Valorization of (Bio)Ethanol over MoO₃/(WO₃-ZrO₂) Sol-Gel-like Catalysts

Round 1

Reviewer 1 Report

The research covers a wide range of experimental parameters for the catalytic degradation of bioethanol, an issue of high economic impact. The paper can be accepted with minor revision, taking into account:

 1. Please highlight the optimal reaction conditions for increasing the selectivity.

2.”Results and Discussion” should contain a ranking of the catalysts from the point of view of technological valorization

Author Response

Reviewer #1

The research covers a wide range of experimental parameters for the catalytic degradation of bioethanol, an issue of high economic impact. The paper can be accepted with minor revision, taking into account:

1. Please highlight the optimal reaction conditions for increasing the selectivity.

As mentioned in the introduction section, ethene, and acetaldehyde are two products with commercial value, so the manipulation of the catalytic system should be carried out to produce the most valuable product, which is a function of market supply/demand. The reaction conditions for obtaining the maximum dehydrogenation product and ethanol dehydration product have not been optimized. The authors emphasize the versatility of the catalytic system prepared so that either of the two reaction routes, dehydration or dehydrogenation, can be favored.

2.”Results and Discussion” should contain a ranking of the catalysts from the point of view of technological valorization

The authors disagree on the need to include a table with different catalysts in the results and discussion section, as there is already one in the introduction section. In any case, the manuscript is not a review paper but a research paper, so it doesn't make sense to include it. The catalytic activity results have already been discussed on the basis of literature results for similar catalytic systems

3.”Conclusions”- Please explain with various economic and environmental advantages”

The sol-gel procedure for preparing catalysts is considered a green chemistry process because it does not use environmentally aggressive reagents or generate wastewater. Burning the citrate precursor generates CO₂ which can be retained by adsorption on CaO (Ca looping). The production of ethylene from bioethanol has environmental advantages compared to the petrochemical process of cracking oil since bioethanol is a renewable product. There is no doubt that Zr, Mo and Fe are more economical than any noble metal.

Reviewer 2 Report

The paper is well written and bring new information concerning catalytic transformation of ethanol by non-noble metals. 

A wrong indexation of Figure is located page 9. Figure 10 must be changed in Figure 9.

Author Response

Reviewer #2

A wrong indexation of Figure is located page 9. Figure 10 must be changed in Figure 9.

As suggested by the Reviewer, figures 9 and 10 have been exchanged.

Reviewer 3 Report

Ethanol, as an easily available and cheap renewable substrate, can be a source of obtaining many important products, such as acetic acid, acetaldehyde or ethylene. Therefore, it is important to search for conditions and catalysts that allow the synthesis of these products in environmentally friendly conditions.

The reviewed article presents the results of using MoO₃ deposited on tungstated zirconia catalyst for the conversion of ethanol. The introduction to the article is written in a very comprehensive manner, perhaps too extensive, based on new and recent literature. While discussing the results, the authors noted several errors and inaccuracies that require clarification.

1.       Line 188 - it should probably be Table 2, not Table 3.

2.       In my opinion, Table 2 is not very clear and needs to be corrected.

3.       Line 191 - The authors write “because Mo content is always higher than the value used in the sample preparation”. Do the authors have any data to support this thesis?

4.       Line 232 - it should probably be Table 9, not Table 10.

5.       The source of the reagents and the description of the analytical methods and their conditions as well as the equipment used are better placed in a separate subchapter at the beginning of the Experimental chapter. This makes their analysis much easier for the reader.

6.       Authors should devote more time to proofreading the text. Line 154 - Feed mixtures (6.5%, v/v) - v/v of what? Line 155 - this time V/V with a capital letter.

Author Response

Reviewer #3

Ethanol, as an easily available and cheap renewable substrate, can be a source of obtaining many important products, such as acetic acid, acetaldehyde or ethylene. Therefore, it is important to search for conditions and catalysts that allow the synthesis of these products in environmentally friendly conditions.

The reviewed article presents the results of using MoO₃ deposited on tungstated zirconia catalyst for the conversion of ethanol. The introduction to the article is written in a very comprehensive manner, perhaps too extensive, based on new and recent literature. While discussing the results, the authors noted several errors and inaccuracies that require clarification.

1. Line 188 - it should probably be Table 2, not Table 3.

There is no table 3. In line 185, Table 3 has become Table 2.

2. In my opinion, Table 2 is not very clear and needs to be corrected.

As suggested the Table was ameliorated.

3. Line 191 - The authors write “because Mo content is always higher than the value used in the sample preparation”. Do the authors have any data to support this thesis?

The statement in line 191 is based on the fact that the Mo contents determined by EDS, a surface analysis technique, were higher than the nominal values used to prepare the catalysts. The masses of reagents used were weighed on an analytical balance, so the values are known with precision (0%, 5%, 10%... 30% molar %) because in sol-gel preparation nothing is lost through dissolution in mother liquors, as happens in preparation methods involving precipitation.

4. Line 232 - it should probably be Table 9, not Table 10.

The manuscript only has Table 1 and Table 2. Figures 9 and 10 had the wrong numbering and this error was corrected.

5. The source of the reagents and the description of the analytical methods and their conditions as well as the equipment used are better placed in a separate subchapter at the beginning of the Experimental chapter. This makes their analysis much easier for the reader.

The reagents and equipment used are described in the experimental section, which is divided into 3 sections: catalyst preparation, catalyst characterization and catalytic tests. The authors consider the experimental part to be well structured and in line with what is usually presented in the literature in the field of heterogeneous catalysis.

6. Authors should devote more time to proofreading the text. Line 154 - Feed mixtures (6.5%, v/v) - v/v of what? Line 155 - this time V/V with a capital letter.

Correct as suggested

Reviewer 4 Report

This manuscript reports the preparation and use of some sol-gel type catalysts for the valorization of ethanol. The work comes at a time where this process is the focus of significant attention. The results presented here, while adding to the literature in the field, are not particularly impressive. As such, there is limited novelty to the approach. The introduction is rather rambling and long and does not really fully contextualize the study. In addition, the schemes and figures are of poor quality and seem to have been taken from previous literature reports. The Methods and the Results and Discussion sections are a bit better.

Overall, in my mind, the work lacks the novelty and quality requisite for publication in Reactions and so I cannot recommend its acceptance.

The quality of the language is acceptable, although some editing would be required.

Author Response

Reviewer #4

This manuscript reports the preparation and use of some sol-gel type catalysts for the valorization of ethanol. The work comes at a time where this process is the focus of significant attention. The results presented here, while adding to the literature in the field, are not particularly impressive. As such, there is limited novelty to the approach.

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The authors disagree because the results are innovative and the catalysts are not mentioned in the literature for the conversion of ethanol or any other reaction.

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The introduction is rather rambling and long and does not really fully contextualize the study. In addition, the schemes and figures are of poor quality and seem to have been taken from previous literature reports. The subject is extensive and it is impossible to refer to all the work published in this area.

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The manuscript is a research paper and not a review article, so it is impossible to cover all the areas relating to the catalytic conversion of bioethanol.

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The Methods and the Results and Discussion sections are a bit better.

Overall, in my mind, the work lacks the novelty and quality requisite for publication in Reactions and so I cannot recommend its acceptance.

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All figures shown are originals. We have changed the color of the graphs in Figure 8 to make them more legible.

Round 2

Reviewer 1 Report

The paper may be accepted for publication

Reviewer 2 Report

The improvements which mainly concerned the form were made in accordance with the proposals of the reviewers.

Reviewer 3 Report

In the revised version, the authors fully addressed my comments on the original version of the manuscript.

Reviewer 4 Report

The manuscript still lacks novelty and is not well put together. My recommendation remains the same.

It is OK