Downsizing Sustainable Aviation Fuel Production with Additive Manufacturing—An Experimental Study on a 3D printed Reactor for Fischer-Tropsch Synthesis
Round 1
Reviewer 1 Report
The paper of Metzger et al reports the use of additive manufactured reactors for the intensification of FT synthesis for the production of SAF. The topic is of extreme relevance nowadays and worth to be addressed in a scientific publication. The results reported by the authors are outstanding, more than 5 times the ever recorded productivities for gram of catalyst of C5 species. I recommend this manuscript for publication after some points are addressed.
Introduction : The style of the introduction is rather uncommon. Is this asked by the journal? I suggest a more standard/ fluid style. Several research works in the field are documented, however I suggest to include other structured catalyst applications to this process : see papers of Tronconi and coworkers, AL Tonkovic and coworkers, Tatarchuk and coworkers.
In section 2 space velocities and contact time are given. Which volume was considered? Is it the void volume of the reactor or the overall volume of the device? Please provide details of the oil type and circulation system.
The activation procedure is uncommon, typically N2/H2 mixtures are employed. Can the author comment more on the procedure adopted?
The author provided a simple correlation for the estimation of the CO conversion. Since the author claim almost isothermal reactor, do the author think that the CO conversion can be estimated with a standard PFR deriving kinetic parameters? Do the author think that a more advanced model that takes in account rate formation velocities of different species can be derived on the basis of these observations? Towards understanding the exothermicity of the system, methane formation is rather more exothermic than other reactions, and typically display an higher activation energy, leading to possible thermal runaway risks
In my opinion, the possibility of using this reactor under dynamic operations should be explored with more detail. A 1D dynamic model with heating/cooling rate should be considered. I suggest for this – in industrial practice – to not rely on GC measurements but maybe on dynamic analysis methods ( MassSpec i.e).
A comment on the scalability of the concept is required. How the author think that this system can be scaled towards industrial productivities (i.e. scaling up by numbering or increase reactor size) and do the authors envision at the moment a feasible/unfeasible productivity that can be achieved with this concept?
A last comment : the ratio H2/CO of 2.0 was chosen but several authors claim that this may be suboptimal in system with strong H2 back-diffusion. Do the authors tried to work with higher H2 content?
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The authors reported a reactor concept suitable for the decentralized production of Sustainable Aviation Fuels (SAF). The labscale reactor was operated successfully under fluctuating and challenging input conditions for Fischer-Tropsch synthesis (FTS). The results showed that excellent temperature management, high C5+ productivity, and low methane selectivity. The measured temperatures inside the reactor confirmed quasi isothermal behavior, and there was no observed catalyst deactivation during the experimental period. The reactor achieved leak-free operation at pmax = 20 bar and Tmax = 400 °C using wall thicknesses of 1 mm or less. Overall, the paper provided full and convincing experimental evidence. However, there are some problems that need to be addressed before publication:
1. The author mentioned GC abbreviations multiple times throughout the article but without providing any explanation for them.
2. The author used Eq.5 to evaluate the experimental results, in which a clear description of STYmod and STY was not provided.
3. The background of FTS and Compact Reactors in the Introduction Section can be more comprehensive, with a clearer logical relationship between them.
4. The English language could be further polished.
Moderate editing of English language required
Author Response
Please see the attachment.
Author Response File: Author Response.docx
