Lignin-Derived Ternary Polymeric Carbon as a Green Catalyst for Ethyl Levulinate Upgrading from Fructose
Round 1
Reviewer 1 Report
In the present paper, the preparation of an acid layered biochar is shown, as well as its possible use as catalyst for the fructose transformation in ethyl levulinate through reaction in ethanol. The first part, preparation and characterization of the material is typical and, in my opinion, quite complete. Perhaps a discussion on the repeatability of the preparation technique would be appropriate: are the properties of different batches of solid similar within the limits of the experimental error?
Regarding the catalytic reaction, I have some questions:
11 The particle size of the catalyst used in experiments should be reported
22 Reaction between ethanol and fructose is complex. It involve a series-parallel reaction network. Such reaction network must be reported and described.
33. Fructose conversion is complete, but ethyl levulinate yield is about 70%. Therefore, other compounds are formed. Such compound have to be identified and quantified I.e. ethyl formate, levulinic acid, formic acid. In addition, in these systems the formation of humins is an important issue. The amount of humins formed has to be reported.
44 The changes experienced by the reused catalyst should be reported
55 The accuracy of experiments is not quoted in the paper
66 In the X-axis of figure 2c, it seems that a little mistake of spelling occurs: It seems that the correct legens is binding energy, not binding energy.
Author Response
Reviewer 1
In the present paper, the preparation of an acid layered biochar is shown, as well as its possible use as catalyst for the fructose transformation in ethyl levulinate through reaction in ethanol. The first part, preparation and characterization of the material is typical and, in my opinion, quite complete. Perhaps a discussion on the repeatability of the preparation technique would be appropriate: are the properties of different batches of solid similar within the limits of the experimental error?
Answer: As you kindly mentioned, we have prepared three batches of catalysts and used them for the recycling study in fructose conversion (Figure 9). The small error values (≤ 1.1%) indicate that different batches of the prepared catalysts have similar catalytic performance. Thank you!
Regarding the catalytic reaction, I have some questions:
- The particle size of the catalyst used in experiments should be reported.
Answer: The particle size data of the catalyst have been collected in Figure 4. Thanks!
- Reaction between ethanol and fructose is complex. It involve a series-parallel reaction network. Such reaction network must be reported and described.
Answer: We totally agree with your comments, and have added the corresponding description in section 2.2.1., which is also inserted in a schematic diagram (Scheme 1) in the revised manuscript.
- Fructose conversion is complete, but ethyl levulinate yield is about 70%. Therefore, other compounds are formed. Such compound have to be identified and quantified i.e. ethyl formate, levulinic acid, formic acid. In addition, in these systems the formation of humins is an important issue. The amount of humins formed has to be reported.
Answer: Many thanks for your meaningful suggestions. The contents of the formed by-products (mainly ethyl formate, and humin) have been added in the revised manuscript (Page 7).
- The changes experienced by the reused catalyst should be reported.
Answer: Thanks for your useful suggestions. The changes and descriptions of the catalyst reusability have added in the section 2.2.3 (Figure 9b).
- The accuracy of experiments is not quoted in the paper.
Answer: We totally agree with your comments. We have conducted error analysis on all the catalytic experiments in the revised manuscript.
- In the X-axis of figure 2c, it seems that a little mistake of spelling occurs: It seems that the correct legens is binding energy, not binding energyb.
Answer: The kindly raised error has been corrected in the revised manuscript. Many thanks!
Reviewer 2 Report
The paper “Layered Biochar Acid-Enabled Catalytic Upgrading of Fructose to Ethyl Levulinate” presents the production of a carbon based material, its characterization and the evaluation of catalytic performances in the production of Ethyl Levulinate from fructose precursors.
The paper is well conceived, the characterization is complete, and results are worth publication. There are, however, some issues especially conceiving the quality of presentation which should be improved.
First, I suggest to revise the terminology for a better consistency along the paper, especially regarding the used catalyst. This material, in my opinion, cannot be considered as biochar, since the thermal treatment is limited in terms of temperature. Accordingly I would suggest to revise the title to focus on the greenness of the material, such as “Lignin-derived Ternary polymeric carbon as a green catalyst for Ethyl Levulinate upgrading from Fructose”.
I would also suggest to revise the abstract, adding a few more details on the obtained results and highlighting the potential outlooks of this study. I also suggest to define the acronym TPC here, when first mentioned, instead that in the method section.
Then there are different fragmented and unclear sentences which should be rephrased in my opinion. For example, in lines 149-151, authors can rephrase more clearly the sentences, e.g., “The surface morphology of TPC-S, revealed by SEM images, is instead shown in Figure 4g-i. The evident porous structure is due to the release of CO and CO2 gases during sulfonation...". Similarly, other section should be rephrased for clarity, such as in lines 29-31, 80-85, 88-91, 163-165, 193-194,
Finally, there are some issues which should be improved I the discussion of results. In lines 176-179, when discussing the Thermogravimetric results, authors should indicate the gaseous media used for thermogravimetric analysis (e.g., nitrogen or oxygen), since this can highly affect the measures.
Then, in section 2.2., while it is good to present the optimization of surrounding conditions for Ethyl Levulinate production, it should be more effective to also compare the performances with other similar catalysts in literature (such as Peixoto et al., 2021 https://doi.org/10.1016/j.fuel.2021.121227 and Kumari et al. 2022 https://doi.org/10.1016/j.catcom.2022.106467).
Author Response
The paper “Layered Biochar Acid-Enabled Catalytic Upgrading of Fructose to Ethyl Levulinate” presents the production of a carbon based material, its characterization and the evaluation of catalytic performances in the production of Ethyl Levulinate from fructose precursors.
The paper is well conceived, the characterization is complete, and results are worth publication. There are, however, some issues especially conceiving the quality of presentation which should be improved.
Answer: Thank you very much for your comments and kind recommendation. The manuscript has been further improved, according to your kind suggestions listed below.
First, I suggest to revise the terminology for a better consistency along the paper, especially regarding the used catalyst. This material, in my opinion, cannot be considered as biochar, since the thermal treatment is limited in terms of temperature. Accordingly I would suggest to revise the title to focus on the greenness of the material, such as “Lignin-derived Ternary polymeric carbon as a green catalyst for Ethyl Levulinate upgrading from Fructose”.
Answer: As you kindly suggested, we have modified the title of the article accordingly and corrected the “biochar” word throughout the manuscript. Thanks!
I would also suggest to revise the abstract, adding a few more details on the obtained results and highlighting the potential outlooks of this study. I also suggest to define the acronym TPC here, when first mentioned, instead that in the method section.
Answer: Both obtained results and the potential outlooks have been included in the abstract, and the acronym TPC has also been explained. Thank you!
Then there are different fragmented and unclear sentences which should be rephrased in my opinion. For example, in lines 149-151, authors can rephrase more clearly the sentences, e.g., “The surface morphology of TPC-S, revealed by SEM images, is instead shown in Figure 4g-i. The evident porous structure is due to the release of CO and CO2 gases during sulfonation...". Similarly, other section should be rephrased for clarity, such as in lines 29-31, 80-85, 88-91, 163-165, 193-194,
Answer: We are grateful for your kind comments. All the mentioned unclear sentences and other issues have been carefully modified or adjusted, which are all marked in blue in the revised manuscript.
Finally, there are some issues which should be improved I the discussion of results. In lines 176-179, when discussing the Thermogravimetric results, authors should indicate the gaseous media used for thermogravimetric analysis (e.g., nitrogen or oxygen), since this can highly affect the measures.
Answer: The gaseous media used for thermogravimetric analysis is nitrogen, and the relevant description has been included in the revised manuscript (Pages 6, 11). Other related issues are also checked and resolved accordingly. Thanks a lot!
Then, in section 2.2., while it is good to present the optimization of surrounding conditions for Ethyl Levulinate production, it should be more effective to also compare the performances with other similar catalysts in literature (such as Peixoto et al., 2021 https://doi.org/10.1016/j.fuel.2021.121227 and Kumari et al. 2022 https://doi.org/10.1016/j.catcom.2022.106467).
Answer: As you kindly suggested, we have added a new section and a table in section 2.2 with relevant references and discussions. Thanks!
Round 2
Reviewer 1 Report
The paper has been substantially upgraded. All my queries has been addressed apropriately. The paper is publishable now as it is
