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Experimental Methods, Results and Discussion It is interesting to notice that the Gibbs energy of solvation has similar values for all the systems studied. This is a consequence of the similar solubility of oxygen at 298.15 K for the different systems. It is also clear from the reported values that the enthalpy and the entropy of solution decrease significantly along the linear perfluoroalkanes series. Another interesting observation results from the comparison between the enthalpy of solvation of perfluoro-n-octane and the corresponding substituted 1Br-perfluoro-n-octane, 1H-perfluoro-n-octane and 1H,8H-perfluoro-n-octane. The enthalpy of solvation decreases from fully saturated perfluoroalkane to 1H,8H-perfluoro-n-octane where both extremities have a fluor atom substituted by an hydrogen atom. The enthalpies of solvation for the perfluoralkanes that have only one extremity substituted (by an atom of hydrogen or bromide) lay between the values obtained for perfluoro-n-octane and 1H,8H-perfluoro-noctane. These results seem to indicate that the temperature dependence of the solubility data is related with the structure of the molecule, essentially with the degree of substitution of the terminal CF3 group in the perfluorocarbon molecule and also that the interaction between oxygen and the CF3 group is stronger than between oxygen and other end-groups. Supporting this evidence is the fact that, the solubility of oxygen in perfluorodecalin, a cyclic compound without any CF3 terminal group, is also temperature independent as is the case of the linear 1H,8H-perfluoro-n-octane. To assess the validity of any assumption about special solute-solvent interactions, it is necessary to analyse the different contributions to the overall solubility process namely cavity formation, mixing and interaction. This can be done by using the appropriate expressions from the scaled particle theory applied to solutions of gases in liquids considering a two step mechanism of the solution process (Pierotti, 1963) * cav int Δ G2 = G + G (II.27) where G cav and G int are the partial molar Gibbs energy of cavity formation and interaction respectively. In this work, G cav was calculated as suggested by Reiss et al. (1960) as a function of parameters of the solute and the solvent, namely the hard sphere diameter (HSD) and the density of the solvent. The HSD for oxygen was taken from the work of Wilhelm and Battino (1977) and is equal to 3.46 Å. For the solvents, the HSDs were calculated from enthalpy of vaporization and thermal expansivity data of the solvents, as suggested by Wilhelm and Battino (1971b), using the vapor pressure and density - 65 -
Experimental Methods, Results and Discussion measured. Table II.16 resumes the parameters for the different solvents studied along with the different enthalpic contributions. The calculated enthalpies of cavity formation are very similar for the different solvents within the uncertainty of the calculation. The results presented in Table II.16 indicate that the differences observed in the enthalpies of solution reported in Table II.15 are mainly caused by differences in the enthalpies of interaction. The interaction energy between oxygen and perfluoro-n-octane is significantly higher than the interaction energy between oxygen and substituted perfluoroalkanes. The study of the solubility of oxygen in linear fluorinated molecules presenting different degrees of substitution on the terminal CF3 groups seems to indicate that the solvation of oxygen is carried by the end groups of the perfluorocarbons and the existence of interactions between the oxygen and the CF3 group on the fluorinated molecules that is more than 2 kJ/mol higher than with other end groups. Table II.16. Enthalpies of Cavity Formation, H cav and Solute-Solvent Interaction, H int for Oxygen in Different Fluorinated Compounds. Also Reported are the Solvent’s Hard Sphere Diameter, σ and Molar Volume, V1 0 Compound σ Å V1 0 cm 3 .mol -1 H cav kJ.mol -1 H int kJ.mol -1 C6F14 6.62 201.69 9.53 - 22.94 C7F16 7.04 226.34 10.61 - 20.27 C8F18 7.38 248.24 10.64 - 14.99 C9F20 7.70 273.01 10.67 - 15.08 CF3 (CF2)6 CF2Br 7.67 260.58 11.12 - 13.37 CF3 (CF2)6 CF2H 7.38 240.06 11.43 -13.07 CF2H (CF2)6 CF2H 7.34 229.31 11.93 -10.71 C10F18 7.42 239.38 10.54 - 10.49 - 66 -
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Ana Maria Antunes Dias Universidade
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o júri presidente Prof. Dr. Joaqui
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palavras-chave resumo perfluoroalca
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Contents Notation List of Tables Li
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Notation Abbreviations AAD EoS LCST
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List of Tables Table I.1 Average Bo
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Table III.6 Adjusted Binary Paramet
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Figure II.9 Comparison between corr
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Figure III.8 Temperature-density di
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Figure III.25 Vapor-phase mole frac
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I.1. Fluorine Properties General In
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Table I.2. Physicochemical Properti
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General Introduction order to compa
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General Introduction the numerous a
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General Introduction carbon dioxide
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General Introduction animals. That
Page 33 and 34: General Introduction Table I.3. Lit
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
Page 83: Experimental Methods, Results and D
Page 93 and 94: P / MPa 6 5 4 3 2 1 0 P / MPa 14 12
Page 95 and 96: II.6. Liquid - Liquid Equilibrium I
Page 101 and 102: 0 τ β Δ1 2Δ1 [ 1+ B τ + B τ +
Page 103 and 104: References Experimental Methods, Re
Page 111 and 112: III.1. Introduction Modeling Most c
Page 113 and 114: Modeling The pioneering work of Wer
Page 115 and 116: III.2. Soft-SAFT Model Modeling A S
Page 117 and 118: Modeling The equation of state is w
Page 119 and 120: Chain Term Modeling Originally Wert
Page 121 and 122: Modeling The model is easily extend
Page 123 and 124: ( ) ( ) ∑∑∑ 3 2 2 2 2 qq 32π
Page 125 and 126: Modeling HRT is a promising theory,
Page 127 and 128: ( ρ) ρ , 0 ≤ ρ ( ρ) 2 Modelin
Page 129 and 130: III.3. Application to Pure Compound
Page 131 and 132: Modeling From the optimised paramet
Page 133 and 134: 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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