Biofuels of Green Diesel–Kerosene–Gasoline Production from Palm Oil: Effect of Palladium Cooperated with Second Metal on Hydrocracking Reaction
Round 1
Reviewer 1 Report
This work addresses the preparation of different Pd-Fe/Al2O3 catalysts for the production of bio-fuels from palm oil via a hydrocracking reaction. The idea is interesting, however the design, experimental procedure and quality of the manuscript in terms of presentation and discussion of the results, are not sufficiently good for publication. More detailed comments are given below.
The feedstock (palm oil) characterisation by means of chemical composition and/or fractional distillation is not provided. The products characterisation is not sufficient, as the chemical composition should be provided. The discussion of the results is very weak. The operating conditions used in the experiments are not clear. Table 2 and the conclusions indicate that an initial pressure of 40 bar and a reaction time of 1 h were used, while lines 240-241 indicates that the reactions were conducted using an initial pressure of 60 bar for 2 h. There are many English mistakes throughout the manuscript.Author Response
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Reviewer 2 Report
The manuscript of Pakawadee Kaewkannetra (Biofuels of green diesel-kerosene-gasoline production from palm oil: Effect of palladium cooperated with second metal on hydrocracking reaction) reports the influence of synergetic behavior of Pd-Fe active phase applied for biofuels production in terms of green diesel-kerosene-gasoline from palm oil via hydrocracking reaction. However, many sentences are not well explained.
The authors should consider the following points:
The authors did not give the surface area BET of the support – Al2O3. How does it change after introduction of the active phase (Pd and PdFe). How does the porosity change - authors should compare pore size distribution of catalysts with support if they write about micro- and mesopores structure – page 3, line 99. What is the real metal loading? Authors did not present any ICP or XRF results concerning the practical composition of the prepared samples. Page 3 lines 107-108 – Authors write – “…SEM images of synthesised catalysts were exhibited small particles of metal distribution on surface area of the catalyst as well as on supporting material …” - was the size of Pd and Fe crystallites determined? The quality of SEM images (Figure 2) is not enough to see Pd or Fe crystallites. The TEM or H2 chemisorption have not been used to study the particle size of the catalyst. In my opinion it is a very important parameter describing catalysts especially if authors compare the hydrogenation activity. Authors must solve this problem. The authors have presented catalytic activity and textural properties of the palladium and Pd-Fe bimetallic catalysts. It would be interesting for the reader to see also the activity and textural properties of 0.5%Fe/Al2O3 catalyst. What grounds have the authors to claim that “…It was due to loading Fe could increase acidity and active site of catalyst resulting in high catalytic efficiency of catalyst …” 5 lines 125-127. ” - did the authors determine the acidity of the surface – NH3-TPD for example? How the acidity of the support surface (Al2O3) changes after the introduction of active phases? Authors must solve this problem. The reference [25] concerns Co-Fe catalysts supported on SiO2 not Al2O3. The discussion of the catalytic performance must include information related to carbon balance, stability of catalysts, conversion and selectivity values, among others. In this sense, the physico-chemical characterization of used catalysts should be carried out. Otherwise, the explanation of the catalytic results would be too descriptive. Did authors perform any repeat experiments to see the reproducibility of activity experiments? Authors must solve this problem. Do authors have any reasonable explanation for the observed synergistic effect in the PdFe catalysts? Finally, some mistakes/errors can be found along the text. For example: - page 8, line 175 – “…the results showed in Table. 1, both Pd monometallic…” – Table 1 present “Physical properties of catalysts…”; Table 2 is twice – pages 5 and 9; p.10 line 252 should be diesel not “deisel”; Figure 6 – hydrodeoxygenation path – C17 to C18?.Author Response
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Reviewer 3 Report
This manuscript adresses an interesting process that allows obtaining biofuels without generating glycerin. Since the experimental work, its discussion and teh results obtained are adequate, the manuscript can be accepted for publication.
Author Response
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Round 2
Reviewer 1 Report
The authors have addressed the vast majority of the reviewers' comments and the manuscript has been substantially improved. However, there are many English mistakes, including typographic errors and grammar issues, which must be amended before this work can be published.
Author Response
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Reviewer 2 Report
After revision, authors have added some information and improved the quality of the paper by following most of comments and suggestions. Nevertheless, remarks (1), (2), (3) and (4) remain unanswered and need further explanations and/or modifications in the text by the authors.
1. The authors did not give the surface area BET of the support – Al2O3. How does it change after introduction of the active phase (Pd and PdFe). How does the porosity change - authors should compare pore size distribution of catalysts with support if they write about micro- and mesopores structure – page 3, line 99.
Authors' response: We have given more details for how the surface area BET of Al2O3 support changed into the Section 2.2 in Table 2. and Figures 2-3. The porosity of supporting material has been changed after loading high palladium and it caused metallic agglomeration as well as the addition of Fe also has an effect for both specific surface area and reduce metallic particles.
New Reviewer comment: Unanswered.
The authors did not provide any additional information how the surface area BET of Al2O3 support changed. Section 2.2 in revised manuscript is the same as in the previous work.
2. What is the real metal loading? Authors did not present any ICP or XRF results concerning the practical composition of the prepared samples.
Authors' response: We have presented XRD results which indicated the composition in each prepared catalysts replacing for the ICP and XRF results.
New Reviewer comment: Unanswered.
The XRD method allows to identify a crystalline structure of catalysts but it cannot determine the real composition of the sample. What is the real content of palladium and iron in the sample?
3. Page 3 lines 107-108 – Authors write – “…SEM images of synthesised catalysts were exhibited small particles of metal distribution on surface area of the catalyst as well as on supporting material …” - was the size of Pd and Fe crystallites determined? The quality of SEM images (Figure 2) is not enough to see Pd or Fe crystallites. The TEM or H2 chemisorption have not been used to study the particle size of the catalyst. In my opinion it is a very important parameter describing catalysts especially if authors compare the hydrogenation activity. Authors must solve this problem.
Authors' response: We have used SEM technique to observe metals dispersion on surface area of catalyst. The pore diameter in each catalyst was reported in Table 2. We have provided more high magnification of SEM images (1200 dpi) We haven’t used the TEM of H2 chemisorption. Since, these techniques could know more the torturous path of inside the catalyst that we think it was not necessary. However, we have used SEM and BET techniques to characterise pore size pore diameter and pore volume which refer to their structure and can be enough used to describe their catalytic efficiency. Furthermore, particle size of mesoporous Al2O3 supporting material has been given in materials and methods.
New Reviewer comment: Unanswered.
The SEM technique does not allow to determine the size metal crystallites and dispersion. Authors must provide the adequate evidences of the Pd and Fe particles existence.
4. The authors have presented catalytic activity and textural properties of the palladium and Pd-Fe bimetallic catalysts. It would be interesting for the reader to see also the activity and textural properties of 0.5%Fe/Al2O3 catalyst.
Authors' response: We have given more information about the catalytic activity of Fe/Al2O3 catalyst in Table 3.
New Reviewer comment: Unanswered.
Table 3 in revised version is the same as in the previous work. I don't see any additional information about the activity of Fe/Al2O3 catalyst.
Author Response
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Round 3
Reviewer 2 Report
The manuscript can be accepted for publication.
