Vapor–Liquid Equilibrium in Binary and Ternary Azeotropic Solutions Acetonitrile-Ethanol-Water with the Addition of Amino Esters of Boric Acid

Round 1

Reviewer 1 Report

REVIEW

Obtaining new VLE experimental data and refinement of UNIFAC parameters confirms the actuality of the research. The reliability of the data obtained and the correctness of the experiment was confirmed by comparing the experimental and literary data obtained for the acetonitrile + water system.

Comments:

1) I recommend the authors to replace some terms, for example, «the entire range of concentrations» for «the entire composition range»; «extractant» for «extractive agent» (extractant is usually used for extraction process).

2) Page 1, line 32 «In industrial technologies, acetonitrile and ethanol are often present in mixtures with water», please, provide the reference for industrial technologies or at least list the productions

3) The current international standard for the metric system is the International System of Units (SI). Boiling points should be indicated in Kelvin.

4) The Abstract states " Residual curves and the conditions of phase vapor – liquid equilibrium (TPXY data) at atmospheric pressure were experimentally measured ". This may mislead the reader, since the full-scale experiment was conducted only for one constituent of the ternary system. The authors should clearly state in Abstract which data were obtained experimentally and which using thermodynamic modeling.

5) The authors should add the paper in the list of references, the output of which is given below. The paper describes the process of extractive distillation of a mixture containing acetonitrile, ethanol, water and methanol. Selective agents have been found.

Dmitry A. Ryzhkin, Valentina M. Raeva. ANALYSIS OF ENERGY CONSUMPTION OF EXTRACTIVE DISTILLATION FLOWSHEETS OF FOUR-COMPONENT SOLVENT MIXTURE. ChemChemTech , Volume 64, pp 47-55; https://doi.org/10.6060/ivkkt.20216406.6326

6) Usually, the section «Materials» provides a comparison of the properties of the chemicals used with literature data (density, boiling point, etc.). This information allows verifying the correctness of the experiment.

7) How was the pressure kept constant in the experiment? Did the authors record the number of drops in the drop counter (the number of drops per minute also had to be maintained for 2.5 hours)

8) Figure 4: the experimental values (red circles) for liquid phase are almost everywhere lower than the literature data. What is the reason for this?

9) To study the composition of the mixture the authors used chromatographic analysis. The paper contains only the equipment used (the length and width of the column, filler, carrier, detector temperature, etc. are not specified). This information should be added.

10) Figure 7: there are fractures on the blue line (they should be removed)

11) Table 1: data for AEBA-TEG 0.4 mas. frac., the concentration of acetonitrile is shown in descending order, for other cases - in increasing order (lead to one type).

12) Unfortunately, the authors do not give quantitative changes in the relative volatility values in the ternary mixture, at least as an example (the relative volatility of component pairs in the initial mixture for a specific composition and in the presence of, for example, 60% of the agent). It is not always correct to make conclusions about the change of this parameter in a trernary mixture only based on binary data.

13) The authors study the change in the relative volatility of azeotrope-forming pairs in the presence of a separating agent. According to conclusion “acetonitrile becomes a highly volatile component, water becomes a non-volatile component, and ethanol occupies an average position in terms of volatility”, in the extractive distillation column, either pure acetonitrile or an acetonitrile- ethanol mixture can be separated as a distillate flow (the phrase presented, unfortunately, does not make it possible to assess the volatility of ethanol in relation to acetonitrile). Thus, a mixture of water - ethanol or only water remains in the bottom. That is, in any case, repeated use of the agent will be required to separate the acetonitrile-ethanol or ethanol-water pairs. The flowsheet should contain 3 or 4 columns (depending on how the authors plan to regenerate the agent). A discussion of a potential separation flowsheet should be added to the conclusion.

Conclusion: The paper can be published in “Processes” after making the appropriate corrections.

Comments for author File: Comments.pdf

Author Response

1) I recommend the authors to replace some terms, for example, «the entire range of concentrations» for «the entire composition range»; «extractant» for «extractive agent» (extractant is usually used for extraction process).

In the literature on extractive rectification, the term "entrainer" is used, so the article replaced "extractant" with "entrainer"

2) Page 1, line 32 «In industrial technologies, acetonitrile and ethanol are often present in mixtures with water», please, provide the reference for industrial technologies or at least list the productions

Added links to industrial technologies:

1. Jhoany, A.E.; Ivonne, R.D.; Ulises, J.H.; Lauro, N.P.; Eladio, P.F. Recovery of acetonitrile from aqueous waste by a combined process: Solvent extraction and batch distillation. Sep. Purif. Technol. 2006, 52, 95–101.
2. McConvey, I. F., Woods, D., Lewis, M., Gan, Q., & Nancarrow, P. (2012). The Importance of Acetonitrile in the Pharmaceutical Industry and Opportunities for its Recovery from Waste. Organic Process Research & Development, 16(4), 612–624. doi:10.1021/op2003503
3. Vane, L. M. (2018). Membrane Materials for the Removal of Water from Industrial Solvents by Pervaporation and Vapor Permeation. Journal of Chemical Technology & Biotechnology. doi:10.1002/jctb.5839

3) The current international standard for the metric system is the International System of Units (SI). Boiling points should be indicated in Kelvin.

All data on boiling points, which were indicated in Celsius, were replaced with Kelvins, in accordance with the International System of Units (SI).

4) The Abstract states "Residual curves and the conditions of phase vapor – liquid equilibrium (TPXY data) at atmospheric pressure were experimentally measured". This may mislead the reader, since the full-scale experiment was conducted only for one constituent of the ternary system. The authors should clearly state in Abstract which data were obtained experimentally and which using thermodynamic modeling.

Abstract: The effect aminoesters of boric acid (AEBA) on the conditions of vapor–liquid equilibrium in binary mixtures of acetonitrile–water, ethanol-acetonitrile and a three-component mixture of ethanol–acetonitrile–water is investigated. Residual curves and vapor-liquid phase equilibrium conditions (TPXY data) were experimentally measured at atmospheric pressure for a binary mixture of acetonitrile- AEBA and a triple mixture of acetonitrile–water-AEBA. Previously unknown energy binary parameters of groups B, CH₂N with group CH₃CN have been determined for the UNIFAC model. The correction of the value of the binary parameter water – acetonitrile was carried out. On the basis of thermodynamic modeling, the degree of influence of AEBA on the relative volatility of acetonitrile in binary and ternary mixtures is analyzed. It is shown that the use of AEBA removes all azeotropic points in the studied mixtures. In this case, acetonitrile turns out to be a volatile component, and water is a non-volatile component in the entire concentration range.

5) The authors should add the paper in the list of references, the output of which is given below. The paper describes the process of extractive distillation of a mixture containing acetonitrile, ethanol, water and methanol. Selective agents have been found.

Dmitry A. Ryzhkin, Valentina M. Raeva. Analysis of energy consumption of extractive distillation flowsheets of four-component solvent mixture. ChemChemTech , Volume 64, pp 47-55; https://doi.org/10.6060/ivkkt.20216406.6326

An article on the research topic has been added to the list of references.

6) Usually, the section «Materials» provides a comparison of the properties of the chemicals used with literature data (density, boiling point, etc.). This information allows verifying the correctness of the experiment.

We did not measure the different properties of the substances used in the experiments, so we purchased them from reliable manufacturers confirming the quality of their products with certificates. In addition, the article compares the measured data on the vapor-liquid equilibrium in the acetonitrile-water mixture with experimental data from other authors (Fig. 4). This comparison shows that our experimental data are in good agreement with the data of other authors.

7) How was the pressure kept constant in the experiment? Did the authors record the number of drops in the drop counter (the number of drops per minute also had to be maintained for 2.5 hours)

The installation for measuring vapor-liquid equilibrium is connected to the atmosphere through a rubber valve. Atmospheric pressure was measured by a barometer. The difference in the atmospheric pressure values at which the experiments were conducted was no more than 1.5%. The accuracy of the experimental data obtained was verified by comparing them with data from other authors for the acetonitrile-water mixture (Fig. 4).

The number of drops was controlled by a counter (on average 150 drops per minute) throughout the experiment, the required number the number of drops was determined by the test system.

8) Figure 4: the experimental values (red circles) for liquid phase are almost everywhere lower than the literature data. What is the reason for this?

Indeed, Figure 4 shows a qualitative underestimation of the boiling point of the mixture, measured by us, relative to the data of other authors. However, quantitatively, the difference between the temperatures indicated by circles of different colors is more than 1.3%. In text, we give these errors at a temperature of 1.3% at a concentration of 2%. In principle, these are not big discrepancies when measuring PVT data by different authors. For example, Figure 5 shows that the data discrepancy between the works [53-54] is several percent.

9) To study the composition of the mixture the authors used chromatographic analysis. The paper contains only the equipment used (the length and width of the column, filler, carrier, detector temperature, etc. are not specified). This information should be added.

Added information on chromatographic analysis. The research was carried out on the basis of the Chromatek - Kristall 5000 gas chromatograph (CJSC SKB Chromatek) with a thermal conductivity detector. During the research, a capillary column ZB-FFAP 50x0.32x0.50 was used in the temperature control mode 348.15 K, carrier gas - helium, detector temperature 493.15 K.

10) Figure 7: there are fractures on the blue line (they should be removed)

Made the appropriate changes.

11) Table 1: data for AEBA-TEG 0.4 mas. frac., the concentration of acetonitrile is shown in descending order, for other cases - in increasing order (lead to one type).

Adjustments have been made to table 1

12) Unfortunately, the authors do not give quantitative changes in the relative volatility values in the ternary mixture, at least as an example (the relative volatility of component pairs in the initial mixture for a specific composition and in the presence of, for example, 60% of the agent). It is not always correct to make conclusions about the change of this parameter in a trernary mixture only based on binary data.

We agree that information on the relative volatility of components in a three-component mixture would be useful, but this is too much data. The parameters presented in the article for the UNIFAC model allow, if necessary, to easily calculate the relative volatility of the components of the mixture of the required composition. In addition, the behavior of the residual concentration curves presented in Fig. 13 provide some information about the behavior of the relative volatility of components in a triple mixture.

13) The authors study the change in the relative volatility of azeotrope-forming pairs in the presence of a separating agent. According to conclusion “acetonitrile becomes a highly volatile component, water becomes a non-volatile component, and ethanol occupies an average position in terms of volatility”, in the extractive distillation column, either pure acetonitrile or an acetonitrile- ethanol mixture can be separated as a distillate flow (the phrase presented, unfortunately, does not make it possible to assess the volatility of ethanol in relation to acetonitrile). Thus, a mixture of water - ethanol or only water remains in the bottom. That is, in any case, repeated use of the agent will be required to separate the acetonitrile-ethanol or ethanol-water pairs. The flowsheet should contain 3 or 4 columns (depending on how the authors plan to regenerate the agent). A discussion of a potential separation flowsheet should be added to the conclusion.

The following text has been added to the article at the end of section 3.3:

On the basis of the data obtained, it is possible to propose a conceptual scheme for the separation of a three-component mixture of acetonitrile-ethanol-water by extractive distillation using AEBA-TEG as an extractant. In this scheme, there should be two extractive distillation columns and an extractant regeneration column. In the first column, the distillate will be enriched with acetonitrile, the ethanol-water-AEBA-TEG mixture remains in the bottom , which is fed into the second column. Ethanol is removed in the second column with distillate, and water and AEBA-TEG are accumulated in the bottom. Further, in the regeneration column, water is separated from AEBA-TEG. It should be noted that there are options for carrying out extractive distillation using side sections or partitions in extractive columns, which can reduce the number of columns in the conceptual scheme as well as reduce energy costs. The task of determining the most efficient option for the separation of a three-component mixture of acetonitrile-ethanol-water using extractive distillation requires additional significant research..  

Reviewer 2 Report

Recommendation: Publish after major revisions noted.

The authors reported the measurements of aminoesters effect on the conditions of vapor-liquid equilibrium in two binary systems, acetonitrile (1) + water (2) and ethanol (1) + acetonitrile (2), and one ternary ethanol (1) + acetonitrile (2) + water (3) system under isothermal conditions. The research idea is novel and the presented data is fundamentally important for process design. I have reviewed the manuscript carefully. Major comments should be addressed before publication as follows.

1.      Please improve the writing style of the introduction so that it is more attractive to read.

2.      The ionic liquid of AEBA-TEG was prepared by synthesize. The authors need to provide the NMR data to confirm the synthesized ionic liquid.

3.      The authors need to provide the thermodynamics consistency test for the studied system.

4.      Please add the details of the analysis measurements of liquid and vapor compositions, i.e. GC TCD/FID which column was used and conditions.

5.      Please provide the uncertainty of measurements of temperature, pressure, and compositions in each Tables data. Please sequences the presented data in Table 1 (from small to larger values).

6.      The vapor-liquid equilibrium (VLE) for acetonitrile-water-[AEBA][TEG] ionic liquid was mentioned in Figure 7, but what about the xy acetonitrile composition in the VLE? Those VLE data also need to present in the Figure.

7.      Please add %ARD for temperature and compositions using UNIFAC model for each studied systems.

8.      Please add the Figures of calculated temperatures and vapor-phase compositions for studied systems.

Comments for author File: Comments.pdf

Author Response

1) Please improve the writing style of the introduction so that it is more attractive to read.

Made changes

2) The ionic liquid of AEBA-TEG was prepared by synthesize. The authors need to provide the NMR data to confirm the synthesized ionic liquid.

The AEBA-TEG NMR data are presented in articles devoted directly to the analysis of synthesis details [Davletbaeva, I.M., Nurgaliyeva, G.R., Akhmetshina, A.I., Davletbaev, R.S., Atlaskin, A.A., Sazanova, T.S., Vorotyntsev, I.V. (2016). Porous polyurethanes based on hyperbranched amino ethers of boric acid. RSC Advances, 6(112), 111109–111119. doi:10.1039/c6ra21638b]. Here we do not provide these data as they are far from the subject of the article.

3) The authors need to provide the thermodynamics consistency test for the studied system.

The thermodynamic consistency of the simulation results is determined by the UNIFAC model. For any parameter values, the dependences of the activity coefficients on the composition satisfy the Gibbs-Dugem ratio. It is difficult to show the thermodynamic consistency of experimental data due to the fact that AEBA is non-volatile and is not contained in the vapor phase. Therefore, it is impossible to determine the activity coefficients of AEBA from experimental PVT data

4) Please add the details of the analysis measurements of liquid and vapor compositions, i.e. GC TCD/FID which column was used and conditions.

Information on chromatographic analysis has been added to section 2.3. The research was carried out on the basis of the Chromatek - Kristall 5000 gas chromatograph (CJSC SKB Chromatek) with a thermal conductivity detector. During the research, a capillary column ZB-FFAP 50x0.32x0.50 was used in the temperature control mode 348.15 K, carrier gas - helium, detector temperature 493.15 K.

5) Please provide the uncertainty of measurements of temperature, pressure, and compositions in each Tables data. Please sequences the presented data in Table 1 (from small to larger values).

The data has been ordered

6) The vapor-liquid equilibrium (VLE) for acetonitrile-water-[AEBA][TEG] ionic liquid was mentioned in Figure 7, but what about the xy acetonitrile composition in the VLE? Those VLE data also need to present in the Figure.

Figure 7 shows the effect of [AEBA][TEG] on the distribution of the components of the acetonitrile-water mixture between steam and liquid. The concentration of acetonitrile in steam and liquid is deposited along the X and Y axes, respectively.

7) Please add %ARD for temperature and compositions using UNIFAC model for each studied systems.

Added the following text to the conclusion:

The average error according to the equilibrium data for the acetonitrile-water mixture was: 3.5% for the concentration of acetonitrile in steam, 0.82% for temperature. For the acetonitrile – water – AEBA-TEG system, the average discrepancy between the experimental and calculated data for the UNIFAC model was 4.5%. For the ethanol-acetonitrile system, the average discrepancy between the experimental and calculated data on the UNIFAC model for the concentration of ethanol in a pair is 3.5%, 0.1% for temperature.

8) Please add the Figures of calculated temperatures and vapor-phase compositions for studied systems.

Boiling points are given for all the systems considered in the article. Some data are presented in figures, for example 4, 11, some in the table, for example 1. When presenting the data, we were guided by the rule of no duplication, which is usually imposed on scientific articles.

Reviewer 3 Report

The manuscript includes the formation of phase diagram in the presence of AEBA. The data was well predicted by unifac model, leading to the well-fitted diagram. This is applicable for distillation process in AEBA. But the introduction to AEBA presence is weak. from Line 62-82, you need to mention 1) why AEBA?, 2) what should we think if media in presence of AEBA, and 3) why pick up unifac model instead of other models.

Author Response

• why AEBA?

As shown in our previous work [Davletbaeva, I.M.; Klinov, A.V.; Khairullina, A.R.; Malygin, A.V.; Dulmaev, S.E.; Davletbaeva, A.R.; Mukhametzyanov, T.A. Organoboron Ionic Liquids as Extractants for Distillation Process of Binary Ethanol + Water Mixtures. Processes 2020, 8, 628.] AEBA exhibit some properties similar to those of ionic liquids: the melting point is below 100°C, they are practically non–volatile, their aqueous solutions have high electrical conductivity, and also remove azeotrope when added to aqueous-alcoholic solutions. Unlike ionic liquids, the use of which is limited by the high cost of their production, AEBA have a much lower production cost, which makes them promising entrainers for the separation of various mixtures.

2) what should we think if media in presence of AEBA

We hope that the AEBA studies presented in this and our earlier articles will attract attention to this class of substances from both scientific researchers and chemical engineers.

3) why pick up unifac model instead of other models

The UNIFAC method is based on the concept of group contribution, i.e. the interaction between two molecules is represented as interactions between atoms or groups of atoms that make up a molecule. AEBA molecules synthesized with different glycols differ only in the number of similar groups, the parameters of which can be determined on the basis of specific AEBA, for example, AEBA -DEG and AEBA -TAG. In this case, the UNIFAC model has the potential to predict the conditions of phase equilibrium in various solutions with AEBA of different molecular composition.

Round 2

Reviewer 2 Report

Thank you very much for the Authors, I am willing to recommend this paper to publish as is; no revisions needed.