Thermogravimetry Applied for Investigation of Coke Formation in Ethanol Conversion over Heteropoly Tungstate Catalysts

Round 1

Reviewer 1 Report

COMMENTS

·       Page 2, line 42: says Cs2.5PW has a higher specific surface area (SSA). Line 44 says it has a small SSA. Which one is correct?

·       The aim of the study is unclear. Is it to examine the thermal stability of coke or the catalyst

·       In Page 5, line 160: SA of Cs2.5PW is mentioned as 105 m2/g. In the next sentence, it is mentioned as 130 m2/g. Which one is correct?

·       Table 2 shows Ethanol conversion, ET, and DEE selectivity at 200 ℃. What is the ET selectivity corresponding to the conversion of ethanol in Figures 4 and 5 at 300 ℃

·       Page 8, line 300: It is stated that ethanol conversion has increasing values during the temperature increase from 200 to 300 ℃. But, figures 4 and 5 show a downward trend in that temperature range. How is it justified?

·       The ET selectivity values in the temperature range of 200 to 300 ℃ are not mentioned.

·       Figures 6, 7, 8 and 9: Please make a comparison with SBA-15 alone. Also, according to the plots, the mass loss % appears to be higher in the case of supported catalysts, especially for Cs2.5PW/SBA-15.

·       Figure 6 shows Cs and PdCs catalysts, while Figure 8 shows for PdCs/SBA and Pd/SBA. That does not give a clear picture of the coke formation on different catalysts.

·       Figure 8 caption: the catalysts mentioned in the figure caption are different from the ones shown in the plot.

·       The introduction section misses detailed discussion on the topic

Author Response

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Reviewer 2 Report

The manuscript showed the heteropoly tungstate catalysts are used for ethanol dehydration reaction, which is characterized by XRD, FTIR, N2 sorption, TPO, and TGA. The manuscript is well organized and written. The only question is why do authors choose SBA-15 as catalytic support, the author should be explain it. 

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Reviewer 3 Report

The current manuscript deals with the analysis of the catalytic activity in ethanol conversion, and the subsequent deactivation by coke formation, of heteropoly acid HPW based catalysts, doped with Pd and/or Cs and supported on SBA-15 zeolite. The analysis of coke-induced deactivation is carried out by means of TGA and FTIR characterization, with the aim to correlate the formation of hard and soft coke compounds with the Cs and Pd doping, as well as with the effect of the SBA-15 support vs the unsupported catalysts.

However, in this respect, the main points and results obtained by the authors appear to be lost among many characterization and activity tests results which contribute in making the discussion difficult to follow.

As a general comment, I would focus more on the TGA/TPO results of the supported catalysts in order to better highlight the conclusions and remark the significance of the present work.

In addition, there are several specific points that need to be considered and addressed:

1. In the abstract, TPO is reported with no explanation of the acronym.

2. In the introduction there are two contradictory statements (page 2, lines 42-44). This makes the goal of the work confusing.

3. Some references are missing in key points of the manuscript, see for example page 1 line 25, page 2 line 62, page 3 line 80.

4. Partially correlated with the above point, Figure 4 and 5 report the catalytic activity of the catalytic samples, supported or not. Pd-doped catalysts show a more significant deactivation trend, which is not commented in the text. This should be addressed or additional references must be included, if it is a previously known behavior.

5. The quality of the Figures could be improved for better understanding. For example, the different band frequencies in Figure 2 should be indicated for all catalysts, and also added in Figure 10; check Figure 3 for typos. Figures 4 and 5, and Figures 6-9, respectively, could be consolidated to aid the comparison between pure and supported samples.

5. The conclusions could be a little expanded for the sake of clarity.

Author Response

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Round 2

Reviewer 1 Report

accepted

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Reviewer 3 Report

I thank the authors for their efforts in improving the quality and understanding of the Figures, as well as for the inclusion of additional references which help the readers gain a wider background for the current studies.

I appreciate the changes done in almost all of my previous comments. 

Regarding point 4, which I report here again for the sake of clarity: "Partially correlated with the above point, Figure 4 and 5 report the catalytic activity of the catalytic samples, supported or not. Pd-doped catalysts show a more significant deactivation trend, which is not commented in the text. This should be addressed or additional references must be included, if it is a previously known behavior", what I meant is that beside highlighting this behavior, which is correctly reported by the authors, no hypothesis or explanation is proposed. It would have been a nice addition by the authors.

Nonetheless, I agree that the focus is the coke characterization by TGA analysis on the supported acids, which is sufficiently explained.

A minor point: in line 356, there are still references to the previous figure numbers (6 and 8, now 8 and 10). Please correct them.

Author Response

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