Experimental Study on Liquid-Liquid Equilibria of Alcohol- Ester-Water-CaCl2System

Fu Jiquan; Fu Die

(1. Center of Chemical Engineering, Beijing Key Laboratory, Beijing Institute of Fashion Technology, Beijing, 100029; 2. Impact Environmental Consulting, Inc., 170 Keyland Ct, Bohemia, NY 11716, USA)

Experimental Study on Liquid-Liquid Equilibria of Alcohol- Ester-Water-CaCl2System

Fu Jiquan1; Fu Die2

(1. Center of Chemical Engineering, Beijing Key Laboratory, Beijing Institute of Fashion Technology, Beijing, 100029; 2. Impact Environmental Consulting, Inc., 170 Keyland Ct, Bohemia, NY 11716, USA)

The binary liquid-liquid equilibrium (LLE) data for salt-containing systems of 1-butanol+water+CaCl2,n-butyl acetate+water+CaCl2and ethyl acetate+acetic acid+water+CaCl2were determined and the salt effect was analyzed. The results showed that an obvious salt effect could be identified for the systems of 1-butanol+water+CaCl2and ethyl acetate+acetic acid+water.

1-butanol, n-butyl acetate, salt effect, salt-containing, liquid -liquid equilibria

1 Introduction

Extraction process is an important method for separation of liquid mixture. According to the liquid-liquid equilibrium (LLE) and liquid-liquid extractive operation principle, the bigger the two-phase region is, the better the effect of liquid-liquid extractive separation would be. The two-phase region may extend when an inorganic salt is added to a mixture. Therefore, addition of inorganic salt is a good approach for improving the effect of separation due to the existence of salt effect. The saltcontaining data of LLE is the base for research and design of separation process, and the research and design would be limited because of the lack of necessary data[1-4]. For a certain system, the magnitude of two-phase region can be affected by two factors: (1) Temperature: according to the information[5], the region will change with an increasing or a decreasing temperature. Indeed, in some systems, temperature change not only can change the region and the slope of the tie line, but also can change the type of liquid-liquid system. For example, the type-II system at low temperature may change into type-I system when temperature increases. (2) Salt effect: When a kind of salt is added into a system, the solubility of the compounds may change due to static effect of cations and anions. Increase in solubility (salting in) and decrease in solubility (salting out) are the results of two kinds of salt effects.

Because of the difficulty in measuring the salt-containing equilibrium composition, it is not easy to carry out laboratory research. Therefore, the number of reports relating to the study on salt-containing liquid-liquid equilibria is limited. This paper provides the LLE data which are experimentally measured on three systems containing alcohol+ester+water+CaCl2. In addition, the salt effect of the systems was also analyzed.

2 Experimental

2.1 Experimental materials

The reagents grade and the supply companies are listed Table 1.

Table 1 Reagent Grade and Supply Company

2.2 Experimental equipment

A glass reaction vessel equipped with a thermostatic water-bath was used to measure the data of salt-added liquid-liquid equilibrium. The temperature was measured with a mercury thermometer (with a division of 1/10 ℃). Atmospheric pressure was adopted in the experiments.

2.3 Method of analysis

Methods combining chromatography and titration were used to determine the composition of two liquid phases[6]. Chromatography was used to determine the non-electrolyte composition in liquid-liquid equilibria system, while titration was used to measures the salt content in the organic phase and the water phase.

Chromatographic analysis: A gas chromatograph (type 102G, manufactured by the Shanghai Analytical Instrument Factory) and an electronic integrator (HP 3390A) were used to determine the non-electrolyte content in liquid-liquid equilibrium system.

Titration: The concentration of CaCl2in two phases is measured by complexometric titration with EDTA, using EDTA as the indicator.

2.4 Experiments

Salt-containing LLE of three systems were investigated by experiments.

1) 1-Butanol+water+CaCl2system

The content of CaCl2was 10 m% (based on water used as the solvent), and the temperature was 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃ and 80 ℃, respectively.

2)n-Butyl acetate+water+CaCl2system

The content CaCl2was 10 m% (based on water used as the solvent), and the temperature was 30 ℃, 40 ℃, 50 ℃, 60 ℃ and 70 ℃.

3) Ethyl acetate+acetic acid+water+CaCl2system

The content of CaCl2was 10m% (based on water used as the solvent), and the temperature was 30 ℃, 50 ℃ and 70 ℃, respectively.

3 Results and Discussion

3.1 LLE for the system of 1-butanol (1)+water(2)+CaCl2(3)

The experimental LLE data of 1-butanol (1)+water (2)+CaCl2(3) system were determined at six temperatures covering 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃ and 80 ℃, respectively (under atmospheric pressure). The LLE data for the system are shown in Table 2.

The data in Table 2 were transformed into the saltfree form, from which a diagram is developed in order to make a comparison with the general binary data of 1-butanol(1)+water (2) system as referred to in the paper[7-8]. The results are shown in Figure 1.

Figure 1 Effect of CaCl2on the LLE of the 1-butanol (1)+water (2) system (data established on salt-free basis)

It can be seen from Figure 1 that the addition of inorganic salt could have great impact on the solubility of an organic compound in the aqueous solution. If an increase in solubility is observed, it is the phenomenon of “saltingin”, whereas if a decrease in solubility is detected, it is the phenomenon of “salting out”. In Figure 1, the two-phase region became larger after adding CaCl2into the 1-butanol-water system. The solubility significantly decreased. These facts indicate that CaCl2has a notably produced effect of “salting out” for the 1-butanol+water system.

Table 2 Experimental LLE data of 1-butanol (1)+ water (2) + CaCl2(3) systeme

It can be also seen that with the increase of temperature, the two-phase region decreases. The reason is that the solubility between 1-butanol and water increases with an increasing temperature. Therefore, the solubility curves change and the two-phase region of the system decreases.

3.2 LLE for the system ofn-butyl acetate (1)+water (2)+CaCl2(3)

The LLE data of n-butyl acetate (1)+water (2)+CaCl2(3) system were determined at five different temperatures, namely: 30 ℃, 40 ℃, 50 ℃, 60 ℃ and 70 ℃ (under atmospheric pressure). The LLE data are listed in Table 3. Similar to Section 3.1, the data in Table 3 were transformed into the salt-free form to draw a diagram (in Figure 2) for making comparison with the system ofn-butyl acetate (1)+water (2) reported by Liu Jiaqi[8]. As indicated in Figure 2, it can be concluded that the solubility curves remain almost unchanged and the “salting out” phenomenon is not distinctive after adding a salt into the system. Generally speaking, strong or weak salt effects are not only influenced by the kind of salt used, but are also affected by the different ingredients making up the system. With respect to then-butyl acetate (1)+water (2)+CaCl2(3) system, CaCl2may not be a good salt to produce the salt effect. In addition, the low salt concentration might be the reason leading to weak salt effect.

Table 3 Experimental LLE Data of n-Butyl Acetate (1)+Water (2)+CaCl2(3) System

Figure 2 Effect of CaCl2on the LLE of the n-butyl acetate (1)+ water(2) system (data established on salt-free basis)

3.3 LLE for the system of ethyl acetate (1)+acetic acid (2)+water (3)+CaCl2(4)

LLE data were measured for the system of ethyl acetate (1)+acetic acid (2)+water (3)+CaCl2(4) at three different temperatures of 30 ℃, 50 ℃, and 70 ℃ (under atmospheric pressure). The LLE data for this system are shown in Table 4. The salt-fee triangle phase diagram and the comparison with ternary system without addition of salt reported in reference [9] are shown in Figure 3. It is observed that the two-phase region with CaCl2is larger than that of the same system without salt addition. The results show that an extra amount of the salt does have an influence on the solubility of organic compounds in the organic phase. It can also be concluded that the solubility increases with the temperature increasing from 30 ℃ to 70 ℃. In other words, in the presence of CaCl2, the two-phase region has been shrunk when the temperature increases from 30 ℃ to70 ℃. The results indicate that the temperature has the ability to influence the two-phase region.

Figure 3 Effect of CaCl2on the LLE of ethyl acetate (1)+acetic acid (2)+water (3) system (data established on salt-free basis)

Table 4 Experimental LLE Data of Ethyl Acetate (1)+Acetic Acid (2)+Water (3)+CaCl2(4) System

4 Conclusions

(1) With respect to the system of 1-butanol (1)+water (2), the solubility between organic compound and water decreases after adding CaCl2. Obvious “salting-out” effect can be found in the system. However, for n-butyl acetate (1)+water (2) system, salt effect of the LLE is not affected by addition of CaCl2.

(2) With respect to the system of ethyl acetate (1)+acetic acid (2)+water (3), the concentration of water in organic phase decreases obviously in the two-phase region after adding CaCl2and a distinctive salting-out effect can be found. In addition, the two-phase region (with salt) decreases slightly with the increase of temperature. The result indicates that the system is not very sensitive to temperature change.

Acknowledgement:The project is financially supported by the SINOPEC (408069).

Reference

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Recieved date: 2013-12-26; Accepted date: 2014-03-28.

Prof. Fu Jiquan, Telephone, +86-10-64288291, E-mail: fujq010@sina.com.