An Assessment of Zeolite Framework Effect for Low-Temperature NOX Adsorbers
, Sara Morandi 2,*, Pierfrancesco Ticali 2, Roberto Matarrese 1 and Luca Lietti 1
Round 1
Reviewer 1 Report
The authors studied the effect of the zeolite framework on low-temperature NOx adsorbers. Some revisions might be needed for the manuscript to be continued for publication.
Comments:
1. Some abbreviations were not mentioned prior to their usage, making it difficult for readers to understand the abbreviations. Please add more clarity for the abbreviations used.
2. Many tables, figures, and equations are not consistent in terms of their formatting to the rest of the manuscript. Please fix them to make it easier for the readers to read.
3. SEM images are not clear, please replace them with clearer images. With these images it is difficult to distinguish the materials morphology…
Although the data is good, I can’t recommend this manuscript for publication without revising the manuscript thoroughly. As I mentioned above, please improve the figures and tables to meet the average standard of the journal.
I hope the authors read the manuscript carefully, then revise it thoroughly.
Extensive editing of English language required
Author Response
Reviewer 1
The authors studied the effect of the zeolite framework on low-temperature NOx adsorbers. Some revisions might be needed for the manuscript to be continued for publication.
Comments:
- Some abbreviations were not mentioned prior to their usage, making it difficult for readers to understand the abbreviations. Please add more clarity for the abbreviations used.
ANS: The reviewer's suggestion has been considered; all the abbreviations have been clarified.
2.Many tables, figures, and equations are not consistent in terms of their formatting to the rest of the manuscript. Please fix them to make it easier for the readers to read.
ANS: The layout of Figures, tables and equations has been corrected.
3.SEM images are not clear, please replace them with clearer images. With these images it is difficult to distinguish the materials morphology…
ANS: The reviewer is right, the SEM images are not so clear; unfortunately, our instrument does not allow to obtain much better images for this kind of materials. However, the main scope of this analysis is to verify whether the addition of Pd significantly modifies the main morphological features of the zeolite support. In any case we tried to improve as much as possible the quality of the images and we think that it can be easily recognizable that the Pd-doping does not alter the original morphology of the zeolite.
Although the data is good, I can’t recommend this manuscript for publication without revising the manuscript thoroughly. As I mentioned above, please improve the figures and tables to meet the average standard of the journal.
I hope the authors read the manuscript carefully, then revise it thoroughly.
ANS: in fact we have carefully revised thoroughly the manuscript
Comments on the Quality of English Language: Extensive editing of English language required
ANS: we have made efforts to improve the English quality of the manuscript throughout the whole text (see correction in the revised manuscript with marked corrections)
Reviewer 2 Report
Interesting work. One question, in the sample preparation for BET. You mentioned that you degassed the samples at 350oC for 1 hour only. To my knowledge, zeolite samples for BET preparation will need at least 3 hours to be sure that completely degassed. Do you have any experimental data showing that 1-hour degas doesn't affect the results of your research?
good
Author Response
Reviewer 2
Interesting work. One question, in the sample preparation for BET. You mentioned that you degassed the samples at 350°C for 1 hour only. To my knowledge, zeolite samples for BET preparation will need at least 3 hours to be sure that completely degassed. Do you have any experimental data showing that 1-hour degas doesn't affect the results of your research?
ANS: Thanks to the reviewer for the observation. Indeed, the text has been corrected because we degas the sample for 3 hours (see the corrected conditions at line 395 of the revised manuscript).
Comments on the Quality of English Language: good
Reviewer 3 Report
I have received a manuscript "AN ASSESSMENT OF ZEOLITE FRAMEWORK EFFECT FOR LOW-TEMPERATURE NOX ADSORBERS" for consideration to be published in Catalysts MDPI. I must however recommend the manuscript to be rejected.
1) The literature presented in the manuscript is old. Most of the references are older than 3-5 years
2) The investigated zeolites differ significantly in their Si/Al ratio, which makes no sense in terms of their comparison. The Si/Al ratio should be familiar to allow better understanding of the effect of framework.
3) What is the explanation for selection of about 1% Pd into zeolite structure? It is rather high, and some lower concentrations should be also evaluated. Also EDX analysis of metal concentration would bring high error. I would recommend using XRF or ICP analysis to get a better quantity of metal within the materials.
4) There is lack of comparison to other scientist results. What makes your materials better than the other reported ones?
Author Response
Reviewer 3
I have received a manuscript "AN ASSESSMENT OF ZEOLITE FRAMEWORK EFFECT FOR LOW-TEMPERATURE NOX ADSORBERS" for consideration to be published in Catalysts MDPI. I must however recommend the manuscript to be rejected.
1) The literature presented in the manuscript is old. Most of the references are older than 3-5 years
ANS: The literature reported in the manuscript presents the experimental data on which our investigation is based and from which our work has moved on. We added some very recent references in the introduction (refs 18-21 of the revised manuscript)
2) The investigated zeolites differ significantly in their Si/Al ratio, which makes no sense in terms of their comparison. The Si/Al ratio should be familiar to allow better understanding of the effect of framework.
ANS: the reviewer is right, the zeolites differ for the cage dimension and also for the Si/Al ratio. However our results show that the Si/Al ratio is not the most critical parameter governing the Pd dispersion and catalyst performances, as discussed in the revised version of the manuscript (see e.g. lines 165-178).
3) What is the explanation for selection of about 1% Pd into zeolite structure? It is rather high, and some lower concentrations should be also evaluated. Also EDX analysis of metal concentration would bring high error. I would recommend using XRF or ICP analysis to get a better quantity of metal within the materials.
ANS: Actually the loading of Pd is very typical for this kind of application (NOx adsorption at low temperature), as also demonstrated by the reported literature. The reported EDX analysis is very close to the nominal value and this is expected in view of the preparation method here adopted (impregnation with excess solvent and then drying of the obtained slurry with no washing steps), where no losses of Pd are in fact expected. This was indeed further demonstrated for the SSZ-13 sample where the Pd content has also been evaluated by ICP, but we are rather confident that the Pd loading is near the nominal one for all samples as indeed revealed by EDX analysis.
4) There is lack of comparison to other scientist results. What makes your materials better than the other reported ones?
ANS: Probably the reviewer misrepresented the scope of the work. Indeed, we don't aim to propose better materials than others, but try to correlated the performances of them in term of NOx adsorption and desorption with their morphological characteristics. The text has been modified to better explain this point (lines 60-73).
Round 2
Reviewer 1 Report
The authors addressed most of my concerns. I recommend the paper for publication. note to authors: please add the Y-axis in intensity (a.u.) in figs 3,4 and 5. You missed it.
Reviewer 3 Report
The manuscript has been significantly improved and the reviewers questions have been well addressed. For this reason I can recommend the article for publication in Catalysts MDPI.
