Slide 1
1Ionic liquids for gas separationANIL VIBHUTE15CH60R03
Outline:What are Ionic Liquids.Role of Ionic Liquids in Gas
separation.Types of Ionic Liquid Membranes.Review of research in
this area.Case studies.Applications.Challenges and
Opportunities.References
2
What are Ionic Liquids-Salts having melting points below 1000C
and whose melts contain discrete ions are called as Ionic
liquids.1000 Ionic liquids have been commercialized out of 1014
ionic liquids.
Properties-Negligible Vapor Pressure.Thermally Stable above
1000C.High CO2/H2 selectivity.Tunable physicochemical
properties.High hydrophobicity.
3
Classes of ionic liquids
4
some of the ionic liquidsSr.No.NameAbbreviationCompounds to
separate11-ethyl-3-methyl-imidazolium bis(trifluoromethyl-sulfonyl)
imide[emim][NTf2]N2,CO2,CH421,3-dimethylimidazolium
bis(trifluoromethyl-sulfonyl)
imide[dmim][NTf2]N2,H2,O2,CO31-(3-aminopropyl)-3-methylimidazolium
bis(trifuoromethyl-sulfonyl) imide[H2NC3H6mim][NTf2]H2,CO2
5
Role of Ionic Liquids in gas separations?6
Comparison of solubility of gases in solvents (gm/ml)A key
feature of ionic liquids is that their physical properties can be
tailored by correct selection of cation, anion and
substituents.Henrys Constant
Types of Ionic Liquid Membranes-71) Emulsion Ionic Liquid
Membranes:Rarely gas separation. Mostly for extraction of
liquids.
application of emulsion liquid membrane for extraction
benzimidazole by tri-n-octyl methyl ammonium chloride (ph1) &
HCL solution (ph2)
studied emulsification time ,speed ; carrier concen; agitation
speed.
Separation efficiency
8
Permeability = solubility * diffusivity
solubility study of the particular gases with respect to
pressure and temperature is done.
As pressure of gas , solubility of gases but temperature ,
solubility of gases
Conclusion :- this technique is more effective than L-L
extraction method .
2) Supported ionic liquid membraneTwo types of
mechanisms1)Solubility-diffusivity mechanism solubility study of
gases should be done. While according to size of molecule, gas will
diffuse into the membrane.
2) facilitated transport of gases With Complexing agent,
complexing agent becomes carrier for the gas through the
membrane.
9
Review of research in this area-Michiaki Matsumoto et.al. in
2007 studied separation of cyclohexane and benzene using ionic
liquids based upon 1-alkyl-3-methylimidazolium and quaternary
ammonium salts. Separating problem have close boiling points.
Energy intensive operations like azeotropic distillation or
extractive distillation.
Through this innovation Michiaki et.al. suggested to use ionic
liquid based supported membranes for their separation. However they
are failed to give stability assurance for higher temperatures for
these particular membranes.
10
CO2/CH4 separation case studyFor experiments, two ionic liquid
membranes and polymeric membrane are taken.A] Polymeric
Membrane:Poly (vinylidene fluoride-co-hexa-fluoro-propylene)
B] Ionic Liquid Membranes:1-hexyl-3-methylimidazolium bis
(trifluoromethylsulfonyl) imide ([hmim][Tf2N])
&1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl)
imide ([emim] [Tf2N])
11
12
13
Removal of Acidic Gases
Removal of acidic gases was also addressed by the research from
group of Park in 2009.
In this research they studied the permeability rates of three
gases namely CH4, H2S and CO2. This is rather very interesting
topic for research since selectivity of these two acidic gases were
studied using 1-butyl-3-methylimidazolium tetra fluoroborate as
membrane and support as PVDF (poly-vinylidene fluoride).
Selectivity comparison of H2S/CH4 and CO2/CH4 was a major key
output of the whole process. And it was found that selectivity in
case of former case was about five times more than latter one.
Applications-
14
15
2] CO2 Sequestration:Ionic liquids have very high affinity for
CO2. Being a green-house gas, CO2 can be separated out from flue
gases using relatively cheaper techniques such as ionic liquid
membrane separation technology.
3] Fuel Cell Membrane:Since Ionic liquid possesses charge when
it is molten state, it can be used for manufacturing of fuel cell
membrane.Preparing ionic liquid as a membrane or incorporation of
ionic liquid into membranes makes them to act as fuel cell
membrane
15
Challenges And OpportunitiesEnergy intensive operations like
distillations can be replaced with membrane separation techniques.
Ionic liquids coming out to be the most efficient separation media
since they hardly have any vapor pressure, selection of cation and
anion can give very long range of properties. A very big problem is
associated with them is their cost-effectiveness. Ionic liquid can
cost around ten times more than what one can get by selling the
product obtained after purification. Cost of ionic liquids is by
far the most challenging issue related with ionic liquids as gas
separation media.
16
ReferencesBakonyi, P.; Nemestothy, N.; Belafi-Bako, K.
Biohydrogen Purification by Membranes: An Overview on the
Operational Conditions Affecting the Performance of Non-Porous,
Polymeric and Ionic Liquid Based Gas Separation Membranes. Int. J.
Hydrogen Energy 2013, 38, 96739687.
Bara, J. E.; Gabriel, C. J.; Carlisle, T. K.; Camper, D. E.;
Finotello, A.; Gin, D. L.; Noble, R. D. Gas Separations in
Fluoroalkyl-Functionalized Room-Temperature Ionic Liquids Using
Supported Liquid Membranes. Chem. Eng. J. 2009, 147, 4350.
Brennecke, J. F.; Maginn, E. J. Ionic Liquids: Innovative Fluids
for Chemical Processing. AIChE J. 2001, 47, 23842389.
And more
17
17
18
