Synergy Effects of Cobalt Oxides on Ni/Co-Embedded Al2O3 for Hydrogen-Rich Syngas Production by Steam Reforming of Propane
Round 1
Reviewer 1 Report
This manuscript presents a detailed investigation into the structural and compositional causes of improved propane steam reforming over mixed Ni-Co-Al2O3 catalysts. They determine an optimal ratio of Al/Co = 1-2 at a set 10 wt% Ni based on XRD, TPR, XAFS, XANES, and activity measurements due to the formation of stable metallic Ni and Co clusters as well as spinel Ni and Co phases. I greatly appreciate the level of detail given by the authors in terms of the materials and activity characterization of their Ni-Co-Al2O3 catalysts. I find this manuscript thorough, well structured, and an intriguing and useful addition to the literature. Overall, I recommend that this manuscript be published with minor revisions in Catalysts. My minor comments are given below.
- The abstract should be improved by adding in key quantitative details from the text (e.g. conversion of optimal Ni-Co-Al2O3 compared to the support, XANES composition analysis of metallic Ni and Co and spinel phases).
- The grammar and writing need some revision. The manuscript at times is difficult to read.
Author Response
Reply to Reviewer(#1)’s Comments
This manuscript presents a detailed investigation into the structural and compositional causes of improved propane steam reforming over mixed Ni-Co-Al2O3 catalysts. They determine an optimal ratio of Al/Co = 1-2 at a set 10 wt% Ni based on XRD, TPR, XAFS, XANES, and activity measurements due to the formation of stable metallic Ni and Co clusters as well as spinel Ni and Co phases. I greatly appreciate the level of detail given by the authors in terms of the materials and activity characterization of their Ni-Co-Al2O3 catalysts. I find this manuscript thorough, well structured, and an intriguing and useful addition to the literature. Overall, I recommend that this manuscript be published with minor revisions in Catalysts. My minor comments are given below.
(Response) We appreciate the referee’s useful comments, and the manuscript was revised and brushed up as possible as we can to meet the referee’s comments as well.
(1) The abstract should be improved by adding in key quantitative details from the text (e.g. conversion of optimal Ni-Co-Al2O3 compared to the support, XANES composition analysis of metallic Ni and Co and spinel phases).
(Response) The superior activity and stability for the SRP reaction in terms of conversions and phases measured by XAFS and XRD and so on were added in the revised abstract part as follows. Key findings as well as phenomena for the enhanced catalytic performances were also clearly explained for readers to understand while reading the manuscript.
Abstract: Synergetic effects of Co oxides on the Ni/CoAl (NCA) catalysts were observed at an optimal molar ratio of Al/Co = 2 (NCA(2)) due to the partial formations of thermally stable spinel CoAl2O4 phases for steam reforming of propane (SRP). The optimal content of the spinel CoAl2O4 phases on the NCA(2) was responsible for the formation of the relatively active oxophilic metallic Co nanoparticles with smaller amount of less active NiAl2O4 on the surfaces by preserving relative amount of metallic Co of 68% and 52% in the reduced and used catalysts, which enhanced the catalytic activity and stability with the largest specific rate of 1.37 C3H8/(Ni+Co)h-1 among the tested NCA catalysts. The larger or smaller amounts of Co metal on the less active NCA mainly caused the preferential formation of larger aggregated Ni nanoparticles of ~16 nm in size due to their weaker interactions or induced the smaller formations of active metal phases by selectively forming the spinel NiAl2O4 phases with ~60 % in the NCA(4) resulted in a fast deactivation.
(2) The grammar and writing need some revision. The manuscript at times is difficult to read.
(Response) Some grammatical and typo-errors were corrected as possible as we can. The corrections and additions were highlighted by the function of “Track Changes” in Microsoft word as well.
Reviewer 2 Report
The overall study is interesting and well written.
Though a set of corrections is required. Firstly, the authors should improve their figures representation. They are using a group of figures and this creates a big problem during reading. They should break this group and use individual or at least 2 figures as a set. Next, the paper should conclude with a summary (conclusions). Why it is missing? Also, section 4 should be moved to the beggining.
Author Response
Reply to Reviewer(#2)’s Comments
The overall study is interesting and well written. Though a set of corrections is required.
(Response) We appreciate the referee’s positive comments, and the manuscript was revised as possible as we can to meet the referee’s comments as well.
Firstly, the authors should improve their figures representation. They are using a group of figures and this creates a big problem during reading. They should break this group and use individual or at least 2 figures as a set.
(Response) According to the referee’s comments, the Figure 1 was separated into new Figure 1 and Figure S1. In addition, the Figure 4 was also divided into two figures such as Figure 4 and Figure 5 for readers to understand easily. All figures in the revised manuscript were also numbered accordingly to meet the changed numbering of figures as well.
Next, the paper should conclude with a summary (conclusions). Why it is missing? Also, section 4 should be moved to the beginning.
(Response) The templates provided from Catalysts journal suggest the ‘conclusions’ section is not mandatory if the contents are included in the ‘discussion’ section. We briefly summarized and concluded our research by wrapping up the previously reported references with regards to the synergetic effects of the bimetallic catalysts. Section 4 is also recommended at the end of the manuscript. However, to meet the referee’s comment, we change the title of section 3 as “Discussion and Conclusions”.
Round 2
Reviewer 2 Report
No further changes are required.
