Infinite dilution activity coefficient measurements of organic solutes in fluorinated ionic liquids by gas-liquid chromatography and the inert gas stripping method

CHAPTER FIVE: RESULTS

Chapter overview

Results presented in this work consist of the following:

· Infinite dilution activity coefficients data for various organic solutes in n-hexadecane and seven different FILs, obtained from Gas-Liquid Chromatography;

· Excess molar enthalpies at infinite dilution of the same solutes in the fluorinated ionic liquids, calculated from experimental infinite dilution activity coefficients data;

· Correlation of experimental infinite dilution activity coefficient data with temperature and the carbon chain length of solutes;

· Infinite dilution activity coefficients data for six organic solutes in NMP and one fluorinated ionic liquid;

· Limiting selectivities and capacities of the seven investigated fluorinated ionic liquids for selected separation problems;

· Estimation of experimental errors in determining activity coefficients, Excess molar enthalpies, selectivities and capacities at infinite dilution.

Equations (3-10) and (3-90) were used to calculate IDACs from experimental parameters obtained by the GC method and the IGST respectively. Excess molar enthalpies at infinite dilution were determined using equation (2-11). Some experimental data obtained in this study have been published as part of collaborative work with Prof. Nirmala Deenadayalu ([C13C8] [Tf2N]) and Mr. Eugene Olivier ([EMIM] [TfO], [BMIM] [SbF6] and [MOIM] [PF6]). These results are also included in this chapter.

5.1. Results from Gas-Liquid Chromatography

5.1.1. Hexadecane

Table 5-1: Infinite dilution activity coefficients of selected organic solutes in n-hexadecane.

Solutes	T /K				R.D^#./ %	n-pentane n-pentane n-hexane n-hexane n-hexane n-heptane n-heptane
323.15 333.15 303.15 313.15 323.15 303.15 ? ) 1 323.15 lit	0.839 0.870 0.882 0.892 0.896 0.882 0.890	0.814^a 0.833 ^a 0.880-0.904^bc 0.870-0.910^b 0.860-0.905 a bd 0.916-0.927^b 0.867-0.921 ^ad	3.1 4.4 1.8 1.4 0.6 4.3 0.4		Hex-1-ene
323.15	0.862	0.855 ^a	0.8		Hept-1-ene
323.15	0.866	0.902^a	4.0		Cyclopentane
323.15	0.695	0.686^a	1.3		Cyclohexane
303.15	0.775	0.795 ^b	2.5		Cyclohexane
313.15	0.776	0.778 ^b	0.3		Cyclohexane
323.15	0.736	0.739-0.787 ^ad	3.5		Benzene
303.15	1.071	1.105-1.110 ^be	3.3		Benzene
313.15	1.010	1.006-1.051 ^b	0.4		Benzene
323.15	0.953	0.932-0.995 ^ad	2.1		Toluene
323.15	0.953	0.941 ^a	1.3		Dichloromethane
303.15	1.428	1.440^b	0.8

^a Schult et al. (2001); ^bChien et al (1981) ^c Cruickshank et al. (1966b); ^d Castells et al. (1990);
^e Gainey and Young (1968)

# Relative deviation, R.D., given by

5.1.2. Trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide,

[3C6C14P] [Tf2N]

Table 5-2: Activity coefficients at infinite dilution of organic solutes in

trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide with solvent column loading

n3 = 1.577 mmol (29.5 %) at T = (313.15, 333.15,					353.15 and 373.15) K.
Experimental		at /K				Solute
n3/ mmol		T=313.15	T=333.15	T=353.15	T=373.15	n-pentane
1.577		0.970	0.976	0.988	0.990	n-hexane
1.577		1.101	1.119	1.126	1.130	n-heptane
1.577		1.163	1.249	1.315	1.434	n-octane
1.577		1.405	1.443	1.459	1.495	n-nonane
1.577		1.607	1.681	1.769	1.871	Pent-1-ene
1.577		0.810	0.833	0.841	0.862	Hex-1-ene
1.577		0.909	0.932	0.941	0.943	Hept-1-ene
1.577		1.030	1.064	1.102	1.123	Oct-1-ene
1.577		1.163	1.384	1.610	1.905	Pent-1-yne
1.577		0.611	0.640	0.662	0.701	Hex-1-yne
1.577		0.691	0.707	0.718	0.730	Hept-1-yne
1.577		0.730	0.747	0.764	0.780	Oct-1-yne
1.577		0.841	0.872	0.890	0.899	Nony-1-ne
1.577		0.850	0.912	0.954	0.977	Cyclopentane
1.577		0.686	0.696	0.714	0.723	Cyclohexane
1.577		0.797	0.800	0.802	0.805	Cycloheptane
1.577		0.865	0.882	0.895	0.910	Cyclooctane
1.577		0.965	1.000	1.065	1.119	Methanol
1.577		1.077	1.025	0.921	0.865	Ethanol
1.577		1.270	1.096	0.953	0.880	Propan-1-ol
1.577		1.279	1.155	1.070	0.954	Butan-1-ol
1.577		1.425	1.194	1.090	0.949	Benzene
1.577		0.390	0.403	0.414	0.432	Toluene
1.577		0.450	0.471	0.485	0.512	Acetone
1.577		0.299	0.318	0.328	0.332	Butan-2-one
1.577		0.317	0.329	0.331	0.333

Table 5-3: Activity coefficients at infinite dilution of organic solutes in

trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide with solvent column loading

n3 =2.236 mmol (31.7 %) at T = (313.15, 333.15,					353.15 and 373.15) K.
Experimental		at /K				Solute
n3/ mmol		T=313.15	T=333.15	T=353.15	T=373.15	n-pentane
2.236		0.950	0.980	0.992	1.014	n-hexane
2.236		1.091	1.103	1.122	1.130	n-heptane
2.236		1.139	1.257	1.309	1.412	n-octane
2.236		1.403	1.439	1.463	1.491	n-nonane
2.236		1.593	1.659	1.777	1.867	Pent-1-ene
2.236		0.802	0.815	0.843	0.838	Hex-1-ene
2.236		0.905	0.910	0.919	0.941	Hept-1-ene
2.236		1.034	1.066	1.100	1.121	Oct-1-ene
2.236		1.159	1.382	1.606	1.901	Pent-1-yne
2.236		0.615	0.632	0.664	0.697	Hex-1-yne
2.236		0.695	0.711	0.722	0.734	Hept-1-yne
2.236		0.722	0.751	0.760	0.784	Oct-1-yne
2.236		0.831	0.858	0.882	0.899	Nony-1-ne
2.236		0.856	0.918	0.958	0.981	Cyclopentane
2.236		0.688	0.700	0.712	0.719	Cyclohexane
2.236		0.793	0.794	0.794	0.795	Cycloheptane
2.236		0.875	0.880	0.887	0.900	Cyclooctane
2.236		0.961	0.996	1.073	1.121	Methanol
2.236		1.089	1.027	0.923	0.861	Ethanol
2.236		1.268	1.094	0.949	0.884	Propan-1-ol
2.236		1.281	1.149	1.074	0.952	Butan-1-ol
2.236		1.421	1.188	1.080	0.959	Benzene
2.236		0.392	0.407	0.420	0.442	Toluene
2.236		0.454	0.473	0.487	0.508	Acetone
2.236		0.295	0.300	0.320	0.330	Butan-2-one
2.236		0.325	0.326	0.333	0.335

Table 5-4: Average activity coefficients at infinite dilution of organic solutes in

trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide at T = (313.15, 333.15,
353.15 and 373.15) K.

Experimental at /K

Solute	T=313.15	T=333.15	T=353.15		T=373.15	n-pentane
0.960	0.978	0.990	1.002		n-hexane
1.096	1.111	1.124	1.130		n-heptane
1.151	1.253	1.312	1.423		n-octane
1.404	1.441	1.461	1.493		n-nonane
1.600	1.670	1.773	1.869		Pent-1-ene
0.806	0.824	0.842	0.850		Hex-1-ene
0.907	0.921	0.930	0.942		Hept-1-ene
1.032	1.065	1.101	1.122		Oct-1-ene
1.161	1.383	1.608	1.903		Pent-1-yne
0.613	0.636	0.663	0.699		Hex-1-yne
0.693	0.709	0.720	0.732		Hept-1-yne
0.726	0.749	0.762	0.782		Oct-1-yne
0.836	0.865	0.886	0.899		Non-1-yne
0.853	0.915	0.956	0.979		Cyclopentane
0.687	0.698	0.713	0.721		Cyclohexane
0.795	0.797	0.798	0.800		Cycloheptane
0.870	0.881	0.891	0.905		Cyclooctane
0.963	0.998	1.069	1.120		Methanol
1.083	1.026	0.922	0.863		Ethanol
1.269	1.095	0.951	0.882		Propan-1-ol
1.280	1.152	1.072	0.953		Butan-1-ol
1.423	1.191	1.085	0.954		Benzene
0.391	0.405	0.417	0.437		Toluene
0.452	0.472	0.486	0.510		Acetone
0.297	0.327	0.332	0.334		Butan-2-one
0.321	0.328	0.324	0.331

Table 5-5: Partial molar excess enthalpies at infinite dilution for organic solutes in the

ionic liquid trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide, calculated from
the Gibbs-Helmholtz equation.

SOLUTE	Linear regression using Eq.(2-11)

n-pentane	-0.083	0.223	0.995		-0.69	n-hexane
-0.061	0.286	0.982	-0.51		n-heptane
-0.398	1.413	0.987	-3.31		n-octane
-0.116	0.710	0.990	-0.96		n-nonane
-0.306	1.440	0.988	-2.54		Pent-1-ene
-0.107	0.126	0.985	-0.89		Hex-1-ene
-0.072	0.132	0.995	-0.60		Hept-1-ene
-0.166	0.563	0.994	-1.38		Oct-1-ene
-0.953	3.186	0.997	-7.92		Pent-1-yne
-0.253	0.312	0.981	-2.10		Hex-1-yne
-0.105	-0.029	0.997	-0.87		Hept-1-yne
-0.140	0.129	0.991	-1.17		Oct-1-yne
-0.142	0.278	0.984	-1.18		Nony-1-ne
-0.270	0.710	0.970	-2.24		Cyclopentane
-0.097	-0.065	0.990	-0.81		Cyclohexane
-0.011	-0.192	0.982	-0.10		Cycloheptane
-0.075	0.100	0.987	-0.63		Cyclooctane
-0.303	0.923	0.978	-2.52		Methanol
0.459	-1.372	0.978	3.81		Ethanol
0.723	-2.078	0.991	6.02		Propan-1-ol
0.557	-1.528	0.987	4.63		Butan-1-ol
0.757	-2.075	0.990	6.30		Benzene
-0.211	-0.269	0.980	-1.75		Toluene
-0.228	-0.067	0.986	-1.90		Acetone
-0.079	-0.880	0.994	-0.66		Butan-2-one
-0.218	-0.514	0.998	-1.81

0.8

0.6

ln(11₁₃)

0.4

0.2

0

-0.2

2.6 2.7 2.8 2.9 3 3.1 3.2 3.3

1000K/T

Figure 5-1: Plots of versus for alkanes in _[3C6C14P] [Tf2N] together with a

linear correlation of the data using the Gibbs-Helmholtz equation; () n-pentane,
() n-hexane, (?) n-heptane and (?) n-octane, () n-nonane.

2.6 2.7 2.8 2.9 3 3.1 3.2 3.3

1000K/T

ln(13₁₃)

-0.2

-0.4

0.8

0.6

0.4

0.2

0.0

Figure 5-2: Plots of versus for alk-1-enes in _[3C6C14P] [Tf2N] together with a linear

correlation of the data using the Gibbs-Helmholtz equation; () pent-1-ene, () hex-1-ene,
(?) hept-1-ene and (?) oct-1-ene.

ln(1313)

-0.1

-0.2

-0.3

-0.4

-0.5

0.2

0.1

0

2.6 2.8 3 3.2 3.4

1000K/T

Figure 5-3: Plots of versus for cycloalkanes in _[3C6C14P] [Tf2N] together with a linear

correlation of the data using the Gibbs-Helmholtz equation; () cyclopentane, () cyclohexane,
(?) cycloheptane and (?) Cyclooctane.

0.0

-0.1

-0.2

ln( LP ₁₃)

-0.3

-0.4

-0.5

-0.6

2.6 2.8 3 3.2 3.4

1000K/T

Figure 5-4: Plots of versus for alk-1-ynes in _[3C6C14P] [Tf2N] together with a linear

correlation of the data using the Gibbs-Helmholtz equation; ()pent-1-yne, () hex-1-yne,
(?) hept-1-yne, (?) oct-1-yne and () n-nonyne.

lii( LP 13)

0.4 0.3 0.2 0.1 0 -0.1 -0.2

2.6 2.7 2.8 2.9 3 3.1 3.2 3.3

1000K/T

Figure 5-5: Plots of versus for alkanols in _[3C6C14P] [Tf2N] together with a linear

correlation of the data using the Gibbs-Helmholtz equation; () methanol, () ethanol,
(?) propan-1-ol and (?) butan-1-ol.

ln( LP13)

-0.5 -0.6 -0.7 -0.8 -0.9 -1

2.6 2.8 3 3.2 3.4

1000K/T

Figure 5-6: Plots of versus for alkylbenzenes in _[3C6C14P] [Tf2N] together with a

linear correlation of the data using the Gibbs-Helmholtz equation; () benzene and () toluene.

^1n(L13)

-1.08 -1.12 -1.16 -1.20 -1.24

2.6 2.7 2.8 2.9 3 3.1 3.2 3.3

1000K/T

Figure 5-7: Plots of versus for ketones in _[3C6C14P] [Tf2N] together with a linear

correlation of the data using the Gibbs-Helmholtz equation; () acetone and () butan-2-one.

In(m13)

1 0.5 0 -0.5 -1 -1.5

0 1 2 3 4 5 6 7 8 9 10

Number of Carbon atoms, Nc

Figure 5-8: Plots of versus the carbon number of the solute at 313.15 K for () n-alkanes,

() alk-1-enes, (?) cycloalkanes, (?) alk-1-ynes () ketones, (?) alkanols and (?)
alkylbenzenes in _[3C6C14P] [Tf2N].