Hydrodeoxygenation–Isomerization of Methyl Palmitate over SAPO-11-Supported Ni-Phosphide Catalysts

Round 1

Reviewer 1 Report

Shamanaev and coauthors employed the SAPO-11-supported NiP catalysts for the hydrodeoxygenation-isomerization of methyl palmitate. Some parts need to be taken into consideration to enhance the quality of the MS as follows:

1. It is necessary to evaluate the stability of catalysts towards the hydrodeoxygenation-isomerization of methyl palmitate through the reusability and the regeneration catalyst study
2. The author mentioned that the surface area of the NiP catalyst had a low surface area due to pore blocking. How does the author prove this presumption? More characterization regarding the spent catalyst must be conducted.
3. It is necessary to report the yield of the hydrodeoxygenation-isomerization product.
4. It is necessary to propose the mechanism reaction regarding the hydrodeoxygenation-isomerization of methyl palmitate
5. The N2 adsorption-desorption curve was missed. It is necessary to add those curves and elaborate it in order to understand the textural properties of the catalyst.
6. Why does the author only report the selectivity of C-15 and C-16? How about the lower range C fraction? The chromatogram of the product needed to be shown.
7. Why does the author use transitional metal phosphide, whereas there also exist such as transitional metal nitride, and transitional metal sulfide. Refer to this article: http://dx.doi.org/10.1039/D2RA02438A and https://doi.org/10.1039/D2RA03941A
8. The explanation regarding the nickel-phosphate catalysts is insufficient. Refer to this article: https://doi.org/10.1021/acsomega.2c04647

Author Response

We are grateful to the reviewers for reading and evaluating our work.

Please find attached our answers.

 

Answers to the Reviewer 1

1. Q: It is necessary to evaluate the stability of catalysts towards the hydrodeoxygenation-isomerization of methyl palmitate through the reusability and the regeneration catalyst study

A: Ni-phosphide catalysts proved to be stable during 8-9 hours of time on stream without any loss of activity. Conversion and selectivity vs time on stream graphs are added to the Supplementary material.

2. Q: The author mentioned that the surface area of the NiP catalyst had a low surface area due to pore blocking. How does the author prove this presumption? More characterization regarding the spent catalyst must be conducted.

A: The S_BET after phosphide preparation was ~20 m²/g. After reaction S_BET decreased to ~5-8 m²/g. The data are provided in Supplementary material.

3. Q: It is necessary to report the yield of the hydrodeoxygenation-isomerization product.

A: Done for NiP_A catalysts with different Ni/P ratio tested at 290 °C. For the other experiments the temperatures were higher 340-380 °C, and X_MP was 100%. So the selectivities were equal to the yields. We added this to the manuscript.

4. Q: It is necessary to propose the mechanism reaction regarding the hydrodeoxygenation-isomerization of methyl palmitate

A: Done.

5. Q: The N₂ adsorption-desorption curve was missed. It is necessary to add those curves and elaborate it in order to understand the textural properties of the catalyst.

A: The isotherms are quite similar and it is difficult to understand differences between the support and catalysts. Thus, we added pore diameter distributions to the Supplementary material.

6. Q: Why does the author only report the selectivity of C-15 and C-16? How about the lower range C fraction? The chromatogram of the product needed to be shown.

A: Lower range C fraction (C6-14) was also detected over several catalysts The amount of cracked products are shown on Figures 5 and 7. The chromatograms are added to the Supplementary material. Unfortunately it is not possible to determine the amount of individual compounds like C6, C7 and so on, because solven (n-dodecane) also cracks and contributes to cracked products. We can only calculate the total amount of cracked products based on the mass-balance.

7. Q: Why does the author use transitional metal phosphide, whereas there also exist such as transitional metal nitride, and transitional metal sulfide. Refer to this article: http://dx.doi.org/10.1039/D2RA02438A and https://doi.org/10.1039/D2RA03941A

A: Done. Phosphide catalysts and especially Ni phosphides are among the most active in hydroprocessing and HDO.

8. Q: The explanation regarding the nickel-phosphate catalysts is insufficient. Refer to this article: https://doi.org/10.1021/acsomega.2c04647

A: Done.

Reviewer 2 Report

Nickel phosphide catalyst on SAPO-11 was synthesized by temperature programmed reduction (TPR) method and liquid phosphating method. The catalysts were characterized by ICP-AES chemical analysis, N2 physical adsorption, NH3-TPD, XRD and TEM. The effects of preparation methods and conditions on the one pot hydrogenation of methyl palmitate were studied. It was found that the properties of precursors and the amount of phosphorus strongly affected the activity, surface area and acidity of the catalyst. Isomerization only occurred at low phosphorus content (Ni/P=2/1). At higher phosphorus content, unreduced phosphate would block SAPO-11 channel and could not obtain isoalkanes. The experiments on liquid phosphating samples in a continuous flow reactor also showed that the activity was closely related to the phosphating duration and nickel content. The 7% Ni2P/SAPO-11 catalyst prepared by liquid phosphating method can obtain the highest isomerization product yield. The manuscript is very meaningful. The manuscript is well written, the data is detailed, the chart is clear, and the analysis and explanation are reasonable. However, the manuscript still needs to be improved.

1. In the preparation of the target catalyst, the characterization of the target catalyst by the author is not enough to ensure the catalyst yield and purification.

2. How to control the purity and yield of catalysts obtained by (TPR) method and liquid phosphating method?

 3. The influence of catalyst and residual substances on catalytic efficiency during synthesis should be clearly clarified.

Author Response

We are grateful to the reviewers for reading and evaluating our work.

Please find attached our answers.

Answers to the Reviewer 2

1. Q: In the preparation of the target catalyst, the characterization of the target catalyst by the author is not enough to ensure the catalyst yield and purification.

A: The aim of this work was to screen catalysts in autoclave reactor and continuous-flow reactor, to find the most promising candidates and to investigate their physicochemical characteristics. The most promising NiP_P samples were analyzed by XRD and TEM. These methods show presence of Ni₂P particles on SAPO-11 surface. X-ray diffractograms contain signals of SAPO-11, Ni2P and AlPO₄. AlPO4 signals have low intensity and according to TEM there is very small fraction of AlPO4. So, we think that Ni2P/SAPO-11 catalysts prepared by this method are quite pure.

2. Q: How to control the purity and yield of catalysts obtained by (TPR) method and liquid phosphating method?

A: The phase purity for liquid phosphidation method was checked by XRD and TEM methods. 3 wt.% NiP_I TPR catalysts did not show any reflexes in XRD (Figure S1). Probably due to small particle sizes. The TPR catalysts with higher Ni content were not analyzed by these methods because they show low or no isomerization activity.

3. Q: The influence of catalyst and residual substances on catalytic efficiency during synthesis should be clearly clarified.

A: In case of phosphidation method the catalysts were thoroughly washed by solvent flow (n-dodecane) to completely remove PPh₃ and P-containing residual compounds. The TPR catalysts did not need such washing after reduction in hydrogen flow at high temperatures.

 

Round 2

Reviewer 1 Report

The authors have addressed the comments adequately.

Reviewer 2 Report

The authors have considered all my comments and revised the manuscript carefully. It can be accepted for publication as it is.