Evaluation of the 2,2â²,2â³-Nitrilotrisethanol as an Entrainer for

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Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Evaluation of the 2,2′,2″-Nitrilotrisethanol as an Entrainer for Separation of an Isopropanol + Water Mixture Tarun Jain, Hitesh Sharma, Neetu Singh,* and Jai Prakash Kushwaha

J. Chem. Eng. Data Downloaded from pubs.acs.org by UNIV OF WARWICK on 01/01/19. For personal use only.

Department of Chemical Engineering, Thapar Institute of Engineering & Technology, Patiala 147004, India ABSTRACT: The present study focuses on the investigation of 2,2′,2″nitrilotrisethanol (triethanolamine) as an entrainer to effect the separation of an isopropanol−water mixture. The vapor−liquid equilibrium (VLE) data were measured for the binary systems isopropanol + triethanolamine and water + triethanolamine using an improved Othmer still at 101.3 kPa. Experimental data for the ternary mixture isopropanol + water + triethanolamine were also studied for different entrainer concentrations. Three initial triethanolamine concentrations, 5 mol %, 10 mol %, and 15 mol %, were examined in the feed solution for VLE experiments. The results demonstrated that the addition of triethanolamine in the isopropanol + water mixture produces a considerable increment in the relative volatility, which could eliminate the azeotrope successfully. Hence, triethanolamine was found to be an effective entrainer for breaking the isopropanol + water azeotrope. Further, the NRTL model was used for fitting the experimental VLE data, and the binary interaction parameters were regressed. The estimated values for binary and ternary systems agreed well with the experimental data. The overall average deviations for the vapor-phase mole fraction and equilibrium temperature between the experiment and correlation were found to be 0.09 and 0.40 K, respectively. Moreover, the thermodynamic consistency check of experimental VLE data was performed by using the modified McDermott−Ellis test and Wisniak’s L−W test.

1. INTRODUCTION Isopropanol (propan-2-ol) is an important member of the alcohol family and is a widely used raw material in many industries such as production of dyestuffs, preparation of pesticides, cellulose synthesis, cosmetics, paints, pharmaceutical manufacturing, and as solvent in semiconductor industries.1 Isopropanol (IPA) is generally produced by two techniques: direct hydration and indirect hydration of propylene.2 In many industries it is necessary to use pure isopropanol, and for this purpose it is essential to eliminate water from the IPA + water mixture. The IPA + water mixture forms a minimum boiling azeotrope with water at 67.5 mol % (IPA), at standard atmospheric pressure and 353.45 K temperature.3 Thus, it becomes difficult to separate through conventional distillation, and enhanced distillation techniques should be used to get the components of azeotrope in pure form. Many enhanced distillation techniques have been utilized for separating such mixtures like adsorptive distillation,4 azeotropic distillation, membrane distillation,5 pervaporation,6 diffusion distillation,7 extractive distillation, and salt distillation. Hybrid techniques which use a combination of these methods are also available and have been reported in the literature.8 Out of all the available methods, heterogeneous azeotropic distillation using cyclohexane as an entrainer is the most common.9,10 However, more variable sensitivity, various steady states, and nonlinear dynamics11 are the drawbacks which hamper the operating range of this separation process under different feed conditions. Extractive distillation has been © XXXX American Chemical Society

proven as a promising technology for mass production of anhydrous IPA. In the extractive distillation process, a heavyboiling component is introduced in the system, which increases the relative volatility of the azeotropic mixture more than unity without forming any additional azeotrope and without causing separation of liquid−liquid phases.12 Other than these advantages, this process is an energy-efficient technology, and it can be operated in a continuous mode and is capable of separation of complex azeotropic mixtures. Selection of an appropriate solvent/salt is the critical step for designing a distillation sequence in extractive distillation. From the literature available, many salts like magnesium chloride, potassium carbonate,13 magnesium bromide,14 lithium chloride, lithium bromide, sodium bromide,15 sodium chloride, and ionic liquids16 have been proved as feasible entrainers for dehydration of isopropanol. Using salts as an entrainer has many drawbacks like corrosivity, pollution to the environment, and difficulty in recycling/reuse. Moreover, Gmehling and Mö llmann17 studied 1,2-ethanediol, dimethyl sulfoxide (DMSO), N-methyl-6-caprolactam, and N-methyl-2-piperidone entrainers for isopropanol dehydration using extractive distillation. They found DMSO to be the best out of all studied entrainers, as it offered the largest separation factor without any additional azeotrope formation in the system. Other than these, ethylene glycol has also been used for IPA Received: July 16, 2018 Accepted: December 18, 2018

A

DOI: 10.1021/acs.jced.8b00610 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Journal of Chemical & Engineering Data

Article

dehydration.18 For designing an extractive distillation process, prior study of its vapor−liquid equilibrium (VLE) data is essential. In this work, triethanolamine (TEA) was chosen as an entrainer for separation of the IPA + water azeotropic mixture. TEA is proposed as an entrainer because it offers the following advantages over other conventional entrainers:19 (1) TEA is a noncorrosive organic compound which is used as a corrosion inhibitor and antiscaling agent in industries. It will enhance the life of the distillation column. (2) It is completely soluble in water as well as IPA. (3) The high boiling point of TEA (613.15 K) as compared to IPA (355.7 K) and water (373.15 K) offers two additional advantages: easy recoverability of TEA by evaporation and comparatively pure product (anhydrous IPA) as compared to other extracting agents, for example, DMSO. (5) Due to the low volatility of TEA, losses will be low as compared to other entrainers. As a result, there is less requirement of makeup solvent. Experimental VLE data were generated for IPA (1) + TEA (2) and water (1) + TEA (2) binary systems at 101.3 kPa using an improved Othmer still. Other than this, isobaric VLE measurements were also done for the system formed by IPA (1) + water (2) + TEA (3) at atmospheric pressure. The influence of TEA on the VLE behavior of the IPA + water azeotropic system was discussed. The VLE data measured for different systems were fitted with the NRTL model. The correlated parameters for the model and average absolute deviations are given. Further, the VLE data were checked for thermodynamic consistency by applying modified McDermott−Ellis and Wisniak L−W thermodynamic consistency tests.

for proper mixing of the sample in the still. The still is connected to the two condensers: air-cooled and water-cooled recirculation condensers, in sequence. The vapors produced by boiling of samples condense partially in an air-cooled condenser and water-cooled recirculation condenser, respectively. The condensate formed was sent back to the still. In order to measure the equilibrium temperature, a calibrated mercury thermometer was used with an uncertainty of 0.1 K. Approximately 45 min of time was provided to attain the equilibrium. Further, the heating of the sample in the still was stopped, and the samples (liquid phase and condensed vapor phase) were collected for analysis. The liquid-phase sample was collected from the still and the vapor-phase sample from the condensate sample bulb, provided below the water-cooled recirculation condenser. 2.3. Analysis. The equilibrium isopropanol and water compositions in the condensed vapor phase and liquid phase were determined using a gas chromatograph (AIMILNUCON: 5765 GC) which was provided with a thermal conductivity detector (TCD) and a Porapak QS column (2 m × 0.032 m). Hydrogen gas (Analar grade of purity >99.98 vol %) was used as a carrier gas with 4.7 × 10−7 m3·s−1 flow rate and 240 kPa inlet pressure. Temperatures of the injector, detector, and oven were maintained at 375, 375, and 433 K, respectively, with the uncertainty in the temperatures within 1 K. In the vapor phase, the presence of TEA was not detected. As TEA is present in the liquid sample, and it is essential to trap it before it enters in the column. Glass liners (Agilent Technologies) were used for this purpose, and they effectively prevented the column. To check the amount of TEA in a sample, mass balance was applied. A calibration curve was already made for determination of the equilibrium compositions by the relative area method. The compositions of vapor and liquid phases on mole fraction basis were determined with an uncertainty of 0.003.

2. EXPERIMENTAL SECTION 2.1. Materials. Isopropyl alcohol (Analysis grade, SigmaAldrich, >99 wt %) and triethanolamine (reagent grade, SigmaAldrich, >98 wt %) were employed directly without further purification. The description of used chemicals is compiled in Table 1. Double distilled water was used to prepare the IPA− water mixture, for all the experiments. Hydrogen gas of purity (>0.9998 volume fraction) was used for GC analysis.

3. RESULTS AND DISCUSSION 3.1. Effectiveness of TEA on Relative Volatility (α12) of the IPA−Water Azeotropic Mixture. Following the experimental methodology given above, the effectiveness of TEA was examined as an entrainer, for dehydration of the IPA + water azeotropic mixture. Experimental VLE data were generated for the azeotropic mixture of IPA + water (67.5 mol % IPA) in the presence of TEA. Entrainer concentration was varied in the range of 0−15 mol %. Experimental data are presented in Table 2, and the plots of relative volatility versus TEA concentration are presented in Figure 2. It is visible from the figure that, with the increase in the TEA content in the mixture, the relative volatility of IPA to water increases significantly. At 15 mol % TEA α12 reaches 2.6, which is 2.6 times greater than the entrainer-free system. 3.2. Binary Vapor−Liquid Equilibrium Data. Isobaric VLE for binary systems IPA (1) and TEA (2) and water (1) and TEA (2) were measured at 101.3 kPa using an improved Othmer still. Table 3 lists the experimental data obtained which include the equilibrium temperature T, the liquid-phase mole fraction of component i, xi, and activity coefficient, γi, of component i. As depicted in Figure 3(a) and (b), the increment in boiling point Tb of IPA and water occurs by adding the TEA in the system. Boiling points of both were found to increase by increasing the amount of TEA. VLE data for the water− TEA system were also compared with the

Table 1. Chemicals name

CAS no.

source

isopropyl alcohol

67-63-0

triethanolamine

102-71-6

SigmaAldrich SigmaAldrich our laboratory

double distilled water

purity (wt %)

purification method

>99%

none

>98%

none

2.2. Apparatus and Procedure. The isobaric VLE data were investigated by using an improved Othmer recirculation still shown in Figure 1. The detailed description of the equilibrium still, experimental procedure used in this work, and validation of the experimental apparatus are presented in our earlier publication.20 The VLE setup is composed of a still which consists of a heater for boiling of the samples and is operated at atmospheric pressure. A magnetic stirrer was used B



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Figure 1. Schematic diagram of modified Othmer-type recirculation still (1: boiling still; 2: heating mantle; 3: magnetic stirrer; 4: liquid-phase sampling port; 5, 6: thermometers; 7: air-cooled condenser; 8: water-cooled recirculation condenser; 9: condensate sampling port; 10: water-cooled condenser).

Table 2. Effect of TEA Concentration on the Relative Volatility α12 (x1′ ≈ 0.675) of the IPA (1) + Water (2) System at 101.3 kPa: Mole Fraction of IPA in the Liquid Phase Expressed on a TEA-Free Basis (x′1), Vapor-Phase Mole Fraction of IPA (y1), and Relative Volatility (α12)ab mol % of TEA

x′1

y1

relative volatility (α12)

0.0 2.0 3.0 5.0 7.0 10.0 15.0

0.627 0.629 0.628 0.626 0.627 0.630 0.632

0.637 0.649 0.662 0.688 0.721 0.761 0.817

1.04 1.09 1.16 1.32 1.54 1.87 2.60

Table 3. Experimental VLE Data and Correlated Results of Binary Systems at 101.3 kPa: Temperature (T), Mole Fraction of IPA in the Liquid Phase (x1), Experimental Activity Coefficient (γexp 1 ), Deviation in Activity Coefficient (Δγi), and Deviation in Equilibrium Temperature (ΔT)a water (1) + TEA (2)

TEA = 0−15.0 mol %. bStandard uncertainty u(x′1) = u(y1) = u(mole fraction of TEA ) = 0.003, u(α) = 0.025. a

Figure 2. Effect of triethanolamine concentration on relative volatility α12(x1′ ≈ 0.675) of the IPA (1) + water (2) system at 101.32 kPa.

S.No.

T (K)

TEA(Mole %)

1 2 3 4 5 6 7 8 9 10 11 12 13

373.1 373.7 374.1 375.0 376.2 377.3 378.1 378.6 379.4 380.3 381.7 382.3 384.6

0.00 1.90 3.30 7.30 12.70 17.70 21.10 23.60 26.50 30.80 33.10 39.00 45.80

S.No.

T (K)

TEA(Mole %)

x1

1 2 3 4 5 6 7 8 9 10 11 12

355.7 356.1 357.1 357.9 359.8 361.9 364.2 366.7 368.1 370.2 372.8 374.1

0.00 2.20 5.40 8.40 14.70 20.80 26.60 30.40 35.80 41.90 45.60 49.00

1.000 0.978 0.946 0.916 0.853 0.792 0.734 0.696 0.642 0.581 0.544 0.510

x1

γexp 1

Δγ1b

ΔTc (K)

0.0000 0.0003 −0.0001 −0.0006 −0.0010 −0.0011 −0.0050 −0.0014 0.0018 −0.0009 0.0083 −0.0011 −0.0021

0.00 −0.01 0.00 0.02 0.03 0.03 0.13 0.04 −0.05 0.02 −0.21 0.03 0.05

γexp 1

Δγ1b

ΔTc (K)

1.000 1.001 0.999 0.997 0.993 0.987 0.980 0.975 0.970 0.968 0.971 0.973

0.0000 0.0011 −0.0004 −0.0015 −0.0026 −0.0046 −0.0068 −0.0084 −0.0077 −0.0028 0.0045 0.0108

0.00 −0.03 0.01 0.04 0.07 0.12 0.18 0.22 0.21 0.08 −0.12 −0.30

1.000 1.000 0.981 1.001 0.967 1.002 0.927 1.009 0.873 1.026 0.823 1.048 0.789 1.062 0.764 1.080 0.735 1.101 0.692 1.127 0.669 1.152 0.610 1.187 0.542 1.240 IPA (1) + TEA (2)

a Standard uncertainty u(x1) = u(mole fraction of TEA) = 0.003, u(T) cal c exp − Tcal. = 1 K, u(P) = 0.5 kPa. bΔγ1 = γexp 1 − γ1 . ΔT = T

21

literature data in Figure 3(b). Experimental data in this study were found to be in good agreement with the literature data. C



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mole fraction, x′i . As shown in the figure, the curve for conventional distillation (x3 = 0)19 intersects with the α12= 1 line at 0.67 mol fraction. The addition of TEA changes the pattern of the curve. Although for x3 = 0.05 it could not break the azeotrope completely, for higher TEA mole fractions (x3 = 0.10 and 0.15), curves lie above the α12 = 1 line over the entire concentration range. Therefore, TEA is found as an appropriate entrainer for IPA dehydration via extractive distillation. It is visible from Table 4 that TEA is quite functional to enhance the relative volatility of the studied system above unity for 10 mol % and 15 mol % concentrations for the complete concentration range, but at 5 mol % TEA concentration, it could not break the azeotrope completely. 3.4. Correlation of VLE Data. VLE has been determined by the Fugacity equality (eq 1) in both the phases by using the γ−ϕ approach v

fi ̂ = fi ̂

L

(1)

V

yi ϕ ̂ p = xiγipis ϕisPEi

(2)

where fvî and fLî are the fugacities of the ith component in the vapor and liquid phase, respectively. xi and yi are mole fraction of the ith component in the liquid and vapor phase, respectively. ϕVi and ϕSi represent fugacity coefficients of the ith component in the vapor phase and of saturated pure i at system temperature T, respectively; γi is the ith component activity coefficient in the liquid phase; pis denotes the ith component saturation vapor pressure; and P is the total system pressure. The Antoine equation parameters19 are given in Table 5. The Fugacity coefficients were calculated using the virial equation of state truncated at the second coefficient with the Tsonopoulo correlations.22 Properties (vapor pressures and saturated liquid molar volumes) required for the estimation of Poynting effect (PE) were calculated using DIPPR equations.23 ÄÅ L É ÅÅ v (p − ps ) ÑÑÑ ÅÅ i i Ñ ÑÑÑ PEi = expÅÅÅ ÑÑ ÅÅ RT ÑÑÖ (3) ÅÇ

Figure 3. (a) Effect of triethanolamine on the normal boiling point of IPA at 101.32 kPa. (▲) Experimental data and (solid lines) calculations based on the NRTL model. (b) Effect of triethanolamine on the normal boiling point of water at 101.32 kPa. (●) Experimental data, (△) literature,21 and (solid lines) calculations based on the NRTL model.

3.3. Ternary Vapor−Liquid Equilibrium Data. The isobaric VLE data for the ternary system IPA (1), water (2), and TEA (3) were investigated at 101.3 kPa for three initial TEA (entrainer) concentrations in the feed solution: 5 mol %, 10 mol %, and 15 mol %. The experimental data are summarized in Table 4. To describe the effect of TEA as an entrainer, the temperature vs composition (T−x, y) diagrams for different TEA concentrations are plotted in Figure 4. The system equilibrium temperature increases due to very high boiling point of TEA. The more TEA that is added to the system, the higher the equilibrium temperature. Moreover, Figure 5 represents the effect of different TEA concentrations on the vapor and liquid phase mole fractions. As shown in Figure 5, the content of IPA increases in the vapor phase with increasing concentration of TEA. The relative volatility of the IPA + water system increases as the concentration of the entrainer increases, shifting the azeotropic point to higher IPA concentrations. As a result, the azeotrope of the system was terminated at 0.10 and 0.15 mol fractions of TEA. The 0.05 mol fraction of TEA in the mixture could not eliminate the azeotrope completely, but it shifted to higher IPA concentration. For the azeotropic mixture, the relative volatility for IPA to water is one, and to terminate this azeotrope, value of α12 should be higher than unity. The experimental and calculated α12 are represented in Figure 6 with respect to TEA-free liquid

So, the activity coefficients can be presented as eq 4 V

γi =

yi ϕ ̂ p xipis ϕisPEi

(4)

The value of PE is nearly one at low or moderate pressure; therefore, eq 2 can thus be reduced to V

yi ϕî p = xiγipis ϕis

(5)

Equation 5 was used to calculate the experimental activity coefficients for IPA + TEA and water + TEA binary systems, and further calculated experimental activity coefficients were fitted to the NRTL model. For the purpose of regression analysis and NRTL model parameters calculation, the MatLab program with least-squares error objective function (OF) (eq 6) was used.24 ÄÅ exp ÉÑ2 n Å ÅÅ γi − γicalcd ÑÑÑ Å ÑÑ OF = ∑ ÅÅ ÑÑ exp ÅÅ γ ÑÑ i (6) i=1 Å ÑÖ ÇÅ D



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Table 4. Experimental Isobaric VLE Data for the IPA (1) + Water (2) + TEA (3) System at 101.3 kPaa,b,c T (K)

S.No.

x1′

x1

x2

y1

γexp 1

0.000 0.145 0.312 0.432 0.574 0.616 0.660 0.732 0.837 0.884 0.932 0.934 1.000

1.954 1.672 1.701 1.493 1.384 1.106 1.053 0.999 0.992 0.991 1.977 1.005

0.000 0.189 0.365 0.453 0.596 0.652 0.759 0.808 0.829 0.888 0.932 0.954 0.976 1.000

2.958 2.667 2.241 1.747 1.436 1.239 1.199 1.177 1.120 1.093 1.077 1.065 1.048

0.000 0.193 0.388 0.526 0.621 0.719 0.786 0.848 0.889 0.955 0.969 0.987 1.000

3.862 3.324 2.966 2.589 1.740 1.415 1.322 1.254 1.148 1.126 1.106 0.924

γexp 2

α12

1.039 1.050 1.080 1.092 1.082 1.179 1.450 1.525 1.790 2.039 2.452 2.570

3.67 3.03 3.04 2.69 2.28 1.48 1.34 1.08 0.94 0.78 0.74

1.085 1.043 1.000 1.038 0.999 1.130 1.189 1.191 1.235 1.271 1.251 1.259 1.284

5.59 5.23 4.22 3.41 2.47 2.02 1.95 1.85 1.71 1.69 1.66 1.61

1.129 1.052 0.983 0.921 0.870 0.888 0.941 0.892 0.880 0.817 0.839 0.828

7.23 6.65 6.29 5.81 3.82 2.93 2.89 2.77 2.73 2.61 2.59

TEA = 5 mol % 1 2 3 4 5 6 7 8 9 10 11 12 13

373.5 370.1 366.0 362.9 360.4 358.8 358.2 357.8 357.3 357.0 356.9 356.8 356.8

0.000 0.044 0.130 0.200 0.334 0.413 0.567 0.671 0.826 0.890 0.946 0.950 1.000

1 2 3 4 5 6 7 8 9 10 11 12 13 14

373.8 370.2 366.4 363.5 361.3 359.5 358.4 357.9 357.6 357.4 357.2 357.2 357.1 357.1

0.000 0.040 0.099 0.164 0.302 0.431 0.609 0.683 0.724 0.823 0.890 0.926 0.962 1.000

1 2 3 4 5 6 7 8 9 10 11 12 13

374.3 371.2 367.1 363.9 361.8 360.4 359.6 359 358.5 358.1 357.9 357.7 357.6

0.000 0.032 0.087 0.150 0.220 0.401 0.556 0.659 0.743 0.886 0.923 0.967 1.000

0.042 0.124 0.190 0.318 0.392 0.539 0.638 0.785 0.845 0.900 0.903

0.909 0.827 0.760 0.633 0.558 0.411 0.313 0.165 0.105 0.051 0.048 TEA = 10 mol %

0.036 0.089 0.148 0.272 0.389 0.549 0.616 0.652 0.740 0.802 0.833 0.865

0.865 0.813 0.752 0.628 0.513 0.352 0.286 0.248 0.159 0.099 0.067 0.034 TEA = 15 mol %

0.027 0.074 0.127 0.187 0.341 0.473 0.560 0.631 0.753 0.785 0.821

0.823 0.776 0.723 0.664 0.509 0.377 0.290 0.218 0.097 0.066 0.028

Temperature (T), mole fraction of IPA in the liquid phase expressed on a TEA-free basis (x1′), mole fraction of IPA in the liquid phase (x1), mole fraction of water in the liquid phase (x2), experimental activity coefficient (γexp i ), and relative volatility (α12). The presence of TEA was not observed in the vapor phase. bStandard uncertainty u(x1) = u(x′1) = u (y) = u(mole fraction of TEA ) = 0.003, u(T) = 1 K. cu(α) = 0.025. x′1 is mole fraction of IPA in liquid phase expressed on a TEA-free basis. a

In the above equation, x′1 and x′2 are the mole fraction of IPA and water, respectively, in liquid phase expressed on a TEAfree basis, whereas IPA and water mole fractions in the vapor phase are denoted by y1 and y2, respectively. For binary systems (IPA + TEA and water + TEA), the correlation results for the maximum and average deviation in boiling points and activity coefficient are presented in Tables 3 and Table 6. The values obtained by calculations employing the NRTL activity coefficient model are plotted with experimental data in Figure 3 for comparison. Results advocate the good correlation between experimental and predicted VLE data.

In eq 6, i denotes a component, and n is the number of experimental data. Superscripts exp and calcd denote the experimental and calculated values, respectively. To estimate the binary and ternary parameters for constituents in the IPA + water + TEA system, the OF was set to be minimum. The relative volatility (α12) for IPA (1) + water (2) system is estimated by the following eq (eq 7). α12 =

y1 /x1′ y2 /x 2′

(7) E



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Figure 6. Relative volatility α12 of IPA (1) to water (2) using TEA (3) as an entrainer at 101.32 kPa: (▲) 5 mol %, (●) 10 mol %, and (◆) 15 mol % TEA; dotted line, TEA free;20 solid line, correlated by the NRTL model. xi′, liquid phase mole fraction (TEA-free basis).

Figure 4. Temperature−composition diagram for the IPA (1) + water (2) + TEA (3) system at 101.32 kPa with TEA= 5 mol % x′i vs T (▲) and y1 vs T (Δ), TEA = 10 mol %, xi′ vs T (●), and y1 vs T (○), TEA= 15 mol %, x′i vs T (◆) and y1 vs T (◇), --- TEA = 0%, ref 20.

Table 5. Antoine Constants for Pure Substances19 Antoine constants component

Ai

Bi

Ci

isopropanol water

8.87829 8.07131

2010.32 1730.63

252.636 233.426

Bi where T − 273 + Ci

log pisat = Ai −

a

psat i is in mm Hg and T is in K.

namically consistent if local deviation value (D) < maximum deviation value (Dmax), where D is defined as n

D=

∑ (xib + xia)(ln γib − ln γia) i=1

(8)

where n is the number of component and a, b are two successive experimental points. According to Wisniak and Tamir,25 the maximum deviation value can be defined as ij

1 1 1 yz + + zzzzΔx x yia xib yib z i=1 k ia { n n Δp + ∑ |ln γib − ln γia|Δx + ∑ (xib + xia) p i=1 i=1 n ÅÄÅ ÑÉÑ Å ÑÑ 1 1 ÑΔT + ∑ (xib + xia)Bi ÅÅÅÅ + 2 2Ñ ÑÑ Å + + ( T C ) ( T C ) ÅÅÇ a i b i Ñ i=1 ÑÖ

∑ (xib + xia)jjjjj 1 n

Dmax = Figure 5. Experimental and calculated VLE data for the IPA (1) + water (2) + TEA (3) ternary system at 101.32 kPa. For TEA = (▲) 5 mol %, (●) 10 mol %, and (◆) 15 mol %, dotted line, solvent free20 and solid lines, correlations based on the NRTL model.

Experimental VLE data of the ternary system IPA + water + TEA were also correlated to the NRTL model on a solvent-free basis. The evaluated results of the average and maximum difference in equilibrium temperatures, DT and dT, and those in IPA mole fraction in the vapor phase, Dy1 and dy1, are summarized in Table 6 and represented in Figure 5. The calculated mole fraction of IPA in the vapor phase and the average value of difference in equilibrium temperature were found to be 0.40 K and 0.09, respectively. 3.5. Thermodynamic Consistency Check of Experimental Data. To assess the acceptability of the experimental VLE data, the thermodynamic Wisniak’s L−W test25 and modified McDermott−Ellis test27 were applied on the ternary VLE data. McDermott−Ellis27 suggested that in a ternary system two experimental points can be considered thermody-

+

(9)

where Ai, Bi, and Ci are the parameters of the Antoine equation B ln pi0 = Ai − T +i C , and Δx, ΔT, and ΔP are the measurement i

i

errors in mole fraction, temperature, and pressure, respectively. The results of thermodynamic consistency check are represented in Table 7. It is found that D < Dmax for the entire data points. Hence, the modified test of McDermott− Ellis indicates that the experimental ternary data are consistent. Moreover, experimental data were also checked by Wisniak’s L−W26 point-to-point test and found thermodynamically consistent as the values of Li satisfy the criterion value Wi

recommended by Wisniak’s L−W and lie between 0.92 and 1.08 for all data points. F



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Table 6. Parameters and Correlation Deviations of the NRTL Model at 101.3 kPaa,b,c,d,e,f systems

Δg12

Δg21

α

DT (K)

dT (K)

Dy1

dy1

IPA (1) + TEA (2) water (1) + TEA (2) IPA (1) + water (2) + TEA (3)

1988.6 4986.5 85.3

−2045 −1399.6 3353.8

0.3 0.3 0.3

0.11 0.047 0.40

0.3 0.211 0.60

0.09

0.19

Binary interaction parameters (Δg12, Δg21) and nonrandomness factor (α).

a

b

Δg12 = (g12 − g22) .

c

n

DT = (1/n) ∑ |T exp − T calc|k k=1

.

d

dT = max(|T exp − T calc|) .

e

n

Dy1 = (1/n) ∑ |y1exp − y1calc |k k=1

.

f

dy1 = max(|y1exp − y1calc |) .

Table 7. Results Obtained in Application of Wisniak−Tamir’s Modification26 of McDermott−Ellis27 to the Ternary System IPA1 + Water2 + TEA3 for Different TEA Concentrations: Temperature (T) and Mole Fraction of IPA in the Liquid Phase (x1)a TEA = 10 mol %

TEA = 15 mol %

T (K)

x1

D

Dmax

|D| − |Dmax|

T (K)

x1

D

Dmax

|D| − |Dmax|

373.8 370.2 366.4 363.5 361.3 359.5 358.4 357.9 357.6 357.4 357.2 357.2 357.1 357.1

0.000 0.036 0.089 0.148 0.272 0.389 0.549 0.616 0.652 0.740 0.802 0.833 0.865 0.902

---−0.102 0.005 −0.201 −0.001 −0.161 −0.077 −0.028 −0.145 −0.137 −0.104 −0.149 -------

---0.049 0.051 0.055 0.057 0.059 0.061 0.062 0.066 0.072 0.079 0.097 -------

---−0.151 −0.046 −0.256 −0.058 −0.220 −0.138 −0.090 −0.211 −0.209 −0.183 −0.246 -------

374.3 371.2 367.1 363.9 361.8 360.4 359.6 359.0 358.5 358.1 357.9 357.7 357.6

0.000 0.027 0.074 0.127 0.187 0.341 0.473 0.560 0.631 0.753 0.785 0.821 1.000

---−0.161 −0.160 −0.165 −0.262 −0.189 −0.205 −0.158 −0.422 −0.133 −0.296 -------

---0.051 0.052 0.056 0.063 0.065 0.069 0.075 0.097 0.114 0.169 -------

---−0.212 −0.212 −0.221 −0.325 −0.254 −0.274 −0.233 −0.519 −0.247 −0.465 -------

a

n

D=

∑ (xib + xia)(ln γib − ln γia)Dmax

1 1 1 yz + + zzzzΔx x yia xib yib z i=1 k ia { n n Δp + ∑ |ln γib − ln γia|Δx + ∑ (xib + xia) p i=1 i=1 ÄÅ ÉÑ n ÅÅ ÑÑ 1 1 Å ÑÑΔT Å + ∑ (xib + xia)Bi ÅÅ + ÑÑ 2 2 Å Ñ + + ( T C ) ( T C ) Å i b i Ñ i=1 ÅÇ a ÑÖ n

=

ij

∑ (xib + xia)jjjjj 1 i=1

+

. G



Article

(10) Arifin, S.; Chien, I. L. Combined Preconcentrator/Recovery Column Design for Isopropyl Alcohol Dehydration Process. Ind. Eng. Chem. Res. 2007, 46, 2535−2543. (11) Widagdo, S.; Seider, W. D. Azeotropic Distillation. AIChE J. 1996, 42, 96−130. (12) Arifin, S.; Chien, I. L. Design and Control of an Isopropyl Alcohol Dehydration Process via Extractive Distillation Using Dimethyl Sulfoxide as an Entrainer. Ind. Eng. Chem. Res. 2008, 47, 790−803. (13) Zhigang, T.; Rongqi, Z.; Zhanting, D. Separation of isopropanol from aqueous solution by salting-out extraction. J. Chem. Technol. Biotechnol. 2001, 76, 757−763. (14) Gironi, F.; Lamberti, L. Vapour-liquid equilibrium data for the water-2-propanol system in the presence of dissolved salts. Fluid Phase Equilib. 1995, 105, 273−286. (15) Sada, E.; Morisue, T.; Yamaji, H. (1975) Salt effects on isobaric vapour-liquid equilibrium of isopropanol-water system. Can. J. Chem. Eng. 1975, 53, 350−353. (16) Pereiro, A.; Araújo, J.; Esperança, J.; Marrucho, I.; Rebelo, L. Ionic liquids in separations of azeotropic systems − A review. J. Chem. Thermodyn. 2012, 46, 2−28. (17) Gmehling, J.; Möllmann, C. Synthesis of Distillation Processes Using Thermodynamic Models and the Dortmund Data Bank. Ind. Eng. Chem. Res. 1998, 37, 3112−3123. (18) Ladisch, M. R.; Dyck, K. Dehydration of ethanol: new approach gives positive energy balance. Science 1979, 205, 898−900. (19) Perry, R. H. Perrys chemical engineering handbook, 7th ed.; McGraw-Hill: New York, 1934; pp 1313−1321. (20) Sharma, B.; Singh, N.; Jain, T.; Kushwaha, J. P.; Singh, P. Acetonitrile dehydration via extractive distillation using low transition temperature mixtures as entrainer. J. Chem. Eng. Data 2018, 63, 2921−2930. (21) Zhang, Z.; Zhang, Q.; Zhang, Q.; Zhang, T.; Li, W. Isobaric Vapor−Liquid Equilibrium of tert-Butyl Alcohol + Water + Triethanolamine-Based Ionic Liquid Ternary Systems at 101.3 kPa. J. Chem. Eng. Data 2015, 60, 2018−2027. (22) Tsonopoulos, C. An empirical correlation of second virial coefficient. AIChE J. 1974, 20, 263−272. (23) Daubert, T. E.; Danner, R. P. Physical and Thermodynamic Properties of Pure Chemicals. Data Compilation; AIChE: New York, 1992; pp 3−27. (24) Kim, I.; Svendsen, H. F.; Børresen, E. Ebulliometric determination of vapor-liquid equilibria for pure water, monoethanolamine, N-Methyldiethanolamine, 3-(methylamino)-propylamine, and their binary and ternary solutions. J. Chem. Eng. Data 2008, 53, 2521− 2531. (25) Wisniak, J. A New Test for the Thermodynamic Consistency of Vapor-Liquid Equilibrium. Ind. Eng. Chem. Res. 1993, 32, 1531−1533. (26) Wisniak, J.; Tamir, A. Vapour−liquid equilibriums in the ternary systems water−formic acid−acetic acid and water−acetic acid−propionic acid. J. Chem. Eng. Data 1977, 22, 253−260. (27) McDermott, C.; Ellis, S. R. M. A multicomponent consistency test. Chem. Eng. Sci. 1965, 20, 293−296.

4. CONCLUSIONS In this study, isobaric VLE of the IPA + water + TEA ternary system and its two binary combination systems, IPA + TEA and water + TEA, were measured at 101.3 kPa using an improved Othmer recirculation still. The VLE results represent that addition of TEA enhances the α12 of IPA to water, which ultimately leads to removal of the azeotropic point. Thermodynamic modeling of the experimental data was performed by using the NRTL activity coefficient model to correlate the equilibrium data. For this purpose, the binary thermodynamic parameters were optimized by calculating the activity coefficients. From the results, a higher level of accuracy was obtained by using the NRTL model. The average absolute differences for the equilibrium temperature and vapor-phase mole fraction of IPA were calculated to be 0.40 K and 0.09, respectively. Other than this, to examine the reliability of the VLE data, the thermodynamic consistency was checked by using the modified McDermott−Ellis test and Wisniak’s L−W test. Results demonstrated the good thermodynamic consistency.

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AUTHOR INFORMATION

Corresponding Author

*Tel.: +91-9876019399. Fax: +91-175-2393005. E-mail: neetu. [email protected]. ORCID

Neetu Singh: 0000-0002-1970-7095 Jai Prakash Kushwaha: 0000-0003-4077-8805 Funding

Financial support from the Thapar Institute of Engineering & Technology, Patiala, grant no. TU/SEED/2014/CHE/NS, is gratefully acknowledged. Notes

The authors declare no competing financial interest.

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REFERENCES

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