Influence of Y Doping on Catalytic Activity of CeO₂, MnO_x, and CeMnO_x Catalysts for Selective Catalytic Reduction of NO by NH₃

Round 1

Reviewer 1 Report

This paper presents the de-NO_x properties of CeO₂, MnO_x and CeMnO_x catalysts, and focus on the influence of yttrium doping by different methods. In spite of rare earth metals doped MnCe catalysts for NH₃-SCR was widely investigated, this paper reveals the different influences of yttrium doping and carried out enough experiments. Herein, the CeMnO_x catalyst exhibited excellent low-temperature de-NO_x than others and gave the related experiments to demonstrate, such as Raman spectra, H₂-TPR, NH₃-TPD, etc. Although there are some doubts about the negative effects of yttrium, the explanations of whole paper are clear and logical in general. For above comment, this work is recommended to be accepted after some advises. To further improve the quality of this paper, some detailed comments are as followings:

1.         There some format errors such as subscript in Abstract and extra spaces between numbers and Celsius symbols. Please check and correct carefully.

2.         This work introduced yttrium by two methods but catalysts both presented negative effective in NH₃-SCR of CeMnO_x. Please give more discuss about the influence of Y doping and different modified methods.

3.         In N₂ selectivity patterns, please give the reason of the improvement of N₂ selectivity by yttrium doping of these catalysts.

4.         There are doubts about the experimental conditions. The initial concentrations of NH₃ and NO are 800 ppm in Figure 7, which contradicts the description in section 3.3.

5.         The NH₃-TPD result is not persuasive and directly because it’s inconsistent with NH₃-SCR patterns. Please re-edit the pattern to show different desorption in different temperature and discuss.

6.         There are some inaccurate descriptions in conclusion part because the yttrium didn’t improve the activity of MnO_x and “NH₃ conversion” should be “NO conversion”.

7.         Some new published papers about this topic should be cited and referred, such as “Journal of Environmental Chemical Engineering, 2022, 10: 108239; Journal of the Energy Institute, 2022, 105:114-120, etc ”.

It can be further improved.

Author Response

Dear reviewer, we are very grateful for the suggested revisions. Details are reported in the attached file. 

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper provides useful information on Influence of Y-doping on the catalytic activity of CeO2, MnOx2 and CeMnOx catalysts for ammonia-SCR applications in NOx removal from flue gas.

This work is very interesting in the field of NOx emission control from flue-gas. For this reason, it would deserve chances at publication in this Journal but provided that the authors solve some minor points, which I list in detail below.

 

1. Introduction

Although NOx emissions are a problem related to transport as road vehicles, a big impact is also given by maritime transport which in recent years has released a series of regulations dedicated to NOx in some geographical areas which go under the name of NECA (https://doi.org/10.1007/s11804-021-00213-2).

Furthermore, another relevant contribution is given by the industrial activities that currently already adopt SNCR and SCR systems to contain NOx emissions.

I suggest that authors take into account these other two important sources of emission in the introductory section, adding some references.

Furthermore the authors should report a complete overview for the state of the art on NOx capture systems. Before discussing SCR and NSR systems which are well-known and mature technologies in industrial and transportation fields, the authors may mention some of the most emerging technologies for NOx control.

For example, authors should consider these references that report the use of technologies, such as:

-          Electron Beam Processes (https://doi.org/10.1016/S0969-806X(02)00340-7);

-          Low-Temperature Adsorption (https://doi.org/10.1038/s41598-021-90532-9) or

-          Wet Oxidative Scrubbing (https://doi.org/10.3303/CET2186067), which is also capable of simultaneously control of NOx/SOx emissions (several works are available in the pertinent literature).

However, these technologies are currently limited by energy consumption or wastewater treatment costs so further investigations should be done to make them as mature as SCR technologies which currently still find wide applicability in these sectors..

 

2. Results

Have the authors also investigated the reproducibility of their data? Probably plots with error bars should be reported, or at least a discussion should be made in the text if the uncertainties are low and barely visible in the plot.

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Author Response

Dear reviewer, we are very grateful for the suggested revisions. Details of all the changes made are reported in the attached file

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The revised manuscript can be accepted.