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Tc / K 700 600 500 400 300 200 100 Pc /MPa 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ρc / g.ml -1 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 1 3 5 7 9 11 CN 1 3 5 7 9 11 CN MM / g.mol -1 600 500 400 300 200 100 General Introduction (a) (d) (b) (c) 1 3 5 7 9 11 CN 0 1 3 5 7 9 11 CN Tb / K 500 450 400 350 300 250 200 150 100 (e) 1 3 5 7 9 11 CN Figure I.1. Comparison between physical properties for the homologous linear series of alkanes and perfluoroalkanes (filled symbols): (a) critical temperature, (b) critical pressure, (c) critical density, (d) molecular weight, (e) boiling temperature and (e) acentric factor. Data from NIST DataBase. Tb and acentric factors for C > 6 calculated from vapour pressure data measured in this work. - 5 - w 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0.0 (f) 1 3 5 7 9 11 CN
General Introduction order to compare the liquid-phase structure of the pure perfluoroalkanes and the corresponding alkanes (Watkins and Jorgensen, 2001 and Gomes and Padua, 2003). Conformational and structural properties of the liquid phases were obtained applying the molecular dynamics method using flexible, all-atom force fields containing electrostatic charges. The new OPLS-AA (optimised potentials for liquid simulations) model adds explicit sites and partial charges to individual atoms in addition to a finer representation of the conformational energetics. These recently proposed models for long-chain perfluoroalkanes (Watkins and Jorgensen, 2001) provide a more detailed, and probably more accurate, molecular description than previous attempts based on the united-atom framework (Shin et al., 1992 and Cui et al., 1998). The results obtained showed that most of the dihedral angles in the carbon skeleton of n-alkanes adopt values close to 180º with occasional occurrence gauche defects. When compared to the corresponding nperfluoroalkanes, the population of gauche defects is smaller in the latter case, indicating a more rigid molecular backbone. This suggests that cavities present naturally in the liquid phase may be larger in fluoroalkanes than in alkanes. In addition, it was verified that spontaneous cavities are larger and more easily formed in the fluorocarbon, corresponding to smaller free energies of cavity formation, than in the equivalent hydrocarbon (Gomes and Pádua, 2003). Experimentally, it was also verified that, the excess chemical potential, i.e., work needed to insert the 133Xe radioisotope into a solvent, was much lower for perfluoroalkanes than for alkanes (Kennan and Pollack, 1988 and Pollack et al., 1989). Perfluoroalkanes behave like typical non-associated, non-polar liquids, with solubility for gases depending essentially on the molecule’s shape (Chandler, 1978). A formal two-step dissolution process, consisting first on the opening a cavity in the solvent large enough to fit the gas molecule and then the introduction of the gas in this cavity, is often postulated for the purpose of discussing and predicting solubility data. Based on this model the molecular simulations discussed above justify the higher capacity of these compounds to solubilize gases as oxygen and carbon dioxide but cannot explain why carbon dioxide, being a bigger molecule, is more soluble than oxygen. Moreover, solubilities of gases decrease in the order CO2 > O2 > CO > N2 > H2 > He, following a decrease in molecular volume of the solute (Bonaventura et al., 1998). The dissolution of O2 or NO in diverse liquid PFCs has been investigated by NMR using the perturbation induced on the nuclear relaxation of the 13 C nuclei of the PFC by the - 6 -
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: Table I.2. Physicochemical Properti
Page 27 and 28: General Introduction the numerous a
Page 29 and 30: General Introduction carbon dioxide
Page 31 and 32: 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
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Experimental Methods, Results and D
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x2 (T,P2) 7.0E-03 6.0E-03 5.0E-03 4
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L 2,1 0.70 0.60 0.50 0.40 0.30 285
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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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