n - PATh :.: Process and Product Applied Thermodynamics research ...

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General Introduction In 1996, a method based on molecular descriptors was proposed to predict a host of unknown physicochemical properties of perfluoroalkanes (Gabriel et al., 1996). The input parameters were categorized as empiric properties, geometric indices, or quantum mechanical descriptors and then, individual algorithms were developed for each independent variable function, namely, oxygen solubility, log P, vapour pressure, viscosity, and density. Those algorithms were expected to assist in the prediction of the physical properties of perfluoroalkane liquids, such that the design of new perfluoroalkanes and selection from currently available perfluoroalkane liquids could be optimised for each application (Gabriel et al., 1996). Modelling of the thermodynamic properties of pure perfluoroalkanes and their mixtures in an extended range of thermodynamic conditions is a recent research field. Since 1998, essentially molecular simulation and different versions of the SAFT equation of state (EoS) are being used to model perfluoroalkanes and their mixtures. Table I.3 resumes literature data available mentioning the method and the systems used by the different authors. These works helped to elucidate some questions relating perfluoroalkanes and their behaviour but new questions/discussions appeared and there are still many aspects to elucidate. This work intends to be a contribution in the effort devoted to the characterization of perfluoroalkanes and their mixtures. Recent publications relating perfluoroalkanes systems apply different approaches to describe their properties but the conclusions taken cannot be generalized once experimental data is not available to confirm their accuracy and applicability. The main objective is to complement/validate experimental data available in the literature and also present new experimental data that, besides the practical direct interest, can help to answer/validate the theories and models relating highly fluorinated systems. The thesis is organized in two parts. The first part deals with the experimental data measured: density, vapour pressure, solubility of gases, namely oxygen at atmospheric pressure and carbon dioxide at high pressure and liquid-liquid equilibrium for alkane + perfluoroalkanes mixtures. The apparatus built to measure vapour pressure and oxygen solubility data are presented as well as the experimental procedure used. Among the studied perfluoroalkanes are the ones that are currently been used for the applications - 13 -
General Introduction Table I.3. Literature data relative to the modelling of thermodynamic properties of pure perfluoroalkanes and their mixtures. PFC = Perfluoroalkane; HC = Alkane; MC = Monte Carlo; MD = Molecular Dynamics System Modelling Reference PFC (C1-C4) + HC (C1-C8) SAFT - VR McCabe et al., 1998 Pure PFCs C5 - C16 Molecular Simulation: MC Cui et al., 1998 CO2 + C6H14 CO2 + C6F14 Molecular Simulation: MC Cui et al., 1999 Xe + PFC (C1-C2) SAFT - VR McCabe et al., 2001 Xe + C6H14 Xe + C6F14 Molecular Simulation: MD SAFT – VR Bonifácio et al., 2002 PFC + HC Molecular Simulation: MD Song et al. 2003 CO2 + C6H14 CO2 + C6F14 O2 + C6H14 O2 + C6F14 Molecular Simulation: MD Gomes and Pádua, 2003 Molecular Simulation: MD Dias et al. 2003 Pure PFCs (C4-C7) Molecular Simulation: MD McCabe et al., 2003 CO2 + HC (C6-C8) CO2 + PFC (C6-C7) O2, CO2, H2O + Substituted PFCs SAFT - VR Colina et al., 2004 Molecular Simulation: MD Deschamps et al., 2004 Pure PFCs (C6; C9) Cubic EoS Piñeiro et al., 2004 CO2 + HC (C6-C13) + PFC (C6-C8) CO2 + HC (C6;C10) + PFC (C6;C10) SAFT - VR Colina and Gubbins, 2005 Molecular Simulation: MC Zang and Siepman, 2005 PFC (C5-C8) + HC (C5-C8) SAFT - VR Morgado et al. 2005 mentioned above, as is the case of perfluoro-n-hexane, perfluoro-n-octane, perfluorodecalin and 1Br-perfluoro-n-octane. The second part addresses the thermodynamic modelling of the properties and solubilities measured. In this work, the soft-SAFT equation of state (EoS) is used to study the behaviour of bulk properties of fluid systems at thermodynamic equilibrium, mainly vapour-liquid equilibria, but also liquid-liquid coexistence and critical behaviour. The main difference between the soft-SAFT EoS and the other SAFT versions is that the reference - 14 -
Page 1 and 2: Ana Maria Antunes Dias Universidade
Page 3 and 4: o júri presidente Prof. Dr. Joaqui
Page 5 and 6: palavras-chave resumo perfluoroalca
Page 7 and 8: Contents Notation List of Tables Li
Page 9 and 10: Notation Abbreviations AAD EoS LCST
Page 11 and 12: List of Tables Table I.1 Average Bo
Page 13 and 14: Table III.6 Adjusted Binary Paramet
Page 15 and 16: Figure II.9 Comparison between corr
Page 17 and 18: Figure III.8 Temperature-density di
Page 19 and 20: Figure III.25 Vapor-phase mole frac
Page 21 and 22: I.1. Fluorine Properties General In
Page 23 and 24: Table I.2. Physicochemical Properti
Page 25 and 26: General Introduction order to compa
Page 27 and 28: General Introduction the numerous a
Page 29 and 30: General Introduction carbon dioxide
Page 31: General Introduction animals. That
Page 35 and 36: References General Introduction Ban
Page 37 and 38: General Introduction Hildebrand, J.
Page 39 and 40: General Introduction Rowinsky EK. N
Page 41 and 42: II. Part EXPERIMENTAL METHODS, RESU
Page 43 and 44: Experimental Methods, Results and D
Page 49 and 50: Table II.3. (continued) T K ρexp g
Page 51 and 52: ρ / g.cm-3 1.750 1.730 1.710 1.690
Page 55 and 56: I. 3. Vapour pressure I.3.1. Biblio
Page 57 and 58: I.3.2. Apparatus and Procedure Expe
Page 59 and 60: I.3.3. Experimental Results and Dis
Page 63 and 64: Table II.8. (continued) T K Pexp kP
Page 67 and 68: ΔH vap = TΔS vap 2⎛ d ln P ⎞
Page 69 and 70: I.4. Solubility at atmospheric pres
Page 79 and 80: x2 (T,P2) 7.0E-03 6.0E-03 5.0E-03 4
Page 81 and 82: L 2,1 0.70 0.60 0.50 0.40 0.30 285
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Experimental Methods, Results and D
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Page 87 and 88:
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P / MPa 6 5 4 3 2 1 0 P / MPa 14 12
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II.6. Liquid - Liquid Equilibrium I
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0 τ β Δ1 2Δ1 [ 1+ B τ + B τ +
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References Experimental Methods, Re
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III.1. Introduction Modeling Most c
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Modeling The pioneering work of Wer
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III.2. Soft-SAFT Model Modeling A S
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Modeling The equation of state is w
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Chain Term Modeling Originally Wert
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Modeling The model is easily extend
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( ) ( ) ∑∑∑ 3 2 2 2 2 qq 32π
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Modeling HRT is a promising theory,
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( ρ) ρ , 0 ≤ ρ ( ρ) 2 Modelin
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III.3. Application to Pure Compound
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Modeling From the optimised paramet
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T / K 400 350 300 250 200 150 100 5
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ln Pvap 1.0E+01 1.0E+00 1.0E-01 1.0
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Modeling Table III.2. Absolute Aver
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Modeling The correlation coefficien
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Pvap (MPa) 4.00 3.50 3.00 2.50 2.00
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Modeling The mixture parameters a a
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Modeling the assumptions made by th
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Modeling between oxygen and perfluo
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xSolute 5.5E-03 5.0E-03 4.5E-03 4.0
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Modeling previous work, dealing wit
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Modeling These results confirm that
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Modeling CO2 binary mixtures using
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Modeling average deviation (AAD) be
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P / MPa 14 12 10 8 6 4 2 0 0 0.2 0.
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Modeling Figures III.16, III.17 and
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Modeling calculations from the orig
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Table III.9. References for VLE exp
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P / MPa 20 18 16 14 12 10 8 6 4 2 0
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Modeling Finally, Figure III.24 pre
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III.4.4. VLE and LLE of Alkane and
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Modeling number of perfluro-n-alkan
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y C6F14 1.0 0.8 0.6 0.4 0.2 0.0 0.0
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P / MPa 0.08 0.07 0.06 0.05 0.04 0.
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P / MPa 0.12 0.10 0.08 0.06 0.04 0.
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Modeling approach based on the meth
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Modeling Blas, F. J.; Vega, L. F.,
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DIPPR, Thermophysical Properties Da
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Modeling Hildebrand, J. H.; Fisher,
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Modeling McCabe, C.; Jackson, SAFT-
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Modeling Poling, B.; Prauznitz, J.;
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Modeling Wertheim, M. S., Fluids wi
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