Ionic Liquid Solvents for Gas Sweetening Operations

1
Ionic Liquid Solvents for Gas Sweetening
Operations

• Lara Galán Sánchez, G. Wytze Meindersma and André
  de Haan
• The Netherlands

11th July 2007 - Kingston, Canada
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Contents

• Room Temperature Ionic Liquids (RTILs)
• Process advantages
• Research
• Gas absorption and selectivity
• Conclusions
• Acknowledgments

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Room Temperature Ionic Liquids (RTILs)

• Organic salts with a melting
• point below 100 ?C
• Wide liquid range
• -96 ?C up to 300 ?C
• Negligible vapour pressure
• Non-volatile
• Non-flammable
• High thermal, chemical and electrochemical
  stability
• Dissolution of many organic and inorganic
  compounds
• Variable miscibility with water and organic
  solvents

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Process features

• Big volume operations
• No or very low vapour pressure
• Reduction of volatile emissions and contamination
• Decreased solvent inventory and solvent make-up
  volume
• High thermal resistance
• RTILs can be regenerated
• Designer character
• Enhanced selectivity of a specific compound
• Defined physical properties required for an
  economical operation
• Promote specific interactions

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Research

• Identification of the potential of the designed
  RTILs as suitable solvents for CO2/CH4 separation
• Comparison of performance to that of existing
  solvents
• NFM (N-formyl morpholine)
• NMP (N-methyl pyrrolidone)
• Sulfolane
• Aqueous amine solutions

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Room Temperature Ionic Liquids (RTILs)
Tetrafluoroborate, BF4-
1-Butyl-3-methyl-imidazolium, bmim
Bis(trifluoromethanesulfonyl)imide, NTf2-
N(CF3SO2)2-
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Tested RTILs
Standard RTILs and NH2-functionalized
Gravimetric Balance IGA 002 - Hiden
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Solvent Regeneration
NH2-PyrrBF4
Regenerated T gt 353 K P lt 10-2 MPa
CO2
NH2-PyrrBF4
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CO2 absorption
343 K
344 K
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CH4 absorption at 343 K

• CH4 solubility increases due to physical affinity
  with the liquid

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CH4 absorption at 333 K

• 1 Henni, A., et al. 2006, J Chem. Eng. Data,
  51, 64-67

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CO2 volumetric load at 333 K
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Selectivity

• Individual gas absorption
• Comparison at low and high CO2 concentration
• Comparison of selectivity of standard ILs with
  functionalized ILs and physical solvents
• Advantage of ILs for CO2 absorption combination
  of physical and chemical interactions

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CO2/CH4 selectivity
NH2-PyrrBF4 at 333 k
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Selectivity individual gas 0.1 M Pa
T 333 K

• 2 Henni, A., et al. 2005, Canadian J Chem.
  Eng., 83, 358-361.
• 3 Murrieta, F., et al.1988, Fluid Phase
  Equilibria, 44, 105-115.

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Selectivity individual gas 1 M Pa
T 333 K
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Process selectivity PTotal 1 MPa
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Process selectivity PTotal 1 MPa
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Solvent effects in the process

• Heat of absorption of CO2 and CH4 comparable
  with those of physical solvents
• High viscosity affects mass transfer and
  kinetics selection of equipment and operation
  conditions
• Environmental aspects
• Opportunity for design

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Ethylene - ethane solubility
T 333 K

• 1 Henni, A., et al. 2006, J Chem. Eng. Data,
  51, 64-67
• 4 Rivas, O., Prausnitz, J., et al. 1979, AIChE
  J., 25, 975-984.

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Solvent effects in the process

• Solubility of ethane comparable to NMP, NFM,
  sulfolane
• Solubility of other gases O2, H2 very low
• Co-absorption effect needs to be studied

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Conclusions

• RTILs good potential solvents for gas sweetening
  operations
• Advantages of physical and chemical solvents are
  combined by the designed RTILs
• The designer ability of the RTILs allows to
  have a suitable solvent for a specific process

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Acknowledgments

• Special thanks to Jan de With from Shell Research
  Technology Center, Amsterdam for the synthesis
  of the functionalised ILs
• Project funded by the Dutch EET program(Ecology,
  Economy, Technology)Cooperation with
• ECNShellTNOHyflux CEPAration BV