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