Next Article in Journal
Manganese Salan Complexes as Catalysts for Hydrosilylation of Aldehydes and Ketones
Next Article in Special Issue
Hydroformylation of Alkenes over Phosphorous-Free Rhodium Supported on N-Doped Silica
Previous Article in Journal
Effect of MnO2 Crystal Type on the Oxidation of Furfural to Furoic Acid
Previous Article in Special Issue
Synthesis and Investigation of Zeolite TiO2/Al-ZSM-12 Structure and Properties
 
 
Article
Peer-Review Record

Supported Ionic Liquid Catalysts for the Oxidation of S- and N-Containing Compounds—The Effect of Bronsted Sites and Heteropolyacid Concentration

Catalysts 2023, 13(4), 664; https://doi.org/10.3390/catal13040664
by Vladislav Gorbunov 1, Aleksey Buryak 2, Kirill Oskolok 1, Andrey G. Popov 1 and Irina Tarkhanova 1,*
Reviewer 1:
Reviewer 2: Anonymous
Reviewer 3:
Catalysts 2023, 13(4), 664; https://doi.org/10.3390/catal13040664
Submission received: 1 March 2023 / Revised: 24 March 2023 / Accepted: 26 March 2023 / Published: 28 March 2023

Round 1

Reviewer 1 Report

 

This manuscript fabricated a series of catalysts with tunable Bronsted and Lewis acidic sites, based on the combination of betaine and sulfuric or phosphomolybdic acids, to enhance the oxidation of sulfur- and nitrogenous- containing compounds with H2O2. A series of characterizations were conducted to illustrate the structure-performance relationship. Generally, although some characterizations are not adequate, most conclusions of this work are well constructed by characterizations, experiments and simulations. I suggest it can be published after micro revision.

 

1. The synthesis description is unclear and needs to be revised. A scheme diagram for the synthesis of the catalyst is favorable. Additionally, the amounts of the synthesis materials need to be verified. For example, the mass of 0.3 mmol PMA is 0.49 g, so the mass of 0.8 mmol PMA would be 1.31 g instead of 1.63 g.

 

2. Would the catalyst containing S/N be degraded during the oxidation reaction? The authors need to check the mass and the content of S/N on the catalyst before and after the reaction.

 

3. It is recommended to label the attribution of each peak in the infrared spectrum figure (Figure 2).

 

4. Authors infer that “Brønsted acids are poor catalytic sites for thiophene oxidation” is based on the experimental results comparing different catalysts, which showed that the SA catalyst containing high concentration of Brønsted acid sites had the lowest activity. Is it possible that the poor catalytic activity of SA is due to the extremely unstable structure of SA in the oxidation reaction? However, the issue of the stability of the SA catalyst and its potential impact on its catalytic activity was not discussed in the literature.

 

5. Several valuable references on pollutant treatment published recently should be cited. (Nano Lett. 22, 838 (2022); Nano Lett. 22,8381 (2022); Adv. Mater. 33, 2103186 (2021); etc)

 

6. What does HPA mean? The abbreviated full name needs to be given.

Author Response

Thank you very much for the detailed analysis of our work. Responding to comments point by point:

  1. We've fixed the typo, sorry. The calculation of the number of moles was carried out with an accuracy of tenths.
  2. The ratio S/N after the reaction, of course, changed since the surface was enriched with the products of substrate oxidation. Therefore, the surface coating saving of the catalyst was evidenced by its stability with several successive cycles of the reaction.

  3. We followed the recommendations of the reviewer (Fig. 2).

  4. The acid action in oxidation is associated with H2O2 electrophilic properties increase. Since thiophene has a low electron density on the sulfur atom (see table from Stanislaus, A., Marafi, A., Rana, M.S. Catal. Today. 2010. 153. Р. 1–68), the reaction of nucleophilic substitution with its participation is weak.

  5. We analyzed very interesting articles and chose one that is closest to us in terms of topics (ref. 45)

  6. We gave full name at the beginning of the article

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors reported the oxidation of S- and N-containing compounds using supported ionic liquids. This can be considered worth publishing in “Catalysts” after following modifications.

1. Please provide the SEM images to show the whole catalyst particles and give some explanation to them. It is also interesting to us that if the loading of IL will change the catalyst’s surface.

2. It is recommended to use some color on the Figure 3 and 4.

3. Abbreviation: a) the use of abbreviation in the title will be difficult to understand; b) Please give the full name when the abbreviation shows at the first time in the manuscript.

4. In line 228, the authors claimed that Mo is partial reduced during recording of the spectra. It is difficult to understand because it is not a reduction condition during this process. Please give a more detailed and reasonable explanation.

5. In Figure 7, it seems that the thiophene removal activity decrease with the time except for SA. At this point, SA might show the highest thiophene removal activity after a long enough time. Please give some comment on it.

Author Response

Thank you very much for the detailed analysis of our work. Responding to comments point by point:

  1. We sent (Please see the attachment) pictures of the whole catalyst particles (PMo2 and PMo3). After the reaction, the SEM images practically did not change.

  2. We followed the recommendations of the reviewer, but the image quality did not improve.

  3. We have given the full name despite this abbreviation is well established in the literature on ionic liquids in catalysis.

  4. Under the conditions of recording the spectra, the sample is exposed to soft X-ray radiation and the flux of low electrons from the neutralizer, which can lead to recovery due to radiation effects. And the ultra-high vacuum in the spectrometer additionally contributes to the removal of volatile atoms that were formed as a result of radiation exposure. Organic fragments under spectrometer conditions can reduce molybdenum, what can be observed visually after analysis.
  5. Theoretically, the curves will intersect, but in this system there is a thermal H2O2 decomposition of the oxidizer, so after a few hours it will fade.

Author Response File: Author Response.pdf

Reviewer 3 Report

The manuscript described a promising methodology to remove N- and S-containing compounds from fuel, using a catalytic system based on ionic liquid and heteropolyacids.

The catalysts have been well characterized and applied with sucess in the proposed oxidation reaction.

Only a few spelling corrections on the language should be done, specially in the use of abbreviation, that are missed, such as HPA, BET, ....

Author Response

Thank you very much for the positive evaluation of our work.

We have made corrections according to your comments.

Round 2

Reviewer 2 Report

I believe this paper can be published after addressing the following minor point:

I would suggest the authors to use the full name, that is supported ionic liquids, in the manuscript TITLE.

Author Response

We have corrected the title of the article.

Back to TopTop