Perovskite-Derivative Ni-Based Catalysts for Hydrogen Production via Steam Reforming of Long-Chain Hydrocarbon Fuel
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsComments are part of the attached file.
Comments for author File: 
Comments.pdf
Requires noticeable editing.
Author Response
Responses to referees’ comments and descriptions for revisions
Dear Editor of Stefania,
Thank you and the referees very much for your patience and precious time to read and evaluate our manuscript, “Perovskite Derivatives Ni-Based Catalysts for Hydrogen Production via Steam Reforming of Long-Chain Hydrocarbon Fuel (Catalysts-2904497)”. The referees’ valuable comments are very helpful for improving our manuscript, and also very useful for our further research work. According to the referees’ comments, we have revised the manuscript. Our responses to the referees’ comments and the descriptions for the revision are listed below. The changes are highlighted by red color in the revised manuscript.
Reviewer #1:
Comments:
The manuscript “Perovskite Derivatives Ni-Based Catalysts for Hydrogen Production via Steam Reforming of Long-Chain Hydrocarbon Fuel” by Guo et al. provides an experimental understanding of using rare earth metal-doped lanthanum nickelates as catalysts for steam cracking of higher-chained hydrocarbons with the focus on activity, stability, and low/no coke forming properties. The presented study has thorough evaluations of catalyst characterization and performance analysis and offers novel insights on the mechanistic behavior to drive hydrogen production. The relative effects of rare-earth metals on the observed differences in conversion and hydrogen production needs further validation (or at least acknowledgement for future works) using post-run TEM characterizations (to understand the surface support interactions, potential surface segregation, and surface-bulk interactions). Additional comments are listed below:
Comment 1: Please include supplemental information containing additional XPS spectra with calibration approaches, results of any additional TEM testing, and experimental setup for testing the catalysts for H2 production.
Response: We thank the referee for his/her good suggestion. The experimental setup for hydrogen production has been added in the supporting information as shown in Figure R1 (Supporting information, Figure S1), additional TEM results (Supporting information, Figure S2), XPS spectra of Ce-3d and Pr-3d (Supporting information, Figure S3), and SEM images of spent catalysts of LaNiO3 and LaCePrNiO3 (Supporting information, Figure S4, Figure R3) were added in the supporting information.
Figure R1. The schematic diagram of experimental apparatus.
Comment 2: Page 2 of 15
“Tammann” temperature of Ni metal is 591 °C. Please validate and correct the manuscript accordingly.
Response: Thank you very much for your suggestions, we have revised this part in our revised manuscript (page 4, line 21).
Comment 3: Page 3 of 15 Please rephrase section 2.2 (Preparation of catalysts) to state how the catalysts were synthesized rather than how to synthesize the catalysts.
Response: We thank the referee for his/her rigorous suggestion. The statement of how the catalysts were synthesized were revised (2.2 Preparation of catalysts).
Comment 4: Page 7 of 15 a. Figure 4 carries a shoulder between 300 and 350 °C which for the rare-earth metal-doped catalysts (except LaCeTbNiO3). Please elaborate on the same in the discussion section. b. Kindly check the statement “Explain that the proportion of nickel metal in the three catalysts is similar, excluding the influence of different nickel metal contents on catalytic performance.” In the manuscript – editing error?
Response: We thank the referee for his/her rigorous suggestion. The shoulder reduction peak between 300 and 350 oC were explained in our revised manuscript (page 13, line 10; and page 14, first two lines). “The shoulder peak between 300 and 350 °C which belong to the reduction of surface oxygen as confirmed by previous work. The peak intensity increases with rare-earth elements doping, suggesting increase surface oxygen vacancy.”
In fact, the active center of the catalyst is mainly nickel metal, its content will have a certain impact on catalytic performance. The ratio of Ni0/(Ni0 + Ni2+) was also calculated, and the Ni0 ratios for LaNiO3, LaCeNiO3, and LaCePrNiO3 were about 54.1%, 55.6%, and 56.8%, respectively. This result suggests that the proportion of nickel metal in the three catalysts is similar, excluding the influence of different nickel metal contents on catalytic performance.
Comment 5: Page 9 of 15 and Page 10 of 15 In figure 6 and 8, please include the legend for the green tracer (C12 conversion).
Response: We thank the referee for his/her rigorous suggestion. The legend for green tracer (C12 conversion) has been revised.
Comment 6: Page 11 of 15 a) The statement “Secondly, the addition of rare-earth elements results in abundant oxygen defects on the surface of the catalyst, which helps to eliminate carbon deposition and suppress them.” needs further validation. It is unclear how the surface defects (creating the oxygen vacancies) sustain with time. b) Please spell check the Y-axis in Figure 9.
Response: We thank the referee for his/her rigorous suggestion. The statement has been revised. The Y-axis in Figure 9 is correct.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments and Suggestions for AuthorsIn this ms, the authors synthesized LaNiO3 perovskites doped with Ce and various rare earth elements and tested their performance in steam reforming of dodecane. The introduction of rare earth dopants improved Ni dispersion, increased conversion and H2 yield, and decreased carbon deposition.
I have a few suggestions to improve the manuscript:
- It was interesting that CeO2 peak appeared after reduction (Figure 1b) only for the LaCeNiO3 catalyst, but not for the other catalysts. The authors should explain why.
- Figures 6, 7 and 8 are too small and should be enlarged, or have the font size increased.
- For figures 6 and 8, it is helpful to plot each sub-plot using the same y-axis scale so it is easier to compare the values.
- The nature of carbon deposition on the spent catalysts should be clarified using TEM and/or SEM images.
Comments on the Quality of English LanguageThe writing is generally adequate.
Author Response
Responses to referees’ comments and descriptions for revisions
Dear Editor of Stefania,
Thank you and the referees very much for your patience and precious time to read and evaluate our manuscript, “Perovskite Derivatives Ni-Based Catalysts for Hydrogen Production via Steam Reforming of Long-Chain Hydrocarbon Fuel (Catalysts-2904497)”. The referees’ valuable comments are very helpful for improving our manuscript, and also very useful for our further research work. According to the referees’ comments, we have revised the manuscript. Our responses to the referees’ comments and the descriptions for the revision are listed below. The changes are highlighted by red color in the revised manuscript.
Reviewer #2:
Comments: In this manuscript, the authors synthesized LaNiO3 perovskites doped with Ce and various rare earth elements and tested their performance in steam reforming of dodecane. The introduction of rare earth dopants improved Ni dispersion, increased conversion and H2 yield, and decreased carbon deposition. I have a few suggestions to improve the manuscript:
Comment 1: It was interesting that CeO2 peak appeared after reduction (Figure 1b) only for the LaCeNiO3 catalyst, but not for the other catalysts. The authors should explain why.
Response: We thank the referee for his/her good suggestion. The CeO2 peak appeared after reduction (Figure 1b) only for the LaCeNiO3 catalyst may be attributed to the content of Ce in LaCeNiO3 is higher than that of other catalysts (page 10, line 21-23) as shown in experiment section (page 7, line 20-22).
Comment 2: Figures 6, 7 and 8 are too small and should be enlarged, or have the font size increased.
Response: We thank the referee for his/her rigorous suggestion. The Figure 6, 7, and 8 have been revised.
Comment 3: For figures 6 and 8, it is helpful to plot each sub-plot using the same y-axis scale so it is easier to compare the values.
Response: We thank the referee for his/her good suggestion. The Figure 6, and 8 have been revised. In order to easier to compare the values, the same y-axis scale was used in the Figure 6f (Figure R2).
Figure R2. Comparison the conversion of n-dodecane. Reaction condition: 600 oC, 0.1 MPa, LHSV of C12H26 15 ml/gcat∙h, with mole ratio of H2O:C12H26 at 24.
Comment 4: The nature of carbon deposition on the spent catalysts should be clarified using TEM and/or SEM images.
Response: We thank the referee for his/her good suggestion. The nature of carbon deposition on the spent catalysts were characterized by SEM as shown in Figure S4 (Figure R3). The corresponding discussion are added in revised manuscript (page 23, line 17-20).
Figure R3. SEM images of spent catalysts for a) LaNiO3, and b) LaCePrNiO3.
Author Response File: Author Response.docx
Reviewer 3 Report
Comments and Suggestions for AuthorsThe article “Perovskite Derivatives Ni-Based Catalysts for Hydrogen Pro-duction via Steam Reforming of Long-Chain Hydrocarbon Fuel” by Kai Guo et all. is an important research concerning the H2 production through steam reforming of n-dodecane with the use of LaNiO3 catalyst modified by reare earth elements (Ce, Pr, Sm and Tb). Catalytic tests showed that LaCePrNiO3 composition was the best for this purpose.
All the investigations are carried out on a high experimental level and clearly described. As was found, introduction of lattice modifiers significantly improved LaNiO3 catalytic activity due to changes in physicochemical properties of the samples obtained. Unfortunately, there is no clear explanation why Pr is preferable for co-doping.
There are several comments:
- Page 4. Equation 6. This formula gives conversion of n-dodecane only in C1 products, as should be mentioned in the text. The total conversion can’t be calculated, probably, due to difficulties in analyzing all the products. Equation 7. The yield unit is percent (%). Mmol/min is a unit of the rate of product formation or the process capacity.
- Page 5. Fig. 1 and its description. Have authors any assumption why amorphous component appeared in X-ray patterns of reduced powders in the range of 2Ï´ = ~20-38o where the most intensive CeO2 peaks exist? Is there any effect of catalyst components amorphization on catalytic properties?
- Page 6. Description for Fig. 4. Catalytic activity of LaCePrNiO3 is remarkably better then that of LaNiO3. However, intensity of the high-temperature H2-TPR peak of the LaNiO3 is significantly larger, and Tmax (500 and 513 oC) are very close. Is one entities to make conclusions about Ni state on the surface and effect of such a state on catalytic activity on a base of this data?
- Page 9. Again: If authors give parameter in units of mmol/min, it means that they give the rate of formation.
Minor editing of English language required
Author Response
Responses to referees’ comments and descriptions for revisions
Dear Editor of Stefania,
Thank you and the referees very much for your patience and precious time to read and evaluate our manuscript, “Perovskite Derivatives Ni-Based Catalysts for Hydrogen Production via Steam Reforming of Long-Chain Hydrocarbon Fuel (Catalysts-2904497)”. The referees’ valuable comments are very helpful for improving our manuscript, and also very useful for our further research work. According to the referees’ comments, we have revised the manuscript. Our responses to the referees’ comments and the descriptions for the revision are listed below. The changes are highlighted by red color in the revised manuscript.
Reviewer #3:
The article “Perovskite Derivatives Ni-Based Catalysts for Hydrogen Pro-duction via Steam Reforming of Long-Chain Hydrocarbon Fuel” by Kai Guo et all. is an important research concerning the H2 production through steam reforming of n-dodecane with the use of LaNiO3 catalyst modified by rare earth elements (Ce, Pr, Sm and Tb). Catalytic tests showed that LaCePrNiO3 composition was the best for this purpose.
All the investigations are carried out on a high experimental level and clearly described. As was found, introduction of lattice modifiers significantly improved LaNiO3 catalytic activity due to changes in physicochemical properties of the samples obtained. Unfortunately, there is no clear explanation why Pr is preferable for co-doping.
There are several comments:
Comment 1: Page 4. Equation 6. This formula gives conversion of n-dodecane only in C1 products, as should be mentioned in the text. The total conversion can’t be calculated, probably, due to difficulties in analyzing all the products. Equation 7. The yield unit is percent (%). Mmol/min is a unit of the rate of product formation or the process capacity.
Response: We thank the referee for his/her good suggestion. Page 4. Equation 6. This formula gives conversion of n-dodecane only in C1 products, as should be mentioned in the text. The total conversion can’t be calculated, probably, due to difficulties in analyzing all the products, especially the liquid phase products after the reaction. The Equation 7 has been revised (page 9, line 20).
Comment 2: Page 5. Fig. 1 and its description. Have authors any assumption why amorphous component appeared in X-ray patterns of reduced powders in the range of 2θ = 20~38o where the most intensive CeO2 peaks exist? Is there any effect of catalyst components amorphization on catalytic properties?
Response: We thank the referee for his/her rigorous suggestion. The CeO2 peak appeared after reduction (Figure 1b) only for the LaCeNiO3 catalyst may be attributed to the content of Ce in LaCeNiO3 is higher than that of other catalysts (page 10, line 21-23) as shown in experiment section (page 7, line 20-22).
Comment 3: Page 6. Description for Fig. 4. Catalytic activity of LaCePrNiO3 is remarkably better than that of LaNiO3. However, intensity of the high-temperature H2-TPR peak of the LaNiO3 is significantly larger, and Tmax (500 and 513 oC) are very close. Is one entities to make conclusions about Ni state on the surface and effect of such a state on catalytic activity on a base of this data?
Response: We thank the referee for his/her good suggestion. In fact, it was found that after doping with rare-earth elements, the reduction temperature of the catalysts shifted towards the high-temperature region, indicating an enhanced interaction strength between NiO and the support. The two main reduction peaks of LaNiO3 are at 350 °C and 500 °C. After doping with rare-earth elements, these two reduction peaks both shift towards the high-temperature region. The two main reduction peaks of LaCePrNiO3 are concentrated at temperatures of 425 °C and 513 °C, and the two reduction peaks for LaNiO3 were located at 340 °C and 500 °C. In addition, the particles size of Ni for LaCePrNiO3 are 20 nm, which is small than that of LaNiO3 (25 nm). Therefore, LaCePrNiO3 exhibit good catalytic performance.
Comment 4: Page 9. Again: If authors give parameter in units of mmol/min, it means that they give the rate of formation.
Response: We thank the referee for his/her good suggestion. The parameter in units of mmol/min is the formation rate of product. The Equation 7 has been revised (page 9, line 20).
Author Response File: Author Response.docx
