Preparation of di-[EMIM]CoCl3 Ionic Liquid Catalyst and Coupling with Oxone for Desulfurization at Room Temperature
Round 1
Reviewer 1 Report
Reviewer comment: Thanks for inviting me to review this paper titled " Preparation of di-[EMIM]CoCl3 ionic lqiuid Catalyst and coupling with Oxone for desulfurization at room temperature.". In this work, the authors showed the desulfurization technique and identified the oxidation products using GC-MS. I found the manuscript interesting, which will be helpful for the possible future readers of the "Catalysts" journal. Therefore, I recommend publishing this research paper in the "Catalysts", but only after a manuscript revision. Please find my comments below.
1. Why this work is important, and what is the major drawback of this work should be added briefly in the introduction section.
2. There are some minor typo errors (for example, Title: lqiuid, I guess it must be liquid, line number 12, 114, 126: (105℃), please leave a space between 105 and ℃. line number 229: 20wt%, please leave a space between 20 and wt%) in the manuscript. Be very careful about the single and double space throughout the manuscript. Please re-check the spelling. Improve the quality of equation 1 for better visibility.
3. The FTIR explanation needs to be improved a lot instead of just pointing out the peaks.
4. Figure 4.- Each figure should be defined properly using like a, b, c…. The topmost right figure (Fig. 4) should be changed with a better-quality figure.
5. It would be excellent if authors could add SEM, EDS and mapping images of di-[EMIM]CoCl3 after 6 recycles and could explain the reason why sulfur removal efficiency decreased.
6. Please add the error bar in Fig. 5, 6, 7, 8, 9, & 10.
Good luck.
Author Response
Thank you very much for giving me such a precious opportunity for resubmitting this manuscript, “Preparation of di-[EMIM]CoCl3 ionic liquid catalyst and coupling with oxone for desulfurization at room temperature” (catalysts-2197770). The reviewer’s comments are all valuable and very helpful for improving this manuscript, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction, point by point, which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as follow.
Q1: Why this work is important, and what is the major drawback of this work should be added briefly in the introduction section.
A1: The novelty and drawback has been added in the introduction section of revised manuscript in red text. The details are also as follow:
The cobalt ion and oxone together in aqueous exhibit an excellent oxidation ability and is widely used in the organic wastewater treatment. In our previous study, single cobalt ion was fixed in ionic liquid to form desulfurization ionic liquid[14] ([Bmim]/CoCl3). The physical property of [Bmim]/CoCl3 in desulfurization process was viscous liquid in room temperature. The drawback was the high price due to large dosage. The solid technology of ionic liquids is a strategy to reduce the dosage. In this study, a new double cobalt containing ionic liquid (di-[EMIM]CoCl3) was prepared by carbon chain connection of the single cobalt containing ionic liquid catalyst. The double cobalt containing ionic liquid expressed solid physical property at room temperature, which could increase the density of cobalt ion in catalyst and decrease the dosage of catalyst. As it should be, the high price of functional ionic liquids is still the drawback of this study.
Q2: There are some minor typo errors (for example, Title: lqiuid, I guess it must be liquid, line number 12, 114, 126: (105℃), please leave a space between 105 and ℃. line number 229: 20wt%, please leave a space between 20 and wt%) in the manuscript. Be very careful about the single and double space throughout the manuscript. Please re-check the spelling. Improve the quality of equation 1 for better visibility.
A2: Thanks to reviewer for reminder the typo errors. All the errors have been revised. We re-checked carefully and tried our best not to make these mistakes.
Q3: The FT-IR explanation needs to be improved a lot instead of just pointing out the peaks.
A3: We were sorry to make some mistakes about FT-IR picture which led to the interpretation of FT-IR was inconsistent with the picture content. In the revised manuscript, the right FT-IR has been uploaded. More clear explanation has been exhibited.
Q4: Figure 4.- Each figure should be defined properly using like a, b, c…. The topmost right figure (Fig. 4) should be changed with a better-quality figure.
A4: In the revised manuscript, all the pictures have been defined using a, b, c, d and e and the better-quality figures have been unloaded.
Q5: It would be excellent if authors could add SEM, EDS and mapping images of di-[EMIM]CoCl3 after 6 recycles and could explain the reason why sulfur removal efficiency decreased.
A5: Because the dosage of catalyst added in the desulfurization system was relatively small, the catalyst could not be recovered in the recycling experiment. For another reason, our lab is currently in the winter holiday and we only have ten days to revise the manuscript. So, we could not complete the characterization of recovered catalyst. he reason for the deactivation of the catalytic system was the accumulation of sulfate and the oxidation products of DBT.
Q6: Please add the error bar in Fig. 5, 6, 7, 8, 9, & 10.
A6: The error bar is an important. However, we are so sorry that we couldn’t provide error bars. The reason is we did not conduct error analysis about the experiment data. Last year, our lab was forced to close for a long time because of COVID-2019. Now, our lab is closed because of the winter holiday. In our previous study (Journal of Chemistry, 2018, 6495826), the error analysis for desulfurization was studied.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors have presented the paper in standard publishing format with a decent introduction and presentation of results and discussion. However, the reviewer believes the article could be significantly improved if the following concerns could be addressed:
1. Line 103, the sentence that begins with "Added simulated fuel" should be improved.
2. Why the authors did not include the H-NMR spectrum of the synthesized di-[EMIM]Cl ?
3. In the experimental section, what grade chemicals and where it was purchased were missing. Please include that information
4. Leaching is a common issue in catalysts. Have authors studied if Cobalt in the catalyst had not leached during the experiment? If so, please provide the results in the supplementary information. In the absence of leaching studies it is difficult to conclude if the catalytic activity is due to the actual catalyst or by the leached cobalt.
5. What is the control experiment for the results presented in section 3.3 (effect of di-[EMIM]CoCl3 dosage)?
6. Fonts are inconsistent with figures and typos in Figure 6 y-axis
7. The word "organism" in the title for section 3.7 does not seem appropriate. It must be changed.
Control experiment missing for the results presented in section 3.3
Author Response
Thank you very much for giving me such a precious opportunity for resubmitting this manuscript, “Preparation of di-[EMIM]CoCl3 ionic liquid catalyst and coupling with oxone for desulfurization at room temperature” (catalysts-2197770). The reviewer’s comments are all valuable and very helpful for improving this manuscript, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction, point by point, which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as follow.
Q1: Line 103, the sentence that begins with "Added simulated fuel" should be improved.
A1: Sorry about this unclear description. In the revised manuscript, “Added 500 ppm DBT solution” was instead of "Added simulated fuel".
Q2:Why the authors did not include the H-NMR spectrum of the synthesized di-[EMIM]Cl ?
A2: The di-[EMIM]Cl ionic liquid was the Intermediate during synthesized process. Some articles only provided the data of H-NMR spectrum without picture. So, this study did not show the H-NMR spectrum picture. The H-NMR spectrum of the synthesized di-[EMIM]Cl is as follow:
Q3: In the experimental section, what grade chemicals and where it was purchased were missing. Please include that information.
A3: All the chemical reagents were analytical reagent and were purchased from Aladdin Reagent Company (Shanghai).
Q4: Leaching is a common issue in catalysts. Have authors studied if Cobalt in the catalyst had not leached during the experiment? If so, please provide the results in the supplementary information. In the absence of leaching studies it is difficult to conclude if the catalytic activity is due to the actual catalyst or by the leached cobalt.
A4: It is a very good question. The leaching of cobalt should be studied. We should recover the catalyst and analyze catalyst after desulfurization. However, Because the dosage of catalyst added in the desulfurization system was relatively small, the catalyst could not be recovered in the recycling experiment. For another reason, our lab is currently in the winter holiday and we only have ten days to revise the manuscript. So, we could not complete the characterization of recovered catalyst. he reason for the deactivation of the catalytic system was the accumulation of sulfate and the oxidation products of DBT.
Q5: What is the control experiment for the results presented in section 3.3 (effect of di-[EMIM]CoCl3 dosage)?
A5: We are so sorry to miss this data in the manuscript. In the revised manuscript, the data has been added. Without catalyst, only [Bmim]BF4 extractant showed 15.4% sulfur removal after 30 min extraction process.
Q6: Fonts are inconsistent with figures and typos in Figure 6 y-axis
A6: This mistake has been revised.
Q7: The word "organism" in the title for section 3.7 does not seem appropriate. It must be changed.
A7: We used “organic compounds” to replace the word “organism”.
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors report the synthesis of bi-[EMIM]CoCl3 ionic liquid catalyst and perform sulfur removal with oxone in different sulfur-containing organics (dibenzothiophene, benzothiophene and 4,6-di-methyldibenzothiophene). The oxidation product was determined by GC-MS analysis, and the oxidation mechanism was discussed.
I believe that before the article is accepted, the authors should address the following comments:
1. line 2, correct lqiuid by liquid
2. line 212, correct "rose" to "rise"
3. In tests 3.4 and 3.5 the authors must include an experiment in the absence of the catalyst as a standard test.
3. In the proposed mechanism of Fig. 11, correctly place the signs (charges) in each of the atoms that correspond to it.
Author Response
Thank you very much for giving me such a precious opportunity for resubmitting this manuscript, “Preparation of di-[EMIM]CoCl3 ionic liquid catalyst and coupling with oxone for desulfurization at room temperature” (catalysts-2197770). The reviewer’s comments are all valuable and very helpful for improving this manuscript, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction, point by point, which we hope meet with approval. Revised portion are marked in red in the paper. The main corrections in the paper and the responds to the reviewer’s comments are as follow.
Q1: line 2, correct lqiuid by liquid.
A1: This mistake has been revised.
Q2: line 212, correct "rose" to "rise"
A2: This mistake has been revised.
Q3: In tests 3.4 and 3.5 the authors must include an experiment in the absence of the catalyst as a standard test.
A3: In section 3.4 and 3.5, the effects of oxone dosage and extractant were discussed. For our preliminary studies, if there was no catalyst, the sulfur removal was only affected by extraction of [Bmim]BF4. Only the presence of oxidant hardly affected desulfurization process.
Q4: In the proposed mechanism of Fig. 11, correctly place the signs (charges) in each of the atoms that correspond to it.
A4: The Figure 11 has been revised according to the suggestion from reviewer.
Round 2
Reviewer 1 Report
Decision: The authors have revised the manuscript accordingly. Now the manuscript is ready to be published.
Author Response
Thanks for your approval for this paper.
Reviewer 2 Report
Dear Authors,
Please fix the following :
The control information section 3.3 must be included in the graph. Just the number is not adequate.
Without leaching studies, the whole study is pointless. The authors must present results of leaching studies.
Author Response
Q1: The control information section 3.3 must be included in the graph. Just the number is not adequate.
A1: For re-submitted manuscript, all the graphs was revised to add the control information in the Figure 5 to Figure 10.
Q2: Without leaching studies, the whole study is pointless. The authors must present results of leaching studies.
A2: We are very sorry that the answer to this question did not satisfy to the reviewer. It is very difficult for us to complete the characterization after catalyst recovery. The reason is the dosage of catalyst added in the desulfurization system was relatively small. It was difficult for us to recover catalyst in the recycling experiment. For another reason, our lab is currently in the winter holiday. So, leaching studies for catalyst is hard for us to finish. Due to the coordination bond between the active center cobalt ion and supporter ionic liquid, we believe that the leaching rate of cobalt ion is not high. However, in the future study, we will discuss the leaching of the active center of the catalyst in detail.
