Reduction of Typical Diesel NOx Emissions by SCR-NH₃ Using Metal-Exchanged Natural Zeolite and SBA-15 Catalysts

Round 1

Reviewer 1 Report

The article presents results of research on different type catalyst for SCR method for diesel engine conditions. Researchers made structural and NOx reduction potential tests for catalyst made on the basis SBA-15 and CLIN zeolites doped with Cu and Fe. Results of the tests were compared with literature data and vanadium-based catalyst normally used in diesel engine SCR systems. Findings presented in article are curious and match scope of journal. There is the list of suggestions to improve article quality:

1. Point 2.1 information about purity of used chemicals should be added to this paragraph.

2. Section 3 should be divided for subsections. There are only one subsection 3.1  and all results were described as “ XDR and FTIR Structural characterization” but in this section other test were described eg NOx reduction efficiency tests.

3. Symbols used at table 1 should be described in text or after the table. Maybe authors may consider addition of aberration list at the beginning of article ?

4. Why at figure 7 there is no results for CATCO catalyst as reference study ?

Best regards for Authors

Author Response

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Reviewer 2 Report

The manuscript (air-2312983) described an interesting metal exchanged natural zeolite for the de-NOx reaction. I think the topic is important and the developed catalyst showed a promising catalytic performance. To make it more publishable, the followin comments should be addressed. 

1. The font size is not uniform in the manuscript, please modify that.

2. Please pay attention to the format of the horizontal axis in Fig.1 and make modifications.

3. Please make more introduction of the physichemical properties of clinoptilolite, so as to exhibit the superiority of this material.

4. Please specify the meaning of dhkl, a0 in Table 1.

5. Why Fe-CLIN has a better hydrothermal performance than that of Cu-CLIN?

6. The following manuscript are suggested for the citation: Applied Energy 86 (2009) 2283–2297, Nano Research, 2022, DOI: doi.org/10.1007/s12274-022-5250-1

 

Author Response

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Reviewer 3 Report

Exhaust gases from a diesel engine depend on a multitude of engine operating conditions. The presented experimental setup demonstrates that the authors do not know how a diesel engine works. 

This manuscript does not have an appropriate title and the keywords are not correct. 

Many references are missing.

Author Response

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Reviewer 4 Report

 

 

Journal: Air

Manuscript ID: air-2312983

Type of manuscript: Article

Title: Reduction of NOx Emissions from Diesel vehicle by SCR-NH3 using
Metal-Exchanged Natural Zeolite and SBA-15 Catalysts 

Authors: Amanda Pontes Maia Pires Alcantara, Mona Lisa Moura de Oliveira *,
Jesuína Cássia Santiago de Araújo, Rinaldo Dos Santos Araújo, Rita
Karolinny Chaves de Lima, André Valente Bueno, Maria Eugênia Vieira da
Silva, Paulo Alexandre Costa Rocha *, Enrique Rodriguez-Castellón

 

Reviewing report

 

The manuscript presents various data on NH3-SCR of NOx using clinoptilolite (CLIN) and SBA-15 catalysts doped with Fe and Cu. The CLIN and SBAs based catalysts were prepared respectively by impregnation and ion exchange methods. Their activities were compared with a standard diesel vehicles commercial  V2O5/WO3/TiO2 catalyst.      

Deactivation was followed with testing the catalysts during a time on stream of 10 h with checking the effects of sulfur and steam.  The authors based their characterization on structure using  XRD and FTIR, texture using N2 adsorption and surface acidity using IR analysis of adsorbed pyridine as probe molecule.  

 They concluded the Cu-doped samples showed better NO conversion values than Fe-doped samples. Clinoptilolite catalysts were more active than those based on SBA-15.

 

 This paper contains in its major experimental work, structure and intrinsic properties of the catalysts prepared. Catalytic activity is well addressed. However, I have some main concerns with this manuscript that need to be clarified before being considered to be published.

  1-     What is the exact role of NH3 in the SCR process based on the surface acidity elucidation? 2-     In this process there is a complicate issue to explain, reducing process in an excess of O2, in various windows of temperature? 3-     Stability should be discussed with much attention. The surface must be checked before and after the catalytic tests. The dispersion of Cu and Fe must also be determined.   4-     Analysis of active surface - There is no convincing evidence for the chemical state of copper and Iron during the reaction and the role of catalyst sites in the NH3-SCR process. Further comparison should be made using in situ monitoring techniques such as DRIFT-MS. separately check the catalysts with SO2 and H2O then successively in alternate regime and simultaneously. - - This approach must be followed for the deactivation process in the presence of sulfur and steam, we do not know anything and what happens on the surface. -  Did the authors try using N2O by re-reducing the catalysts after N2O adsorption, this will allow the copper coverage to be calculated; and use another probe molecule like CO or H2 for Fe - It is strongly recommended to exploit surface analyzes with more appropriate way  

Surface acidity is not addressed to explain the NH3-SCR mechanism. The redox behavior of catalysts is a crucial problem for a process like SCR, I encourage authors to develop this part.

 

 

Finally,

 

-         Your literature review needs improvement by expanding and diversifying it. Many articles published very recently on NH3-SCR using acidic catalysts have not been addressed.

 

-        In my opinion, the manuscript as it is proposed in this work is interesting but not sufficiently developed.

Author Response

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Reviewer 5 Report

The authors present the use of natural zeolite (CLIN) for ammonia SCR applications, with and without functionalization by metals such as Cu and Fe. Their structure and catalytic activity is presented in comparison with other standard zeolites (such as SSZ-13 and SBA-15) as well as a commercial CATCO catalyst. The structure of the natural zeolites after metal addition and their performance in the decomposition of NOx is well elucidated, and it is of interest for the readers. However, the comparison with the standard materials is poor and difficult to understand, despite it being also the focus of the study. Therefore, I recommend publication after the authors address the following issues:

1. Table 1: how is Dp of the materials calculated? There is no explanation in the table description, text, nor in the experimental section.

2. The Section 3.2, Textural properties and acidity, ends up including reactivity data as well. This is confusing for the reader; a separate catalytic activity section should be included.

3. In addition, reference CATCO sample is included in Py adsorption data (Figure 5) and in the following activity results, but no additional textural information is given on the sample. Perhaps, some data can be added as supplemental info, as it might be useful to compare it with the CLIN and SBA supported catalysts of the study.

4. The discussion section is not clear. Literature results on SSZ-13 are quickly summarized but not clearly compared to the present study, except for conversion values in Table 3. As this is the main object of the paper, I feel that more attention should be paid to the comparison with literature/standard materials results.

Other minor issues include:

5. Figure 2 description has inverted reference (a, and b) for SBA and CLIN samples.

6. Figure 3 graphics should be improved, e.g. fixing abscissa graduation steps and font size.

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Round 2

Reviewer 4 Report

The authors did a significant improvement compared to the original DRAFT. Some aspects are missing, in particular,  surface analysis, I hoe for the next paper they will do better. 

Reviewer 5 Report

The authors have appropriately amended the discussion to include all comments and issues raised by the reviewer(s), significatively improving the quality of the work as well as the clarity for the readers. In my opinion, the manuscript is now suitable for publication.