Levulinic Acid Production from Delignified Rice Husk Waste over Manganese Catalysts: Heterogeneous Versus Homogeneous

Round 1

Reviewer 1 Report

The paper "Levulinic Acid Production from Delignified Rice Husk Waste over Manganese Catalysts: Heterogeneous versus Homogeneous" represents an interesting topic and gives an opportunity to compare two diversified catalytic approaches. 

The paper is well written and the reference list is up to date. The introduction supports a relevant bacground for the carried research. 

The sentence "To obtain cellulose from lignocellulosic biomass, it is
 necessary to optimize the delignification pre-treatment or lignin structure reduction process [15]"  needs to be rewritten, the Authors should mention hemicelullose as well. Lignin removal approach may differ for different plants, this should be adressed. Also the interaction between lignin derivatives is of great concern. The presence of intermediates may affect the catalysis.

Rice husk was supplied from Darmaga area, Bogor, Indonesia. If possible, the Authors should provide geographical coordinates. The plants may vary depending on the area, climate or season. It would be easier to compare with other research when the details are provided. 

You should unify the units, i.e. °C and % throughout the paper. The lines numbering is not provided in the whole text. Please refer. Whenever proportions are mentioned (i.e. 1:2) you shouls explain whether its volumetric or mass.

"under vigorous stirring" please provide the apparatus and RPM

The sentence "TEM measurement was also carried out Tecnai F20 FEI Company,KAIST" needs to be rewritten.

4.4. The amount of delignified rice hust must be provided. Why were the mentioned wavelenghts chosen? Please use molarity instead of "0,005 N"

4.5. It is very possible that cellulose [mg] contains also hemicellulose. Please expalin.

The cataysts description and characterisation is accurate. 

line 120 "This is in agreement" it would be better to write "this corresponds"

line 128 why is italic used?

Standard deviation needs to be provided in the results section. It seems, the research were carried in single run and therefore control is missing. Please, refer.

Figure 8 needs to be confronted with the literarure. The conclusions should also be compared with the ones published in the field, even if the represent other types of biomass.

An information about the number of cycles for catalyst would be of good value. Also a discusision on by-poducts removal and their environmetal impact would improve the papers visibility and citescore.

The conclusions are supported by the results.

 

 

 

 

 

 

 

Author Response

Dear Reviewer 1, 

Thank you for your questions and valuable suggestions on our manuscript. We have revised the manuscript as suggested. Please see the attachment.

 

Sincerely

Authors

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper focussed on the preparation of multifunctuional catalysts for levulinic acid production from rice husk.
The work is interesting, relevant and well described.
Still some points need to be considered before publication:

1. Graphical presentation, why using to types of graphs in figures 6 and 7 ? shouldnt standard x-y plots be sufficient ?
Would also be good to align them above each other in the order of formtion. That helps to follow the conversion according to the proposed mechanism.

2. The points in those graphs are not really showin gsome nice curves, but are fluctuating quite a bit, especlally for HMF.
Could you give an indication about the repeatability of those numbers ? What is the standard error ?

3. Could you also show the yields of glucose and fructose, as they are important intermediates ?

4. In the conversion experiments you use phosphoric acid as solvent and add H2O2. Can you give an indication about the effect of acid strength and type as well as of H2O2 concentration ?

5. Could you think of ways for simplifying the process with respect to used chemicals ?

6. The spelling/grammar needs to be improved.

Author Response

Dear Reviewer,

Thank you for your valuable questions and suggestions, they are very useful to improve our manuscript. We have revised the manuscript and answered your questions. Please see the attachment.

 

Sincerely,

authors

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Thank you for claryfying my doubts. The paper has been improved significantly.