Efficient and Stable Ni/SBA-15 Catalyst for Dry Reforming of Methane: Effect of Citric Acid Concentration

Round 1

Reviewer 1 Report

The manuscript is well prepared with full and relieble characterization results. The catalyst shows high activity and stability in DRM. The effect of citric acid on the despersion of Ni is interesting, however, the coordination of Ni2+ by citric acid as precursor is unclear and some in situ imformation is required.

Line 140 and 143, "spectra" cannot link with XRD.

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Reviewer 2 Report

1.       The introduction contains no numerical information about the results obtained in this study. Please bring the main results in terms of catalyst efficiency in the abstract.

2.       The novelty of this study is not emphasized in the Introduction part in respect to the state of the art.

3.       The surface area and pore volume of pure SBA-15 support should be given in Table 1

4.       TEM images in Figure 2 should be given at the same magnification if the aim is to compare them.

5.       The influence of the operating parameters on the catalytic activity (reaction products yields, conversion) should be studied and the results presented in the manuscript.

6.       A comparison of the catalytic activity with the same catalyst published in the literature should be provided.

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Reviewer 3 Report

This work is devoted to the effect of citric acid additions on the Ni dispersion in the impregnated Ni/SBA-15 catalysts and their activity in the DRM reaction. It was clearly shown that the introduction of citric acid at the stage of nickel impregnation leads to increased metal-support interaction, higher dispersion of nickel particles, higher catalytic activity and less carbon formation however it should be added in the optimal concentration. The work can be published after minor revisions.

- L.37-38 - “…to produce the syngas (CO2 + CH4 → CO + H2)” - reaction coefficients in products are missing.

- L. 45-49 – There are two almost identical sentences.

- L. 42 – “mounted on the Al2O3, SiO2, CeO2, ZrO2, and TiO2 [1, 4-9]” - most links are dedicated to MgAl2O4 spinel, add links to catalysts based on other supports.

- L. 135-139 – the description of the citric acid effect is better to be transferred to the introduction.

- L. 298 – “ascribed to metallic Ni [17, 24]” – but both papers are not about Ni.

- Add description of hydrogen chemisorption experiments to 2.2. Catalyst characterization.

- Why do you use such low temperature (400C) for calcination after Ni impregnation? Did you check that all the organic matter burned out at that temperature?

- Do you have explanation, why Ni particle size estimated from H2 chemisorption decreased with citric acid concentration as opposed to microscopy results?

- Have you measured the pH of the impregnating solution without citric acid and with different citric acid content? Could it be that its effect is associated with change in the acidity of the solution, and not with chelation?

There are some mistakes, minor editing of English language is required.

Author Response

Thank you for valuable comment.

I attached a file on this website.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Paper improved.