The Contribution of Commercial Metal Amides to the Chemical Recycling of Waste Polyesters
Round 1
Reviewer 1 Report
This work studied on the catalytic behavior of commercial metal amides in the chemical degradation by alcoholysis of polylactide (PLA) and polyethylene terephthalate (PET). They compared the effect of several metal catalysts on the degradation of PLA and PET. However, the whole manuscript has some shortcomings. Particularly, the experiment data and results aren't enough to support their conclusions. And some errors in writing the manuscript are listed below.
In Table 1 and Table 2, the explanation of the superscript b is missing.
In Table 2, the column name was wrong. The second column should be named as Temperature. Me-La should be corrected to be “Et-La”.
In Figure 3, the scale bar of Y axis is wrong, because the name of Y axis is percentage content.
For the results of Y amide catalyst, the results in Table 2 aren’t consistent with that in Figure 3. Or in Table 2, the data aren’t consistent with the corresponding column name. The author must check them carefully.
4. For PET degradation, the study was shortage of analyzing the chemical structures of degradation products by NMR and MS. No corroboration supported the results.
5. The reference formation is not uniform. Many references lack the paper linkage address.
Author Response
- In Table 1 and Table 2, the explanation of the superscript b is missing.
Answer: A note for superscript b was added in the Table caption.
- In Table 2, the column name was wrong. The second column should be named as Temperature. Me-La should be corrected to be “Et-La”.
Answer: the author apology for these mistakes derived by a wrong cut and paste in the template file. The column titles were corrected.
- In Figure 3, the scale bar of Y axis is wrong, because the name of Y axis is percentage content.
Answer: the author thank the reviewer for noting this mistake, the name of Y axis was corrected.
- For the results of Y amide catalyst, the results in Table 2 aren’t consistent with that in Figure 3. Or in Table 2, the data aren’t consistent with the corresponding column name. The author must check them carefully.
Answer: The author thank the reviewer for noting this mistake. The column titles were corrected.
- For PET degradation, the study was shortage of analyzing the chemical structures of degradation products by NMR and MS. No corroboration supported the results.
Answer: The 1H NMR spectrum of the products obtained by the degradation of PET, the final clean product (BHET), was added in the paper as figure 4. The BHET was also characterized by ESI spectrometry.
The reference formation is not uniform. Many references lack the paper linkage address.
Answer: The reference section was carefully checked according to the style require by the journal.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The present paper describes the use of various commercial metal amides (Zn, Mg and group 4 metals essentially) as depolymerization catalysts of PLA and PET in the presence of an alcohol source. The subject is of high topical importance given the current context/urgent need to develop to develop mild and non-toxic methods for chemical recycling of waste polyesters. The study is well carried-out and the results well-exposed showing that simple commercial precursors may reveal of interest for polyesters degradation. Publication in Catalysts is strongly advised, essentially as is. The following very minor points should be fiwed:
- Both tables 1 and 2 include a “[b]” superscript but the authors forgot to include its description
- Are the alcoholysis depolymerization reactions of PLLA free of any epimerization side-reaction? Metal amido/alkoxide may potentially deprotonate the beta-CH group of the coordinated PLLA (depicted in scheme 3)
- There are some typos, but they may be corrected at the editing stage.
Author Response
1 Both tables 1 and 2 include a “[b]” superscript but the authors forgot to include its description
Answer: The note for superscript b was added in the Table caption.
- Are the alcoholysis depolymerization reactions of PLLA free of any epimerization side-reaction? Metal amido/alkoxide may potentially deprotonate the beta-CH group of the coordinated PLLA (depicted in scheme 3)
Answer: To exclude the presence of epimerization side-reactions, ethylactate samples were analyzed by optical rotation measurements in methylene chloride. The [α]D 25 values were coherent with the commercial ethylactate.
- There are some typos, but they may be corrected at the editing stage.
Answer: The whole manuscript was carefully checked for removing typos.
Round 2
Reviewer 1 Report
The revised manuscript is all right for being accepted.
