Egg-Shell-Type MgAl2O4 Pellet Catalyst for Steam Methane Reforming Reaction Activity: Effect of Pellet Preparation Temperature
Round 1
Reviewer 1 Report
This manuscript investigated the effect of calcination temperature on the SMR catalyst of egg-shell Ni/MgAl2O4 pellet. The results show that higher calcination temperature is advantageous for coke resistance. This topic is interesting for industrial catalysis. The manuscript could be published after addressing the following issues.
1. The introduction should be improved regarding the coke resistance literature.
2. In the introduction ,the authors mentioned that the commercial catalysts usually show the effectiveness factor of 0.03-0.07. Can the authors provide effectiveness factors of the investigated catalysts? which would dramatically improve the scientific soundness of this paper.
3. Can the authors provide more characterizations for the used catalysts? For example, the cross-sectional image, the surface area and pore structures, ect.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
1. H2/CO should also be reported.
2. Is the condition for the Com-Catalyst the same? The author needs to clarify the GHSV, using the mass of the catalyst or using the mass of Ni sites.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
In this manuscript, the authors demonstrated the preparation of egg-shell-type of Ni-MgAl2O4 pellet catalyst with different calcination temperatures and proved that optimum shell thickness showed superior activity and longer lifetime in steam methane reforming (SMR) reaction. However, the manuscript is lack of novelty and importance to the field as such material has been reported extensively for SMR reaction and the key finding in this manuscript is not sufficient and it requires additional experiments to showcase the significance of the content and improve the overall quality. I recommend rejecting this manuscript. The content in this manuscript is similar as one article that has been published in Catal. Today. 352 (2020): 157-165. The materials used in both articles are much analogous. The only key finding in this manuscript is the calcination temperature, which cannot support the novelty and importance as it is. Also, there are several minor comments that must be considered or addressed as well:
1. Line 80, the author mentioned MgO peak slight shifted to the right as an impurity in the material. Any reason to explain the peak shift. Also, is there a way to quantify the % of MgAl2O4 at different calcination temperatures shown in Figure 1 and 2?
2. Why the intensity of MgAl2O4 increases after the second calcination shown in Figure 2? Is this phase more thermodynamic favorable than MgO? In Figure 2, it would be better to add the XRD pattern of Sup-1173K as a baseline to compare with that in Figure 1?
3. In Figure 3, material in powder-type should be noted to check the shape effect as the SA and PV are too low to believe the accuracy of the data. Any hypothesis to support the loss of SA and PV after high-pressure tableting?
4. In Session 2.3.2, The author declared that the carbon deposition can break the catalyst pellet but samples with various amount of carbon deposits did not show significant difference in the methane conversion. Can author explain the reason behind this? Also, in the experiment session, the author did not write down the equation of activity calculation in SMR reaction? Please add. Also, the selectivity (or yield) should be addressed as well when discussing the catalytic data.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
The revised manuscript looks good to me.
