Departamento de Ingeniería Química y Quíáímica Inorgánica Universidad de Cantabria (SPAIN) IONIC LIQUIDS FOR CARBON DIOXIDE CAPTURE: PROCESS SELECTION ALBO Jonathan, CRISTOBAL Jorge and IRABIEN Ángel ICEPE 2011 – 2nd International Conference on Energy Process Engineering. Efficient Carbon Capture for Coal Power Plants June 20 – 22, 2011, Frankfurt/Main – Germany 0. Research group 010.1. L oca tion: CANTABRIA SANTANDER SPAIN 0.2. SOSPROCAN DEPRO Group: Development of Chemical Processes and Pollution Control Group UNIVERSITY OF CANTABRIA E.T.S de Ingenieros Industriales y de Telecomunicación Dpto Ingeniería Química y Química Inorgánica Tel: 942 20 15 90 Fax: 942 20 15 91 http://departamentos.unican.es/quimica/ 1/21 1. Introduction Motivation Carbon dioxide (CO2) is one of the major contributors to climate change Electricity generation: 41% of world total CO2 emissions Europe – 1365.94 mmTCO Europe: 30 % of the electricity from coal 2 World - 12064.64 mmTCO2 Separation/Concentration of CO2 in fossil fuel combustion is required to mitigate climate change 2/21 1. Introduction 1.3. Recovery of CO2 by dispersive absorption (Amine- based scrubbing ) Drops dragging Flue gas Solvent volatilization Amines Amines + CO2 (≈90% Eff . ) Total solvent losses: Residual Gas 15 vol.% CO 2 1.5 Kg MEA/1 tonne CO2 captured (38ºC) 3/21 1. Introduction 1.3. Recovery of CO2 by dispersive absorption (Amine- based scrubbing ) Environmental, socia High dependence between streams (G and L) landeconomic Bigger equipment drawbacks Solvent evaporation and drops dragging (loss of solvent and air pollution) Amines as absorption liquid: Toxicity solvent SlSolven tlosses avoide d inprocessitintensifi ifided - Drops dragging avoided: membrane contactor - Solvent evaporation avoided: ionic liquid ZERO SOLVENT EMISSION PROCESS Luis,P., Garea, A., Irabien, A. J. Membrane Sci ,2009 4/21 1. Introduction 1.4. Process intensification I. Equipment changes: NON-DISPERSIVE ABSORPTION Independent control of gas and liquid flow rates Advantages LdkLarger and known gas-liquid i nt erf aci al area Avoid solvent drops dragging Gas Polypropylene Liquid Bulk of gas Boundary layer membrane boundary layer Bulk of liquid CO ,g C 2 * C CO2,g * C CO2,l CCO2,ll ≈ 0 C´CO2,g Solvent volatilization 5/21 1. Introduction II. Solvent changes: LIQUIDS WITH LOW VAPOR PRESSURE (e.g. Ionic Liquids) Avoid solvent evaporation Advantages Specific solvent for specific applications: e.g. tailor-made ionic liquids for CO2 recovery Organic salts with negligible vapour pressure Avoid solvent evaporation RTIL: Room Temperature Ionic Liquids Cations: Melting point< Room Temperature 5 2 3 1 1 3 2 Imidazolium (IM) Pyridinium (Py) Structure: cation – anion etc… Anions Cl, BR, BF4, PF6,FeCl4 CH3SO4, C2H5SO4…. Product design according to the requirements Tailor-made ionic liquids 6/21 1. Introduction Experimental setup N2 1. Hollow Fibre Module (Gas-Liquid 1 Contactor, Liquicel, USA) Membrane material polypropylene [EMIM][EtSO4] Fibre o.d., m 3·10-4 ations itions Composition of CO2 8.7 to 41 cc -4 dd Fibre i.d ., m 22102.2·10 fdfeed gas s tream, N2 Rest to blbalance Fibre length, m 0.115 vol.% Number of fibres 2300 Temperature, K 287± 1 ting con le specifi -1 2 aa Gas flow rate, LLmin·min 0.01 uu Effective membrane area, m 0180.18 -1 Membrane pore diameter, µm 0.04 Liquid flow rate, L·min 0.05 Mod Oper 7/21 1. Introduction ItIntens ifitiification of CO2 non-dispers ive abtibsorption: The overall mass transfer coefficient, Koverall: ∆ylm ⋅ PT N = K overall ⋅ CO2 ,g R ⋅T 1,5E-07 Diethanolamine (DEA) -1 -7 NCO2(l)·R·T·PT = 3,690·10 . ∆γlm (-) 2 -1 ) 1,3E-07 R = 0, 9932 Koverall (m·s ) -1 ~3·10-7 (m·s 1,0E-07 -1 T [2] Rongwong W., et al. Sep.Purif. ·T·P 7,5E-08 R R Technol., 2009. · CO2(g) 5,0E-08 Amines N 2,5E-08 0,0E+00 0,0E+00 4,0E-02 8,0E-02 1,2E-01 1,6E-01 2,0E-01 2,4E-01 2,8E-01 3,2E-01 3,6E-01 Ionic liquid ∆γlm (-) 1-Ethyl-3-methylimidazolium -1 ethylsulfate Gas feed composition Koverall (m·s ) -7 ([EMIM][EtSO4] or EMISE) 8.7 – 41 vol.% CO2 / N2 (3,69 ± 0,18)·10 [1] Albo et al., Ind. Eng. Chem. Res. 49, 11045-11051, 2010. 8/21 1. Introduction Ionic liquids (ILs) are compounds of high interest for industry because of their attractive properties as solvents. Experimental CO2 solubility of gases on ILs is required but.. Need to evaluate their properties by estimative methods Estimation by means of structure- Effect of different combinations of activity method (QSARs) groups in the CO2 solubility on ionic liquids Group contribution methods have been applied previously to predict ionic liquids properties, among them… TiiToxicity est imat ion wi ihVibifihth Vibrio fischery usi ng mol ecul ldar descri ptors [3] Luis P. et al., Ecotox. Environ. Safety. 67, 423-429, 2007. Ionic liquids water solubility in terms of anion/cation hydrophobicity [4] Rankes et al., Int. J. Mol. Sci. 10 (3), 1271-1289, 2009. Conductivities, Viscosities, Ostwald solubility and partition coefficient [5] Yansheng et al., Progress in Chemiestry. 21 (09), 1772-1781, 2009. 9/21 Aim Design a Tailor-made ionic liquid for CO2 capture Specific aims: Property estimation by a database including experimental values of CO2 solubility reporting in literature Evaluation of operating conditions influence on the process Stu dyof cation /an ion stttructure iflinfluence on solubilit y Santander, 2010 2. Methodology 2.1. Database Composed of CO2 solubility experimental values from literature Number of data: 4.843 Minimum Maximum s cc Solubility (%wt) 0.014 70.242 cteristi Pressure (bars) 0.09 946 aa Temperature (ºC) 5 300 a char tt Da Cations Anions Ionic liquids 3 x 29 = 1015 5 11/21 3. Results 313.1. Pressure Pressureinfluenceonsolubility influence on solubility Cation Anion Nitrate ([NO3]) Dicyanamide ([DCA]) 1-Butyl-3-methylimidazolium ([bmim]) Tetrafluoroborate ([BF4]) Hexafluorophosphate ([PF6]) ct Trifluoromethanesulfonate ([TfO]) ee Bis(trifluoromethylsulfonyl) ([Tf2N]) 70,0 [bmim] [NO3] [bmim] [BF4] ion eff 60,0 [bm im ] [DCA] 50,0 [bmim] [TfO] An [bmim] [PF6] Favorable interactions (bar) 40,0 [bmim] [Tf2N] ure 30,0 fluoroalkyl-CO ss 2 20,0 Pres Increased size of the anion 10,0 0,0 [6] S.N.V.K.Aki et al., J. Phys. Chem. B, 108, 20355- 0,00 0,20 0,40 0,60 0,80 20365, 2004. Mole fraction (x) 12/21 3. Results 3.1. Pressure influence on solubility Cation Anion ([hmim]) ([C5mim]) Bis(trifluoromethylsulfonyl) ([Tf2N]) ([dmim]) ([emim]) ([C6H4F9mim]) ect ff ([C8H4F13mim]) 50 ion ef 45 [hmim] [Tf2N] tt Less s iign ificant th an th e ani on 40 [C5mim] [Tf2N] [dmim] [Tf2N] effect Ca 35 [emim] [Tf2N] (bar) 30 25 [C6H4F9mim] [Tf2N] ure Solubility ss P 20 [C8H4F13mim] [Tf2N] Pres 15 10 5 0 [7] P.J. Carvalho et al, J. Phys. Chem. B, 113, 6803- 6812, 2009. 0,0 0,2 0,4 0,6 0,8 [8] M.J. Muldoon et al., J. Phys. Chem. B, 111, 9001- Mole fraction (x) 9009, 2007. 13/21 3. Results 3.2. Temperature influence on solubility Tª Solubility Cation selection is less significant than the anion selection Anion effect Cation effect This negative influence is more evident at higher mole fractions of CO2 14/21 3. Results 3.3. Quantitative analysis Database is restricted for a quantitative analysis at the range of possible operating conditions of CCS Number of data 64 So lu bility = H⋅ P Solubility (H) 0.003-0.85 abase tt Pressure (bars) 1-50 CS Da CC Temperature (C) (ºC) 25 (A1, A2…, C1, C2…) Linear regression Descriptors: Presence/ absence anion QSAR Analysis (A) and cation (C) 15/21 3. Results 3.4. Influence on Cation/Anion structure Cation/Anion on 3.4. Influence ‐ ‐ 0,5 0 0,5 0,5 ‐ ‐ ,5 0 1 1 0 1 1 Vinvbenzyl trimethylammonium [VBTMA] [p-VBTMA] trimethylammonium CATIONS: Hexafluorophosphate [PF6] bis(trifluoromethylsulfonyl) [Tf2N] trifluorophosphate[FEP] ANIONS: Ac (ETO)2IM BF4 bhea CiC Anions CH3SO4 bmim at tris(heptafluoroethyl) trimethylammonium i (p-vinybenzyl) (p-vinybenzyl) Cl bmpy ons dca C5mim EtSO4 C6H4F9mim FEP C8H4F13mim bFEP DMFH [Tf2N] pFEP dmim FOR [VBTMA] emim IAAC ETT ISB he lactate hea LEV hemim MDEGSO4 hheme [DMFH] CATIONS: NO3 ANIONS: hmim PF6 hmmim PRO hmpy SCN Thyocynate [SCN] Thyocynate omim N,N-dimethylformamidium N,N-dimethylformamidium SUC Tf2N TBP TFA thea TFES THTDP TfO VBTMA TMA P(VTMA) 16/21 3. Results 3. 5. Process operating conditions 1.2 bar 370ºC 40ºC CO2 PRODUCT P Solubility COMPRESSION 130 bar CO2 solubility at 40ºC and real process pressures Solvent Pressure Solubility (X) Ratio IL/MEA MEA (22.7 wt%) 0.639 [bmim][PF6] 1.2 0.11 0.17 ns rocess oo [bmim][Tf N] 0190.19 030.3 pp 2 MEA (22.7 wt%) 1.159 conditi [bmim][PF6] 130 0.89 0.77 S real CC C [bmim][Tf2N] 10.87 [9] Vranchos et al., Ind. Eng. Chem. Res. 45 (14), 5148-5154, 2006. 17/21 4. General conclusions CO2 recovery: - Selective absorption using organic solvents (e.g. amines) on equipment based on dispersive absorption (e .g . scrubbers) Since a direct contact between gas and liquid phases takes place: - Drops dragging SOLVENT LOSSES - Solvent volatilization Development of tailor made ionic liquids for CO2 recovery: Process intensification: -Cation selection result of less significance when designing the IL 1. Substitution of conventional equitipment for amembrane didevice - Inclusion of fluorinated groups in the IL structure increase solubility value ZERO SOLVENT EMISSION 2 PROCESS - ILscould become strong competitor of MEA at high pressures 2. Substitution of the absorption Ongoing research: Magnetic Ionic solvent for ionic liquids Liquids (MILs) 18/21 5.