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II. 1. Introduction Experimental Methods, Results and Discussion The increasing number of applications of fluorinated compounds in medicine, environment, and industry requires a precise knowledge of the thermophysical properties of these substances. In spite of their many applications, literature data relating these compounds is in some cases old and many times discrepant; in other cases only one set of results can be found and, for some compounds with current application, experimental data is completely inexistent. It is therefore of both practical and theoretical interest to measure the thermophysical properties of these compounds to create a wide and reliable experimental database in order to understand their different behaviour and to be able to accurately predict it. In this work, densities, vapour pressures, solubility of gases, oxygen at low pressure and carbon dioxide at high pressure, and liquid – liquid equilibria data for alkane + perfluoralkane mixtures were measured. Density and vapour pressure data is needed not only to select the best perfluoroalkane for a given application but also for solubility data calculation as will be explained later. Density data was measured with a commercial vibrating tube Antón Paar DSA-48 densimeter between 288.15 and 313.15 K at atmospheric pressure based on the mechanical oscillator principle using a thermostatized cell with a U shape. An apparatus based on the static method was built to measure vapour pressure data between 288 K and 333 K. Pressure on this apparatus was measured with a high precision temperature compensated, quartz pressure transducer (ParoScientific Inc. model 2100A- 101). The solubility of oxygen and carbon dioxide were measured at different thermodynamic conditions chosen according to the main application of each system. An accurate apparatus based on the saturation method was built to measure the solubility of oxygen in pure perfluoroalkanes at atmospheric pressure and temperatures ranging from 288 to 313K. The solubility is determined by measuring the quantity of gas dissolved in an accurately known volume of solvent at constant pressure and temperature. The apparatus has a simple design and can be easily adapted to measure the solubility of systems with different solubilities. Linear and cyclic fully saturated fluorochemicals (from C6 to C9 and perfluorodecalin) and also substituted fluorochemicals (1Br-Perfluorooctane, 1H-Perfluorooctane, 1H, 8H-Perfluorooctane) were studied in order to conclude about the - 23 -
Experimental Methods, Results and Discussion influence of the structure, chain length and the substitution of terminal groups on the solubility of oxygen. The solubility of carbon dioxide was studied for different perfluoroalkanes including linear (perfluoro-n-octane), cyclic (perfluorodecalin and perfluoromethylcyclohexane) and aromatic compounds (perfluorobenzene and perfluorotoluene), at pressures up to 120 bar and temperatures ranging from 293 to 353 K. Measurements were performed using a high-pressure cell with a sapphire window that allows observation of the point at which the phase boundary is crossed. The different molecular architectures were chosen aiming at checking the influence of the structures on their miscibility with carbon dioxide. The liquid-liquid equilibria (LLE) of binary mixtures of perfluoro-n-octane plus alkanes, n-CnH2n+2 (n = 6 - 9), were measured, using the synthetic method, by turbidimetry at atmospheric pressure, and using a light scattering technique for measurements at pressures up to 1500 bar. The main objective is to collect and compare data for different saturated and nonsaturated fluorinated compounds that are being studied/used for different applications. Experimental data are correlated using appropriate equations for the temperature ranges studied. Whenever possible, experimental data measured is compared with literature data available; comparison is done among the different methods and purities of samples used. For some of the fluorinated compounds studied, new experimental and correlated data is presented. II.1.1. Materials The origin and purities, checked by gas chromatography, of the compounds used in this work are summarized in Table II.1. Both solvents and gases were used without further purification. Most of the fluorocarbon samples used by earlier authors for measurements of thermodynamic properties of perfluoroalkanes were prepared by the fluorination of the corresponding hydrocarbons with cobalt trifluoride. The resulting crude fluorocarbons were then submitted to a sequence of purification procedures to obtain the purest sample possible. Among those procedures where the reflux with an alkaline solution of potassium permanganate to remove unsaturated compounds, silica gel adsorption, fractional - 24 -
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 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: II. Part EXPERIMENTAL METHODS, RESU
Page 45 and 46: 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 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
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Experimental Methods, Results and D
Page 99 and 100:
Page 101 and 102:
0 τ β Δ1 2Δ1 [ 1+ B τ + B τ +
Page 103 and 104:
References Experimental Methods, Re
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
III.1. Introduction Modeling Most c
Page 113 and 114:
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
Page 121 and 122:
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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