Study of H2O2/Cu2+ Catalyzed Oxidation Process of Maltodextrin
Round 1
Reviewer 1 Report
In this manuscript, Li and co-workers reported the synthesis of oxidized maltodextrins with high carboxyl group content using CuSO4 as a catalyst and H2O2 as an environment-friendly oxidant. The structure and properties of oxidized maltodextrins were studied through IR, NMR, and TG analyses. The reaction conditions were optimized in terms of oxidant content, catalyst content, temperature, pH, and reaction time. Study on the preparation process of oxidized maltodextrin with high carboxyl content provides a good basis for its application in the biomedical field. Therefore, I support the publication of this paper in Catalysts after addressing the following minor issues.
1. In the abstract and throughout manuscript replace “nuclear magnetic resonance hydrogen spectroscopy” with “Proton- nuclear magnetic resonance spectroscopy”
2. Authors should mention in the beginning which Cu2+ compound has been used as catalyst.
3. Page 1: Replace NaOCl with NaClO. Replace “Chlorination by-products” with “chlorine by-products”
4. From figure 2.1, it is observed that the intensity of band due to –OH group (3368 cm‑1) is very high even in the oxidized maltodextrin. But, the authors claimed that the carboxyl content is more than 100%. Authors should justify the statement.
5. There are some issues concerning the pictures in this manuscript. For example: (1) the figure number should be changed from Figure 2-1 to Figure 1, Figure 2-2 to Figure 2 etc.; (2) Figure (a) and (b) should be kept horizontally when they were aligned side by side.
6. There are some grammatical issues in this manuscript, including but not limited to the following examples.
(a) The authors should play attention to the utilized tense throughout the manuscript. There is the present tense, the past tense, as well as the future tense. Please try to make appropriate modifications.
(b) “Proton signals for CH and CH2 groups on the glucose unit are determined between 3.37 ~ 3.62 ppm” instead of “Proton signals for CH and CH2 groups on the glucose unit are reported to have chemical shift values between 3.37 ~ 3.62 ppm”, “catalyst content” instead of “catalyst loading”
(c) Ensure that “full name (abbreviation)” is used when it is mentioned for the first time, while only the abbreviation should be used in the latter descriptions.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript reports the process optimisation of a homogeneous Cu catalyst for the oxidation of Maltodextrin with hydrogen peroxide. The manuscript is generally well written and would be of interest to the catalysis community, and I would recommend publication upon the authors addressing the following points.
1. While the authors discuss the industrial alternative oxidation system (sodium hypochlorite) in the introduction, they should also provide a literature review of the use of Cu and H2O2 for the oxidation of different alcohol/organic compounds, both homogeneous and heterogeneous, to set the current scene and state of the art systems.
2. Analysis of the HNMR focuses on the decrease of hydroxyl protons yet neglects to discuss increases/emergence of new peaks (e.g. 1 and 8.25 ppm)
3. The investigation only studies Copper sulphate, yet no explanation for the choice of this salt over others is provided. The authors should conduct studies under optimal conditions with other copper salts to confirm if the anion affects performance.
4. The authors discuss the green credentials/sustainability of the system yet do not discuss or attempt to recover and recycle the Cu catalyst. Insight into the possibility of this, ideally experimental, would strengthen the paper considerably.
5. Stating the reaction condition repeatedly in the manuscript is unnecessary and should be moved to the figure captions.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
1- There are some punctuation errors. The file should be checked accurately.
2- The figures are not arranged well. It would be better if Figure 1 and 2 mix together.
3- A comparison with other methods and research must be added to bold and highlight the advantageous of this method.
4- The kinetic study should be explained.
5- The references are too old. Add more recent references.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have addressed the comments, however, there is still outstanding insight that is required to truly understand the catalysis. The major concern is that changes in performance, including the effects of temperature and Cu conc., are attributed to either formation of radical (desirable) or the decomposition of 2H2O2 to 2H2O and O2 (undesirable). However, they provide no analytic evidence or support literature to back these claims. Thus the discussion is very weak. Additional experiments to confirm differences in the species, or literature to support their arguments are needed.
Author Response
Dear Reviewer,
Thank you for carefully reading our manuscript.We appreciate the comments and suggestions. In the following, we includce apoint-by-point response to the comments. In the revised manuscript, all the changes have been highlighted in red.
Point 1: The authors have addressed the comments, however, there is still outstanding insight that is required to truly understand the catalysis. The major concern is that changes in performance, including the effects of temperature and Cu conc., are attributed to either formation of radical (desirable) or the decomposition of 2H2O2 to 2H2O and O2 (undesirable). However, they provide no analytic evidence or support literature to back these claims. Thus the discussion is very weak. Additional experiments to confirm differences in the species, or literature to support their arguments are needed.
Response 1: Thank you for your comments. We refer to relevant literature on the catalytic oxidation kinetics of hydrogen peroxide to support our views. Relevant literature has been added in the discussion section of the revised manuscript.
Reviewer 3 Report
Dear author,
Thank you for providing my views to the manuscript.
Regards,
Author Response
Dear Reviewer,
We appreciate the comments and suggestions.
Best regards，
