Sengeløv, Louise With

Thomsen, Kaj

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Downloaded from orbit.dtu.dk on: Dec 18, 2017Phase Equilibrium in Amino Acid Salt Systems for CO2 CaptureSengeløv, Louise With; Thomsen, KajPublication date:2011Document VersionEarly version, also known as pre-printLink back to DTU OrbitCitation (APA):Sengeløv, L. W., & Thomsen, K. (2011). Phase Equilibrium in Amino Acid Salt Systems for CO2 Capture[Sound/Visual production (digital)]. WORKSHOP - Amino Acid Salts for CO2 Capture, Adminiet, Porsgrunn,Norway, 01/01/2011Phase Equilibrium in Amino Acid Salt Systems for CO2 CaptureLouise With Sengeløv and Kaj Thomsen (kth@kt.dtu.dk)Porsgrunn, February 3rd 2011Outline• General introduction• Experimental data  for amino acid salt systemsIntroduction • Methionine as a case study• Equilibrium constants• Vapor‐Liquid equilibrium dataCarbonate‐Methionine system• Freezing point depression data• Thermodynamic modelling• Absorber conditions• Desorber conditionsComparison of absorbents• Heat of desorption• Conclusion2IntroductionAdvantages in using amino acid salts instead of alkanolamines:• Might be less prone to degradation in oxygen rich environments• Less volatile than alkanolamines due to their ionic nature             • Same affinity towards CO2  as alkanolamines• Form carbamatesAmino acids participate in the transportation of CO2 in the blood b th f ti f b ty  e  orma on o  car ama eProblems and drawbacks:• More expensive• Limited solubility of amino acids in water• Limited amount of experimental data available in literature3Experimental data for amino acid salt solutions• CO Equilibrium data2– Potassium taurate – Kumar et al. (2003) 38 data points, T=25 and 40°C– Potassium glycinate (Portugal et al. 2009) 103 data points, T= 20‐50°C– Potassium methionate (Kumelan et al. 2010) 65 data points, T= 80‐120°C– Potassium sarcosinate (Aronu et al. 2010)  graph with 55 points, T=40‐120°C– Potassium prolinate (unpublished, DTU, UTwente)• Absorption kinetics– Kumar et al. (2003) (potassium salt of taurine and glycine)– Van Holst et al. 2009 (potassium salts of 7 different amino acids)– Prakash et al. 2010 (potassium salts of taurine and glycine)• Equilibrium constants– Sharma et al. 2003– Hamborg et al. 2007• Heat capacity and other thermal properties ‐ none• Freezing point depression data– Sengeløv (2010) (loaded and unloaded potassium salt of methionine)  20 data points ‐14 to 0°C4Methionine C H NO S,  5 11 2• Molar mass 149.21 g/mol• Decomposition temperature 281°C• Solubility in water at 25°C: 0.38 molal• pKa 2.28 and 9.21• Found in cereal grains and in nuts5Iso electric point of methionine‐    0.80.91Isoelectric point: 5,740.60.7pKa 2 28 pKa=9 210.40.5= , ,0 10.20.30.0 2 4 6 8 10 12pH6Solubility of methionine in water O and in NaCl solution X Hill and Robson, BiochemicalJournal,  28(1934)1008‐10137Potassium salt of methionine –Equilibrium constants• Sharma VK;  Zinger A;  Millero FJ;  De Stefano C; Dissociation constants of protonated methionine species in NaCl media, Biophysical Chemistry 105(2003)79‐87  , – Determined in temperature range 5 – 45°C• Hamborg ES;  Niederer JPM;  Versteeg GF; Dissociation constants and thermodynamic properties of amino acids used in CO2 absorption from (293 to 353) K, J. Chem. Eng. Data, 52(2007)2491‐2502 – Determined in temperature range 20 – 80°C• Equilibrium constant for the carbamate formation of methionine not available• Equilibrium constant for the protonated form of methioninenot relevant at pH above 6         8Potassium salt of methionine –experimental dataK l J Pé S l d K A M G S l bilit f• ume an ,  rez‐ a a o  amps ,  aurer  ,  o u y o  CO2 in Aqueous Solutions of Methionine and in Aqueous Solutions of (K2CO3 + Methionine), Ind. & Eng. Chem. Res. ( )49 2010 3910‐3918– VLE‐data for the system CO2‐H2O‐K2CO3‐Methionine at 80‐120°C– It corresponds to loaded solutions of potassium salt of                 methionine– Some precipitation in experiments at 80°C with 2.5 molal K2CO3and 0 83 molal methionine  .  • Sengeløv L., Bachelor Thesis, Technical University of Denmark, 2010– Freezing point depression data for potassium salt of methionineand for loaded solutions of this salt           978910aKumelan et al. (2010), 353KExtended UNIQUACExtended UNIQUAC, CO2 in waterWithout K2CO3353.15 K456essure in MPaResults for the CO2‐H2O‐ 0123Total prm(Met)=0.4826 mol/(kg H2O)K2CO3‐Methionine t910Kumelan et al. (2010), 353K0.83 molal Methionine2 5 molal K CO0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9m(CO2) in mol/(kg H2O)sys em(Eq. constant from Sharma et 678n MPaExtended UNIQUAC 353.1 KExtended UNIQUAC 353.1 K without methionine.     2 3al.)45otal pressure inKumelan et al. (2010), 373KExtended UNIQUAC 373.1 K123T o Extended UNIQUAC 373.1 K without methionineKumelan et al. (2010), 393K1001.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9m(CO2) in mol/(kg H2O)Extended UNIQUAC 393.1 KExtended UNIQUAC 393.1 K without methionineResults for the CO2‐H2O‐K2CO3‐Methionine system (Equilibrium constant from Sharma et al.)Pitzer model,Kumelan et al.910 Kumelan et al. (2010), 353K0.42 molal MethionineExtended UNIQUAC model 78Extended UNIQUAC 353 KExtended UNIQUAC 353 K without hi i1.27 molal K2CO356ressure in MPamet on neKumelan et al. (2010), 373KExtended UNIQUAC 373 K34Total prExtended UNIQUAC 373 K without methionineKumelan et al. (2010), 393K012 Extended UNIQUAC 393.1 KExtended UNIQUAC 393 1 K without0.8 1 1.2 1.4 1.6 1.8m(CO2) in mol/(kg H2O).      methioninem(K2CO3)≈1.27 mol/(kg H2O) & m(Met) ≈0.42 mol/(kg H2O)11Measurements of freezing point depressions for mixtures of 1:1 (mole ratio) aqueous Met KOH and 1:3 (mole ratio) aqueous      ‐            Met‐K2CO312Freezing point depressions: Results and model correlation (Equilibrium constant from Sharma et al.)‐11mol ratio methionine:K2CO3 1:3‐7‐5‐3ng point in °C‐13‐11‐9FreezinExperimentalExtended UNIQUAC0‐150 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9m (Potassium salt of methionine) in mol/(kg H2O)‐3‐2‐1oint in °Cmol ratio methionine:KOH   1:1‐5‐4Freezing poExperimentalExtended UNIQUAC13‐7‐60 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6m(potassium salt of methionine) in mol/(kg H2O)The potassium salt of methionine as an absorbent in post‐combustion contra MEA, MDEA and K2CO31 l l b b t 30 °C 2 l l b b t 30 °CAbsorberconditions22.53f CO2in kPa mo a a sor en ,   MDEAPotassiumcarbonateP t i lt f456f CO2in kPa mo a a sor en ,   MDEAPotassiumcarbonateEquilibrium constant fromSharma et al.11.5artial pressure of o ass um sa  o  methionineMEA23artial pressure ofPotassium salt of methionineMEA   00.50 0.1 0.2 0.3 0.4 0.5PaCO2 loading010 0.1 0.2 0.3 0.4 0.5PaCO2 loading2.532in kPa MDEAPotassiumcarbonate1 molal absorbent, 30 °C56n kPaMDEAPotassiumcarbonate2 molal absorbent, 30 °CEquilibrium1.52l pressure of CO2Potassium salt of MethionineMEA 34pressure of CO2iPotassium salt of MethionineMEAconstant fromHamborg et al.00.51Partia012Partial p140 0.1 0.2 0.3 0.4 0.5CO2 loading0 0.1 0.2 0.3 0.4 0.5CO2 loadingThe potassium salt of methionine as an absorbent in post‐combustion contra MEA, MDEA and K2CO3Desorberconditions12001400PaPotassium salt of methionine1 molal absorbent, 115 °C8000900010000kPa Potassium salt of 2 molal absorbent, 115 °CEquilibrium constant fromSharma et al 6008001000ssure of CO2in kP      MDEAMEA4000500060007000ssure of CO2in k methionineMDEAMEAPotassiumcarbonate    .200400Partial presPotassiumcarbonate100020003000Partial pre00 0.1 0.2 0.3 0.4 0.5CO2 loading00 0.1 0.2 0.3 0.4 0.5CO2 loading3330)    1 molal absorbent 115 °C 4330) 2 molal absorbent 115 °C23302830kg CO2captured)  ,   Potassium salt of methionineMEAMDEA 283033303830kg CO2captured)   ,   Potassium salt of methionineMEAMDEA83013301830f reactionin kJ/(kPotassiumcarbonate133018302330f reaction in kJ/(kPotassiumcarbonate153300 0.2 0.4 0.6 0.8 1Heat ofCO2 loading3308300 0.2 0.4 0.6 0.8Heat ofCO2 loadingThe potassium salt of methionine as an absorbent in post‐combustion contra MEA, MDEA and K2CO3Desorberconditions7008009001000in kPa Potassium salt of methionineMDEA1 molal absorbent, 115 °C300035004000in kPaPotassium salt of methionineMDEA2 molal absorbent, 115 °CEquilibrium constant fromHamborg et al400500600pressure of CO2MEAPotassiumcarbonate150020002500pressure of CO2iMEAPotassiumcarbonate  .0100200300Partial 05001000Partial 0 0.1 0.2 0.3 0.4 0.5CO2 loading0 0.1 0.2 0.3 0.4 0.5CO2 loading19002100)1 molal absorbent, 115 °CPotassium salt of methionine2600ed)2 molal absorbent, 115 °CPotassium salt of 130015001700/(kg CO2captured)MEAMDEAPotassiumcarbonate2100kJ/(kg CO2caputre methionineMEAMDEAPotassiumcarbonate7009001100at of reaction in kJ/11001600Heat of reaction in 163005000 0.2 0.4 0.6 0.8 1HeaCO2 loading6000 0.2 0.4 0.6 0.8HCO2 loadingConclusion I • The extreme difference between the properties of the potassium salt of methionine at absorber conditions and at desorber conditions indicates:– A strong temperature dependence of the equilibrium constant of methionine– Acidic properties of methionine strongest at desorber temperature• Portugal et al. found that the carbon dioxide solubility in potassium glycinate did not change much in the temperature range investigated (20‐50°C)17Conclusion II • Due to the limited amount of experimental data available, it is possible to model CO2 solubility in amino acid salt solutions without taking carbamateformation into account• The potassium salt of methionine seems to have very interesting                 properties for post‐combustion usage. However VLE‐data at absorber column conditions are needed to validate the results• The limited solubility and risk of precipitation provide challenges in the                     use of the potassium salt of methionine and must be investigated further– The 2 molal solutions for which calculations were shown here might be precipitating! • More research is required to clarify the role of methionine in the absorption process: Especially regarding carbamate formation and kineticsM h h i i d i id l l i Th h• uc  more researc   s requ re  on am no ac  sa t so ut ons.  ey  ave very interesting properties and could be real alternatives to alkanolamines.18

Phase Equilibrium in Amino Acid Salt Systems for CO2 Capture

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Phase Equilibrium in Amino Acid Salt Systems for CO2 Capture

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