Theoretical Calculation of Enthalpy of reactions

involved in PZ-CO2-H2O system at infinite dilution

Mayuri Guptaa, Eirik Falck da Silvab, Ardi Hartonoa, Hallvard F. Svendsena

aDepartment of Chemical Engineering, Norwegian University of Science and Technology, Trondheim, Norway bDepartment of Process Technology, SINTEF Materials and Chemistry, Trondheim, Norway

IEAGHG 2nd Post Combustion Capture Conference (PCCC2) September 17-20, 2013.

Bergen, Norway.

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Outline

1. Introduction 2. Thermodynamic Framework Heat of Absorption 3. Computational Details 4. Results Dissociation constants and Enthalpy of Protonation (MEA, PZ) Carbamate Formation Reaction (MEA, PZ) Protonated Carbamate Formation Reaction Dicarbamate Formation Reaction Heat of absorption at Infinite loading and infinitely Dilute

solution 5. Conclusions and Future Work

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Introduction

1. Temperature dependant Enthalpy (PZ-CO2-H2O) Deprotonation Reaction Carbamate Formation reaction Protonated Carbamate Formation Reaction Dicarbamate Formation Reaction Overall enthalpy Infinite dilution 2. Gibbs Helmholtz Equation 3. Experimental Data

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Thermodynamic Framework

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Weiland, R. H.; Chakravarty, T.; Mather, A. E. Ind Eng Chem Res 1993, 32, 1419.

Gupta, M.; da Silva, E. F.; Svendsen, H. F. J Phys Chem B 2012, 116, 1865.

P.W. Atkins (1978). Physical chemistry. Oxford University Press. ISBN 0-198-55148-7.

Edwards, T. J.; Maurer, G.; Newman, J.;

Prausnitz, J. M. Aiche J 1978, 24, 966.

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Aqueous Phase Chemical Equilibrium

Kamps, A. P. S.; Balaban, A.; Jodecke, M.; Kuranov, G.; Smirnova, N. A.; Maurer, G. Ind Eng Chem Res 2001, 40, 696.

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Computational Details

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Gas phase calculations and geometry optimizations were carried out using AM1 and Density Functional Theory (DFT) at B3LYP/6-311++G (d, p)//B3LYP-6-311++G (d, p) level. Composite methods(G3MP2B3, G3MP2, CBS-QB3, G4MP2) are also used.

All PCM1 and SM8T1 calculations were done using

Density Functional Theory (DFT) at SM8T/B3LYP/6-311++G (d, p)//B3LYP-6-311++G (d, p) level.

ESS

*Ref: 1Tomasi, J.; Miertus, S.; Scrocco, E.;Chem. Phys. 1981, 55, 117-129. 2Chamberlin, A. C.; Cramer, C. J.; Truhlar, D. G. J. Phys. Chem. B. 2008, 112, 3024-3039.

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Continuum Solvation Model (PCM)

s electrostatic cavitation van der WaalsG G G GD = D + D + D

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Solvation Model 8 (SM8)

ε

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∆GS T0( ) = ∆GENP T0( )+GCDS T0( )

change in the solute free energy due to electrostatic interactions between the solute and the bulk solvent and distortion of the solute’s electronic structure in solution

The solvent is modeled as a dielectric continuum.

Solvation Model 8 (SM8)

Electronic Nuclear Polarization

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Solvation Model 8 (SM8)

∆GS T0( ) = ∆GENP T0( )+GCDS T0( )

non-bulk electrostatic contributions to the free energy of hydration: first solvation shell effects

The GCDS term is a parameterized term intended to minimize the deviation between the predictions and experiment.

It involves atomic surface tensions.

Cavitation Dispersion Structure

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ESS (Explicit Solvation Shell model) Developed for ionic solutes

Solvent molecules extracted from classical simulations Interaction energies with 5 solvent molecules calculated at Hartree-Fock level This cluster is inserted into a continuum solvation model ref: Silva, Svendsen and Merz J.Phys. Chem. A 2009

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Most Stable ESS Clusters Obtained

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Results

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pKa

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pKa values determination using computational chemistry

• The calculations of pKa values are based on following thermodynamic cycle

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The pKa values are calculated as

*

ln(10)aqG

pKaRT

∆=

N products N reactants* * * *

, ,1 1

aq gas i solv i j solv ji j

G G n G n G= =

∆ = ∆ + ∆ − ∆∑ ∑AH (aq) A ( ) ( )aq H aq− +→ +

* 0 * * * *( ) ( ) ( ) ( ) ( )aq gas s s sG AH G AH G A G AH G H G− + °∆ = ∆ + ∆ − ∆ + ∆ + ∆

0 0 0 0( ) ( ) ( )gas gas gas gasG G A G H G AH− +∆ = + −** ln(24.46)G RT∆ =

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Temperature Depndency of pKa

• Model 1:

• Model 2:

T calc,T(pKa) =(pKa) +correctionfactor1

* *aq T aq calc,T(” G ) =(” G ) +correctionfactor2

*Ref: Gupta, M. da silva, E. F. Svendsen, H. F. J. Phys. Chem. B, 2012, 116 (6), 1865–1875.

Correction factors

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Dissociation constants (a) and Enthalpies of deprotonation (b) for MEA as function of temperature compared with available literature data.

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First Dissociation constant (a) and Enthalpies of deprotonation (b) for Diprotonated Piperazine as function of temperature compared with available literature data.

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First Dissociation constant (a) and Enthalpies of deprotonation (b) for Protonated Piperazine as function of temperature compared with available literature data.

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Carbamate Stability Constants (Kc)

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Carbamate Stability Constants

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Gupta, M.; da Silva, E. F.; Svendsen, H. F. J Phys Chem B 2012, 116, 1865.

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Heats of each of the individual reactions of PZ-CO2-H2O system as a function of Temperature at infinite dilution and infinitely low loading of CO2.

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Conclusions Results from determining the temperature dependency of enthalpy of absorption

of CO2 in PZ show that computational chemistry provides a good tool for screening solvents for PCC where experimental data for enthalpy values are scattered or missing.

One main finding of this work is that from the fundamental Gibbs Helmholtz equation it is shown that the enthalpy of absorption of CO2 in PZ solutions is temperature dependent.

Computational chemistry is a powerful tool to provide temperature dependencies for the various equilibrium constants for amines and alkanolamines where experimental determination is difficult, such as the carbamate and deprotonation constants at higher temperatures.

Methods and correlations given in this work can be used in future fitting models to predict the absorption of CO2 into other amines and alkanolamines important for CO2 capture processes.

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Acknowledgements

• Financial support from Aker Clean Carbon, the Research Council of Norway, Gassnova, EON and Scottish Power through the CLIMIT program SOLVit project is greatly acknowledged

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Acknowledgement

The work is done under the SOLVit project, performed under the strategic Norwegian research program CLIMIT.

The authors acknowledge the partners in SOLVit,

Aker Clean Carbon, Gassnova, EON, EnBW and the Research Council of Norway for their support.

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