Amine-Functionalized Ceramic Materials for
Enhanced Gas Absorption
Jerimiah C. Forsythe
April 23, 2012
Introduction: The CO2 Problem
Power generation by fuel type in the United States:
Base Case 2009
Oil
1%
Reference Case 2030
Natural Gas
23%
Coal
45%
Coal
44%
Oil
1%
Nuclear
20%
Renewable
11%
Other
0%
2009 CO2 emissions by fuel type:
Coal
34%
Natural Gas
23%
Nuclear
18%
Other
0%
Renewable
14%
Overall power requirements for the US:
Oil
43%
313 GW of power produced
600 coal-fired power plants in the US
~ 850 million tons of coal burned annually
Natural Gas
23%
DOE/NETL CO2 Capture Update, May 2011
http://www.eia.gov/tools/faqs, Accessed April 2012
~ 4 million L of CO2 produced annually
1
Introduction: The CO2 Problem
280 ppm CO2 from pre-industrial ages (1832)
1.9 ppm CO2 average increase per year
Projected CO2 for 2030: 420 ppm
Clearly, we will be producing CO2 for the long-term to meet our energy demands
We need systems in place to assist in addressing the overall CO2 concentrations in
the immediate future
http://www.eia.gov/tools/faqs, Accessed April 2012
http://www.esrl.noaa.gov/gmd/ccgg/trends/, Accessed April 2012
2
Flue Gas Composition and Regulations
Component
N2
70%
CO2
13-16 %
H2O
5-7 %
O2
3-4 %
HCl
10-100 ppm
SO2
100-1200 ppm
SO3
1-40 ppm
NOx
300-1000 ppm
Hg
1 ppb
Fly Ash
10%
EPA issued ruling for removal in 4 years
Already removed before
entering exhaust stack
25 years for EPA to regulate Hg emissions from power plants, expected to increase price by
0.1 ¢ per KWh
EPA just issued regulations for CO2 emissions, final announcements on December 2012
Expected to double overall cost of electricity with current carbon capture technology
Lu, D. Y.; Granatstein, D. L.; Rose, D. J. Ind. Eng. Chem. Res. 2004, 43, 5400-5404
Granite, E. J., personal communication
3
Current CO2 Removal Systems
Post-combustion capture systems with aqueous solvent absorption
Comment solvents:
amines, carbonates, or
bicarbonates
Current amine standard:
Fluor’s Econamine using MEA
Monoethanolamine
(MEA)
Diglycolamine (DGA)
Diethanolamine (DEA)
Rapid reaction rate with CO2
Rapid reaction rate with CO2
Corrosive at 0.4 mol CO2 per 1
mol amine
Volatile, loss in absorber
overhead
pKa = 9.6
High heat (> 100 °C) required
for unloading
Corrosive at 0.4 mol CO2 per 1
mol amine
pKa = 8.6
Low volatility
Low reaction rates
Corrosive at 0.4 mol CO2 per 1
mol amine
pKa = 9.0
Outstanding issue of cost and
http://www.co2crc.com.au/aboutccs/cap_absorption.html, Accessed April 2012
corrosive nature of amines
4
Post-Combustion CO2 Capture Systems
Performer
Location
Capture
Technology
Capture Rate
Ton/yr
Start Date
NRG Energy
Thompsons,
TX
Amine
550,000
2015
American
Electric Power
New Haven,
WV
Chilled
Ammonia
1,650,000
2015
Mitsubishi Heavy Industries has been operating several carbon capture facilities on
natural gas using Kansai Mitsubishi Carbon Dioxide Recovery (KM-CDR) technology
with KS-1™
Test operations on 25 MW coal-fired plant in Al since 2011
Additional efforts in pre-combustion capture and oxy-combustion capture, coming
on-line between 2014-2016
DOE/NETL CO2 Capture Update, May 2011
http://www.mhi.co.jp/en/products/detail/km-cdr_process.html, Accessed April 2012
http://www.eia.gov/tools/faqs, Accessed April 2012
5
CO2 Absorption in Aqueous Systems
Carbonic acid formation and equilibria
CO2 + H2O
H2CO3
pKa at 25 °C =
6.352
–
pKa at 25 °C =
10.329
–
pKH2CO3 at 25 °C =
3.7
or above pH = 7 and 25 °C
CO2 +
HO–
HCO3
So, overall:
H2CO3 + B
HCO3 + HB
Predominate species in solution will be HCO3– at any pH ≥ 6
Two feasible pathways for amine with carbonic acid:
H2CO3 + RNH2
RNHCO2H + H2O
HCO3– + RNH2
RNHCO2– + H2O
Or...we can have direct interactions with CO2 (aq)
Gibbons, B. H. J. Biol. Chem. 1963, 238, 3502
McCann, N. J. Phys. Chem. A 2009, 113, 5022-5029
6
CO2 Absorption in Aqueous Systems
Three proposed interactions with amines:
1. Carbamate Intermediate1
2nd order reaction
R1R2NHCOOH
Carbamic acid formation rate
determing
–
+
R1R2NHCOO + BH
Rapid proton transfer assumed
CO2 + R1R2NH
R1R2NHCOOH + B
2. Zwitterion Intermediate2
CO2 + R1R2NH
R1R2NH+CO2–
R1R2NH+CO2– + B
R1R2NCO2– + BH+
Assumed rapid deprotonation
Mechanistically favored from kinetic
data
3. Single-Step3
R1R2NCO2– + BH+
Arstad, B. J. Phys. Chem. A 2007, 111, 1222-1228
McCann, N. J. Phys. Chem. A 2009, 113, 5022-5029
Termolecular reaction for carbamate
formation
B = base acting as proton
acceptor/donor (water or amine)
Reaction rates are very rapid with unstable
intermediates
Difficult to determine exact reaction mechanism
Carbamate product stable and easily detected
7
Project Aims and Goals
Primary Goal: To functionalize alumina foams with amines to enhance the absorption of CO2
by
solution based-amines
Specific Aim: What effect does calcinated α-alumina (Al2O3) have on our test system?
Specific Aim: What effect does APTES functionalized calcinated α-alumina (Al2O3) have on
our test
system?
Ultimate Goal: To insert functionalized alumina foams into the absorber for enhanced CO2
removal
8
Project Aims and Goals
Tower packing to increase gas-liquid surface area and gas absorption
Current use of either trays or packing material (e.g. Raschig Rings)
Type and design depends on application and solution viscosity, operating temperature, and
pressure conditions
However, if we can select a material that can accept functionalization by chemical groups, we
can enhance the surface properties and make the absorption process more effective
Alumina foam (Al2O3)
9
Instrumental Set-up
Mass Flow
Controller #2
Purge
0.8 L min-1
N2 Tank
N2 Purge
0.2 L min-1
0.2 L min-1
13% CO2/N2 Tank
“simulated flue
gas”
N2 Dilution
Mass Flow
Controller #1
Rotameter
Line
Purge Gas dispersion tube
Gas collection tube
Purge
1.0 L min-1
50-25 mL
Amine/Water solution
IR Detector
10
Bubbler System Trials
25 mL of 30% (w/w) DGA in water with 220 mL min-1 “simulated flue gas”
30% (w/w) DGA in water
Water “blank”
11
Bubbler System Trials
50 mL of 30% (w/w) DGA in water with 220 mL min-1 “simulated flue gas”
30% (w/w) DGA in water
+ 5 g alumina
+10 g alumina
α-alumina (Al2O3), calcinated, 125-350 mesh
pKa measured to be 5.5Alumina itself has an effect on the total loading of
CO2
Competition with amines for acid/base chemistry
12
Surface Functionalization with APTES
3% H2O in EtOH (v/v)
pH = 5.0, 5 min, RT
+
Hydrolysis
H-bond
formation
(3aminopropyl)triethoxysilane
(APTES)
Silanol
condensation
Condensation
- H 2O
EtOH wash, cure at
110 °C for 30 min.
2 hour
contact time
with 1.0 g of
Al2O3
powder
H-bond
formation with
surface -OH
groups
13
TGA Analysis
Ramp rate: 10 °C min-1 from 250 to 650 °C under Ar
CO2 Loss:
0.02 mg
Functionalized Alumina
Post-bubbler Alumina
CO2 Loss:
0.04 mg
APTES Loss:
0.04 mg
APTES Loss:
0.02 mg
Amine and water catalysis removing APTES from
14
APTES Functionalized Alumina
30% (w/w) DGA in water
+ 1 g APTES Alumina
+ 1 g alumina
15
Conclusions
Acidic alumina lowers the CO2 loading capacity of the DGA solutions due to acid/base
equilibria competition
APTES functionalization of alumina is ineffective for generating significant surface
coverages
APTES is easily removed from alumina surface by catalysis via water and amines
Future Work
Increase surface coverage of surface-bound amines while minimizing bond catalysis
by surrounding water/amine solution
Demonstrate effectiveness of surface amines in CO2 capture when coupled with
circulating amine solutions
16
Acknowledgments
Funding:
US Department of Energy (DOE)
Schlumberger
Prof. George Hirasaki
Prof. Michael Wong
Prof. Ed Billups
Sumedh Warudkar
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