Photocatalytic Oxidation of Propane Using Hydrothermally Prepared Anatase-Brookite-Rutile TiO₂ Samples. An In Situ DRIFTS Study

Round 1

Reviewer 1 Report

Casanova et al reported the photocatalytic oxidation of propane by using TiO₂ NPs with complex phases and studied their oxidation process by in-situ DRIFTS. Although the results of the in-situ experiment are interesting, there is a lack of typical characterizations that should be addressed. After appropriate revision, I could consider this manuscript published in Nanomaterials. The specific comments are showed as followed:

1. The motivation and statement of TiO₂ with mixed phases used in this study are ambiguous, and their conversion performances are not superior to commercial P25.
2. Under the dark conditions, the correlation between the adsorption activity and surface chemistry of the three phases should be explained clearly.
3. The possible mechanism and charge transfer route of photocatalytic reaction by using TiO₂ should be provided.
4. What is the factor dominating the adsorption of intermediator then inhibiting the activity?
5. The authors emphasized the phase composition of TiO₂ NPs dominated the activity of propane oxidation. The related XRD pattern should be provided.
6. For the completeness of the study, the morphology of various TiO₂ by using SEM and TEM might be shown.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

The paper focuses on the removal of propane using hydrothermally synthesized TiO2. Moreover, intermediates byproducts are investigated in order to obtain a correlation between IR and propane oxidation.   

 In general, the results mostly support the authors' conclusions. However, some aspects of the manuscript must be carefully reviewed, discussed and improved.

1°) the originality, mechanism, and scientific reliability of the work are unclear. In my opinion, there are some major points that the authors should address: 

2°) why do authors study the removal of propane (R–CO2  species formation ?) ?. the choice of concentration of this compound must be justified?

3°) the bibliographic part about carbonate-carboxylate-formate (R–CO2  ) species  is too short, please give more information and other studies (line 52 page 2)

4° please add mores references about investigations on compound removal with photocatalysis. I suggest adding these refs (Chemical Engineering and Processing: Process Intensification 111, 1-6 ( 2017); Chemical Engineering Research and Design 106, 308-314 (2016))

5°) It is better to add flowsheet about the reactor. Please give the spectrum of irradiation   

6°) In Figure 2. (a) about Propane conversion why all curves reached a maximum of around 30-40% (with the exception of TiO2-P25). The scientific explanation is needed

7°) the study of intermediates byproducts with photocatalytic and absorption proportions is very interesting but at any moment the authors discussed the results of the mass balance.

8°) what about the reusability of catalyst?

Author Response

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Author Response File: Author Response.docx