In-Depth Kinetic Modeling and Chemical Analysis for the Epoxidation of Vegetable Oils in a Liquid–Liquid–Solid System

Round 1

Reviewer 1 Report

It seems a good work with enough contribution to deserve publication. I congratulate the authors for presenting the modeling section and the model fitting in a very clear manner. 

I have the following comments for the authors' consideration:

(1) Please make correction in the number of Figure presented on page 19 (it should be Figure 15, not Figure 13 as written).

(2) In Figures 10, 13 and 15, please represent the model simulations by continuous curves rather then by symbols. Use symbols only for the experimental data (that were measured only at specific time instants), and use continuous curves for model simulations (model predictions can be calculated at all time instants, not only at the specific times of the measurements).

(3) I suggest to include the model curves (continuous curves) in Figures 6, 7 and 8.

(4) The authors said (on page 10) they used a hold-out method (10 experiments used for the regression stage, and 2 experiments  used for the validation stage), which is a correct and useful procedure for model fitting. However, apparently, this hold-out method was employed only for the fitting of the epoxidation model (Table 5 and Table 6), but not for the propionic acid perhydrolysis (Table 4). Why ? 

(5) Finally, the overall organization of the text (putting the the Materials and Methods section at the end, after presenting the Results and Discussion section) is strange. I know that some journals adopted this strange format, but I personally prefer the way adopted by most of the journals of Chemical Engineering scope (first Materials and Methods, then Results and Discussion).

Author Response

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Reviewer 2 Report

The paper was well written and needs only minor edits.

Ln 52, I believe the authors wanted to add a reference

Fig 3 & 4, are the y-axis absorbance or transmittance?

More explanation needed for fig 4. Did the intensity of the band at 850 cm-1 correlates with the number of oxirane or ring opening? The key “5, 35, …, 185” refer to what? Nothing about the trend was mentioned in the text.

Ln 373 a little description of the agitator is needed since different stirring speeds were tested. At 600 rpm, different agitators will provide different mixing dynamic, hence, detail is needed.

Ln 374 what was the amount of cottonseed oil epoxidized?

Ln 378 specify the different times samples were collected.

The abbreviations HP, PA, DB, Ep needs to be clarified in each table and figure. The authors need to remember that the figures and tables can stand alone, hence, need to be clear.

Author Response

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Reviewer 3 Report

A well structured work. I recomend it for publication without any change. There are only two minors to be corrected on page 2:

1) Line 52 - Probably a reference must be introduced in the square brackets.

2) Line 82 "of" instead of "ofr"

My review report was short because my evaluation of the article was completely positive and I have no suggestions for improving it. The article has been written by accurately considering all the aspects characterizing the epoxidation of cottonseed oil with the aim to solve some negative aspects of the traditional Prileschajew method. The choice of the authors to use propionic acid to reduce the contribution to reduce the contribution of ring opening side reactions is one innovating aspect of this study. The use of a solid acid catalyst (Amberlite - 120) although not new is another positive factor investigated by the authors. The analytical methods used to follow the reaction are precise and accurately described. At last, the multiphasic kinetic approach for elaborating the kinetic data is correct and exhaustively described.

Author Response

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Reviewer 4 Report

Addition of usage of epoxidation vegetable oil as, please cited,

1.       - Catalytic Epoxidation of Oleic Acid and Subsequent Ring-Opening by In Situ Hydrolysis for Production Dihydroxystearic Acid

2.      - Synergistic epoxidation of palm oleic acid using a hybrid oxygen carrier solution

How about this sentence? Besides, it is 51 an exothermic reaction system, and the risk of a thermal runaway is high [ref?]

Highlight the main contribution of knowledge and significant of this manuscript in this manuscript?

How to determine concentration of double bond?

Less characterization. Add characterization using TGA to give more impactful meaning.

Formula of epoxide content and hydrogen peroxide content?

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Reviewer 5 Report

In my opinion, the article is very interesting, I highlight the use of proper analytical methods to identify the degradation pathways of the epoxide. I have some questions and some comments about the article.

 

Comments

 

1.       The article is well writing, but with some format mistakes (lines 52, 82, 214 and 215). 

2.       I suggest that in some parts of the paper the authors change the word kinetic for rate, although both are synonyms, I think “rate” is most appropriate to describe the instantaneous change and “kinetic” is more general.

3.       In many Figures 7B and 8B (Concentration of epoxide group), and 13 (C and F), there are some bullets repeated for the same time, ¿are these error bars? In fact, I suggest the authors to improve the format of the Figures, for example the axis titles are too close to the values, add axes marks, etc.

4.       I suggest that authors rewrite line 188.

 

Questions

 

1.       The epoxidation reaction is very exothermic, and the authors assume an isothermal system, ¿how it was possible? ¿why they didn't present some thermograms? 

2.       When the authors compare runs 2, 5 and 6 (i.e. Figure 7) they are analyzing the effect of the initial ratio of hydrogen peroxide to propionic acid, however, according to Table 5, in my opinion, the changes must be related to the molar excess of hydrogen peroxide to unsaturations.

3.       If I understood the line 188, the authors try to say that at 600 rpm there is not mass nor heat transfer effects, ¿how they can probe that? maybe the evaluation of the Reynolds number is needed. Besides, it is important that the authors make explicit that in the kinetic model intraparticle transport phenomena are not considered.

4.       From my point of view, an important concern about the procedure made by the authors is related to the study of the perhydrolysis separately of the epoxidation, I understand the needing to reduce the number of parameters. However, the system in the epoxidation has three phases and is possible that some particles of the catalyst remain in the oily phase instead of the aqueous phase, then the real mass of catalyst used in the reaction is different to that charged at the beginning of the experiment.

5.       The authors should present in the text the assumption of constant volume for the two fluid phases.

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