Kinetics of Heavy Reformate Conversion to Xylenes over MCM-41 on Zeolite Beta Composite Catalyst
Round 1
Reviewer 1 Report
Kinetics of heavy formate conversion to xylenes considering dealkylation, disproportionation, isomerization, and transalkylation reactions in a batch fluidized reactor (riser-simulator). A composite catalyst composed of MCM-41 and zeolite beta with Mo incorporation was used. Experimental data were compared with a kinetic model. It is a good paper and reports valuable kinetic data. I have a couple of minor comments:
1. The reasons for the addition of Mo and the impregnation procedure should be described.
2. I recommend the addition of some more details of the experimental system, such as dimensions etc.
3. A deactivation function is included in the model, considering coke formation. I recommend inclusion of more information about the coke formation mechanism.
Author Response
Reviewer # 1:
Kinetics of heavy reformate conversion to xylenes considering dealkylation, disproportionation, isomerization, and transalkylation reactions in a batch fluidized reactor (riser-simulator). A composite catalyst composed of MCM-41 and zeolite beta with Mo incorporation was used. Experimental data were compared with a kinetic model. It is a good paper and reports valuable kinetic data. I have a couple of minor comments:
Response: The authors would like to express gratitude for the valuable comments.
- The reasons for the addition of Mo and the impregnation procedure should be described.
Response: As mentioned in the introduction (lines 32-34), that incorporation of a mild hydrogenating metal is reported to improve the overall transalkylation process. The bifunctional catalyst was prepared by loading the composite zeolite with 4 wt.% Mo via incipient wet impregnation method. The above sentence is included in the revised manuscript (lines 278-279). The details of impregnation procedure are not included in this manuscript because the paper is focused on the kinetic modeling. However, a reference to our recent paper is provided in which the details of catalyst preparation are published.
- I recommend the addition of some more details of the experimental system, such as dimensions etc.
Response: As recommended, additional details about the experimental system are included in the revised manuscript (Section 4.3, lines 307-314).
- A deactivation function is included in the model, considering coke formation. I recommend inclusion of more information about the coke formation mechanism.
Response: Some information and a reference about coke formation is added in the revised manuscript (Section 2.2, Lines 83-85).
Reviewer 2 Report
1. Page 2, lines 72-73: The authors are stating that “the catalyst possesses sufficient mesoporous volume and acidity required for heavy reformate conversion to xylenes”. Is there any data supporting this information? A reference or more arguments should be provided.
2. Page 8, line 240: The authors are mentioning that they obtained nanocomposites, but no analyses are provided in order to support this information.
3. The authors are mentioning (page 3, lines 92-99) that some of the chemical reactions could be thermodynamically limited. In order to assess this aspect, an equilibrium composition calculation in the working conditions should be provided.
4. Please improve the quality of Figure 3.
5. It is not clear which date are plotted in Figure 5.
6. How was the parameter l estimated? Please provide more details.
7. Page 6, line 197: The authors are stating that “The kinetic parameters should exhibit a low-interactions” but no information regarding this aspect is provided in the discussion section.
8. The conclusion section is poor. Also, a more consistent discussion section along with a comparison with other literature studies should be provided.
Author Response
Reviewer # 2:
- Page 2, lines 72-73: The authors are stating that “the catalyst possesses sufficient mesoporous volume and acidity required for heavy reformate conversion to xylenes”. Is there any data supporting this information? A reference or more arguments should be provided.
Response: Hierarchical composite zeolites, which has secondary porosity in the mesopore range (2-50 nm), facilitate access of larger reactant molecules to catalyst active sites while maintaining the acidity and crystallinity. Table 1 is added to the revised manuscript which presents the textural and acidic properties of the parent zeolite and the synthesized catalyst. The BET surface area and total pore volume of the parent zeolite in-creased by hierarchical pore generation. About 72% of the total porosity in the catalyst is in the mesoporous range that facilitates access of larger reactant molecules to catalyst active sites while maintaining the crystallinity. The total acidity of the catalyst, as determined by NH3-TPD, was 668 μmol/g. Hence, the catalyst possesses sufficient mesoporous volume and acidity required for heavy reformate conversion to xylenes. The above information is included in the revised manuscript (Section 2.1, Lines 69-75) and a reference about is also provided.
- Page 8, line 240: The authors are mentioning that they obtained nanocomposites, but no analyses are provided in order to support this information.
Response: The term ‘nanocomposites’ is replaced by ‘composites’ in the revised manuscript (Section 2.1, line 276) as further characterization will be required as proof.
- The authors are mentioning (page 3, lines 92-99) that some of the chemical reactions could be thermodynamically limited. In order to assess this aspect, an equilibrium composition calculation in the working conditions should be provided.
Response: The equilibrium composition of the alkylbenzenes under the reaction conditions was calculated and included in the revised manuscript (Section 2.2, Lines 102-106). It can be observed the reactions did not reach equilibrium and, under the process conditions, the reactions were within the kinetic regime.
- Please improve the quality of Figure 3.
Response: Figure 3 has been redesigned and its quality is improved.
- It is not clear which data are plotted in Figure 5.
Response: Figure 5 caption has been changed to make it clear that the plots show mass fractions of reactants and products.
- How was the parameter l estimated? Please provide more details.
Response: The method employed to estimate the kinetic parameters has been explained in Section 2.4.
“The kinetic parameters, incorporating the individual rate expressions and the catalyst deactivation expression, were evaluated by a least-squares fitting of the experimental data using MATLAB® software. The regression analysis was carried out by Levenberg-Marquardt algorithm, while the differential equations were numerically solved by making use of the Runge-Kutta-Gill method.”
- Page 6, line 197: The authors are stating that “The kinetic parameters should exhibit a low-interactions” but no information regarding this aspect is provided in the discussion section.
Response: The statement is deleted from the revised manuscript as we are not reporting the correlation matrix.
- The conclusion section is poor. Also, a more consistent discussion section along with a comparison with other literature studies should be provided.
Response: The discussion and conclusion sections have been revised and more comparison with the literature studies is provided in the revised manuscript.
Reviewer 3 Report
The manuscript titled " Kinetics of Heavy Reformate Conversion to Xylenes Over MCM-41 on Zeolite Beta Composite Catalyst"
In this manuscript, authors reported synthesis of MCM-41 on Zeolite Beta Composite Catalyst and its application as an efficient catalyst for the conversion of Commercial heavy reformate to xylenes. The results of this research are conveyed thoughtfully and completely, and they are consistent with the experimental findings. However, the authors failed to explain and draw out the novelty of the work, this aspect needs to be improved. This work is worthwhile to be publish in this journal after major revision. The following issues should be addressed:
1. Introduction is well-organized and well-written, but the importance and novelty of the research should be highlighted and more clearly stated. The authors give some examples of works in the bibliography, but which is the advantage of their work in comparison with those works.
2. In section 4.1, Please provide the purity and the origin of your chosen precursors.
3. In section 4.2, the conditions used for all characterization techniques should be added.
4. Why authors choose NaOH not NH4OH in the preparation of MCM-41? Can the author please explain in detail?
5. The authors should measure the by-products that produced after complete the catalytic activity if exists.
6. A more comprehensive background for applications of MCM-41 should be illustrated in the introduction for a wider readership. For example, some papers, which describe applications of MCM-41 should be cited https://doi.org/10.1016/j.colsurfa.2021.127753, https://doi.org/10.1016/j.colsurfa.2021.127261, International Journal of Modern Chemistry, 2013, 5(1): 55-70
7. The authors are responsible for the English, which should be polished throughout the manuscript to clear some minor typo/grammar errors.
8. Maybe the author should compare their results clearly with other reported works, highlighting the advantage and disadvantages of their novel composite.
9. Error bars need to be displayed for all experimental data in the graphs.
Author Response
Reviewer # 3: The manuscript titled " Kinetics of Heavy Reformate Conversion to Xylenes Over MCM-41 on Zeolite Beta Composite Catalyst" In this manuscript, authors reported synthesis of MCM-41 on Zeolite Beta Composite Catalyst and its application as an efficient catalyst for the conversion of Commercial heavy reformate to xylenes. The results of this research are conveyed thoughtfully and completely, and they are consistent with the experimental findings. However, the authors failed to explain and draw out the novelty of the work, this aspect needs to be improved. This work is worthwhile to be publish in this journal after major revision. The following issues should be addressed:
Response: The authors would like to express gratitude for the valuable comments.
- Introduction is well-organized and well-written, but the importance and novelty of the research should be highlighted and more clearly stated. The authors give some examples of works in the bibliography, but which is the advantage of their work in comparison with those works.
- Response: The authors would like to express gratitude for the valuable comments. The importance and novelty aspects are included in the Section 2.1 of the revised manuscript.
- In section 4.1, Please provide the purity and the origin of your chosen precursors.
Response: A new section (Section 4.1 Materials) is added to include the origin and purity of the precursors used for catalyst preparation.
- In section 4.2, the conditions used for all characterization techniques should be added.
Response: The conditions used for characterization techniques are added (Section 4.3).
- Why authors choose NaOH not NH4OH in the preparation of MCM-41? Can the author please explain in detail?
Response: Since NaOH is much stronger alkali than NH4OH, NaOH is used for disintegrating the zeolite Beta. As explained in our previous publication (Reference [12]), the strength of NaOH was varied to obtain different levels of zeolite disintegration. The catalyst prepared by using 0.2 M NaOH solution exhibited highest activity. Hence, its kinetic study is performed and it is being reported in this paper.
- The authors should measure the by-products that produced after complete the catalytic activity if exists.
Response: Complete product analysis shows formation of negligible amounts of benzene (<2 wt.%) and C1-C4 gases (<3 wt.%). Hence, the reactions that form benzene are not included in the kinetic model. All other unconverted reactants and products are presented in Table 2 and used in kinetic modeling.
- A more comprehensive background for applications of MCM-41 should be illustrated in the introduction for a wider readership. For example, some papers, which describe applications of MCM-41 should be cited. https://doi.org/10.1016/j.colsurfa.2021.127753, https://doi.org/10.1016/j.colsurfa.2021.127261, International Journal of Modern Chemistry, 2013, 5(1): 55-70
Response: As per the recommendation, two references are added as examples of applications of MCM-41.
- The authors are responsible for the English, which should be polished throughout the manuscript to clear some minor typo/grammar errors.
Response: The manuscript has been reviewed and typographical and grammatical errors are corrected.
- Maybe the author should compare their results clearly with other reported works, highlighting the advantage and disadvantages of their novel composite.
Response: The discussion and conclusion sections have been revised and the advantages of the novel composite catalyst in terms of characteristics and performance are presented in the revised manuscript.
- Error bars need to be displayed for all experimental data in the graphs.
Response: It is mentioned at the end of Section 4.4 that the reproducibility of experimental data is within ±2%. An attempt was made to draw error bars. However, error bars were too small and not noticeable. Hence, error bars are not included in the figures in which experimental data is presented (Figures 1, 2, 4 and 5). In Figure 6, however, the -lnk values were shown with error bars based on the 95% confidence limits of the estimated values of kinetic parameters.
Round 2
Reviewer 2 Report
The paper was sufficiently improved and it can be published in the present form.
Reviewer 3 Report
Accepted in the present form
