Transfer Hydrogenation of Biomass-Like Phenolic Compounds and 2-PrOH over Ni-Based Catalysts Prepared Using Supercritical Antisolvent Coprecipitation

Round 1

Reviewer 1 Report

Title length can be reduced

The introduction part can be improved and the novelty statement to be highlighted clearly 

Structure of the manuscript can be revised like materials and method to be next to introduction and results should be at the back

For improving the discussion part the following ref can be referred 

https://doi.org/10.1016/j.fuel.2022.124236

https://doi.org/10.1016/j.fuel.2022.125668

Conclusion can be reframed to concluded in the clear way 

 

Author Response

We would like to thank the Reviewer for reading our work and excellent suggestions. We believe that this significantly improves the quality of the text making it more convenient for readers. All the Reviewer’s comments were taking into account, and our explanations are given below.

1. Title length can be reduced

The title length has been reduced.

2. The introduction part can be improved and the novelty statement to be highlighted clearly

The novelty of this study lies on the fact that the high-loaded Ni and Ni-Cu catalysts prepared via supercritical coprecipitation were used in transfer hydrogenation of guaiacol and dimethoxybenzenes for the first time. The novelty also includes some additional aspects, such as the effect of the copper addition, and comparison of transformations of dimethoxybenzene positional isomers in terms of reactivity and selectivity. The last paragraph in the Introduction section has been improved.

3. Structure of the manuscript can be revised like materials and method to be next to introduction and results should be at the back

We agree that the manuscript structure suggested by the Reviewer seems to be more typical. At the same time, instructions for authors say that the Materials and methods section should be provided after Results and discussion. All the published articles we have seen have the same structure, which is done according instructions for authors.

4. For improving the discussion part the following ref can be referred

https://doi.org/10.1016/j.fuel.2022.124236

https://doi.org/10.1016/j.fuel.2022.125668

The second reference was already mentioned in the text (reference 4). Other mentioned reference has also been added to the text.

5. Conclusion can be reframed to concluded in the clear way

The conclusion section has been reframed.

Reviewer 2 Report

The authors described “ Transfer hydrogenation of biomass-like phenolic compounds 2 and supercritical 2-PrOH over high-loaded Ni-based catalysts 3 prepared using supercritical antisolvent coprecipitation”  The article  conforms to scientific guidelines and it is technically sound.

Authors should take note of the following suggestions.

 1.       After careful study of this manuscript authors well written.  Every figures and graphs and calculations are good.

2. A through grammatical check, Space, Commas (,), spelling mistakes must be performed for the entire manuscript.

Author Response

We thank the Reviewer for agreeing to review our manuscript and for the time the Reviewer spent. We were happy to see the Reviewer’s opinion high appreciation of our study. Below we provided our response for the Reviewer’s comments.

1. After careful study of this manuscript authors well written. Every figures and graphs and calculations are good.

We appreciate the Reviewer’s opinion on the quality of our manuscript.

2. A through grammatical check, Space, Commas (,), spelling mistakes must be performed for the entire manuscript.

The entire manuscript was checked for different types of mistakes. Some of them have been found and corrected.

Reviewer 3 Report

The manuscript presented by Philippov and co-workers describes preparation of the Ni and Ni/Cu catalysts and their use as a transfer hydrogenation catalysts for the reduction of guaiacol and 1,2- ; 1,3-; and 1,4-dimethoxybenzenes. These types of reductions are of high importance in nowadays chemistry. The overall structure of the manuscript is clear, and the graphical representations are very well done. However, there are certain major points, which need to be fixed:

- lines 33-34, authors claim that H₂ gas  is corrosive. This is not quite true! The key advantages of transfer hydrogenation over hydrogenation with H₂ are the absence of the need of high-pressure equipment, as well as lower hazard. H2 possesses some corrosive properties, but this is easy to solve. Any industrial reactor which is used for hydrogenation is stable to hydrogen gas. This has to be changed.

- In the introduction authors also claim the greeness of transfer hydrogenation over hydrogenation. This is also not correct and has to be changed. Indeed, most of H₂ is produced from natural gas, but the amount of H₂ produced by the electrolysis of water increases all the time. In the mean time, isopropanol is not currently produced from renewables. On top of this, acetone is formed, which will be an extra impurity to get rid of and will also be a waste. Thus the statement has to be removed!

- authors claim in the introduction, that their procedure for the catalyst preparation is greener. However, supercritical CO₂ is highly energy demanding! There is a reason why there are only several operating processes on supercritic solvents out there. The idea is interesting, but I would not claim the green aspects of this. This has to be changed. Focus can be given on the actual procedure of catalyst preparation, which is different from classical methods, but certainly not greener. In case authors really want to claim the green aspect of that, proper calculations have to be presented, where all price aspects must be shown, including the costs of pure CO₂, what happens to supercritical CO₂ in the end (i.e. how much of it can be recycled) and costs of operation under super critical conditions.

- minor point - acknowledgements - lines 312-314 - not properly filled out.

- English language - overall it is fine, but in some cases some clear mistakes exist, which may disturb the reader. Examples: line 9 - should be "ways" instead of "way", line 60 - should be "advantages" instead of "advantage" etc.

I recommend publication of this article in the journal after the above mentioned points are addressed.

Author Response

We thank the Reviewer for the time spent reading our manuscript. We think that the Reviewer provided excellent suggestions given us the fresh sight on the work and some of its basic aspects. We appreciate the Reviewer’s comments very much and we firmly believe that they improve this work and will be extremely helpful for our future studies! Our responses to the Reviewer’s comments are given below.

1. lines 33-34, authors claim that H2 gas is corrosive. This is not quite true! The key advantages of transfer hydrogenation over hydrogenation with H2 are the absence of the need of high-pressure equipment, as well as lower hazard. H2 possesses some corrosive properties, but this is easy to solve. Any industrial reactor which is used for hydrogenation is stable to hydrogen gas. This has to be changed.

We agree that high pressure, which is required for H₂ hydrogenation, is one of the important disadvantage of conventional process compared to transfer hydrogenation. This has been added to the text (page 1 in the revised manuscript). At the same, we think that corrosive activity is also important because it anyway shortens reactor life time and forces the use of expensive alloying metals.

2. In the introduction authors also claim the greeness of transfer hydrogenation over hydrogenation. This is also not correct and has to be changed. Indeed, most of H2 is produced from natural gas, but the amount of H2 produced by the electrolysis of water increases all the time. In the mean time, isopropanol is not currently produced from renewables. On top of this, acetone is formed, which will be an extra impurity to get rid of and will also be a waste. Thus the statement has to be removed!

The statement has been removed according to the Reviewer’s suggestion, at the same time, the mentioned issue is not very obvious. Producing hydrogen from fresh water via electrolysis is also questionable from environmental point of view. We do not have a lot of fresh water on the planet and people in some countries suffer from its lack, whereas, salt water cannot be used in electrolysis. Another issue is electricity production. The current energy crisis shows that, unfortunately, we are far from effective technologies of electricity producing from wind or sun energy.

We agree that nowadays 2-PrOH is produced from fossils, at the same time, there are many studies showing that almost every lower aliphatic alcohol can be produced from biomass via biotechnologies, for example, Gehrmann S, Tenhumberg N. Production and Use of Sustainable C2-C4 Alcohols – An Industrial Perspective. Chemie-Ingenieur-Technik 2020; 92: 1444–1458. [DOI: 10.1002/cite.202000077].

3. authors claim in the introduction, that their procedure for the catalyst preparation is greener. However, supercritical CO2 is highly energy demanding! There is a reason why there are only several operating processes on supercritic solvents out there. The idea is interesting, but I would not claim the green aspects of this. This has to be changed. Focus can be given on the actual procedure of catalyst preparation, which is different from classical methods, but certainly not greener. In case authors really want to claim the green aspect of that, proper calculations have to be presented, where all price aspects must be shown, including the costs of pure CO2, what happens to supercritical CO2 in the end (i.e. how much of it can be recycled) and costs of operation under super critical conditions.

Unfortunately, proper cost calculations of the possible SAS method applied to catalysts preparation requires the special separated study. We would not like to do it and we have not found the proper literature data. So, the Reviewer’s suggestion has been followed.

4. minor point - acknowledgements - lines 312-314 - not properly filled out.

This section has been removed in the revised text.

5. English language - overall it is fine, but in some cases some clear mistakes exist, which may disturb the reader. Examples: line 9 - should be "ways" instead of "way", line 60 - should be "advantages" instead of "advantage" etc.

We thank the Reviewer for the attention to details. The mentioned mistakes have been corrected and English has been checked one more time all over the text.

Round 2

Reviewer 3 Report

Thank you very much for taking the comments into account. Indeed, calculations of economic aspects of supercritical CO2 usage would be way above the scope of this study, this is totally understandable. I am happy to suggest the publication of this work in this journal in the current form.