Effect of Basic Promoters on Porous Supported Alumina Catalysts for Acetins Production
, Gilberto D. Saraiva 2, Adriana Campos 3, Alcineia C. Oliveira 1,*, Rossano Lang 4, Larissa Otubo 5, José Jiménez Jiménez 6 and Enrique RodrÃguez-Castellón 6,*
Round 1
Reviewer 1 Report
In this work, Ni/Co loaded MgO, La2O3 or ZnO-γ-Al2O3 catalysts are prepared and characterized. And the catalytic performance of the catalysts for EG reaction were investigated as well. This is a meaningful work which would arouse widespread interest of researchers in the fields of energy production, green catalysis as well as the preparation of high value-added chemicals. Nevertheless, quality of the manuscript need to be further improved. I recommend to publish this work in Catalysts after a minor revision. Some comments are as follows:
1. The progress in acidity modulation of the catalysts for EG reaction should be reviewed in Introduction part.
2. What are the reasons for choosing MgO, La2O3 and ZnO as basic promoters? Some necessary description should be presented.
3. Figure 2 need to be modified well, some important information is missing.
4. NiMo catalysts or NiCo catalysts? Please confirm the description in Line 784.
Author Response
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Author Response.pdf
Reviewer 2 Report
The article is devoted to the development of catalysts for the esterification reaction of glycerol in the presence of acetic acid and the effect of adding the basic component on the performance. To confirm the structure of the synthesized catalysts, many different analytical methods were used, but I have a fairly large number of questions for the authors.
Introduction.
The introduction states that Al2O3 is usually used as a catalyst for the reaction of esterification of glycerol in the presence of acetic acid, but works devoted to Ni-/Co- modified catalysts are not covered. It is worth adding information about previous pappers on modified catalysts and catalysts with the inclusion of basic components. Also, what methods are commonly used to synthesize that type catalysts? Is the used sol-gel method developed by the authors for the synthesis of catalysts of this type or is it generally accepted?
Figure 1. It is better to represent the reaction in the form of a structural formula. The 3D format presented in the work is difficult to perceive.
Result and discussion.
Before describing the structural characteristics, it is necessary to write which catalysts are studied in this work, and what designations correspond to them. What is MA, LA, etc?
Figure 2 - the axes and the legend are truncated. The different arrangement of the spectra in Figures A and B, C significantly complicates the perception of information.
Is the XRD spectrum amplified for the LA sample only or for all samples?
Peak 2 theta = 67.1 (line 98) and peak 1041 cm-1 (line 163) are missed.
Figure 3. Ticks and y-axis values ​​are missed. Also, it's not clear why some graphs are inserted?
Table 1.
It would be better to add a mesopore volume column, as the meso-pores were targeted. Optionally macropore volume values can be added as well.
For the NiCo/ZA catalyst, the micropore volume is much larger than the total pore volume.
For an adequate comparison, the textural characteristics and acidity of the studied catalysts NiCo/LA, NiCo/MA, NiCo/ZA should be compared not only with γ-Al2O3, but also with impregnated NiCo/Al2O3.
Figures 4 and 5: There are (D) TEMs in the figure captions that are not shown in this figures. In addition, in the EDS and EDS mapping pictures, the same colors for the elements should be used, or at least they should be arranged in the same order, otherwise it is very difficult to compare catalysts.
Acid characteristics and textural characteristics are best broken down into two separate chapters.
Table 2. For all three catalysts, the total acidity is less than the sum of desorbed ammonia at three centers of different acidity. Possibly a rounding error.
It is worth adding the TPD spectra themselves, and not just their description.
There are two chapters 2.3 in the work .
Table 3. The sum of the selectivities of mono, di- and tri-acetins is 16-32%. What additional by-products with a selectivity greater than 50% are formed?
As with textural and acid properties, it would be interesting to compare the results not only with γ‑Al2O3, but also with impregnated γ-NiCo/Al2O3.
Figure 9a clearly depicts a gradual increase in the glycerol conversion with increasing reaction time for supported catalysts. Such effect is generally ascribed to the existence of more exposed Ni and Co sites on the support surface, resulting in a high aviability of the active sites to enhance the catalytic performance. - Inappropriate conclusion. It is possible that the concentrations of the components are far from equilibrium and with time the system approaches equilibrium.
Figure 9. Graphs are very difficult to read. In Figures (A) and (D) the selectivities of the formation of the various components are indicated by the same symbols, In Figure (B) the selectivity and yields are indicated by the same symbols.
Why is there duplication of the Y-axis in Figures (A) and (D), if scale divisions are the same?
In Figure (C), the top y-axis is redundant. Moreover, it has different tick marks from the bottom y-axis.
In Figure (D) the glycine conversion is over 60% for a number of points, while in Figures (A) and (B) the maximum conversion is less than 40%.
Figures (A) and (C) - The selectivity cannot be extrapolated to zero.
Figure (A) - At a number of points, the selectivity exceeds 100%. How is this possible?
The results shown in Figures (B) and (C) were obtained at what reaction time?
How long did the catalyst run with each use?Figure (D)?
Line 628. "conversion of catalyst" ?
How was the activation energy of the reaction calculated? (lines 670-672)
The activation energies of 29 and 70 kJ/mol are not "close".
Methodology.
Line 873. Are percentages by mass or by mole used in the selectivity calculation? In addition, the denominator is the sum of the percentages of products formed, which is always equal to 100.
In addition, a large number of questions on methodology were raised in the paragraph Result and discussion.
Author Response
Please, see the attached document
Author Response File: Author Response.pdf
Reviewer 3 Report
Major revision should be carried out on this manuscript before it can be considered for getting a publication in Catalysts.
1) The contents of the main text should be simplified, since it quite hard to get the main point of the research work.
2) To explain the relatively high stability of NiCo/MA, authors declare that “this could be an effect of the lattice oxygen species present in the spinel MgAl2O4 phase, acting as active components to improve the catalytic performance”. This explanation looks very strange since they did not answer the question directly. I suggest that more discussion involving the physicochemical properties of the representative catalysts should be provided for understanding why NiCo/MA has much better stability and recyclability.
3) Table 3 should be improved in order to show more useful information on the catalytic properties of the catalysts.
4) Figure 9 looks quite complicated, and the usage of the symbols is unclear,
5) Many typos and grammar mistakes are present.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Further improvement of the manuscript is still necessary due mainly to the following questions:
1) Authors still did not provide enough information on analyzing and discussing the main reason why NiCo/MA showed higher activity and stability than other supported catalysts. They just give very simple explanation without acceptable evidence and discussion, although the whole manuscript is really very long.
2) I agree with the opinion proposed by other reviewers that the comparison with NiCo/Al2O3 is significant, even more useful than that of NiCo/LA and NiCo/ZA catalysts. However, authors did not give a positive reply to this suggestion. I think authors could consider to focus their work on comparing the physicochemical properties (including catalytic performance) of NiCo/MA with that of NiCo/Al2O3. Other contents related to NiCo/LA and NiCo/ZA could be shorten or move to a document of ESI.
Author Response
Please, the enclosed file
Author Response File: Author Response.pdf
