Download Poster_ESAT

GAS SOLUBILITY OF HFCs IN ORGANIC SOLVENTS
J.P.B. Almeida1, H.C. Fachada2, I. M. A. Fonseca1*
1
Chemical Engineering Department, University of Coimbra, Pólo II, Pinhal de Marrocos, 3030–290
Coimbra, Portugal.
2 Electrical
Engineering Department, Institute Polytechnique of Coimbra , 3030-199 Coimbra, Portugal.
* e-mail: [email protected]
1.E-01
Abstract
Results
This work is inserted in a research program that consists mainly1.E-02
in the
experimental and theoretical study of the effect of association [1]
between solute and solvent molecules in the solubility of gases in
1.E-03
liquids.
To measure the solubility of gases in liquids an automated apparatus
based on Ben-Naim-Baer and Tominaga et al designs has been
1.E-04
implemented [2]. The accuracy of the experimental method was checked
280
by measuring the solubility of carbon dioxide and nitrous oxide in water,
being found to be 0.6%.
The solubilities of hydrofluorocarbons, HFCs, (CH3F, CH2F2, CHF3 and
CF4) in lower alcohols (methanol, ethanol, 1-propanol, 1-butanol) have
been determined in the temperature range [285, 310] K, at atmospheric
pressure.
To represent the temperature dependence of the mole fraction
solubilities, the equation Rlnx2 = A + B/T + ClnT was used. From this
equation the experimental Gibbs energies, enthalpies and entropies of
solution at 298 K were calculated [3].
X2
CHF3
CH3F
CH2F2
CF4
Methanol
290
Ethanol
300
1.E-01
310
1.E-01
T/K
1.E-02
X2
X2
1.E-02
1.E-03
1.E-03
1.E-04
1.E-05
280
290
300
310
1.E-04
280
320
290
300
1-Butanol
1-Propanol
1.E-01
1.E-01
1.E-02
X2
X2
1.E-02
1.E-03
1.E-03
Automated apparatus [2,3] (which embodies a volumetric method)
320
T/K
T/K
Experimental
310
1.E-04
280
290
300
310
1.E-04
280
320
290
300
310
T/K
T/K
PE
LA
CHF3
PT
TC
T
1.E-01
TRAP
DIF
V5
butanol
propanol
etanol
metanol
X2
Gas
V1
V3
V2
Vacuum
V4
V6
GB
1.E-02
280
EQ
290
310
T/K
TB
SAT
300
PC
AGIT
E
Table 2 Comparison of solubility results with literature values
Solubility apparatus: TB, thermostated bath; TC, temperature controller;
T, thermometer; PT, pressure transducer; LA, linear actuator; PC,
pressure controller; PE, Penning gauge; DIF, diffusion oil pump; TRAP,
liquid N2 trap; EQ, equilibrium vessel with connector; GB, gas burette;
V1,…V6, high vacuum Teflon stopcocks; AGIT, magnetic stirrer; E,
System
AAD (%)
Ref.
CH2F2 / Methanol
3.9
[4]
CH2F2 / Ethanol
3.2
[4]
CF4 / 1-Butanol
1.9
[5],[6]
elevator.
AAD = (1 / N)  100 (x2 - x2lit / x2lit)
i
Calculations
Table 1 Thermodynamic functions (J
Gas (2)
CHF3
CH3F
CH2F2
CF4
mol-1)
Conclusions
obtained from Rlnx2 = A + B/T + ClnT, at 298 K.
Solvent (1)
G20
H20
S20
Methanol
9254.09
-7168.81
-55.11
Ethanol
8884.89
-11726.59
-69.17
1-Propanol
8250.34
-9517.25
-59.62
1-Butanol
7720.77
-13872.79
-72.46
Methanol
20486.50
-244659.00
-889.75
Ethanol
15920.76
-57274.00
-245.62
1-Propanol
14628.30
-8124.00
-76.35
1-Butanol
14330.02
-19192.00
-112.49
Methanol
10196.86
-11570.75
-73.05
Ethanol
9639.87
-18034.80
-92.87
1-Propanol
8869.65
-9407.77
-61.33
1-Butanol
8390.15
-7527.62
-53.42
1-Propanol
18622.35
-1211.84
-66.56
1-Butanol
18480.83
-1636.01
-67.51
Acknowledgements
This work was carried out under Research Project POCI/EQU 44056/2002 financed by FCT –
Fundação para a Ciência e Tecnologia (Portugal) and FEDER
 The solubilities of HFCs in the alcohols decrease in the order:
CHF3 > CH2F2 > CH3F > CF4. This is corroborated by the values of Gº2 in
Table 1.
This can be explained by the formation of a complex between solute/solvent
molecules by means of hydrogen-bonding. Actually the presence of the
strongly electron-attracting halogen atom(s) on the carbon of the solute
molecule looses the hydrogen(s) and makes it available for coordination to the
donor atom (of the solvent molecule).
 For each HFC the solubility increases with the C- content of the alcohol
increases. This is related to H-bonding or association in the alcohol; i.e.
solvents with strong H-bonding tendencies dissolve less the same gas those
with weaker H-bonding tendencies.
 The comparison of the solubility with literature values in Table 2 shows a
satisfactory agreement.
References
[1] J.M. Prausnitz, R.N. Lichtenthaler, E.G. Azevedo, Molecular Thermodynamics
of Fluid-Phase Equilibria, 3rd ed., Prentice Hall, Englewood Cliffs, 1999.
[2] I.M.A Fonseca, J.P.B. Almeida, H.C. Fachada, Automated apparatus for gas
solubility measurements, J. Chem. Thermodynamics 39 (2007) 1407-1411.
[3] H.L. Clever, R. Battino, The Experimental Determination of Solubilities, edited
by G.T. Hefter and R.P.T. Tomkins, Wiley, 2003, pp. 101-150.
[4] M. Takenouchi, R. Kato, H. Nishiumi, J. Chem. Eng. Data 46 (2001) 746-749.
[5] S. Bo, R. Battino, E. Wilhelm, J. Chem. Eng. Data 38 (1993) 611-616.
[6] J. Pardo, M.C. Lopez, J. Santafe, F.M. Royo, J.S. Urieta, Fluid Phase
Equilibria 109 (1995) 29-37.