Selective Synthesis of 1,4-Dioxane from Oxirane Dimerization over ZrO2/TiO2 Catalyst at Low Temperature
Round 1
Reviewer 1 Report
This work is devoted to the catalytic synthesis of 1,4-dioxane. This article discusses a selective mechanism for the production of 1,4-dioxane with a ZrO2/TiO2 catalyst at Low Temperature. This topic is relevant, since the use of this solvent in various processes is growing every year. The advantages of 1,4-dioxane are lower toxicity compared to pyridine (one of the most common solvents in organic synthesis). This work is "in the trend" of this kind of research. Despite this, there are some shortcomings that it is desirable to eliminate:
1. Introduction. When describing the importance of 1,4-dioxane it is necessary to add specific applications. Please cite: 10.1016/j.molstruc.2021.131083.
2. Also in the introduction, it is desirable to describe in more detail the various production methods and characteristics of the ZrO2/TiO2 catalyst. You can quote here: https://doi.org/10.1021/acsanm.0c00346, https://doi.org/10.1021/acs.iecr.0c03605, 10.1007/s10853-005-1116-7.
3. Unify the drawings.
4. Figure 3. quality needs to be improved.
5. Equation (1) lacks 100% multiplication.
6. equation (2). "Yield" practically does not appear in the text and tables. Refine it.
7. It is desirable to compare the characteristics of the obtained catalysts with the literature data in more detail.
8. In general, it is desirable to increase the number of references to the literature in the text for greater validity of the conclusions.
9. Table 2. What causes lower conversions at high GHSVs?
10. Table 4. With increasing duration, selectivity for 1,4-dioxane increases, this is logical and beyond doubt. BUT why then the conversion decreases?
11. What is the accuracy when choosing the conversion and other parameters of your reaction?
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this manuscript submitted by Wang et.al., authors prepared mixed metal oxide of ZrO2/TiO2 through coprecipitation, and studied its catalytic performance for oxirane dimerization. Overall, this work extends the potential applications of ZrO2/TiO2 by further utilizing its Bronsted and Lewis acidic properties, and can be of interest to the field of heterogeneous catalysis. However, some revisions are needed to meet the publication standard of Catalysts.
About the references:
ref 7, the correct patent number is KR20220023139A
Some references, including ref 11, ref 12, ref 21, cannot be easily traced. In order to allow the readers to gain easy access to help to understand the research context, I recommend adding the doi to these references.
About the main text:
In section 3.1., the first paragraph, there aren’t changes in the oxidation state from zirconium hydroxide and titanium hydroxide to zirconium oxide and titanium oxide, so they are not reduced during the calcination. The term decomposition or dehydration would be more appropriate.
From the TEM images, it appears that the particle sizes of TiO2 and ZrO2 are much smaller than 25%ZrO2/TiO2. But in Table 2, the surface area of 25%ZrO2/TiO2 is much higher than TiO2 and ZrO2. This doesn’t agree very well. Are the TEM sampling areas representative under the microscope? SEM images need to be provided to show more about the particle morphologies.
In section 3.2., the authors should provide references for all the IR wavenumbers showing different NH3 adsorbed species. Also, the experimental details about NH3 adsorption should be provided. Since the Bronsted and Lewis acidic sites play different roles in oxirane dimerization, then it is important to showcase the Bronsted and Lewis acidic sites densities respectively to demonstrate the synergistic effects between them. This data can be added to Table 1, and the related discussion section needs to be expanded.
In section 2.4., authors mentioned that “The reactor was heated to several temperature points (50, 60, 70, 80, 90 °C) with different pressure (0, 0.1, 0.2, 0.3, 0.4 MPa).”, which is different from the actual temperatures shown in Table 3, what are the actual temperatures for the catalytic testing?
Authors propose the detailed reaction mechanism in section 3.4., though there are no cited references or further evidence provided, an IR study of gaseous ethylene oxide adsorbed on ZrO2/TiO2 may show further details.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Accepted
Reviewer 2 Report
Accept in present form
