Results and Discussions

R EFERENCES

3.3 Results and Discussions

Chapter-3

Chapter-3 acid increases, the hydrogen bonding capacity of the mixture also increases. This allows the water molecules to interact within the system even in the presence of hydrophobic ionic liquids. Finally, the performance of [BMIM][Tf₂N] was also compared with other solvents (ethyl acetate,n-propyl acetate, butyl acetate, amyl acetate, 2-methyl ethyl ac- etate, 2-methyl propyl acetate, isophorone, MTBE) as reported in literature in terms of distribution coefficient and selectivity [Colombo et al., 1999, Xiao et al., 2006, Toikka et al., 2014, Wang et al., 2007b, Wang et al., 2007a, Miao et al., 2007]. This is shown in Figure 3.5. The highest acetic acid distribution coefficients were found for isophorone whereas distribution coefficients were almost same for other solvents. The selectivity for [BMIM][Tf₂N] was lower than other solvents. On the contrary, the mole fraction(%) of [BMIM][Tf₂N] in raffinate phase was close to zero; whereas for other solvents it was in the range of 0.42-12.04 %. Thus, a high concentration of solvent in raffinate phase may add to extra capital and energy cost. Considering both the aspects, Amyl acetate, Isophorone and [BMIM][Tf₂N] are potential solvents for the extraction of acetic acid from aqueous solution.

Table 3.4.:Experimental Tie Lines data for the system [BMIM][Tf₂N] (1) - acetic acid (2) - water (3) atT= 298.15 K andp= 0.1 Mpa.

Sl. Extract phase Raffinate phase Distribution Selec-

No. X1 X2 X3 X1 X2 X3 Co-efficient(β) tivity(S)

1 0.6317 0.0335 0.3348 0.0000 0.0156 0.9844 2.15 6.31

2 0.5917 0.0592 0.3491 0.0000 0.0223 0.9777 2.65 7.43

3 0.5854 0.0780 0.3366 0.0000 0.0337 0.9663 2.31 6.64

4 0.5541 0.1043 0.3416 0.0000 0.0457 0.9543 2.28 6.38

5 0.4594 0.1446 0.3960 0.0000 0.0684 0.9316 2.11 4.97

6 0.4408 0.1620 0.3972 0.0000 0.0881 0.9119 1.84 4.22

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Chapter-3

Figure 3.4.:Experimental tie lines for the ternary system: [BMIM][Tf₂N]-acetic acid-water at 298.15 K and 1 atm.

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Chapter-3

Figure 3.5.:Distribution co-efficient, Selectivity and % mole fraction of solvent in raffinate for acetic acid based ternary system: Present work Vs. Lit.

3.3.2. [EMIM][Tf

2

N]/[BMIM][Tf

2

N]/chloroform/ethyl acetate/ n-propyl acetate/ n-butyl acetate - acetol - water systems

The experimental LLE data of [EMIM][Tf₂N]/acetol/water, [BMIM][Tf₂N]/acetol/water, chloroform/acetol/water, ethyl acetate/acetol/water,n-propyl acetate/acetol/water, and n-butyl acetate/acetol/water systems were measured at 298.15 K under atmospheric pressure. The experimental LLE data of these systems along with distribution coeffi- cients and selectivities are reported in Tables 3.5-3.10. The experimental LLE ternary di- agram for these systems are shown in Figures 3.6-3.11 and Figure 3.12 shows the com-

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Chapter-3 parison between the various solvents. Distribution coefficients are in the range of 0.85- 1.09 for ethyl acetate, 0.62-0.91 for n-propyl acetate, 0.55-0.75 for n-butyl acetate, 1.11-1.57 for chloroform, 1.98-2.69 for [EMIM][Tf₂N] and 1.80-2.23 for [BMIM][Tf₂N].

This suggests acetol can be extracted more effectively from aqueous solution using [EMIM][Tf₂N] and [BMIM][Tf₂N]. Selectivity are in the range of 1.72-4.44 for ethyl acetate, 1.92-5.01 for n-propyl acetate, 3.01-6.70 for n-butyl acetate, 2.96-25.89 for chloroform, 3.89-6.75 for [EMIM][Tf2N] and 3.37-6.12 for [BMIM][Tf2N]. For all sol- vents, selectivity value is grater than one which means that extraction of acetol is possible by all the studied solvents. The highest acetol distribution coefficients were found for [EMIM][Tf₂N] and [BMIM][Tf₂N] whereas distribution coefficients were approximately one for all other solvents. The selectivity was higher for chloroform followed by [EMIM][Tf₂N] and [BMIM][Tf₂N]. Mole fraction (%) of solvent in raf- finate for ethyl acetate, n-propyl acetate, n-butyl acetate, chloroform, [EMIM][Tf₂N]

and [BMIM][Tf₂N] were 9.30%, 6.72%, 3.17%, 1.84%, 0.37% and 0.00% respectively.

This implies that the latter two namely the IL’s may be useful for solvent extraction at ambient condition as trace quantity of ionic liquid in raffinate phase will result in lower process operating cost. For all liquid mixtures, total miscibility was found at high acetol concentrations (> 30 mol%). Overall, [EMIM][Tf₂N], [BMIM][Tf₂N] and chloroform are potential solvents for the extraction of acetol from aqueous solution.

Table 3.5.:Experimental Tie Lines data for the system [EMIM][Tf₂N] (1) - acetol (2) - water (3) atT= 298.15 K andp= 0.1 Mpa.

Sl. Extract phase Raffinate phase Distribution Selec-

No. X₁ X₂ X₃ X₁ X₂ X₃ Co-efficient(β) tivity(S)

1 0.5587 0.0503 0.3910 0.0000 0.0187 0.9813 2.69 6.75

2 0.4951 0.0990 0.4059 0.0000 0.0400 0.9600 2.48 5.85

3 0.4202 0.1513 0.4285 0.0000 0.0717 0.9283 2.11 4.57

4 0.3636 0.2037 0.4327 0.0037 0.0933 0.9030 2.18 4.56

5 0.3087 0.2469 0.4444 0.0000 0.1250 0.8750 1.98 3.89

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Chapter-3

Figure 3.6.:Experimental tie lines for the ternary system: [EMIM][Tf₂N]-acetol -water at 298.15 K and 1 atm.

Table 3.6.:Experimental Tie Lines data for the system [BMIM][Tf2N] (1) - acetol (2) - water (3) atT= 298.15 K andp= 0.1 Mpa.

Sl. Extract phase Raffinate phase Distribution Selec-

No. X1 X2 X3 X1 X2 X3 Co-efficient(β) tivity(S)

1 0.5327 0.1225 0.3448 0.0000 0.0549 0.9451 2.23 6.12

2 0.4878 0.1659 0.3463 0.0000 0.0771 0.9229 2.15 5.73

3 0.4240 0.2304 0.3456 0.0000 0.1050 0.8950 2.19 5.68

4 0.3431 0.2744 0.3825 0.0000 0.1307 0.8693 2.10 4.77

5 0.2726 0.3170 0.4104 0.0000 0.1579 0.8421 2.01 4.12

6 0.2260 0.3390 0.4350 0.0000 0.1880 0.8120 1.80 3.37

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Chapter-3

Figure 3.7.:Experimental tie lines for the ternary system: [BMIM][Tf₂N]-acetol -water at 298.15 K and 1 atm.

Table 3.7.:Experimental Tie Lines data for the system Chloroform (1) - acetol (2) - water (3) atT= 298.15 K andp = 0.1 Mpa.

Sl. Extract phase Raffinate phase Distribution Selec-

No. X₁ X₂ X₃ X₁ X₂ X₃ Co-efficient(β) tivity(S)

1 0.9050 0.0543 0.0407 0.0000 0.0490 0.9510 1.11 25.89

2 0.7752 0.1163 0.1085 0.0000 0.0823 0.9177 1.41 11.95

3 0.7246 0.1812 0.0942 0.0000 0.1267 0.8733 1.43 13.26

4 0.6006 0.2462 0.1532 0.0000 0.1570 0.8430 1.57 8.63

5 0.5181 0.3057 0.1762 0.0000 0.1953 0.8047 1.57 7.15

6 0.3861 0.3436 0.2703 0.0117 0.2331 0.7552 1.47 4.12

7 0.2840 0.3722 0.3438 0.0184 0.2628 0.7188 1.42 2.96

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Chapter-3

Figure 3.8.:Experimental tie lines for the ternary system: Chloroform-acetol-water at 298.15 K and 1 atm.

Table 3.8.:Experimental Tie Lines data for the system ethyl acetate (1) - acetol (2) - water (3) atT= 298.15 K andp = 0.1 Mpa.

Sl. Extract phase Raffinate phase Distribution Selec-

No. X₁ X₂ X₃ X₁ X₂ X₃ Co-efficient(β) tivity(S)

1 0.8005 0.0149 0.1846 0.0139 0.0176 0.9685 0.85 4.44

2 0.7214 0.0544 0.2242 0.0050 0.0582 0.9368 0.93 3.91

3 0.6858 0.0838 0.2304 0.0214 0.0772 0.9014 1.09 4.25

4 0.6125 0.1131 0.2744 0.0375 0.1061 0.8564 1.07 3.33

5 0.4980 0.1533 0.3487 0.0166 0.1610 0.8224 0.95 2.25

6 0.4112 0.1792 0.4086 0.0930 0.1847 0.7223 0.97 1.72

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Chapter-3

Figure 3.9.:Experimental tie lines for the ternary system: Ethyl acetate-acetol- water at 298.15 K and 1 atm.

Table 3.9.:Experimental Tie Lines data for the systemn-propyl acetate (1) - acetol (2) - water (3) atT= 298.15 K andp= 0.1 Mpa.

Sl. Extract phase Raffinate phase Distribution Selec-

No. X1 X2 X3 X1 X2 X3 Co-efficient(β) tivity(S)

1 0.8493 0.0304 0.1203 0.0164 0.0492 0.9344 0.62 4.80

2 0.8005 0.0673 0.1322 0.0283 0.0896 0.8821 0.75 5.01

3 0.7114 0.1152 0.1734 0.0104 0.1417 0.8479 0.81 3.98

4 0.6405 0.1501 0.2094 0.0170 0.1824 0.8006 0.82 3.15

5 0.5657 0.1901 0.2442 0.0276 0.2230 0.7494 0.85 2.62

6 0.4336 0.2586 0.3078 0.0672 0.2840 0.6488 0.91 1.92

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Chapter-3

Figure 3.10.:Experimental tie lines for the ternary system: n-propyl acetate-acetol -water at 298.15 K and 1 atm.

Table 3.10.:Experimental Tie Lines data for the system n-butyl acetate (1) - acetol (2) - water (3) atT= 298.15 K and p= 0.1 Mpa.

Sl. Extract phase Raffinate phase Distribution Selec-

No. X1 X2 X3 X1 X2 X3 Co-efficient(β) tivity(S)

1 0.8944 0.0289 0.0767 0.0117 0.0526 0.9357 0.55 6.70

2 0.8411 0.0626 0.0963 0.0317 0.1000 0.8683 0.63 5.64

3 0.8066 0.0946 0.0988 0.0130 0.1499 0.8371 0.63 5.35

4 0.7589 0.1286 0.1125 0.0090 0.1926 0.7984 0.67 4.74

5 0.6984 0.1604 0.1412 0.0095 0.2364 0.7541 0.68 3.62

6 0.6697 0.1949 0.1354 0.0166 0.2923 0.6911 0.67 3.40

7 0.5976 0.2381 0.1643 0.0243 0.3173 0.6584 0.75 3.01

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Chapter-3

Figure 3.11.:Experimental tie lines for the ternary system: n-butyl acetate-acetol -water at 298.15 K and 1 atm.

Figure 3.12.:Distribution co-efficient, Selectivity and % mole fraction of solvent in raffinate for acetol based ternary system: Present work Vs. Literature.

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Chapter-3

3.3.3. [BMIM][Tf

2

N] - furfural - water

The experimental LLE data of [BMIM][Tf₂N]/furfural/water system was measured at 298.15 K under atmospheric pressure. The experimental LLE data of the system along with distribution coefficients and selectivities is reported in Table 3.11. The experimen- tal LLE ternary diagram for the system is shown in Figure 3.13. The experimental data measured the distribution coefficient which was in the range of 84.79-164.88; while selectivity in the range of 315.83-543.85. Selectivity value grater than unity implies a possible extraction of furfural by [BMIM][Tf₂N]. Another significant aspect is the fact that the quantity of ionic liquid in raffinate phase is zero which will again result into lower process operating cost. Another important finding is that [BMIM][Tf₂N] can be an effective solvent at close to 0.50 mole fraction of furfural. Finally, the performance of [BMIM][Tf₂N] was also compared with other solvents (ethyl acetate, propyl acetate, 1- butanol, tert-pentanol) as reported in literature in terms of distribution coefficient and selectivity [de Almeida et al., 2012, Mannisto et al., 2016] and shown in Figure 3.14.

The highest furfural distribution coefficients were found for propyl acetate followed by [BMIM][Tf₂N]. Similarly, selectivity also followed the same trend i.e. propyl acetate followed by [BMIM][Tf₂N]. However mole fraction(%) of [BMIM][Tf₂N] in raffinate phase was close to zero; whereas for other solvents it was in the range of 0.10-2.55 %.

Overall, [BMIM][Tf₂N] and propyl acetate are potential solvents for the extraction of furfural from aqueous solution.

3.3.4. Regeneration of Ionic Liquids

Most ionic liquids exhibit negligible vapor pressure as well as high thermal and chem- ical stabilities. These properties make usage of ionic liquids as solvents economical as regeneration can be easily carried out and the same solvent can be reutilized with in- significant quantity loss. Figure 3.15 shows the TG/DTG curves of [BMIM][Tf2N]. The curve clearly shows that [BMIM][Tf2N] remains in liquid phase till 350^◦ C. In present work ionic liquids, [BMIM][Tf₂N] and [EMIM][Tf₂N], were regenerated several times

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Chapter-3 (more than 10) and it was found the its property remain the same after each regener- ation. Figure 3.16 shows the ¹H NMR plot of regenerated [BMIM][Tf₂N] after acetic acid extraction. No peak was detected at 1.90 ppm due to methyl group of acetic acid.

Table 3.11.:Experimental Tie Lines data for the system [BMIM][Tf2N] (1) - furfural (2) - water (3) atT= 298.15 K and p= 0.1 Mpa.

Sl. Extract phase Raffinate phase Distribution Selec- No. X₁ X₂ X₃ X₁ X₂ X₃ Co-efficient(β) tivity(S)

1 0.5653 0.1319 0.3028 0.0004 0.0008 0.9988 164.88 543.85 2 0.4617 0.2210 0.3173 0.0002 0.0022 0.9976 100.45 315.83 3 0.3400 0.3840 0.2760 0.0002 0.0036 0.9962 106.67 385.00 4 0.2873 0.4986 0.2141 0.0004 0.0055 0.9941 90.65 420.92 5 0.1913 0.5681 0.2406 0.0000 0.0067 0.9933 84.79 350.05

Figure 3.13.:Experimental tie lines for the ternary system: [BMIM][Tf₂N]-furfural -water at 298.15 K and 1 atm.

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Chapter-3

Figure 3.14.:Distribution co-efficient, Selectivity and % mole fraction of solvent in raffinate for furfural based ternary system: Present work Vs. Literature.