On the Application of an In Situ Catalyst Characterization System (ICCS) and a Mass Spectrometer Detector as Powerful Techniques for the Characterization of Catalysts
Round 1
Reviewer 1 Report
The manuscript presents a study related to In situ characterization of catalysts such as the PID-Micromeritics ICCS system and a mass spectrometer detector as powerful techniques for catalyst characterization.
I consider that for the manuscript to be accepted the authors must address the following comments.
1.- The introduction must be improved. Authors should extend their state-of-the-art research by including the best bibliographic review.
2.- The quality of the figures presented in the manuscript must be improved
3.- The description of the figure should be improved in the manuscript.
4.- Figure 4 shows labels on the graph “650 °C” and “725°C”. It is not clear where these values were obtained. Could the authors present the behavior of this graph time vs temperature?
5.- Figure 5 shows a situation similar to figure 4. The authors should clarify how the temperature values shown in the graph were obtained.
6.- In figures 8 and 9. The authors show the reaction temperatures. However, you could improve the description and mention how these temperature values were obtained.
Author Response
We, the authors of this manuscript, would like to thank you for the time you have taken to review and make suggestions about our manuscript. We understand and appreciate your valuable suggestions, which we will take very seriously and respond with the best we know how to satisfy all your concerns about our manuscript. Thank you so much.
I consider that for the manuscript to be accepted the authors must address the following comments.
Q1: The introduction must be improved. Authors should extend their state-of-the-art research by including the best bibliographic review.
Reply: We have revised and improved the Introduction Section from this comment.
Q2: The quality of the figures presented in the manuscript must be improved
Reply: All figures were edited and were improved. We added the figures as they were reported originally by the software in order to safeguard the original data of the experiments.
Q3: The description of the figure should be improved in the manuscript.
Reply: All descriptions were improved according to your suggestions.
Q4: Figure 4 shows labels on the graph “650 °C” and “725°C”. It is not clear where these values were obtained. Could the authors present the behavior of this graph time vs temperature?
Reply: All TPR figures show now consumption of H2 versus ramping temperature. Now is clear where these temperatures came from.
Q5: Figure 5 shows a situation similar to figure 4. The authors should clarify how the temperature values shown in the graph were obtained.
Reply: Please, see reply from question 4.
Q6: In figures 8 and 9. The authors show the reaction temperatures. However, you could improve the description and mention how these temperature values were obtained.
Reply: These two last figures show the ramping temperature now. They were not added at the beginning because we did not want to overload the figures.
Author Response File: 
Author Response.docx
Reviewer 2 Report
This paper reports the construction of an in-situ catalyst characterization system and its application in a case study. It is interesting and can be published after addressing the following issues.
1. Are there any other reports on the similar system? More literatures should be cited in the introduction section.
2. The references [3-24] should be marked seperately rather than like the current style.
3. The photos in Figure 1 & 2 are blurred, and should be replaced by photos with better quality.
4. The equation 7 is not properly displayed. As a equation, it should include the "=" symbol. Also, the several terms in denominator should be seperated by the operational character.
Author Response
We, the authors of this manuscript, would like to thank you for the time you have taken to review and make suggestions about our manuscript. We understand and appreciate your valuable suggestions, which we will take very seriously and respond with the best we know how to satisfy all your concerns about our manuscript. Thank you so much.
This paper reports the construction of an in-situ catalyst characterization system and its application in a case study. It is interesting and can be published after addressing the following issues.
Q1: Are there any other reports on the similar system? More literatures should be cited in the introduction section.
Reply: We have revised and improved the Introduction Section from this comment.
Q2: The references [3-24] should be marked seperately rather than like the current style.
Reply: References were edited as modified as per your suggestions.
Q3: The photos in Figure 1 & 2 are blurred, and should be replaced by photos with better quality.
Reply: Photos included in Figures 1 and 2 were improved.
Q4: The equation 7 is not properly displayed. As a equation, it should include the "=" symbol. Also, the several terms in denominator should be separated by the operational character.
Reply: Equation 7 has been revised taking in consideration this comment.
Author Response File: Author Response.docx
Reviewer 3 Report
This ms describes the use of an instrument for the temperature programmed characterization of heterogeneous catalysts. The advantage of this instrument over other comparable instruments is the ability to characterize the spent catalyst without intermediate exposure to air. The case study involving two different Ni/Al2O3 catalysts for CO2 methanation was used as an illustrative example. On the whole, the ms reads more like a technical/application note rather than a scientific article. While potentially still of interest to prospective users of the instrument, the editors should carefully consider if such is within the scope of the journal.
I have the following suggestions for the authors to improve clarity:
- The abbreviations (TPX, TPR, TPO) should be defined in the abstract.
- The authors mention that "Performing these analyses in-situ virtually eliminates the possibility of contamination from atmospheric gases or moisture which may damage the active catalyst and undermine the relevance of post-reaction characterization data." Often, it is spectroscopic characterization of the chemical state of the catalyst, rather than destructive bulk techniques such as TPO, that is most sensitive to such contamination. The authors should elaborate on this point.
- Figures 1-3 appear blurry and should be provided in higher resolution.
- The sources of the catalyst supports used should be stated for reproducibility purposes.
- The H2-TPR reduction temperature is very often taken as an indicator of the NiO particle size and speciation. Well-dispersed NiO and spinel NiAl2O4 requires a higher reduction temperature than bulk NiO. The authors should mention this with appropriate references (there are many in the literature).
- The relative activity cannot be evaluated without knowing the CO2 conversion (if close to equilibrium, then the activity may not be proportional to the MS signal). Preferably, the authors should calibrate the MS and report turnover frequencies.
- The lower dispersion after regeneration (section 4.2) may be caused by the highly exothermic combustion process rather than the reaction itself. It may be more meaningful to perform the regeneration under H2 or CO2.
Author Response
We, the authors of this manuscript, would like to thank you for the time you have taken to review and make suggestions about our manuscript. We understand and appreciate your valuable suggestions, which we will take very seriously and respond with the best we know how to satisfy all your concerns about our manuscript. Thank you so much.
This ms describes the use of an instrument for the temperature programmed characterization of heterogeneous catalysts. The advantage of this instrument over other comparable instruments is the ability to characterize the spent catalyst without intermediate exposure to air. The case study involving two different Ni/Al2O3 catalysts for CO2 methanation was used as an illustrative example. On the whole, the ms reads more like a technical/application note rather than a scientific article. While potentially still of interest to prospective users of the instrument, the editors should carefully consider if such is within the scope of the journal.
I have the following suggestions for the authors to improve clarity:
Q1: The abbreviations (TPX, TPR, TPO) should be defined in the abstract.
Reply: All techniques were defined in the abstract according to the reviewer suggestions.
Q2: The authors mention that "Performing these analyses in-situ virtually eliminates the possibility of contamination from atmospheric gases or moisture which may damage the active catalyst and undermine the relevance of post-reaction characterization data." Often, it is spectroscopic characterization of the chemical state of the catalyst, rather than destructive bulk techniques such as TPO, that is most sensitive to such contamination. The authors should elaborate on this point.
Reply: The paragraph has been rewritten taking in account this comment.
Q3: Figures 1-3 appear blurry and should be provided in higher resolution.
Reply: Photos included in Figures 1-3 were improved.
Q4: The sources of the catalyst supports used should be stated for reproducibility purposes.
Reply: This information, Grace Davison company, has been included in the Experimental Section.
Q5: The H2-TPR reduction temperature is very often taken as an indicator of the NiO particle size and speciation. Well-dispersed NiO and spinel NiAl2O4 requires a higher reduction temperature than bulk NiO. The authors should mention this with appropriate references (there are many in the literature).
Reply: Comments on this aspect were added in the revised version of the manuscript to describe the complete reduction of NiO and that no spinels were formed. See Section 3.1.1.
Q6: The relative activity cannot be evaluated without knowing the CO2 conversion (if close to equilibrium, then the activity may not be proportional to the MS signal). Preferably, the authors should calibrate the MS and report turnover frequencies.
Reply: We agree with the reviewer's comment and will take it into account in our next work. For this time, we only used relative pressure for each one of the products. We understand that our report is just a qualitative indication of the CO2 consumption as CH4 was produced.
Q7: The lower dispersion after regeneration (section 4.2) may be caused by the highly exothermic combustion process rather than the reaction itself. It may be more meaningful to perform the regeneration under H2 or CO2.
Reply: Thank you for your comment. This is a question that can be investigated in a future work. As the reviewer points out, the oxidation of nickel metal is highly exothermic and can cause loss of dispersion of the metal by sintering. It is also possible that the regeneration conditions used do not allow removing all the carbon deposited on the surface and, therefore, it is not possible to evaluate all the Ni present on the surface.
Author Response File: Author Response.docx
Reviewer 4 Report
The manuscript by Yunes et al. clearly presents a new multi-technique tool for in-situ characterizing catalysts. The topic is for sure of great interest for the scientific community, so that the same analysis can be applied in different laboratories and on different catalytic processes.
However, some important points should be addressed before the manuscript can be suitable for publication on PHYSCHEM, reinforcing the scientific rigor.
Figure 1 and 2 are not so clear: the resolution of the photos should be increased and some labels should be described better (maybe in the caption), such as “9 mm SS reactor” and “Cirrus II”.
Concerning the chemical composition of the two catalysts, it would be useful to measure the Ni content by ICP, to be compared with TPR analysis.
In the first paragraph of the introduction, I would suggest to add some references, both about valuable examples of in-situ characterization of catalysts during their whole lifetime (10.1021/acscatal.1c03067, 10.1002/cphc.201800592, 10.1021/acscatal.1c01735, 10.1016/j.cattod.2004.12.017, 10.1002/adma.201101803, 10.1016/j.cattod.2005.11.076) and about the investigation of the catalysts deactivation (10.1016/j.apcata.2018.01.026, 10.1021/acscatal.7b03020, 10.1002/cctc.201402356, 10.1016/j.jcat.2015.04.006).
The discussion of N2 adsorption-desorption in Figure 3 is not sufficient. For instance, with respect to IUPAC indications (10.1515/pac-2014-1117) I would comment: in alumina trilobate the steep uptake at very low p/p0 is reasonably assigned to the presence of micropores, the two hysteresis loops are different, H1 in alumina trilobate (i.e., a narrow range of uniform mesopores) and H3 in alumina tablet (i.e., pores within the aggregation of plate-like particles).
If possible, I would suggest to indicate the temperature and not the time in the X-axis of TPR graphs in Figures 4 and 5. Figures 4 and 5 should be discussed with respect to the literature to assess if the chemical behavior is in line with what already reported, I would suggest 10.1016/S0926-860X(97)00298-6 and 10.1016/S0926-860X(02)00634-8.
The calculations to estimate dispersion (D%) from Figures 6 and 7 should be explicitly reported, so that readers can use this paper as a tutorial for future analysis on other catalytic systems.
Are Figures 8 and 9 comparable as experimental procedure? The temperature evolution in Figure 9 is not clear.
Author Response
We, the authors of this manuscript, would like to thank you for the time you have taken to review and make suggestions about our manuscript. We understand and appreciate your valuable suggestions, which we will take very seriously and respond with the best we know how to satisfy all your concerns about our manuscript. Thank you so much.
The manuscript by Yunes et al. clearly presents a new multi-technique tool for in-situ characterizing catalysts. The topic is for sure of great interest for the scientific community, so that the same analysis can be applied in different laboratories and on different catalytic processes.
However, some important points should be addressed before the manuscript can be suitable for publication on PHYSCHEM, reinforcing the scientific rigor.
Q1: Figure 1 and 2 are not so clear: the resolution of the photos should be increased and some labels should be described better (maybe in the caption), such as “9 mm SS reactor” and “Cirrus II”.
Replay: The quality of the photos included in Figures 1 and 2 has been increased. A detailed description of the photos has also been included in the figures caption. Please, see the revised version of the manuscript.
Q2: Concerning the chemical composition of the two catalysts, it would be useful to measure the Ni content by ICP, to be compared with TPR analysis.
Reply: Yes, we do agree with your comments. However due to the lack of analytical instruments in our laboratory of Micromeritics, we just relied on TPR. In the current study was not critical to have the exact loading of Ni, but rather to have a similar amount of Ni on these two catalysts and that was enough given by TPR as a bulk analysis.
Q3: In the first paragraph of the introduction, I would suggest to add some references, both about valuable examples of in-situ characterization of catalysts during their whole lifetime (10.1021/acscatal.1c03067, 10.1002/cphc.201800592, 10.1021/acscatal.1c01735, 10.1016/j.cattod.2004.12.017, 10.1002/adma.201101803, 10.1016/j.cattod.2005.11.076) and about the investigation of the catalysts deactivation (10.1016/j.apcata.2018.01.026, 10.1021/acscatal.7b03020, 10.1002/cctc.201402356, 10.1016/j.jcat.2015.04.006).
Reply: The Introduction Section has been revised and improved considering the references suggested.
Q4: The discussion of N2 adsorption-desorption in Figure 3 is not sufficient. For instance, with respect to IUPAC indications (10.1515/pac-2014-1117) I would comment: in alumina trilobate the steep uptake at very low p/p0 is reasonably assigned to the presence of micropores, the two hysteresis loops are different, H1 in alumina trilobate (i.e., a narrow range of uniform mesopores) and H3 in alumina tablet (i.e., pores within the aggregation of plate-like particles).
Reply: Section 3.1 and the N2 adsorption results have been revised taking this comment into account. We would like to point out that adsorption at low relative pressures can be due to both the presence of micropores and the adsorption process itself. For the amount of micropores to be relevant, it must be compared with the total amount of N2 adsorbed. As these are two materials with pore sizes mainly in the range of 2 to 50 nm, mesopores, in the event that there are micropores this amount would not be relevant.
Additionally, we would like to point out that the t-plot analysis, microporosity analysis, gave micropore volumes of the order of 0.01 cm3/g. These values are much lower than those obtained for the total pore volumes (0.26 and 0.67 cm3/g, respectively). Which is indicative that the microporous character is practically negligible.
Q5: If possible, I would suggest to indicate the temperature and not the time in the X-axis of TPR graphs in Figures 4 and 5. Figures 4 and 5 should be discussed with respect to the literature to assess if the chemical behavior is in line with what already reported, I would suggest 10.1016/S0926-860X(97)00298-6 and 10.1016/S0926-860X(02)00634-8.
Reply: Figures have been revised.
Q6: The calculations to estimate dispersion (D%) from Figures 6 and 7 should be explicitly reported, so that readers can use this paper as a tutorial for future analysis on other catalytic systems.
Reply: This information has been included in the revised version of the manuscript.
Q7: Are Figures 8 and 9 comparable as experimental procedure? The temperature evolution in Figure 9 is not clear.
Reply: Yes, the experimental procedure is comparable. Now, the temperature evolution in Figure 9 has been included.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have carried out the corrections requested by the reviewers. Therefore, I consider that the article can be published in present form.
Author Response
The authors of this work would like to thank you for the time you have spent reviewing our work, as well as for the comments that have helped us improve its quality.
Reviewer 3 Report
The authors have revised the ms according to the reviewers' comments, it is now ready for publication.
Author Response
The authors of this work would like to thank you for the time you have spent reviewing our work, as well as for the comments that have helped us improve its quality.
Reviewer 4 Report
The revised version of the manuscript is almost ready for publication on Physchem.
I would just recommend to further modify Figures 8 and 9 removing the line of the temperature but implementing the information of temperature and time in the X axes (in the same scale between the two figures), and to add some references in the introduction (it is not reasonable that only 2 cases are representative for in situ characterization of heterogeneous catalysts).
After these last improvements, the manuscript will be acceptable for publication, even without further revision from my side.
Author Response
Figures 8 and 9 have been revised taking into account your comments.
More bibliographical references have been added in the Introduction Section related to the in-situ characterization of heterogeneous catalysts.
Finally, we want to thank you for the time you have used to review our work, as well as your comments that have allowed us to improve its quality.
