The Effect of Preparation Method of Ni-Supported SiO₂ Catalysts for Carbon Dioxide Reforming of Methane

Round 1

Reviewer 1 Report

The authors have studied the catalytic performance of Ni supported SiO2 catalysts for  carbon dioxide reforming of methane, after careful reading of the manuscript, here are some comments to improve the manuscript:

 

1. The crystallite size values which were calculated using Scherrer formula were not given
2. The authors talked about the 002 plane, however, the indexation of the diffractograms has not been carried out (Figures 1 and 2)
3. A standard XRD pattern of NiO should be provided in Figures 1 and 2.
4. The authors have concluded from XRD date that complexed-impregnation has led to smaller NiO particles, it must be confirmed by other techniques (XPS for example)
5. The authors should discuss the conversion mechanism
6. Compare the obtained results with relevant literatures to highlight the superiority of the work
7. Was there any reverse water–gas shift?

 

 

 

 

 

Author Response

 

Otc. 2, 2021

 

 

 

Dear Editor,

I am submitting the revised manuscript entitled “High catalytic performance of Ni supported SiO₂ catalysts for carbon dioxide reforming of methane” (catalysts-1411144) to Catalysts. We have carefully revised the manuscript according to the reviewers’ recommendations as you will see in the manuscript (marked with blue color).

We hope that the revised manuscript will be fulfilled for the publication in Catalysts.

Herein are included the revised manuscript and the reply to the reviewers’ comments.

 

 

 

 

Sincerely yours,

Shao-Peng Tian

 

 

 

 

Reply to Reviewer’s comments

 

Comments and Suggestions for Authors:

The authors have studied the catalytic performance of Ni supported SiO₂ catalysts for carbon dioxide reforming of methane, after careful reading of the manuscript, here are some comments to improve the manuscript:

Reply: Thank you so much for your positive comments on our manuscript. Our point-by-point reply to your each comment is as follows.

 

1. The crystallite size values which were calculated using Scherrer formula were not given

Reply: Thanks for your good suggestions. The Scherrer formula were given in the revised manuscript.

 

2. The authors talked about the 002 plane, however, the indexation of the diffractograms has not been carried out (Figures 1 and 2)

Reply: Thank you and we accept your suggestion. The 002 plane was marked in Figures 1 and 2 in the revised manuscript.

 

3. A standard XRD pattern of NiO should be provided in Figures 1 and 2.

Reply: Thanks for your good suggestions. The figures 1 and 2 were revised in the revised manuscript.

 

4. The authors have concluded from XRD date that complexed-impregnation has led to smaller NiO particles, it must be confirmed by other techniques (XPS for example)

Reply: Thank you and we accept your suggestion. The XRD results showed that the smaller NiO and Ni particles were obtained by the complexed-impregnation, and it was also confirmed by the results of TPR and TEM in the revised manuscript.

 

5. The authors should discuss the conversion mechanism

Reply: Thanks for your good suggestions. The conversion mechanism of CDR has been reported in many literatures, and the mechanism is basically the same. The methane molecules are gradually cracked to CH_x and H on the metal Ni, two H combined into H₂, and CH_x is oxidized to CO by the dissociated O of CO₂. The polymerization of CH_x that has not been converted and the disproportionation of the generated CO are the two main sources of coke deposition.

 

6. Compare the obtained results with relevant literatures to highlight the superiority of the work

Reply: Thank you for your kind advice, in order to compare with similar catalysts, Ni/SiO₂ prepared with conventional impregnation method was also evaluated for CDR. Compared to the Ni/SiO₂, Ni-G/SiO₂ showed higher CDR performance, especially stability. Moreover, this approach is promising applied on industrial scale than those other methods, such as core-shell structure nanocatalysts, confinement of Ni-based catalyst, and plasma treatment method etc., because of its facile synthesis.

 

7. Was there any reverse water–gas shift?

Reply: Yes, you are right. The reverse water–gas shift is also occurred during the CDR reaction, which was reported in the literature, and it has been discussed in the introduction in the revised manuscript.

 

 

Reviewer 2 Report

In the present work, the authors investigated the effect of preparation method on the catalysts of Ni/SiO2 for CDR reaction. The manuscript has regular characterization, studies and nothing special in it. The authors are continuously mentioning the small Ni particle size in the catalysts but they are completely forgetting the effect of the support in the reaction. As a reviewer I would suggest that this manuscript is not acceptable at the present standard, but with a major changes it can be.

First of all, the present catalyst providing an activity of 90% conversion with 0.9 H2/CO ratio. So, I would like to ask authors to change the title “high catalytic performance…” because there are many articles having effective conversion over 95% and production of syngas ratio ~0.98 at 750 C. Also the title is not suitable for the work described in the manuscript.

During the introduction there is a lot of conversation about the greenhouse gases and the metals that are studied for CDR, later the Ni particle size and then the glycine use in the synthesis everything looks good. But what is the use of support? And SiO2 support is not a new for this reaction, it already well studied by many researcher so discuss about the support role and the difference between already published manuscript and this manuscript.

BET surface area number are not coincide with the pore volume and pore diameter values. Increase of surface area values where the pore diameter and pore volume are decreasing… why? To be more clear BET isotherms should be added.

There are many typo errors, contradictory interpretation of the data and controversial claims throughout the manuscript.

• Degree sign should be changed throughout manuscript
• Page 4 line 128, the authors are mentioning that the SiO2 is in amorphous state and in the next line there are referring it as crystalline structure of support
• Line 141 avoids blocking the pores… in BET study one can see that blockage of pore is observed with the usage of glycine.
• Ni dispersed well??? Uniform distribution of Ni???... There is no experimental proof provided in the article.
• Large particles reduces at low temperature and small particles reduces at high temperature… if this claim is true then the glycine method also did not deliver uniform particle size. One can see from Fig 4 that the glycine synthesis method also producing the large particle size?
• Authors should be more careful when interpreting the data. Fig6 where author referred cubic NiO peaks in the text but there are no NiO peaks in the Fig6
• For the coke deposition calculations I would prefer CHNS elemental analysis data. Which more accurate.
• Crystallite size of NiO was calculated by Scherrer equation… but authors did not mentioned it in the manuscript.

The unsupported claims such as high dispersion of Ni and narrower Ni distribution should be modified from the conclusions.

Ni dispersion studies should be included in the manuscript. If possible Ni distribution by elemental analysis should also provide.

Author Response

 

Otc. 2, 2021

 

 

 

Dear Editor,

I am submitting the revised manuscript entitled “High catalytic performance of Ni supported SiO₂ catalysts for carbon dioxide reforming of methane” (catalysts-1411144) to Catalysts. We have carefully revised the manuscript according to the reviewers’ recommendations as you will see in the manuscript (marked with blue color).

We hope that the revised manuscript will be fulfilled for the publication in Catalysts.

Herein are included the revised manuscript and the reply to the reviewers’ comments.

 

 

 

 

Sincerely yours,

Shao-Peng Tian

 

 

 

 

 

Reply to Reviewer’s comments

 

Comments:

In the present work, the authors investigated the effect of preparation method on the catalysts of Ni/SiO₂ for CDR reaction. The manuscript has regular characterization, studies and nothing special in it. The authors are continuously mentioning the small Ni particle size in the catalysts but they are completely forgetting the effect of the support in the reaction. As a reviewer I would suggest that this manuscript is not acceptable at the present standard, but with a major changes it can be.

Reply: Thank you so much for your comments on our manuscript. Our point-by-point reply to your each comment is as follows.

 

1. First of all, the present catalyst providing an activity of 90% conversion with 0.9 H₂/CO ratio. So, I would like to ask authors to change the title “high catalytic performance…” because there are many articles having effective conversion over 95% and production of syngas ratio ~0.98 at 750 C. Also the title is not suitable for the work described in the manuscript.

Reply: Thanks for your good suggestions and we accept your suggestion. The title was revised in the revised manuscript with blue color.

 

2. During the introduction there is a lot of conversation about the greenhouse gases and the metals that are studied for CDR, later the Ni particle size and then the glycine use in the synthesis everything looks good. But what is the use of support? And SiO₂ support is not a new for this reaction, it already well studied by many researcher so discuss about the support role and the difference between already published manuscript and this manuscript.

Reply: Thanks for your good suggestions. Indeed, support play a crucial role in performance, and it was discussed in the introduction. However, in this study, using the commercial SiO₂ as the support, the prepared method of catalysts is focus on.

 

3. BET surface area number are not coincide with the pore volume and pore diameter values. Increase of surface area values where the pore diameter and pore volume are decreasing… why? To be more clear BET isotherms should be added.

Reply: Thanks. Compared with the support, after the loading of Ni, the BET surface area, pore volume, and pore diameter of all Ni based catalysts significantly decreased due to the deposition of NiO on the pore walls of the support. Pore volumes and pore diameter show a negligible difference for the Ni based catalysts with or without addition glycine and the preparation method. But an observable difference of specific surface area was obtained for all Ni supported catalysts, the new pores are formed by the decomposition of the frame of Ni-glycine complexes of Ni-G/SiO₂-P and Ni-G/SiO₂-C, leading to the bigger specific surface area. Those results are discussed in the section of 3.1 in the manuscript.

 

4. There are many typo errors, contradictory interpretation of the data and controversial claims throughout the manuscript.

Reply: Thanks for your careful review of our manuscript. The errors you mentioned have been corrected and highlighted with blue color in the revised manuscript. Moreover, we carefully checked the full manuscript, and the contradictory interpretation of the data and controversial claims throughout the manuscript are also blue colored in the revised manuscript.

 

• Degree sign should be changed throughout manuscript

Reply: Thanks. The degree sign was revised in the revised manuscript.

 

• Page 4 line 128, the authors are mentioning that the SiO₂ is in amorphous state and in the next line there are referring it as crystalline structure of support

Reply: I am very sorry for these mistakes, and it was revised in the revised manuscript with bule color.

 

• Line 141 avoids blocking the pores… in BET study one can see that blockage of pore is observed with the usage of glycine.

Reply: Thank. The blockage of pore by NiO was obtained for the fresh catalyst, this can be explained by the impregnation process, and the Line 141 was revised in the revised manuscript.

 

• Ni dispersed well??? Uniform distribution of Ni???... There is no experimental proof provided in the article.

Reply: Thanks for your good suggestions. All you mentioned, such as Ni dispersed well and Uniform distribution of Ni, were displayed in the revised Figure 3 in revised manuscript with bule color.

 

• Large particles reduces at low temperature and small particles reduces at high temperature… if this claim is true then the glycine method also did not deliver uniform particle size. One can see from Fig 4 that the glycine synthesis method also producing the large particle size?

Reply: Thank you and we accept your suggestion. Indeed, the glycine method did not deliver uniform particle size, but compared with Ni/SiO₂, the smaller Ni particle was obtained over the Ni/SiO₂ by addition glycine, and relatively more uniform the particle sizes distribution of Ni was obtained by addition glycine shown in Figure 3.

 

• Authors should be more careful when interpreting the data. Fig6 where author referred cubic NiO peaks in the text but there are no NiO peaks in the Fig6

Reply: Thanks for your careful review of our manuscript. The error you mentioned have been corrected and highlighted with blue color in the revised manuscript.

 

• For the coke deposition calculations I would prefer CHNS elemental analysis data. Which more accurate.

Reply: Thanks for your good suggestions. Indeed, CHNS elemental analysis and TG can also calculate the carbon content on the catalyst, but we are more concerned about the relative amount of carbon on the used catalyst, and more coke deposition over the used catalysts leading to deactivation.

 

• Crystallite size of NiO was calculated by Scherrer equation… but authors did not mentioned it in the manuscript.

Reply: Thanks for your good suggestions. The Scherrer formula were given in the revised manuscript.

 

5. The unsupported claims such as high dispersion of Ni and narrower Ni distribution should be modified from the conclusions.

Reply: Thanks for your good suggestions. The unsupported claims such as high dispersion of Ni in conclusion were revised in the revised manuscript.

 

6. Ni dispersion studies should be included in the manuscript. If possible Ni distribution by elemental analysis should also provide.

Reply: Thank you for your suggestion. The Ni dispersion was displayed by TEM results, and it was also discussed in the revised manuscript.

 

 

Round 2

Reviewer 1 Report

The authors have answered the asked comments, the revised manuscript can be accepted for publication

Reviewer 2 Report

In the revised manuscript the authors modified the unnecessary statements and this current form is more suitable for publication. However, I would suggest authors, insert the BET isotherms.