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 17