Effect of Different Zinc Species on Mn-Ce/CuX Catalyst for Low-Temperature NH3-SCR Reaction: Comparison of ZnCl2, Zn(NO3)2, ZnSO4 and ZnCO3
Round 1
Reviewer 1 Report
Authors should do the suggested modifications.
Comments for author File: 
Comments.pdf
English is fine, few grammatical corrections are needed.
Author Response
The work highlights the role of different zinc species over the structural and applicability of Mn-Ce co-doped CuX catalyst in low-temperature (75 - 300 °C) settings. The characterization data is adequately presented.
Answer: Thanks for your comment.
Comment 1: Abstract should be rewritten, highlighting the statistical data (such as conversion rate of different zinc species and temperature points).
Answer: Thanks for your comment. Abstract is modified in the revised manuscript.
Comment 2: Authors should include a comparative discussion with the literature available.
Answer: Thanks for your suggestion. The literature of Zn poisoning on catalysts were listed in Introduce section, and the comparative discussion was added in Introduce section in the revised manuscript.
Comment 3: Even though characterization data is adequately presented and discussed, interpretation between the characterization data and their effect over performance was not focused on.
Answer: Thanks for your good comment. More detailed comparative explanations and discussions have been added in the Discussion section in the revised manuscript.
Comment 4: Authors should elaborate more “Line 48 - 52”. ZnCl2 has more negative effects, which is the opposite in the present case. Should provide proper discussion regarding the possible structural implications.
Answer: Thanks for your good advice. For Mn-Ce/AC catalysts [1], the ZnCl2 could change the surface micrograph of the catalyst, and be attached the surface and blocked the holes on AC support, leading to the adsorption of NH3 and NO. As for X zeolite supported catalysts, even though the particles of the Zn -poisoned catalysts agglomerated, the main factor is that the Zn salts could lead to the aggregation of Cu species on catalysts, thereby reducing the Cu active sites and effecting the SCR activity.
References:
[1] Z. Su, S. Ren, J. Yang, L. Yao, Y. Zhou, Z. Chen, T. Zhang, Poisoning Effect Comparison of ZnCl2 and ZnSO4 on Mn‐Ce/AC Catalyst for Low‐Temperature SCR of NO, ChemistrySelect, 5 (2020) 9226-9234. doi.org/10.1002/slct.202002233
Comment 5: Authors should also state the co-doping with two metal ions (Mn-Ce), what is the basis, and as they did not provide necessary information regarding doping with single species (Mn and Ce, separately) and its effects.
Answer: Thanks for your good comment. based on our previous research [1], CuX zeolite supported Mn and/or Ce oxides catalysts were synthesized, the results showed that Mn-Ce/CuX catalyst had more isolated Cu2+ species and chemisorbed oxygen species, and Mn-Ce/CuX catalyst produced more types of nitrite and nitrate species than Mn/CuX and Ce/CuX catalysts. So, in this study, we investigated the effect of different Zn species on Mn-Ce/CuX catalyst for the feasibility of application.
Comment 6: Authors should also provide a schematic representation of possible mechanism involved (https://doi.org/10.1021/acsomega.1c01123).
Answer: Thanks for your suggestion. The mechanism scheme was added in the revised manuscript, as shown in Fig.11.
Minor Comments
Comment 7: Check the representation of “°C” throughout the manuscript (e.g., Line 275).
Answer: Thanks for your careful checking. The corrected “oC” is modified in the revised manuscript.
Comment 8: Check the representation of “ml” and “mL” (e.g., Line 302, 305, 307).
Answer: Thanks for your careful checking.
Comment 9: Line 42: “100%”
Answer: Thanks for your checking. The modification was added in the revised manuscript.
Comment 10: Figure 1c and 1d: Numericals within the figures are not clearly visible.
Answer: Thanks for your careful checking. The figures were modified in the revised manuscript.
Comment 11: Line 271: ZnCO3, respectively.
Answer: Thanks for your careful checking. The sentence was modified in the revised manuscript.
Comment 12: Line 281: Cite reference articles for the methodology and formulae.
Answer: Thanks for your advice. The related references were added in the revised manuscript.
Comment 13: The study conducted was objectively designed to extrapolate the effects of different zinc species over the MCCX catalyst. The conclusions provided were justified based on the characterization and experimental data. However, authors are requested to do minor corrections. Authors should do comparative discussion with the existing literature.
Answer: Thanks for your comment. Some comparative discussion was added in Discussion section in the revised manuscript.
Reviewer 2 Report
In this paper, the authors report the influence of Zn species on Mn-Ce/CuX zeolites for low-temperature SCR process. Although the topic seems interesting, because there are not many studies on poisoning, and the authors have used many techniques, the manuscript should be improved in order to be published in the journal.
- The figures contain several figures together and it is sometimes difficult to see the signals represented. It would be advisable for the figures to be larger and for some of them, which contain complementary information, to be sent to supplementary material.
- Are the species formed with each salt reversible and regenerable?
- The lines 208-211 are not clear. Could the authors detail the explanation?
- A more detailed explanation of the differences between each catalyst modified with a different source of Zn should be provided to improve the quality of the manuscript, particularly in the sections associated with the reaction mechanism.
- A reorganization of the figures by sections, with a larger size and highlighting in more detail the justification of the modifications made by each catalyst, would improve the quality of the manuscript and make it easier to read.
- Sometimes the vocabulary used is not technical. English and typographical errors should be checked throughout the manuscript.
Sometimes the vocabulary used is not technical. English and typographical errors should be checked throughout the manuscript.
Author Response
Reviewer 2:
In this paper, the authors report the influence of Zn species on Mn-Ce/CuX zeolites for low-temperature SCR process. Although the topic seems interesting, because there are not many studies on poisoning, and the authors have used many techniques, the manuscript should be improved in order to be published in the journal.
Answer: Thanks for your comment.
Comment 1：The figures contain several figures together and it is sometimes difficult to see the signals represented. It would be advisable for the figures to be larger and for some of them, which contain complementary information, to be sent to supplementary material.
Answer: Thanks for your good suggestion. The size of figures was changed in the revised manuscript.
Comment 2：Are the species formed with each salt reversible and regenerable?
Answer: Thanks for your comment. The different zinc species on the catalysts were prepared by impregnation method using ZnCl2, Zn(NO3)2, ZnSO4 and ZnCO3, each of them was stable on catalyst from SEM and XPS results.
Comment 3：The lines 208-211 are not clear. Could the authors detail the explanation?
Answer: Thanks for your comments. We are sorry for the vague description before, and we have modified it in the article as follows: ZnCl2 species on MCCX catalysts had a slightly influence on Cu2+ active site, while the bands intensity of nitrate species on Cu2+ active site for MCCX-Zn-S was weaker than that of three catalysts.
Comment 4：A more detailed explanation of the differences between each catalyst modified with a different source of Zn should be provided to improve the quality of the manuscript, particularly in the sections associated with the reaction mechanism.
Answer: Thanks for your good suggestion. The detailed discussion about the effect of different zinc species on Mn-Ce/CuX catalysts was added in the Discussion section in the revised manuscripts.
Comment 5：A reorganization of the figures by sections, with a larger size and highlighting in more detail the justification of the modifications made by each catalyst, would improve the quality of the manuscript and make it easier to read.
Answer: Thanks for your good advice. The display of the figures changed in the revised manuscript. Also, the size of graph changed.
Comment 6：Sometimes the vocabulary used is not technical. English and typographical errors should be checked throughout the manuscript.
Answer: Thanks for your careful checking. The related modification is shown in red color in the revised manuscript.
