Catalytic Properties and Structural Optimization of Solid Transesterification Catalysts to Enhance the Efficiency of Biodiesel Synthesis

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear Prof., Editor of Catalysts,

Thank you very much for inviting me to review the review under the title of “Catalytic Properties and Structural Optimization of Solid 2 Transesterification Catalysts in Enhancing the Efficiency of Biodiesel Synthesis”

This review only discusses general information and there is no deep discussion about the studies that are performed on this topic, some issues should be addressed to improve it

 

Avoid the abbreviation in the abstract section.

Tables 1, 3, 4, Figs. 1-3 are not cited in the text.

The style of the references inside the text is unlike the journal guide.

The authors should discuss papers that are related to this topic in depth to enrich the content of this review.

Page 4, lines 108-110, please complete this sentence or rewrite it.

Page 13, line 377, please change “heavily” to “greatly”

Page 16, what is the meant by FAMEs.

This important article related to this topic should be cited 10.3390/catal12090977

   

 

 

 

 

Author Response

Thank you very much for taking the time to review this manuscript. Please find below our detailed responses to your comments, with corresponding revisions highlighted in the re-submitted document. We are grateful for your valuable feedback and have thoroughly reviewed and enhanced our manuscript accordingly. All modifications are clearly indicated in the uploaded version, with color highlights facilitating further comparison.

 

 

Comments 1：Avoid the abbreviation in the abstract section.

Response 1: Thank you for pointing this out. We agree with this comment. Therefore, We have rewritten the abstract session to avoid all abbreviations. In addition, we have updated the content of Abtract to make it more relevant to the topics of subsequent articles and added typical examples that we felt we needed to mention here

 

Comments 2：Tables 1, 3, 4, Figs. 1-3 are not cited in the text.

Response 2: Thank you for pointing this out. We agree with this comment.Therefore, we have rewriten all references in the article that involved figures and tables to ensure that everything was correctly cited in the article

 

Comments 3：The style of the references inside the text is unlike the journal guide.

Response 3：Thank you for pointing this out. We agree with this comment.Therefore, we have properly updated the citation format by referring to the journal submission template.

 

Comments 4：The authors should discuss papers that are related to this topic in depth to enrich the content of this review.

Response 4:Thank you for pointing this out. We agree with this comment. Therefore,we have added more than a dozen new citations to contemporary journals and added additional analyses, figures, and more to ensure a richer review.

 

Comments 5: Page 4, lines 108-110, please complete this sentence or rewrite it.

Response 5: Thank you for pointing this out. We agree with this comment.Therefore, we have rewritten the sentence. We hope that the rewriting can ensure the rigor of academic English. You can find the update here on page 4 of the updated manuscript.

 

Comments 6: Page 13, line 377, please change “heavily” to “greatly”

Response 6:Thank you for pointing this out. We agree with this comment. Therefore, we have changed the word from ‘’heavily’’ to ‘’greatly’’. You can find the update here on page 14, section 8.1, we marked the sentence into red.

 

Comments 7: Page 16, what is the meant by FAMEs.

Response 7:Thank you for pointing this out. We agree with this comment. Therefore, we have included FAMEs in the article where the abbreviation first appears and in the chapter where the abbreviation first appears

Comments 8：This important article related to this topic should be cited 10.3390/catal12090977

Response 8: Thank you for pointing this out. We agree with this comment.Therefore, we have cited this article in page 25, session 13&nbsp. You can also find him in the citation list [115].

 

Reviewer 2 Report

Comments and Suggestions for Authors

In this manuscript, the authors review the development and optimization of solid transesterification catalysts for enhancing the efficiency of biodiesel synthesis. In addition, the authors also demonstrated the recent advancements in structural optimization to improve catalytic performance and selectivity. The subject of the manuscript clearly falls within the scope of Sustainability. However, there are some changes and improvements that need to be addressed before it can be accepted.

(1) The background of this manuscript could be improved by citing more recent literature, particularly the recent progress about the biodiesel fuels and their physiochemical properties effects on the emissions formation and oxidation, such as Energy. 2021;231:121069.

(2) The font size in the figures are should be united in the revised manuscript.

(3) The authors present many recent progress of the development and optimization of solid transesterification catalysts to improve catalytic performance and selectivity. Why the authors do not illustrate the specific data and trends in the figures?

(4) It is suggested that using several graphic picture to illustrate the upsides and downsides of the nano structuring, acidity/basicity tuning, and hybrid catalyst, such as .

(5) It is also suggested that using the tables or figures to present the performance of the solid transesterification catalysts, biodiesel yield testing.    

(6) The Conclusion section should list some specific results and data and listed one by one. In addition, the future research prospects should also be presented.

(7) It is kindly suggested that the revision with regard to the expression in English language: again, even if understandable, this paper would could improve with the revised grammar errors and more clarity in some sentences.

Comments on the Quality of English Language

 It is kindly suggested that the revision with regard to the expression in English language: again, even if understandable, this paper would could improve with the revised grammar errors and more clarity in some sentences.

Author Response

Thank you very much for taking the time to review this manuscript. Please find below our detailed responses to your comments, with corresponding revisions highlighted in the re-submitted document. We are grateful for your valuable feedback and have thoroughly reviewed and enhanced our manuscript accordingly. All modifications are clearly indicated in the uploaded version, with color highlights facilitating further comparison.

 

 

Comments 1：The background of this manuscript could be improved by citing more recent literature, particularly the recent progress about the biodiesel fuels and their physiochemical properties effects on the emissions formation and oxidation, such as Energy. 2021;231:121069.

Response 1: Thank you for pointing this out. We agree with this comment. Therefore,we have expanded the background content appropriately, mentioned more about the physiochemical properties of biofuels, and cited the literature you mentioned: Energy.2021; 231:121069. These changes can be found in the uploaded new manuscript, which we have highlighted in red. Additional citations are also indicated [4],[6].

 

Comments 2： The font size in the figures are should be united in the revised manuscript.

Response 2:  Thank you for pointing this out. We agree with this comment. Therefore,we have made appropriate adjustments, but because most of the images were modified from other papers, they could not be well repaired. But we made sure that other formats were consistent with the template of the paper, including chart citations, citation formats, etc.

 

Comments 3：The authors present many recent progress of the development and optimization of solid transesterification catalysts to improve catalytic performance and selectivity. Why the authors do not illustrate the specific data and trends in the figures?

Response 3：Thank you for pointing this out.We agree with this comment. Therefore, we have added more analysis of current research, such as current research challenges, future developments, and current catalyst stability, selectivity and reuse issues, etc. These can be found in the new sections on page 12, page 16-19 of the updated manuscript.

 

Comments 4：It is suggested that using several graphic picture to illustrate the upsides and downsides of the nano structuring, acidity/basicity tuning, and hybrid catalyst, such as .

Response 4:Thank you for pointing this out.We agree with this comment. Therefore,we have added relevant materials, such as Table 4 and Figure 5, and at the same time provide more details about the advantages and disadvantages of nanomaterials and heterogeneous hybrid catalysts.

 

Comments 5: It is also suggested that using the tables or figures to present the performance of the solid transesterification catalysts, biodiesel yield testing.

Response 5: Thank you for pointing this out.We agree with this comment. Therefore,we have several new tables have been added and more relevant literature has been cited. These new contents, together with the contents in the previous manuscript, can well present the performance of solid sesterification catalysts and the relevant information of biodiesel yield testing.

 

Comments 6: The Conclusion section should list some specific results and data and listed one by one. In addition, the future research prospects should also be presented.

Response 6: Thank you for pointing this out.We agree with this comment.Therefore, we have rewritten the conclusion and added more detailed data. In addition, we mentioned more useful measures in the outlook for the future, which can be found in page 12-13 and page 29, hoping to better meet the requirements.

 

Response to Comments on the Quality of English Language

Comments 7: It is kindly suggested that the revision with regard to the expression in English language: again, even if understandable, this paper would could improve with the revised grammar errors and more clarity in some sentences.

Response:Thank you for pointing this out.We agree with this comment. Therefore, we have split and revised some long sentences, and have used grammar tools and dictionaries to proofread vocabulary and grammar. We hope that the revised article can meet the requirements of academic English of the journal. If there are more details to be modified, please point out and we will try to improve.

 

We sincerely appreciate your valuable suggestions. We have dedicated considerable time to revising the entire article in accordance with the requirements, which includes enhancing the structure, expanding the content, and conducting a more thorough critical analysis. We hope that these revisions will adequately address your comments and better align with the submission standards of the journal. All significant changes are highlighted in color within the text for your convenient review and comparison.

 

Reviewer 3 Report

Comments and Suggestions for Authors

This review explores solid transesterification catalysts for biodiesel production, focusing on titanium-based, zinc-based, and bio-based systems. These catalysts offer advantages like reusability and thermal stability, with advancements in nano structuring and hybrid development improving performance. The review highlights characterization techniques (e.g., BET, XRD, CO₂-TPD) and discusses challenges in scalability and regeneration, while suggesting future research directions to advance biodiesel technology. I recommend this paper to be accepted by a minor revision after address the following concerns.

• The author should add more results in abstract
• What is the novelty of this research study?
• Could you briefly explain the difference between heterogeneous and homogeneous catalysts and why solid (heterogeneous) transesterification catalysts like TiO₂ and LDHs are particularly beneficial for biodiesel production?
• Authors mention feedstock variability as a challenge. Can you elaborate on the specific types of feedstock (e.g., waste oils, algae, etc.) that pose the most difficulties, and why current catalysts might not work effectively with them?
• What are the primary causes of catalyst deactivation in biodiesel production? Is it due to contaminants, high temperatures, or something else? How can the next generation of catalysts be engineered to combat these issues?
• What are the criteria for measuring the long-term stability of solid transesterification catalysts? Is there a benchmark or threshold that these catalysts must meet to be considered viable for large-scale biodiesel production?
• Break down long sentences into shorter ones in whole manuscript.
• Ensure that the citations are up-to-date and appropriately placed to improve the quality of article. Cite these articles in manuscript doi: 10.1109/TDEI.2024.3487148, doi.org/10.1021/acs.est.4c03478,doi.org/10.1016/j.scitotenv.2024.174128,doi: 10.1109/TDEI.2024.3510476, doi.org/10.1016/j.cej.2024.155012, doi: 10.1021/acs.cgd.4c01357, doi.org/10.1021/acs.est.4c03449
• Improve the conclusion section

Author Response

Thank you so much for taking the time to review our manuscript. We have carefully prepared detailed responses to each of your comments, and the corresponding revisions are highlighted in the re-submitted document. We truly appreciate your valuable feedback and have thoroughly reviewed and enhanced our manuscript based on your suggestions. All significant changes are clearly marked in the uploaded version, with color highlights to make comparison easier for you.

 

Comments 1：The author should add more results in abstract

Response 1: Thank you for pointing this out.We agree with this comment.Therefore,we have rewritten the abstract section and added relevant conclusions with specific data.

 

Comments 2： What is the novelty of this research study?

Response 2:  Thank you for pointing this out. We believe that the innovation of this review paper is mainly reflected in the following aspects: First, we systematically review the research progress of solid sesterification catalysts for biodiesel production, focusing on their catalytic characteristics and structural optimization strategies. We highlight the paradigm shift from traditional homogeneous catalysts to heterogeneous solid catalysts, and explore the key challenges of biodiesel industrialization, such as production efficiency, cost control and environmental impact.

 

In terms of structure optimization, we have proposed several new catalyst design ideas. For example, for advanced catalytic systems such as sulfonic zeolites, layered double hydroxides (LDHs) and metal-organic framework materials (MOFs), the highly selective catalytic mechanisms and efficiency improvement paths have been described. These designs not only significantly speed up the reaction kinetic process, but also achieve a breakthrough in product purity by optimizing the mass transfer efficiency. In particular, strategies to adapt different feedstock characteristics and reaction conditions by adjusting the physicochemical properties of catalysts are discussed, which provides a new perspective for the development of customized catalysts.

 

For the evaluation of catalytic performance, we constructed a multi-dimensional innovative analysis framework, focusing not only on the stability evolution of catalysts in thermodynamic and chemical environments, but also on the ability to resist impurity poisoning. Not only the mechanism of high quality raw materials transformation is analyzed, but also the feasibility of using low grade/waste raw materials to achieve high yield is demonstrated. These systematic findings provide theoretical support for bridging the gap between laboratory research and industrial application, and highlight the transformative potential of solid catalysts in promoting the sustainability and cost reduction of biodiesel production.

 

In addition, we have achieved the first systematic summary and comparative analysis of biodiesel yield measurement methods in the field. The establishment of unified evaluation criteria fills the gap of this technology in the existing literature, and provides an important reference for subsequent researchers to select and optimize the detection protocol.

 

Comments 3：Could you briefly explain the difference between heterogeneous and homogeneous catalysts and why solid (heterogeneous) transesterification catalysts like TiO₂ and LDHs are particularly beneficial for biodiesel production?

Response 3：Thank you for pointing this out.We agree with this comment.In the previous table, we have a part about the comparison of property differences between homogeneous catalyst and heterogeneous catalyst. For the advantages of solid heterogeneous catalyst in production, we have added new tables and chapter for comparison, which can be found in page 12-13, page23 and table 4.

 

Comments 4：Authors mention feedstock variability as a challenge. Can you elaborate on the specific types of feedstock (e.g., waste oils, algae, etc.) that pose the most difficulties, and why current catalysts might not work effectively with them?

Response 4:Thank you for pointing this out. We agree with this comment.Therefore,we have given a more detailed explanation in the challenge section(section 6 page12-13), cited more relevant latest literature, compared the catalytic effects of specific materials, and provided detailed data.

 

Comments 5: What are the primary causes of catalyst deactivation in biodiesel production? Is it due to contaminants, high temperatures, or something else? How can the next generation of catalysts be engineered to combat these issues?

Response 5: Thank you for pointing this out.We agree with this comment.Therefore,in section 6, we made a detailed analysis of the challenges encountered in the current research and the direction of future development, and added references. In addition, section 9.3 has been added to better describe the differences in reusable properties faced by catalysts. In addition, in Table 6, more data are listed, allowing a more intuitive comparison between each catalyst.

 

Comments 6: What are the criteria for measuring the long-term stability of solid transesterification catalysts? Is there a benchmark or threshold that these catalysts must meet to be considered viable for large-scale biodiesel production?

Response 6: Thank you for pointing this out.We agree with this comment.It is difficult to define the definition of long-term stable catalysts in industrial production. However, we have revised our manuscript with your comments. From page 17-19, we have added a number of chapters and tables to better compare the differences in reuse properties between different catalysts. In addition, in the last Section 15 (page 29-page 30), we also discussed the issue of large-scale industrial production of biodiesel, hoping to better conform to your modification suggestions.

 

Comments 7: Break down long sentences into shorter ones in whole manuscript.

Response 7: Thank you for pointing this out.We agree with this comment.Therefore,we have revised several paragraphs and divided lengthy sentences to enhance readability. Additionally, we have proofread certain sentences to ensure the academic rigor of the document. Notable changes are highlighted in different colors, while unchanged portions retain their original formatting.

 

Comments 8: Ensure that the citations are up-to-date and appropriately placed to improve the quality of article. Cite these articles in manuscript doi: 10.1109/TDEI.2024.3487148, doi.org/10.1021/acs.est.4c03478,doi.org/10.1016/j.scitotenv.2024.174128,doi: 10.1109/TDEI.2024.3510476, doi.org/10.1016/j.cej.2024.155012, doi: 10.1021/acs.cgd.4c01357, doi.org/10.1021/acs.est.4c03449

Response 8: Thank you for pointing this out.We agree with this comment.Therefore,we have incorporated citations from approximately twenty recent papers, primarily focusing on the most up-to-date research. Additionally, we appreciate your provision of references. Nearly all the documents you listed have been appropriately cited, which has also facilitated the inclusion of several new analytical sections. Changes in the literature are highlighted both in the final citation list and within the text to assist with further comparison.

 

 

Comments 9:Improve the conclusion section

Response 9: Thank you for pointing this out.We agree with this comment.Therefore,, we have rewritten the conclusion and added more detailed data. In addition, we mentioned more useful measures in the outlook for the future, which can be found in page 12-13 and page 29, hoping to better meet the requirements.

 

 

 

 

 

We truly appreciate your valuable suggestions. We have spent considerable time refining the entire article to better meet the requirements. This includes improving the structure, expanding on the content, and conducting a more in-depth critical analysis. We hope these revisions address your comments effectively and align more closely with the journal's submission standards. For your convenience, all significant changes are highlighted in color for easy review and comparison.

 

 

 

Reviewer 4 Report

Comments and Suggestions for Authors

Dear authors,

The topic of the paper is interesting and current. However, I would like to make some suggestions and remarks.

Shorten the introductory part.

The whole paper is too long. The paper seems more like a review than an article.
You need to include more of your results.
Also, there must be physical and chemical analyses for this topic.
Technically edit the paper
Improve English
Include more recent references.

Author Response

Thank you so much for taking the time to review our manuscript. We have carefully prepared detailed responses to each of your comments, and the corresponding revisions are highlighted in the re-submitted document. Your valuable feedback has been greatly appreciated, and we have thoroughly reviewed and enhanced our manuscript based on it. All major changes are clearly marked in the uploaded version, with color highlights to make comparison easier.

 

Comments 1：Shorten the introductory part.

Response 1:  Thank you for pointing this out.We agree with this comment.Therefore,we have cut out some boring repetitions and added a small amount of analysis, such as about the nature of biofuels, as requested by other reviewers.

 

Comments 2：The whole paper is too long. The paper seems more like a review than an article.You need to include more of your results.

Response 2: Thank you for pointing this out. We believe this article can be classified as a review article. In accordance with your requirements, we have implemented content and structural optimizations. Specifically, we removed general and summary terms that lacked specificity and incorporated substantial data analysis along with relevant charts.In the section dedicated to analyzing existing research limitations and prospects for future development, we have conducted a thorough analysis and critical reflection. This enhances the overall value and academic rigor of the paper.

 

Comments 3：There must be physical and chemical analyses for this topic.

Response 3：Thank you for pointing this out.We agree with this comment.Therefore,we have incorporated additional tables and several figures to systematically present and compare extensive actual data, as detailed in Tables 4, 5, and 6. However, due to the significant structural variations among different catalysts, it is challenging to conduct a comprehensive analysis of their characterization data. Therefore, we concentrate on a acidity, selectivity, reusability, and biodiesel yield. It is hoped that these focused comparisons will provide valuable references for future research.

 

 

Comments 4：Technically edit the paper

Response 4: Thank you for pointing this out.We agree with this comment.Consequently, we have implemented substantial revisions throughout the document. The notable technical modifications encompass, but are not limited to, the following:

Incorporated over 15 new references reflecting cutting-edge developments

According to the requirements of the editor and the reviewers, some chapters have been explained and expanded in more detail

Provided expanded characterization data for biochar-based catalysts and nano material.

Proposed standardized testing protocols to address feedstock variability challenges

 

This study elaborates on the limitations of the current research and provides detailed recommendations for future development.

 

 

Comments 5: Include more recent references.

Response 5: Thank you for pointing this out.We appreciate your feedback and agree with this comment. In response, we have incorporated more recent literature into the article. As other reviewers also highlighted this issue, we have added approximately 15 additional citations as requested. To ensure clarity, we have marked the important references in different colors at the end of the document. We hope this meets the journal's requirements.

 

Comments 6:Improve English

Response 6:Thank you for pointing this out.We appreciate your feedback and agree with this comment.We have carefully revised and proofread the language section to better accommodate the preferences of various reviewers, with the hope that our manuscript now fully meets the academic English standards of the journal.

 

We sincerely appreciate your valuable suggestions. We have dedicated significant time to refining the entire article in order to better meet the requirements. This process involved enhancing the structure, expanding on the content, and conducting a more thorough critical analysis. We hope these revisions effectively address your comments and align more closely with the journal's submission standards. For your convenience, all major changes are highlighted in color for easy review and comparison.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors answered all the questions and this review can be accepted in the present form