muldoon, et al., JPC B, 2007, 111, 9001-9009
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Pure Gas Solubility Other gases

• Gas solubility measured in hmpyTf2N
• Similar trends are seen with other ILs
• CO2 has the highest solubility of the gases
  measured
• Good selectivity!

Anderson, et al., ACR, 2007, 40, 1208-1216
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Comparison to Other Physical Solvents
Anderson, et al., ACR, 2007, 40, 1208-1216
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Pure Gas Solubility CO2
Muldoon, et al., JPC B, 2007, 111, 9001-9009
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Pure Gas Solubility CO2
Muldoon, et al., JPC B, 2007, 111, 9001-9009
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Pure Gas Solubility CO2

• Increasing fluorination increases CO2 solubility
• Anion effect greater than cation effect

Muldoon, et al., JPC B, 2007, 111, 9001-9009
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Pure Gas Solubility SO2

• SO2 solubility in hmimTf2N
• Same as for CO2

Anderson, et al., J Phys Chem B, 110 (31) 2006
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SO2 Pure Gas Solubility

• SO2 has highest solubility in ILs measured
• Possibility of simultaneous removal of both SO2
  and CO2

Anderson, et al., J Phys Chem B, 110 (31) 2006
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Increasing CO2 Solubility

• Preliminary systems analysis indicated needed at
  least 10x higher CO2 solubility
• Best physical absorbent is p5mimbFAP with
  H20 bar at 25 ºC
• Chemical complexation
• Strong enough to increase capacity
• Weak enough to keep regeneration costs low

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Chemical Complexation - Literature

• Chemical capture of CO2 by free amine
• Stoichiometric capture of CO2
• 13C NMR evidence of carbamate formation
• Reversible under vacuum with heating

Bates, E. D. Mayton, R. D. Ntai, I. Davis, J.
H., J. Am. Chem., 2002, 124, 926.
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Chemically Complexing ILs

• Chemical complexation
• High CO2 solubility

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Tuning Complexation Strength
Ionic Liquid Pressure Capacity (bar) (mol
CO2/mol IL) NDIL0017 1.6 0.19 EMD0004 0.5
0.70 NDIL0039 1.6 0.06
Room temperature
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Summary

• ILs are excellent media for performing gas
  separations (low volatility, tunable selectivity)
• Capacity of physical solvents too low for
  post-combustion capture but can enhance capacity
  by chemical complexation with attractive heats
• Important issues
• Reaction rates
• Viscosity changes
• Water content
• Process configuration and operation

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Project Team

• Notre Dame
• Prof. Ed Maginn
• Prof. Bill Schneider
• Prof. Juan de la Fuenta
• Dr. JaNeille Dixon
• Dr. Erica Price
• Dr. Zulema Lopez-Castillo
• Dr. Wei Shi
• Dr. Keith Gutowski
• Dr. Jindal Shah
• Jes Anderson
• Elaine Mindrup
• Burcu Gurkan
• Devan Kestal

• Industrial Partners
• DTE Energy
• Babcock and Wilcox
• EMD Chemicals/Merck KAaG
• Trimeric
• Air Products

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Acknowledgements

• U.S. Department of Energy, National Energy
  Technology Laboratory, Award Nos.
  DE-FC26-04NT42122 and DE-FC26-07NT43091
• State of Indiana 21st Century Fund