Air-Stable Efficient Nickel Catalyst for Hydrogenation of Organic Compounds
, Mykyta O. Ivanytsya 1,2, Anastasiya V. Terebilenko 1,3, Pavel S. Yaremov 1, Olena O. Pariiska 1, Yuri M. Akimov 3, Igor E. Kotenko 1,4, Tomash M. Sabov 5, Mykhailo M. Kurmach 1, Sergey V. Ryabukhin 2,6,7, Dmitriy M. Volochnyuk 2,6,7 and Sergey V. Kolotilov 1,*
Round 1
Reviewer 1 Report
In this manuscript, Kolotilov et al reported the detail investigation of the catalytic activity of Ni and NiO, deposited on the Norit charcoal, towards the hydrogenation of quinoline. The composites were prepared by the decomposition of Ni0 complex Ni(cod)2 (cod = 1,5-cis,cis-1,5-cycloocta- 18 diene), which resulted in the formation of varied Ni content from 1 to 10 % by weight. Supported heterogeneous catalysts containing active material and other species (in this case active carbon), possess catalytically relevant function together with the possibility of reusability. The development of catalytic hydrogenation reactions is an outstanding example for how chemical research influences industry practices and, subsequently, has been honored with two Nobel prizes (i.e., Sabatier 1912, Knowles and Noyori in 2001). Therefore, investigations of catalytic systems involve in these transformations would be valuable. The concept and approach of the study is executed well, however, the explanation and language of the manuscript has to be significantly improved. Therefore, it is only suggested for publication after the authors consider the following major revisions.
The reviewer suggests to change the title of the manuscript, such as,
· “Air-stable efficient supported nickel catalysts for the hydrogenation of quinoline derivatives”
· “Ni content varied from 1 to 10 % by weight” in this sentence in the abstract, add the approach adopted to varied the content of Ni.
· “The composites could be stored on air without loss of their catalytic activity”, give the reason why. This will improve the readability of the abstract.
· “It was found by powder XRD and TEM, that the composites contained nanoparticles, which could be assigned to Ni and NiO”, rewrite this sentence in the abstract.
· Introduction should also contain few sentences about the preparation of nanomaterials by the degradation of organometallic compounds or ionic liquids, together with the importance of supported heterogeneous catalysts with representative references such as,
"Facile synthesis of nickel based nanostructures from Ni [EMIM] Cl 2 ionic liquid precursor: effects of thermal and chemical methods on the properties of nanoparticles." RSC advances 6.89 (2016): 86340-86345.
"Advances in graphene/inorganic nanoparticle composites for catalytic applications." The Chemical Record 22.7 (2022): e202100274.
"Critical review on biochar‐supported catalysts for pollutant degradation and sustainable biorefinery." Advanced Sustainable Systems 4.10 (2020): 1900149.
· Only XRD is not sufficient to confirm the presence of Ni and NiO, these results also have to be corroborated with other techniques such as XPS and at least with EDX, which may indicate the presence of oxygen.
· The size of the nanoparticles should be indicated with the inclusion of size distribution graph, and also if possible DLS will also offer valuable information.
· Schemes of the preparation of catalysts and also for the organic transformation are necessary.
· Prove the efficiency of the catalysts reported in this study, by comparing them with other studies reported for similar transformation in the form of a table.
· Did the authors checked the catalytic activity of pristine complexes? (albeit in homogenous conditions)? Is the study already published?
· How did the identity of organic products obtained after hydrogenation is confirmed, no data is provided? It is mentioned in the experimental section about the NMR and LC-MS but results are not given
· Conclusion should have more discussion about results
· Extensive English changes are required (for example, at several places, it is written as “on air”, it should be “in air”. Authors must carefully read the manuscript and work on sentence construction and use of prepositions and tenses. The composition of the manuscript should also be improved, as several paragraphs are very short which should be merge with other to enhance readability.
Author Response
Reviewer 1
COMMENT
Comments and Suggestions for Authors
In this manuscript, Kolotilov et al reported the detail investigation of the catalytic activity of Ni and NiO, deposited on the Norit charcoal, towards the hydrogenation of quinoline. The composites were prepared by the decomposition of Ni0 complex Ni(cod)2 (cod = 1,5-cis,cis-1,5-cycloocta- 18 diene), which resulted in the formation of varied Ni content from 1 to 10 % by weight. Supported heterogeneous catalysts containing active material and other species (in this case active carbon), possess catalytically relevant function together with the possibility of reusability. The development of catalytic hydrogenation reactions is an outstanding example for how chemical research influences industry practices and, subsequently, has been honored with two Nobel prizes (i.e., Sabatier 1912, Knowles and Noyori in 2001). Therefore, investigations of catalytic systems involve in these transformations would be valuable. The concept and approach of the study is executed well, however, the explanation and language of the manuscript has to be significantly improved. Therefore, it is only suggested for publication after the authors consider the following major revisions.
The reviewer suggests to change the title of the manuscript, such as,
“Air-stable efficient supported nickel catalysts for the hydrogenation of quinoline derivatives”
REPLY
We would like to draw attention, that in this study we performed successful hydrogenation of alkenes, alkynes, carbonyl compounds, nitro-compounds and heterocycles. For this reason, we believe that more "wide" title would be more appropriate.
Indeed, some key experiments were performed using quinoline (such as evaluation of the most efficient catalyst, studies of the influence of pressure or temperature on the yield, etc.). Quinoline was used just because its hydrogenation is more difficult task compared to hydrogenation of many other classes of organic compounds (alkenes, alkynes, nitro-compounds, etc.). If the catalyst is active in hydrogenation of quinoline, with very high probability it will be suitable for other classes (reverse is not true: many catalysts which are active in hydrogenation of nitro-compounds or alkenes cannot be used for hydrogenation of quinoline). We added a comment on this matter to the revised manuscript.
In the revised version we added the results of hydrogenation of 9 additional compounds and we re-formatted Table 1 (Table 4 in the revised version); we highlighted separate classes of organic compounds, such as alkenes, alkynes, carbonyl compounds, nitro compounds, and heterocycles. At present quinoline and its derivatives constitute about 50 % of the list of substrates.
COMMENT
“Ni content varied from 1 to 10 % by weight” in this sentence in the abstract, add the approach adopted to varied the content of Ni.
REPLY
We changed this sentence in the abstract. Regretfully, we cannot add many synthetic details because of the limited length of the abstract.
COMMENT
“The composites could be stored on air without loss of their catalytic activity”, give the reason why. This will improve the readability of the abstract.
REPLY
In our opinion, this property (high catalytic activity was not affected by contact with air) was caused by the fact that the active sites were generated in situ. The composites which were kept in air, contained NiO, and our additional studies performed in course of revision confirmed this. The catalytic activity of such systems in hydrogenation process could be explained by in situ reduction of NiO to Ni, and in such case storage in air did not affect the pre-catalyst. A comment was added to the text of the manuscript, to Conclusions and to the Abstract.
COMMENT
“It was found by powder XRD and TEM, that the composites contained nanoparticles, which could be assigned to Ni and NiO”, rewrite this sentence in the abstract.
REPLY
This sentence was changed.
COMMENT
Introduction should also contain few sentences about the preparation of nanomaterials by the degradation of organometallic compounds or ionic liquids, together with the importance of supported heterogeneous catalysts with representative references such as,
"Facile synthesis of nickel based nanostructures from Ni [EMIM] Cl 2 ionic liquid precursor: effects of thermal and chemical methods on the properties of nanoparticles." RSC advances 6.89 (2016): 86340-86345.
"Advances in graphene/inorganic nanoparticle composites for catalytic applications." The Chemical Record 22.7 (2022): e202100274.
"Critical review on biochar‐supported catalysts for pollutant degradation and sustainable biorefinery." Advanced Sustainable Systems 4.10 (2020): 1900149.
REPLY
These references were cited in the revised version of the manuscript.
COMMENT
Only XRD is not sufficient to confirm the presence of Ni and NiO, these results also have to be corroborated with other techniques such as XPS and at least with EDX, which may indicate the presence of oxygen.
REPLY
We thank Referee for this suggestion. We performed additional studies and we found that the composites contained only NiO. In particular, we added the results of XPS and EDX. Due to these additional results, we made corrections in the manuscript. However, reduction of the composites led to formation of metallic Ni, and we also performed additional measurements of chemisorption of CO for determination of the Ni nanoparticles size.
COMMENT
The size of the nanoparticles should be indicated with the inclusion of size distribution graph, and also if possible DLS will also offer valuable information.
REPLY
Regretfully, we cannot do DLS in principle in this case, because the composites are solids and there is no way to suspend the nanoparticles in liquid medium. However, being inspired by the Referee's suggestion, we carried out experiments on N2 sorption and CO chemisorption. We also calculated particles distribution by size from TEM data, and we added new TEM data for the composites reduced with H2.
COMMENT
Schemes of the preparation of catalysts and also for the organic transformation are necessary.
REPLY
We changed Fig. 1 and added a scheme, illustrating preparation of the catalyst and its use in hydrogenation. At the same time we propose not to add reaction schemes for organic transformations, because they are clear from Table 4 (Table 1 in the previous version of the manuscript): the second column contains formulas of the reagents and the third – formulas of the products. If the one place an arrow between them, it will automatically produce all schemes of organic transformations. In our opinion, there is no need to draw additional schemes for 30 compounds.
COMMENT
Prove the efficiency of the catalysts reported in this study, by comparing them with other studies reported for similar transformation in the form of a table.
REPLY
We added a table (Table 5 in the revised version) with comparison of the performance of the best of our composites with some analogues, reported in literature. The composite developed by us showed better performance compared to many analogues. From the other hand, the performance of some known catalysts was better than in our case, but these catalysts were more expensive.
COMMENT
Did the authors checked the catalytic activity of pristine complexes? (albeit in homogenous conditions)? Is the study already published?
REPLY
The pristine complex immediately decomposes upon contact with organic compounds in conditions, suitable for hydrogenation. There were several studies of use of Ni nanoparticles, obtained by decomposition of Ni(cod)2 without additional carrier, for hydrogenolysis of diaryl, benzyl aryl, and benzyl alkyl ethers [DOI 10.1002/anie.201509133.and DOI 10.1021/ja3085912]. The first one was cited in the previous version of the manuscript. We also added reference to DOI 10.1021/ja3085912 to the revised version of the manuscript.
COMMENT
How did the identity of organic products obtained after hydrogenation is confirmed, no data is provided? It is mentioned in the experimental section about the NMR and LC-MS but results are not given
REPLY
NMR spectra and their description were added. All compounds obtained as the hydrogenation products were well-known ones. Their identity could be proven by comparison of their spectral data with literature data.
COMMENT
Conclusion should have more discussion about results
REPLY
We extended Conclusions and added more discussion of the results. We also extended Discussion section, because the Conclusions, in our opinion, should contain only the most important achievements of the study.
COMMENT
Extensive English changes are required (for example, at several places, it is written as “on air”, it should be “in air”. Authors must carefully read the manuscript and work on sentence construction and use of prepositions and tenses. The composition of the manuscript should also be improved, as several paragraphs are very short which should be merge with other to enhance readability.
REPLY
We corrected English and we consulted native English-speaking colleague in some cases.
We also tried to improve the composition of the manuscript, and to avoid very short paragraphs.
Reviewer 2 Report
This is an interesting paper on the preparation, characterization and reactivity of a series of Ni catalysts for the hydrogenation of a series of organic compounds. As claimed by the authors the major advantage of these materials is their air stability, obtained with a simple and straightforward preparation procedure, that makes storage and manipulations much easier as compared to other common catalysts like e.g. Raney Ni. However, the authors do not seem to be well aware that passivation, i.e. the formation of a very thin surface oxide layer, obtained with air under controlled conditions is a common practice in the preparation of industrial catalysts, particularly pyrophoric ones, in order to make them air stable. This point must be born in mind in order to place the evaluation of the present catalysts in the appropriate context. Clearly, the extent of oxide formation on the metal surface will affect the reaction conditions necessary to reactivate the catalyst in situ. In the present case the uncontrolled and random formation of NiO due to the preparation procedure required relatively high temperatures (150°C) to let the catalysts display their full activity.
That said, the reactivity shown by the optimized catalyst in the hydrogenation of different functional groups in a variety of aromatic compounds is quite interesting. I think the paper could be considered for publication, however only after taking into account the following points.
1. In Fig. 3, left column, a particle size distribution for both Ni and NiO (black and grey particles) must be reported because it is necessary to have a better understanding of the morphology of the catalysts, provide a possible rationale for their behavior and justify the sentence referring to "even distribution of Ni particles ..." reported in p. 5, line 138.
2. The large paragraph in page 5, lines 141-160, must be supported by a Table reporting a summary of the catalytic data. In the present form the various comparisons among the different catalysts are difficult to follow and may be confusing.
3. Page 6, lines 178-180: the effect of catalyst loading is rather strange and should be analyzed in more detail. The dramatic drop in conversion observed on going from 0.5 to 0.1% is odd because the decrease in activity must be linear. I suggest to analyze also 0.3 and 0.2% loadings and make a graph. If the decrease is not linear then an explanation must be given.
4. Finally, in order to put the significance of the paper in the appropriate context, I think that a comparison with a common Ni catalyst, e.g. Raney Ni, in the hydrogenation of 1,2,3,4,-tetrahydroquinoline should be reported.
5. English use require a thorough revision by an expert.
Author Response
Reviewer 2
COMMENT
Comments and Suggestions for Authors
This is an interesting paper on the preparation, characterization and reactivity of a series of Ni catalysts for the hydrogenation of a series of organic compounds. As claimed by the authors the major advantage of these materials is their air stability, obtained with a simple and straightforward preparation procedure, that makes storage and manipulations much easier as compared to other common catalysts like e.g. Raney Ni. However, the authors do not seem to be well aware that passivation, i.e. the formation of a very thin surface oxide layer, obtained with air under controlled conditions is a common practice in the preparation of industrial catalysts, particularly pyrophoric ones, in order to make them air stable. This point must be born in mind in order to place the evaluation of the present catalysts in the appropriate context. Clearly, the extent of oxide formation on the metal surface will affect the reaction conditions necessary to reactivate the catalyst in situ. In the present case the uncontrolled and random formation of NiO due to the preparation procedure required relatively high temperatures (150°C) to let the catalysts display their full activity.
That said, the reactivity shown by the optimized catalyst in the hydrogenation of different functional groups in a variety of aromatic compounds is quite interesting. I think the paper could be considered for publication, however only after taking into account the following points.
REPLY
We thank the Referee for pointing out possible passivation of nickel. We performed XPS measurements and we did not find Ni in the composite Ni/C-3. On the other hand, we carried out CO chemisorption of samples, reduced by H2, and we found very small Ni nanoparticles. These nanoparticles apparently formed upon reduction of NiO, implying that the size of NiO "precursors" was also small. All these data, as well as powder XRD, TEM, N2 sorption, are well consistent with the supposition, that NiO formed microporous phase on the surface of Norit, consisting of very small NiO particles. Thus we come to a conclusion that all Ni was accessible to oxygen, and it could be oxidized. Ni core, if any, could be preserved only in samples with the highest Ni content, but it does not play crucial role in the catalytic performance.
COMMENT
- In Fig. 3, left column, a particle size distribution for both Ni and NiO (black and grey particles) must be reported because it is necessary to have a better understanding of the morphology of the catalysts, provide a possible rationale for their behavior and justify the sentence referring to "even distribution of Ni particles ..." reported in p. 5, line 138.
REPLY
We added graphs showing distribution of particles.
We also revised our description of TEM according to new data, and in view of these new data we think that all particles are NiO.
COMMENT
- The large paragraph in page 5, lines 141-160, must be supported by a Table reporting a summary of the catalytic data. In the present form the various comparisons among the different catalysts are difficult to follow and may be confusing.
REPLY
We added a table with comparison of these composites, as proposed by the Referee (Table 3 in the revised version of the manuscript).
COMMENT
- Page 6, lines 178-180: the effect of catalyst loading is rather strange and should be analyzed in more detail. The dramatic drop in conversion observed on going from 0.5 to 0.1% is odd because the decrease in activity must be linear. I suggest to analyze also 0.3 and 0.2% loadings and make a graph. If the decrease is not linear then an explanation must be given.
REPLY
We repeated the experiments and found that the dependency of the yield on Ni loading was linear in this range of Ni content. Probably we made a mistake, caused by weighting of very small quantity of the catalyst. We thank the Referee for this comment.
In the revised version of the manuscript we present the results of hydrogenation with 0.1, 0.2, 0.3 and 0.4 % loadings (Fig. 9).
COMMENT
- Finally, in order to put the significance of the paper in the appropriate context, I think that a comparison with a common Ni catalyst, e.g. Raney Ni, in the hydrogenation of 1,2,3,4,-tetrahydroquinoline should be reported.
REPLY
We performed own experiments on hydrogenation of quinoline at presence of Raney nickel and we also added literature data on hydrogenation of Raney nickel (Table 5 in the revised version).
COMMENT
- English use require a thorough revision by an expert.
We read the whole manuscript and improved English. In several cases we consulted with native English-speaking colleague.
Reviewer 3 Report
This article is devoted to the production of stable nickel-containing catalysts for the hydrogenation of organic substances. The article is written in a clear and adequate language, the main ideas are well formulated. The practical significance of the results obtained by the authors is obvious. However, there are some points that it is desirable to finalize:
1. Abstract can be slightly expanded.
2. What is the Ni/NiO ratio in the catalysts obtained by the authors?
3. Carefully check the use of subscripts and superscripts.
4. It would be good for the obtained catalysts to have data on the presence and amount of micro- and meso-pores.
5. Please cite: 10.3390/catal12101177.
6. The conclusions can be slightly expanded.
Author Response
Reviewer 3
COMMENT
Comments and Suggestions for Authors
This article is devoted to the production of stable nickel-containing catalysts for the hydrogenation of organic substances. The article is written in a clear and adequate language, the main ideas are well formulated. The practical significance of the results obtained by the authors is obvious. However, there are some points that it is desirable to finalize:
- Abstract can be slightly expanded.
REPLY
We changed the abstract. Please note, that abstract size is limited by the rules for authors.
COMMENT
- What is the Ni/NiO ratio in the catalysts obtained by the authors?
REPLY
We carried out XPS measurements and in view of these new data we think that the composites contain only NiO. In course of hydrogenation process Ni is generated due to in situ reduction. We added respective comments to the revised manuscript.
COMMENT
- Carefully check the use of subscripts and superscripts.
REPLY
We checked the manuscript and did our best to improve writing of subscripts and superscripts.
COMMENT
- It would be good for the obtained catalysts to have data on the presence and amount of micro- and meso-pores.
REPLY
We carried out measurements of N2 adsorption and calculated the parameters of porous structure of the composites. These parameters are presented in Table 1 in the revised manuscript.
COMMENT
- Please cite: 10.3390/catal12101177.
REPLY
We added reference to this work.
COMMENT
- The conclusions can be slightly expanded.
REPLY
The conclusions were expanded.
Round 2
Reviewer 1 Report
The authors have sucessfully addressed all the comments raised by the reviewer, therefore, the quality of the manuscript has increased significantly. Now it can be accepted.
Reviewer 2 Report
All my suggestions have been addressed to satisfaction and I think that now the paper can be accepted for publication.
