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Toward Benign Process of COToward Benign Process of CO22 Separation; Separation;
Facts and OpportunitiesFacts and Opportunities
Absorption
Desorption
Combustiongas
CO2 richabsorber
Leanabsorber CO2, H2OCO2<2%
Kyung Hee UniversityGreen Chemistry Research Group
Red Alert !!
Industrial separationCO2 separation
Industrial process
Post-combustionCO2 separation
Air
Pre-combustionH2 and CO2 separationGasification/reform
Air/O2-steam
Oxyfuel
O2
CO2Compression
Product
CO2
Compression
Heat & Power
CO2
Compression
H2
Heat & Power
Other products
CO2
Compression
Heat & powerO2 separation
Air
Air/O2 + steam
Raw materials
Fossil fuels, biomass
combustion
Combustion
1. http://wcentral.blogspot.com/2007/05/overview-of-carbon-capture.html
CO2 Capture Technology in Industry1,
From Gas Sweetening to Global Warming Issues
Methods for CO2 Capture
Principle of separation
Separating agent
Method
Chemical absorptionPhysical absorptionAdsorption
Gas permeationCryogenic distillationCombination
CO2 solubility
CO2 reactivity
CO2-solid affinity
Diffusion through membrane, pressure, concentration gradient
Liquefaction, distillation
Pressure swing adsorption
LiquidWater, methanol, DME, PEG, NMP, PC
Reacting liquidMEA, DEA, TEA, NaOH, K2CO3
Solid adsorbentZeolite, Active carbon, alumina silicates, hydrotalcites
Polymeric, ceramic, ion transport, membrane
Distillation tower
Pressure swing – solid adsorbent
Physical Versus Chemical Absorption
Physical
No chemical interaction
MeOH, NMP, PEG, PC, water, tri-n-Bu Phosphate, ILs
Regeneration by & ΔP or (limited) & ΔT
• Less energy usage and less maintenance demand under optimal condition and process
Chemical
Chemical interaction occurs
• 1o, 2o, 3o amines (MEA, DEA, MDEA)
• Alkali metal OH- or CO3
2- (NaOH, K2CO3)
Regeneration by & ΔT (req. high temp.) & ΔP
• Concentration limited by solubility
• Susceptible with corrosion, reactivity with oxidator & contaminant
• Better at high inlet P CO2
• Loading proportional to PCO2
• Cannot reach very low outlet P CO2 (0.1-2%)
• Good at low inlet P CO2
• Loading limited by reaction stoichiometry• Can reach very low outlet P CO2 (down to
ppm)
MeOH, 0°C
20wt% DEA, 50 °C
MeOH, 0°C
20wt% DEA, 50 °C
PC
O2 a
bove
Liq
uid
, at
m
CO2, vol/vol absorbent
Chemical absorption using amine indicating sharp rise in outlet PCO2 when loading reaches reaction stoichiometry
Non-functionalized ILs is good candidates for physical CO2 absorption.
• Many variations possible• Physical absorbent may not require
extensive heat input for regeneration• CO2 off-gas often at low pressure• May require pre-compression,
depending on feed gas pressure
Typical CO2 Capture Process from Industrial Process and Power Plant
• Recovery from low pressure (~1 atm) flue gas
• Low CO2 partial pressure (~1-1.5 psi)• Oxygen containing gas (~2-5%)• Hot flue gas ~400-800 oC• May contain NOx, Hg, SO2, H2S, other sulfur
species and particulates
Carbon dioxide absorption using amine solution
Lean Gas
Reboiler
CO2 Off Gas
Separator Drum
Condenser
Stripping Column
Absorber
Interchanger
Trim Cooler
Rich Solution
Lean Solvent
CO2-Rich Feed Gas
CO2 Capture Through Facilitated Membrane; Tons of Works Awaiting2
2. separ & Puri Tech 41(2005)109
Durability & thermal stability
Vapor invasion through membrane pores at high temp. (wetting)
1. Non/less-volatile liquids
2. Surface modification
3. composite
1. Fluorinated polymers
2. Non-aggressive liquids
1. Introduction of less volatile absorbent2. Combination of membrane-novel absorbent3. Membrane modification4. Hybrid absorbent5. Module design
Opportunities
Current status
ProblemsSelectivity
1. Selective liquids2. Composite
1. Process is under rapid investigations & developments2. Numerous absorbents & membranes are available3. Novel processes are possible4. Some problems persist (solutions may directly correspond to costs)5. Model, reaction mechanism, and kinetics are available
CO2 Capture Through Facilitated Membrane, State-of-the-art
Carbon dioxide separation through water-swollen-gel membrane3
3. Energy Convers. Mgmt. 36 (1995) 419; 4. Transaction-MRSJ 29(2004)3299
Stability Vs Selectivity (25 oC)
K2CO3 + complex agents (cryptand, crown ether)
Support membrane
Water-swollen-gel membrane
Liquid m
embran
e
Carrier
Carrier
Carrier + CO2
CO2 absorption
CO2 transportation
CO2 desorption
CO2
CO2N2
Permeate
Porous membrane
Feed gas (CO2/N2)
Hydrophilic micropor. membraneIonic Liquid (pmim)Iodide
Hydrophobic micropor. membrane
Gas and vapor permeation through liquid membrane using ionic liquid4
Permeability comparison of several gases
Sandwiched IL facilitated transport membrane
Permeate
Feed gas
Ionic Liquids, Novel CO2 Absorbents; Escape the Limits ?
Solvent volumetric CO2 load (60 oC)5
Comparison with physical CO2 absorbents5
CO2/CH4 selectivity in specific-task ILs65. A.B. de Haan, TU Eindhoven; 6. G. Wytze Meindersma, Univ. of Twente7. http://www.netl.doe.gov/technologies/carbon_seq/core_rd/breakthrough/42122.html
Henry’s law constants (bar) for several gases in various ILs.Small Henry’s constant indicates high solubility7
Sulfolane333 K
NMP333 K
0
40
80
120
160
200
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
CO2 / M Pa
CO
2 /
CH 4
00.10.20.30.40.50.60.70.80.91
CH4 / M Pa
[NH2-Pyrr]BF4 at 333K [NH2-Im]BF4 at 343K [NH2-Im]NTf2 at 343K
[bmim]BF4 at 343K [emim]NTf2 at 343K
0
10
20
30
40
50
60
70[bmim][PF6]
[bmim][BF4]
[bmim][Tf2N]
[MeBu3N][Tf2N]
[MeBuPyrr][Tf2N]
Henry’s law constants (bar) for CO2 in various ILs
Anion and Cation Effects on the Solubility of CO2
8. Journal of Physical Chemistry B 109 (2005) 6366
determining the CO2 solubility3;
Anion effect Cation effect
The anions
Fluorinated anions are excellent but costly, sometimes not environmentally friendly.
SN
S
O O
O O
F3C CF3 P
F
FF
FF
F
Some strategies in ILs for CO2 absorption8
Controlling the viscosity (using dicyanamide anions, trialkylsulfonium cation)
Creating more free volume (introducing ether and long, branched alkyl chain on the cation
Incorporating with CO2-phylic functional groups (carbonyl, sulfonyl, phosphate, amine groups)
Ionic Liquids for CO2 Absorption
Slow rate and low CO2 capacity (non-fluorinated anions)
Anions play critical role.Expensive anions(Fluorinated anions, effective yet expensive)
Amino acids anionsTask specific ILs (amine or amino acids groups)
1. Additive2. Blending3. Task specific ILs4. High pressure CO2
5. Choline chloride anion exchange
Opportunities
Current status
ProblemsReduction of capacity in the presence of water or other organics9
Underdeveloped
9. J Phys Chem B 106(2002)7315
Cl-, Br -, BF4-, PF6
-
N(CN)2-, SCN -,
Tf2N (bis(trifluoromethanesulfonyl)aminde)
Classical ILs
Task specific ILs (via carbamate formation)
NR
NRR
R
R
PRR
R
R
N
N R
NN R
NH2
Amino acids
H2N
O-
O
H2N
O-
O
Cations Anions
Cl-, Br -, BF4-, PF6
-
N(CN)2-, SCN -,
Tf2N (bis(trifluoromethanesulfonyl)imide)
Classical ILs
Task specific ILs (via carbamate formation)
NR
NRR
R
R
PRR
R
R
N
N R
NR
NRR
R
R
PRR
R
R
N
N R
NN R
NH2N
N R
NH2
Amino acids
H2N
O-
O
H2N
O-
O
Amino acids
H2N
O-
O
H2N
O-
O
Cations Anions
Task Specific ILs for CO2 Capture; Which All Good Things Put Together
Carbamate formation as an intermediate10,11
N NC4H9
NH2
2BF4
-
CO2
10. J of American Chemical Society 124(2002)926; 11. Ind Eng Chem Res 45(2006)2875; 12. Chem Eng Res Des 85(2007)31
N NC4H9
HN
O
O
NNC4H9
H3NBF4
-2
Viscosity problems at high CO2 loading
Slow progress due to some problems
Expensive anions(Fluorinated anions, effective yet expensive)
Amine-tethered ILsCarbamate formation, intensive energy regeneration
UnderdevelopedAlteration with DCA12 or ROSO3
- anions Underdeveloped
1. Hindered 1o or 3o amine-tethered groups
2. Anions modification
Opportunities
Current status
Problems
Poly(ionic liquid)s; Creative Effort13,14,15
*
*
N
R
RR
n
BF4-
*
*
O
n
BF4-
O
N
R
RR
*
*
N
n
BF4-
N R
*
*
O
n
BF4-
O
N
N
R
13. Chem Commun (2005)3325; 14. Ind Eng Chem Res 46(2007)5397; 15. J Membrane Sci 281(2006)130
P[VBTMA][BF4] P[MATMA][BF4] P[VBBI][BF4] P[MABI]BF4
* *
N
O
O
O
O
x1-x
BF4-
n
* *
O
O
O
O
x1-x
BF4-
n
O
O
N
P[VBTMA][BF4]-g-PEG P[MATMA][BF4]-g-PEG
Brittle materialsThermodynamics, kinetics and mechanism
Low efficiency
Grafting polymersIn progress, limited results available
Underdeveloped
1. ILs grafted onto selective polymers
2. Specific membrane
Opportunities
Current status
Problems
Hyperbranched Polymers16; What Else Can We Do ?
16. http://www.3me.tudelft.nl/live/pagina.jsp?id=7990c6da-316f-444b-94aa-334c23d3353e&lang=en
Unknown chemical & Physical properties
Synthesis CO2 absorption
On progress1 Papers & patents available
Underdeveloped
1. Taylor-made amines2. High press. & high temp. applications3. Fundamental researches4. Hot flue gas treatment
Opportunities
Current status
Problems
1. Chemistry & process are underdeveloped2. Candidates for replacing ILs-based absorbents3. Limited numbers of chemical are commercially available
Amine-Based CO2 Absorption Process
17. Green Chem 9(2007)594; 18. Fluid Phase Equilib227(2005)197
1. Process is well established2. Over 400 papers and patents are available3. Model, reaction mechanism, and kinetics are available4. Potential for immediate applications
Limited capacity at high pressure
Thermal instability, volatility, & degradation
Energy intensive regeneration and recycle
3o amine, hindered amines, or polyamines
Activated K2CO3, Poly or 3o amines
3o or poly 3o amines
1. Amines blending17
2. 3o amine & K2CO3 activation18
3. Combination physical and amine-based absorbents
4. Introduction of various unique amines5. Effective stripping study, i.e. stationary
carbamate hydrolysis catalyst in the stripper6. Facilitated transport membrane7. Hot flue gas treatment
Opportunities
Current status
Problems
Some unique amines for CO2 absorption
HO
NH2
HO
HN
OH
Common well-established amines
Relatively new
HO
N
OH
OH
H2N
New introduction of unique amines
HN
OH
AMP (hindered 1o amine)
MEA (1o amine) DEA (2o amine) MDEA (3o amine)
TBAE (hindered 2o amine)19
HN N
2
TMBPA (2o, 3o polyamine)20
N NH2
DMAPA (1o, 3o polyamine)
N NH
NH2
N,N-Dimethyldipropylenetriamine (1o, 2o, 3o, polyamine)
19. J Chem Eng Data 45(2000)1195; 20. J Thermal Anal Cal 65(2001)419; 21. Ind Eng Chem Res 46(2007)5803
H2N
HN
OH
AEEA (1o, 2o, polyamine)21
NH
HN
Piperazine (2o polyamine)
More than 30 unique amines are available commercially, many have not been explored !!
Amine-Based Reaction Mechanism22
Zwitterion mechanism
Less bulky 1o, 2o amine
CO2 + RNH2 RNH2+COO-
RNH2+COO- + RNH2 RNHCOO- + RNH3
+ Carbamate formation
Zwitterion formationk1
k-1
kB
1o hindered amine
R3NH2+COO- + H2O HCO3
- + R3NH3+
kB
CO2 + 2RNH2 RNHCOO- + RNH3+
CO2 + R3NH2 + H2O HCO3- + RNH3
+
Sum of reactions
Sum of reactions
CO2 + R3NH2 RN3H2+COO- Zwitterion formation
k1
k-1
R3NHCOO- + H2O HCO3- + R3NH2 Another possible rnx,
less stable carbamate hydrolysis
Thermolecular mechanism
Less bulky 1o, 2o amine
CO2 + RNH2 - B RNHCOO- - BH+
R3N + H2O + CO2 R3N+H + HCO3- Carbamate formation
Simultaneously
k’
R3N + H2O R3N+H + OH- Amine dissociation in water
Base-catalyzed hydration mechanism
CO2 + R3N RN+COO-k1
k-1
R3NCOO- + H2O R3N+H + HCO3-
Alternative route of 3o amine
Amine-Based Reaction Mechanism
22. Chem Eng Technol 30(2007)1467
3o amine
Current Lab Progress
23. Ind Eng Chem Res 43(2004)3049
1. Isochoric method, based on pressure-decay history (batch analysis)23.2. Using virial gas relationship.3. Rapid, easy and semi quantitative analysis.4. Robust for physical solubility analysis.5. Not optimized for kinetics study.
Screening apparatus set-up
Test equipment
Materials
1. Monoethanolamine (MEA)2. Methyldiethanolamine (MDEA)3. Imidazole4. 1-Methylimidazole5. 2-Methylimidazole6. 1,2-Dimethylimidazole7. K2CO3
8. Guanidine carbonate9. Sodium glycine10. N,N-Dimethylethanolamine (DMEA)11. 3,3-Diaminodipropylamine (DAP)
Data Reduction
Where,V total = V CO2 reservoir + V Equilibrium cellP total = P CO2 + P soln vaporP solution vapor is obtained prior to CO2 introductionZs is obtained from the virial gas equation24
Z mixture is neglected24
24. AIChE Journal 51(2005)2311
Pvreservoir
ZsRTn CO2 before rnx =
(Ptotal – Psoln vapor)vtotal
ZsRTn CO2 after equilibrium =
n CO2 dissolved = n CO2 before rnx – n CO2 after equilibrium
α (Capacity) = nCO2 dissoleved/n absorbent
α (Capacity)P
CO
2 (
KP
a)
Equilibriumcell
CO
2 reservoir
PIsothermal box
to vacuum pump
0.00
20.00
40.00
60.00
80.00
100.00
0.00 5.00 10.00 15.00 20.00
1mL MDEA + 4mL H2O 5mL 23.08%wt K2CO3/H2O5mL 4.76%wt 2- methylimidazole/H2O 5mL 4.76%wt Naglycine/H2O5mL 4.76%wt imidazole/H2O 5mL 4.76%wt 1,2- dimethylimidazole/H2O5mL 4.76%wt guanidine carbonate/H2O 5mL 4.76%wt MEA/H2O5mL 4.76%wt DMEA/H2O 1mL DMEA + 4mL H2O5mL 4.76%wt DAP
0.00
20.00
40.00
60.00
80.00
100.00
0.00 5.00 10.00 15.00 20.00
mole of CO2/kg of absorbent
Tota
l equi
libriu
m p
ress
ure
(KP
a)
Loading (mol of CO2/kg absorbent) of various amines
0
4
8
12
16
30 50 70 90 110
Pequilibrium (KPa)
CO
2 m
ole
frac
tion
(x1
000)
[emim]etOSO3
[emim]etOSO3 + 7.0% w/w ZnBr2
[emim]etOSO3 + 7.0% w/w sugar
[bmim]BF4
Effect of additive on the CO2 absorption capacity of simple ILs
0.0
20.0
40.0
60.0
80.0
0.0 0.4 0.8 1.2 1.6 2.0 2.4a (mol CO2/mol absorbent)
Tota
l Equi
libriu
m P
ress
ure
(KP
a)
0.0
20.0
40.0
60.0
80.0
0.0 0.4 0.8 1.2 1.6 2.0 2.4
a (mol CO2/mol absorbent)2mL MDEA + 3mL H2O 1mL MDEA + 4mL H2O5mL 23.08%wt K2CO3/H2O 5mL 4.76%wt 2- methylimidazole/H2O5mL 4.76%wt Naglycine/H2O 5mL 4.76%wt 1,2- dimethylimidazole/H2O5mL 4.76%wt MEA/H2O 5mL 9.09%wt guan- car/H2O5mL 4.76%wt DMEA/H2O 1mL DMEA + 4mL H2O4mL 4.76%wt DAP + 1 mL DMEA 5mL 4.76%wt DAP
0.0
20.0
40.0
60.0
80.0
0.0 0.4 0.8 1.2 1.6 2.0 2.4
a (mol CO2/mol absorbent)2mL MDEA + 3mL H2O 1mL MDEA + 4mL H2O5mL 23.08%wt K2CO3/H2O 5mL 4.76%wt 2- methylimidazole/H2O5mL 4.76%wt Naglycine/H2O 5mL 4.76%wt 1,2- dimethylimidazole/H2O5mL 4.76%wt MEA/H2O 5mL 9.09%wt guan- car/H2O5mL 4.76%wt DMEA/H2O 1mL DMEA + 4mL H2O4mL 4.76%wt DAP + 1 mL DMEA 5mL 4.76%wt DAP
0.00
20.00
40.00
60.00
80.00
100.00
0.00 5.00 10.00 15.00 20.00
1mL MDEA + 4mL H2O 5mL 23.08%wt K2CO3/H2O5mL 4.76%wt 2- methylimidazole/H2O 5mL 4.76%wt Naglycine/H2O5mL 4.76%wt imidazole/H2O 5mL 4.76%wt 1,2- dimethylimidazole/H2O5mL 4.76%wt guanidine carbonate/H2O 5mL 4.76%wt MEA/H2O5mL 4.76%wt DMEA/H2O 1mL DMEA + 4mL H2O5mL 4.76%wt DAP
Capacity (mol of CO2/mol absorbent) of various amines
Experimental Validation of CO2 solubility test (15.3%wt. MEA)
0
20
40
60
80
100
120
140
160
0.4 0.5 0.6 0.7Capacity (mol CO2/mol of MEA)
PC
O2 e
qui
libriu
m (
KP
a)
J ones et al; J Chem Eng Data4(1959)85Shen et al; J Chem Eng Data 37(1992)96Song et al; J Chem Eng Data 41(1996)497This work
Year Assigned Project
2008
Amine-based absorber development using commercially available unique amines
1 2 3 4 5 6 7 8 9 10
2010CO2 separation using facilitated transport membrane
11 12
Proposal & Schedule (3 years basis)
2009
Introduction of novel CO2 absorbentsPoly(amines)ILs & Poly(ILs)
1st report 2nd report 3rd report
Synthesis of materials
Characterization &mechanism studies
CO2 absorption investigations
Rapid screening
New reactor design
Thermodynamics &kinetics studies
Physical & chemical properties
1st report 2nd report 3rd report
Membraneselection & development
Transport & Kinetics Study
1st report 2nd report 3rd report
Evaluation
Evaluation
Evaluation
Thank You