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How to derive the expressions of ka , Aj, and ky in terms of characteristic parameters of nonelectrolyte and the ions of the salt has been clarified in chapter 1.

6.2.2. Case study (1) The system ofDMF/C4

The method of separating C4 by extractive distillation with DMF is widely used in industry. Herein, the investigated system is composed of DMF, salt NaSCN with weight fraction 10% in DMF, and C4 hydrocarbons. We use the number 1, 2, 3, 4, 5 and s to represent n-butane, butene-1, trans-2-butene, cis-2-butene, 1,3-butadiene and salt respectively [130].

According to scaled particle theory, the three terms ky, ka are calculated, and the sequence of salting coefficients is ks, >ks2 >ks3 >ksi, which is reasonable because the fluidity of electron cloud of C4 hydrocarbons is different and thus the interaction between salt and C4 hydrocarbons is in the following order: Butane < butene < butadiene < butyne.

Furthermore, ks], ks2, ksi and ksA are larger than zero, which means that the salt effect of

C4 hydrocarbons is salting out.

The relative volatilities at infinite dilution of C4 hydrocarbons with salt are calculated by using Eq. (45). To evaluate the accuracy, the calculated values are compared with the experimental values, as shown in Table 24 from which it can be seen that the calculated values are in good agreement with the experimental values. It indicates that scaled particle theory is successful for this system.

Table 24

Comparison of relative volatilities at infinite dilution between calculated and experimental values at T\ = 303.15K and T2 = 323.15K

Table 24

Comparison of relative volatilities at infinite dilution between calculated and experimental values at T\ = 303.15K and T2 = 323.15K

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