The Green Synthesis of Biodiesel via Esterification in Water Catalyzed by the Phosphotungstic Acid–Functionalized Hydrophobic MCM–41 Catalyst
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis paper describes esterification of fatty acids by methanol ander the action of heteropoly acid catalyst in aqueous solution to produce a biodiesel. Taking into account that the reaction runs in water, this is a green rout to biodiesel.
The authors synthesized the catalysts based on phosphotungstic acids and molecular sieves. The catalyst was thoroughly characterized by XRD data, IR spectra, nitrogen adsorption-desorption method, SEM and TEM methods. The acidity of the obtained catalysts was evaluated by ammonium-THD method.
Esterification of some fatty acids C6, C8, C10, C12, C14, C16, C18 was carried out using methanol and the catalysts. The authors found optimal conditions to get methyl esters in high yields.
It should be specially emphasized that the authors conducted this esterification directly in fermentation broth in water. The high efficacy of the process was shown.
In conclusion, the authors provide good and reliable scientific results. The paper is well prepared, and may be accepted for publishing.
Comments on the Quality of English LanguageMinor editing of English language is required.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsIn the current manuscript Li et al., discussed the fabrication of Phosphotungstic acid-functionalized hydrophobic MCM-41 catalyst for the green synthesis of biodiesel by esterification in water. This paper required major revision before further consideration. The following are the points that need to be addressed.
1. The functionalisation mechanism should be explained properly in the manuscript.
2. Characterization details are not there. I would suggest the authors include the characterization.
3. Hydrophobic behaviour of the catalyst can be explained by water adsorption technique. For example, I suggest the authors to read the following papers.
Catalysis Communications,2012, 18, 89-92.
4. What type acid sites are responsible for the esterification of fatty acids. I would suggest the authors to perform the pyridine adsorption FTIR and include the results in the revised with proper correlation of activity.
5. Surface area data is not presented in the manuscript.
6. Not much change in activity was observed by the incorporation of hydrophobic groups. Why?
7. In general, by the calcination of heteropoly acids above 300 ᵒC will be decomposed to corresponding metaloxides. In the present case, even after the calcination at 400 ᵒC the heteropolyacid remains intact. Why?
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsManuscript can be accepted now.
