High-Efficiency Biodiesel Production Using ZnO-Modified Starfish-Based Catalysts

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Before a possible acceptance, I have some comments:

The introduction discusses general challenges in heterogeneous catalysis but does not clearly define the research gap being addressed.

"The choice of feedstock and catalyst plays a crucial role in optimizing biodiesel production efficiency and sustainability. [...] To overcome the limitations of conventional CaO catalysts, ZnO has been introduced for structural stabilization and catalytic enhancement."

Suggestion: The introduction should explicitly highlight the specific research gap and the limitations of current catalysts.

 

There is no indication of experiment repetition or statistical analysis of data variation.

"The catalytic performance of the synthesized catalysts was evaluated by measuring the biodiesel yield at different reaction times (Figure 5). CMZ achieved 31.5 %, 39.8 %, 70.9 %, 94.7 %, and 95.3% for 4 h, 6 h, 10 h, and 12 h, respectively."

The authors should indicate the number of experimental repetitions and provide standard deviations.

The conclusion does not mention the study’s limitations or discuss the economic feasibility of the catalyst. You should discuss technical challenges, such as the catalyst’s stability in continuous operations, and propose more concrete future research directions, such as long-term stability tests and economic feasibility assessments.

 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The authors synthesize one Zn-doped Ca-mg-oxide catalyst and tested it in the transesterification reaction of grapeseed oil to obtain FAME. The present manuscript is not suitable for publication in Catalysts for the following reasons:

1)The present paper is poor of catalytic data. Just one Zn containing catalyst was synthesized and tested for FAME production. Hence no information concerning the optimal Zn content in the Zn-Ca-Mg-Ox catalyst is given. Recycling experiments and leaching tests in particular for the Zn(2+) containing catalyst are completely absent.

2) The XPS data for the pure ZnO phase (i.e. O1s and Zn2p) should be included in the manuscript and compared with those obtained for the Zn-Ca-Mg-Ox catalyst.

3) The manuscript is bad organized and many times the same thinks a repeated. I hence recommend merging the result and discussion part to one chapter.

4) What does CMZ stand for?

5) The conclusion part is much too long. Once again repetitions. The same is true for the introduction. It needs to be much more concise.

6) The reference reported does not correspond to the style used for Catalysts.

7) The HPLC traces reported as Figures in the Supporting Information part needs labelling.

Comments on the Quality of English Language

English is generally acceptable.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors still present just one Zn-based catalyst, which means the dependence of the catalytic activity from  Zn content has not been studied (Comment 1 of the last review report). Also a comparison with ZnO should be carried out. In addition, no ICP analysis of the catalytic solutions to determine the Zn-leaching has been carried out. The conclusion is full of statements that regard the futher plan for this type of chemistry, while it is esential for the present study in order to avoid fractional infromation.

Author Response

Please see the attachment.

Author Response File: Author Response.docx