Origin of the Increase in the Selectivity of Ru Catalysts with the Addition of Amines in the Presence of ZnSO₄ for the Selective Hydrogenation of Benzene to Cyclohexene

Round 1

Reviewer 1 Report

The manuscript entitled „Origin of the increase of selectivity of Ru catalysts with the addition of amines in the presence of ZnSO₄ for selective hydrogenation of benzene to cyclohexene by Sun, Chen and Peng describes the synthesis, analysis, and catalytic application of modified ruthenium nanoparticles in the chemoselective synthesis of cyclohexene. The catalysts are thoroughly characterized before and after use with different analytical techniques (eg. XRD, TEM, AES, N2 porosimetry, IR, TPR). The formation of (Zn(OH)₂)₅(ZnSO₄)(H₂O)x on Ru-surface is unambiguously proved. The beneficial effect of the chemisorbed Zn(II)-containing coverage and its “water content” on the selectivity of the catalytic reaction was nicely demonstrated. Additionally, by the addition of metal-oxide (ZrO₂) the aggregation of the nanoparticles could be suppressed enabling the use of the catalyst in six consecutive runs. The experiments and analytical measurements are carefully designed. The findings and results of the article are important and certainly interesting for a broad readership. Therefore, I strongly suggest the acceptance of the manuscript after addressing the following issues:

1.      Unfortunately, the MS is full of typos and in many cases a significant rephrasing of the English text is necessary.

2.      The authors should have carefully read the text before submission in order to eliminate parts of the journal template: eg. title of Table 2, or the first several lines of “3.1. The preparation of the catalyst” in the Materials and Methods section.

3.      In 3.2. Catalytic experimental procedures line 3: 280 mL of what?

4.      Section 3.3. is again Catalytic experimental procedures.

5.      Fig. 4. has four parts (a-d), in its caption there are only two (a-b) that are given incorrectly. Please, correct!

The quality of English should be improved before publication.

Author Response

The manuscript entitled „Origin of the increase of selectivity of Ru catalysts with the addition of amines in the presence of ZnSO₄ for selective hydrogenation of benzene to cyclohexene by Sun, Chen and Peng describes the synthesis, analysis, and catalytic application of modified ruthenium nanoparticles in the chemoselective synthesis of cyclohexene. The catalysts are thoroughly characterized before and after use with different analytical techniques (eg. XRD, TEM, AES, N2 porosimetry, IR, TPR). The formation of (Zn(OH)₂)₅(ZnSO₄)(H₂O)x on Ru-surface is unambiguously proved. The beneficial effect of the chemisorbed Zn(II)-containing coverage and its “water content” on the selectivity of the catalytic reaction was nicely demonstrated. Additionally, by the addition of metal-oxide (ZrO₂) the aggregation of the nanoparticles could be suppressed enabling the use of the catalyst in six consecutive runs. The experiments and analytical measurements are carefully designed. The findings and results of the article are important and certainly interesting for a broad readership. Therefore, I strongly suggest the acceptance of the manuscript after addressing the following issues:

1. Unfortunately, the MS is full of typos and in many cases a significant rephrasing of the English text is necessary.

Response 1: Thank you very much for your comments. The manuscript has been thoroughly checked and polished.

2. The authors should have carefully read the text before submission in order to eliminate parts of the journal template: eg. title of Table 2, or the first several lines of “3.1. The preparation of the catalyst” in the Materials and Methods section.

Response 2: Thank you very much for your comments. All text has been modified according to the journal template and highlighted.

3. In 3.2. Catalytic experimental procedures line 3: 280 mL of what?

Response 3: Thank you very much for your comments. The text has been modified accordingly and highlighted.

4. Section 3.3. is again Catalytic experimental procedures.

Response 4: Thank you very much for your comments. The text has been modified accordingly and highlighted.

5. Fig. 4. has four parts (a-d), in its caption there are only two (a-b) that are given incorrectly. Please, correct!

Response 5: Thank you very much for your comments. The text has been modified accordingly and highlighted.

Author Response File: Author Response.pdf

Reviewer 2 Report

catalysts-2824801

Origin of the increase of selectivity of Ru catalysts with the addition of amines in the presence of ZnSO4 for selective hydrogenation of benzene to cyclohexene Special Issue: Applied Catalysis in Chemical Industry: Synthesis, Catalyst Design, and Evaluation, 2nd Edition https://www.mdpi.com/journal/catalysts/special_issues/KK47VSA99N

This work aims at improving the yield of cyclohexene in the liquid-phase hydrogenation of benzene in the presence of Ru metal catalyst, which has a significant practical interest. This is a consecutive reaction involving the formation of highly reactive cyclohexadiene, its fast hydrogenation to cyclohexene followed by undesirable hydrogenation of cyclohexene to cyclohexane. The goal is to maximize the selectivity of the desired product cyclohexene by minimizing its conversion to cyclohexane. This requires a thorough optimisation of benzene conversion under kinetic control.

It is claimed that this goal can be achieved by modifying the Ru catalyst with the additives of Zn(II) sulfate and amines, which reduce the activity of Ru catalyst. This claim, however, is not justified in this work because the performance of catalysts was compared under different conditions (Table 3). The unmodified Ru was tested under thermodynamic control at 100% benzene conversion predictably giving 0% cyclohexene selectivity, thus making mainly undesirable cyclohexane. In contrast, the modified Ru was tested under kinetic control at low to medium benzene conversion more favourable for cyclohexene production.

Therefore, to justify their claim, the authors should provide the data for the unmodified Ru catalyst under kinetic control at the same benzene conversion as for the modified Ru. This can be done by using less forcing reaction conditions (lower amount of Ru catalyst, lower temperature and/or lower H₂ pressure).

Some more specific comments:

1.     Proof of the absence of diffusion limitations is needed.

2.     1,2-ethanediamine should read ethylenediamine or 1,2-diaminoethane.

3.     Line 101: hydroxyl ions are generated due to amine basicity, not by amine hydrolysis.

4.     TPR data (Fig. 5): The Ru catalyst as made was already reduced to Ru(0), so why does the TPR show the reduction peak?

5.     Spaces between words and also between units and numbers are often missing.

6.     Table 1: footnote (b) is missing. What is “S”?

7.     Table 2: wrong title; all parameters should be explained.

8.     Table 3: What is given in red?

9.     Table 4: wrong title; footnote (a) is missing.

10.  Lines 324–330 are irrelevant.

11.  Line 341: it should be stated that 280 ml of water was added.

Potentially, this material may be suitable for the Catalysts. However, it requires a major revision to provide additional data as stated above. The quality of manuscript presentation is far below the required standard. The manuscript needs thorough proofreading to correct numerous punctuation, grammar and other errors before being considered for publication.

Extensive editing is required

Author Response

This work aims at improving the yield of cyclohexene in the liquid-phase hydrogenation of benzene in the presence of Ru metal catalyst, which has a significant practical interest. This is a consecutive reaction involving the formation of highly reactive cyclohexadiene, its fast hydrogenation to cyclohexene followed by undesirable hydrogenation of cyclohexene to cyclohexane. The goal is to maximize the selectivity of the desired product cyclohexene by minimizing its conversion to cyclohexane. This requires a thorough optimisation of benzene conversion under kinetic control.

It is claimed that this goal can be achieved by modifying the Ru catalyst with the additives of Zn(II) sulfate and amines, which reduce the activity of Ru catalyst. This claim, however, is not justified in this work because the performance of catalysts was compared under different conditions (Table 3). The unmodified Ru was tested under thermodynamic control at 100% benzene conversion predictably giving 0% cyclohexene selectivity, thus making mainly undesirable cyclohexane. In contrast, the modified Ru was tested under kinetic control at low to medium benzene conversion more favourable for cyclohexene production.

Therefore, to justify their claim, the authors should provide the data for the unmodified Ru catalyst under kinetic control at the same benzene conversion as for the modified Ru. This can be done by using less forcing reaction conditions (lower amount of Ru catalyst, lower temperature and/or lower H₂ pressure).

Some more specific comments:

1. Proof of the absence of diffusion limitations is needed.

Response 1: Thank you very much for your comments. Ca and ηφ²was calculated to prove the absence of diffusion limitations. It was found that Ca and ηφ²was far less than 0.05 and 0.1, respectively. This indicates that the reaction was taking place under the kinetic control. Furthermore, in our previous study [27], the pure Ru catalysts with different particle size and amountwere investigated for benzene hydrogenation. Only cyclohexane was generated over pure Ru catalysts. These observations prove that the improvement of cyclohexene yield cannot be attributed to the diffusion limitation.

2. 1,2-ethanediamine should read ethylenediamine or 1,2-diaminoethane.

Response 2: Thank you very much for your comments. The text is revised accordingly.

3. Line 101: hydroxyl ions are generated due to amine basicity, not by amine hydrolysis.

Response 3: Thank you very much for your comments. The text is revised accordingly.

4. TPR data (Fig. 5): The Ru catalyst as made was already reduced to Ru(0), so why does the TPR show the reduction peak?

Response 4: Thank you very much for your comments. The misunderstanding can be solved by clarifying the procedure of TPR characterization. The sample was firstly oxidized by the air/N₂ mixed gas.

5. Spaces between words and also between units and numbers are often missing.

Response 5: Thank you very much for your comments. The text has been modified accordingly.

6. Table 1: footnote (b) is missing. What is “S”?

Response 6: Thank you very much for your comments. Footnote (b) is added, standing for “in the absence of ZnSO₄·7H₂O”. And “S” means the sulfur element.

7. Table 2: wrong title; all parameters should be explained.

Response 7: Thank you very much for your comments. The text has been modified accordingly.

8. Table 3: What is given in red?

Response 8: Thank you very much for your comments. No special meaning is given in red. The text has been modified accordingly.

9. Table 4: wrong title; footnote (a) is missing.

Response 9: Thank you very much for your comments. The text has been modified accordingly.

10. Lines 324–330 are irrelevant.

Response 10: Thank you very much for your comments. The text has been modified accordingly.

11. Line 341: it should be stated that 280 ml of water was added.

 Response 11: Thank you very much for your comments. The text has been modified accordingly.

Potentially, this material may be suitable for the Catalysts. However, it requires a major revision to provide additional data as stated above. The quality of manuscript presentation is far below the required standard. The manuscript needs thorough proofreading to correct numerous punctuation, grammar and other errors before being considered for publication.

Response: Thank you very much for your comments. The manuscript has been carefully gone thorough and polished.

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript reports an investigation of the promoting effect of ZnSO₄ as well as of amines for the selective hydrogenation of benzene to cyclohexene using Ru nanoparticles. Various characterization methods including XRD, TEM, elemental analysis, N₂-sorption, FT-IR, and TPR were applied. The addition of ZnSO₄ and amines resulted in increased cyclohexene selectivity at the expense of a lower benzene conversion. This observation was explained by the formation of basic ZnSO₄ and a water layer on the surface of the Ru nanoparticles, as the amines due to the reaction of ZnSO₄ with the OH^- ions resulting from the hydrolysis of the amines. The resulting surface coverage leads to improved desorption of cyclohexene from the catalyst surface and prevents further reaction to cyclohexane. The presence of basic ZnSO₄ was confirmed by XRD as well as elemental analysis. In addition, catalytic data proved that the combination of ZnSO₄ and amines is necessary to achieve the increase in selectivity. It was also found that the stability of the catalytic activity and recyclability could be improved by the addition of ZrO₂, which the authors attributed to the prevention of agglomeration of the Ru nanoparticles.

Although the promotion of Ru by ZnSO₄ and amines has already been the subject of research in several studies in the past the authors add additional insight to the topic. They address the lack of clarity in previous studies regarding the fundamental reasons for the beneficial effects of ZnSO₄ and amines. They manage to confirm convincingly that the origin of the promotion effect lies in the formation of chemisorbed basic ZnSO₄. Moreover, the authors demonstrate with their study how to adjust the reaction conditions i.e. amount of amines, type of amine, and addition of ZrO₂ to fine-tune the desired selectivity, yield, and catalytic stability. The authors claim to have achieved the highest yield of cyclohexene reported in the literature.

The experiments were well executed and selected logically, for instance by varying the type of amines and their concentration. It is also very commendable that the authors investigated the catalytic stability. Most importantly, the interpretations were supported by thorough characterization methods including TEM. There is no doubt that this nice and serious investigation should be published in Catalysts. However, there are plenty of spelling, grammar, and formatting errors, which should be corrected before publication. Together with some additional limitations of the manuscript I propose a major revision.

Comments which should be addressed by the authors in the revised manuscript:

1)     Abstract: The abstract should be improved, please include: 1. Short introduction 2. More detailed background 3. Description of the problem/objective for a better understanding of the motivation of the study 4. At the end of the abstract put your results into a more general context / broader perspective. It should also be added (abstract and introduction) that catalysis was performed in a liquid solution/batch reactor (and not a continuous gas phase reaction).

2)     Please check the whole manuscript for spelling, grammar, and formatting errors, for example, there are plenty of blank characters missing: for example “catalystwas” (line 13), “thatthe” (line 17).

3)      Please provide a short discussion about the synthesis of the Ru nanoparticles before going into the characterization section. It is not very helpful for the reader when the Results part starts with Figures.

4)     In line 119, please clarify the solvent used in the reaction conditions (280 mL aqueous 0.6 mol/L).

5)     Line 121: please clarify the abbreviation for Zn LMM.

6)     Line 133: Although it is correct to state that the existence of Zn in its metallic form is highly unlikely, be aware that you analyzed the situation after catalysis ex-situ (probably with air contact before the analysis?), so from this, you can in principle not make any definitive judgment on the situation during the catalysis in-situ. However, the TPR data serves as good proof that no reduction of Zn is expected.

7)     Line 138: please also provide the calculated molar ratios of Zn/Ru and S/Ru for the reader to get a better interpretation of these results.

8)     The best would be to link the observations to the reaction equations 1-5, so basically the more amine is present, the more OH^- and the more basic Zn sulfate will be precipitated on the catalyst surface.

9)     Line 172 and Line 289: Please include the table description.

10)  Line 194: do you also have data with a blank run with only Ru and no ZnSO₄ and no amines?

11)  Lines 216 to 226: this section is a bit hard to digest for the reader, it could profit from some clarifications and an overview table of the three different tests. In test 1 there is no more ZnSO₄ in the aqueous phase, which means that all of it was deposited on the Ru catalyst? Test 2 consists of a spent Ru catalyst, amines and no added ZnSO₄ and also no more chemisorbed ZnSO₄? Test 3 consists of a spent Ru catalyst, amines and added ZnSO₄?

12)  Is there any (qualitative) trend in the amount of crystal water from your XRD data and the selectivity of the respective catalysts?

13)  Line 305: the TEM images of the catalysts were discussed very briefly and it is only stated that the Ru crystallites were distributed uniformly. A comparison with a non-uniformly distributed case would be helpful.

14)  Is there any data on the recyclability of Ru nanoparticles without ZrO₂?

15)  Perhaps give a short explanation of why you selected ZrO₂ and not another metal oxide.

16)  What would be the advantage of using Ru nanoparticles and ZrO₂ as to directly prepare a ZrO2-supported Ru catalyst?

17)   Please remove the default text between lines 324 and 330.

18)  The conclusions are rather specific and should try to give some generalization (real conclusions) and possibly some outlook.

19)  Line 351: 3.3. Catalytic experimental procedure – is given twice! Correct.

Unfortunately, there are plenty of spelling, grammar, and formatting errors, which should be corrected before publication.Also, there are many free electronic tools helping in improving the English, which should be used here (e.g. DeepL).

Author Response

The manuscript reports an investigation of the promoting effect of ZnSO₄ as well as of amines for the selective hydrogenation of benzene to cyclohexene using Ru nanoparticles. Various characterization methods including XRD, TEM, elemental analysis, N₂-sorption, FT-IR, and TPR were applied. The addition of ZnSO₄ and amines resulted in increased cyclohexene selectivity at the expense of a lower benzene conversion. This observation was explained by the formation of basic ZnSO₄ and a water layer on the surface of the Ru nanoparticles, as the amines due to the reaction of ZnSO₄ with the OH^- ions resulting from the hydrolysis of the amines. The resulting surface coverage leads to improved desorption of cyclohexene from the catalyst surface and prevents further reaction to cyclohexane. The presence of basic ZnSO₄ was confirmed by XRD as well as elemental analysis. In addition, catalytic data proved that the combination of ZnSO₄ and amines is necessary to achieve the increase in selectivity. It was also found that the stability of the catalytic activity and recyclability could be improved by the addition of ZrO₂, which the authors attributed to the prevention of agglomeration of the Ru nanoparticles.

Although the promotion of Ru by ZnSO₄ and amines has already been the subject of research in several studies in the past the authors add additional insight to the topic. They address the lack of clarity in previous studies regarding the fundamental reasons for the beneficial effects of ZnSO₄ and amines. They manage to confirm convincingly that the origin of the promotion effect lies in the formation of chemisorbed basic ZnSO₄. Moreover, the authors demonstrate with their study how to adjust the reaction conditions i.e. amount of amines, type of amine, and addition of ZrO₂ to fine-tune the desired selectivity, yield, and catalytic stability. The authors claim to have achieved the highest yield of cyclohexene reported in the literature.

The experiments were well executed and selected logically, for instance by varying the type of amines and their concentration. It is also very commendable that the authors investigated the catalytic stability. Most importantly, the interpretations were supported by thorough characterization methods including TEM. There is no doubt that this nice and serious investigation should be published in Catalysts. However, there are plenty of spelling, grammar, and formatting errors, which should be corrected before publication. Together with some additional limitations of the manuscript I propose a major revision.

Comments which should be addressed by the authors in the revised manuscript:

1)     Abstract: The abstract should be improved, please include: 1. Short introduction 2. More detailed background 3. Description of the problem/objective for a better understanding of the motivation of the study 4. At the end of the abstract put your results into a more general context / broader perspective. It should also be added (abstract and introduction) that catalysis was performed in a liquid solution/batch reactor (and not a continuous gas phase reaction).

Response 1: Thank you very much for your comments. The abstract and introduction is revised accordingly.

2)     Please check the whole manuscript for spelling, grammar, and formatting errors, for example, there are plenty of blank characters missing: for example “catalystwas” (line 13), “thatthe” (line 17).

Response 2: Thank you very much for your comments. The text is thoroughly modified and polished.

3)      Please provide a short discussion about the synthesis of the Ru nanoparticles before going into the characterization section. It is not very helpful for the reader when the Results part starts with Figures.

Response 3: Thank you very much for your comments. It has been mentioned in the introduction: “Moreover, it was reported that most active sites for cyclohexene generation were detected from Ru particles with crystal size of 5 nm[19]. Therefore, Ru catalyst with crystal size of 5 nm was synthesized in this work.”

4)     In line 119, please clarify the solvent used in the reaction conditions (280 mL aqueous 0.6 mol/L).

Response 4: Thank you very much for your comments.The text is modified accordingly.

5)     Line 121: please clarify the abbreviation for Zn LMM.

Response 5: Thank you very much for your comments. The text is modified accordingly.

6)     Line 133: Although it is correct to state that the existence of Zn in its metallic form is highly unlikely, be aware that you analyzed the situation after catalysis ex-situ (probably with air contact before the analysis?), so from this, you can in principle not make any definitive judgment on the situation during the catalysis in-situ. However, the TPR data serves as good proof that no reduction of Zn is expected.

Response 6: Thank you very much for your comments. Zn LMM was obtained after the elimination of surface oxide layer by Ar⁺. The detailed characterization procedure is added.

7)     Line 138: please also provide the calculated molar ratios of Zn/Ru and S/Ru for the reader to get a better interpretation of these results.

Response 7: Thank you very much for your comments. The molar ratios are added in the manuscript.

8)     The best would be to link the observations to the reaction equations 1-5, so basically the more amine is present, the more OH^- and the more basic Zn sulfate will be precipitated on the catalyst surface.

Response 8: Thank you very much for your comments. The text is modified accordingly.

9)     Line 172 and Line 289: Please include the table description.

Response 9: Thank you very much for your comments. The text is modified accordingly.

10)  Line 194: do you also have data with a blank run with only Ru and no ZnSO₄ and no amines?

Response 10: Thank you very much for your comments. The data with only Ru has been added in the text.

11)  Lines 216 to 226: this section is a bit hard to digest for the reader, it could profit from some clarifications and an overview table of the three different tests. In test 1 there is no more ZnSO₄ in the aqueous phase, which means that all of it was deposited on the Ru catalyst? Test 2 consists of a spent Ru catalyst, amines and no added ZnSO₄ and also no more chemisorbed ZnSO₄? Test 3 consists of a spent Ru catalyst, amines and added ZnSO₄?

Response 11: Thank you very much for your comments.An overview table is added and the text is modified accordingly.

12)  Is there any (qualitative) trend in the amount of crystal water from your XRD data and the selectivity of the respective catalysts?

Response 12: Thank you very much for your comments and remind. It is a reasonable assumption that there could a qualitative trend between the amount of crystal water and selectivity of the respective catalysts. Although we haven’t put our focus on that, we will definitely look into that in the future.

13)  Line 305: the TEM images of the catalysts were discussed very briefly and it is only stated that the Ru crystallites were distributed uniformly. A comparison with a non-uniformly distributed case would be helpful.

Response 13: Thank you very much for your comments. The TEM image without addition of ZrO₂ was given in Figure 4b, and the text is revised accordingly.

14)  Is there any data on the recyclability of Ru nanoparticles without ZrO₂?

Response 14:Thank you very much for your comments. It is well established that certain amount of ZrO₂ can prevent the agglomerationof Ru particles. And ZrO₂is used in real industry application. So we didn’t consider running the recyclability test over Ru nanoparticles only.

15)  Perhaps give a short explanation of why you selected ZrO₂ and not another metal oxide.

Response 15:Thank you very much for your comments. Plenty of metal oxides were investigated as support or dispersant for partial hydrogenation of benzene over Ru catalysts in our group. The highest yield of cyclohexene was achieved by applying ZrO₂. The text is modified accordingly.

16)  What would be the advantage of using Ru nanoparticles and ZrO₂ as to directly prepare a ZrO2-supported Ru catalyst?

Response 16:Thank you very much for your comments. The main disadvantage of ZrO₂-supported Ru catalyst is that there is a strong interaction between Ru and the support, which could affect the catalytic activity towards cyclohexene formation. We have reported such observations,Acta Petrolei Sinica (Petroleum Processing Section) , 2017, 33(4): 646-654.

17)   Please remove the default text between lines 324 and 330.

Response 17: Thank you very much for your comments. The text is modified accordingly.

18)  The conclusions are rather specific and should try to give some generalization (real conclusions) and possibly some outlook.

Response 18: Thank you very much for your comments. The text is modified accordingly.

19)  Line 351: 3.3. Catalytic experimental procedure – is given twice! Correct.

Response 19: Thank you very much for your comments. The text is modified accordingly.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors did not address the main issues raised by this reviewer regarding (i) the justification of the effect of Zn(II) sulphate and amine, (ii) diffusion limitations and (ii) proofreading the text (see the previous review). The manuscript still requires a major revision.

1.     To justify the effect of Zn(II) sulphate and amine additives, the authors should provide the data for the unmodified Ru catalyst under kinetic control at the same benzene conversion (70-80%) as for the modified Ru (Table 3). This can be done by using less forcing reaction conditions (lower amount of Ru catalyst, lower temperature and/or lower H₂ pressure).

2.     The proof of the absence of diffusion limitations at the gas-liquid interface should demonstrate no effect of stirring speed on substrate conversion.

3.     Spaces between words and also between units and numbers are still missing even in the highlighted added text.

The manuscript needs thorough proofreading. Spaces between words and also between units and numbers are still missing even in the highlighted added text.

Author Response

Reviewer2

1. To justify the effect of Zn(II) sulphate and amine additives, the authors should provide the data for the unmodified Ru catalyst under kinetic control at the same benzene conversion (70-80%) as for the modified Ru (Table 3). This can be done by using less forcing reaction conditions (lower amount of Ru catalyst, lower temperature and/or lower H2 pressure).

Response 1: Thank you very much for your comments. In our previous study [27], the unmodified Ru catalysts with lower amount were investigated for benzene hydrogenation. It was found that, at the comparable benzene conversion (i.e., 50% ~ 80%), no cyclohexene formation was observed.

2. The proof of the absence of diffusion limitations at the gas-liquid interface should demonstrate no effect of stirring speed on substrate conversion.

Response 2: Thank you very much for your comments. The higher stirring speed was tested and no effect on the catalytic activity and selectivity towards cyclohexene formation was observed. This indicates the absence of diffusion limitations at gas-liquid interface.

3. Spaces between words and also between units and numbers are still missing even in the highlighted added text.

Response 3: Thank you very much for your comments. The text was very carefully gone through to avoid such things. We also found that, after the submission, the submitted text is somehow rearranged. It is probably due to the submission system.

Reviewer 3 Report

The authors addressed most of the reviewers’ comments/concerns and made useful changes and additions to the revised manuscript, thus improving its quality. The changes and additions made are adequate and allow the publication of the manuscript, although a few limitations remain (plenty of missing empty spaces, only slight improvement of abstract and conclusions – obviously did not understand or did not like to understand).

The English has been slightly improved, however, there are e.g. plenty of missing empty spaces, and as mentioned in my first report: use of DeepL would help much.

Author Response

Reviewers3

1)     The authors addressed most of the reviewers’ comments/concerns and made useful changes and additions to the revised manuscript, thus improving its quality. The changes and additions made are adequate and allow the publication of the manuscript, although a few limitations remain (plenty of missing empty spaces, only slight improvement of abstract and conclusions – obviously did not understand or did not like to understand).

Response 1: Thank you very much for your comments. The text was very carefully gone through to avoid such things. We also found that, after the submission, the submitted text is somehow rearranged. It is probably due to the submission system.

Author Response File: Author Response.docx