Batch to Continuous: From Laboratory Recycle Trickle Bed Test Reactor Data to Full-Scale Plant Preliminary Design—A Case Study Based on the Hydrogenation of Resorcinol

Round 1

Reviewer 1 Report

The paper of Polligton and coworkers represents an excellent excersise for process design starting from kinetic data. The paper worth to be published in almost the present form

Few comments/requests

L 64. Probably "catalyst inventory" would make the sentence clearer

L162 Can the authors can provide the packing density of the 5 cases?

L 218 Are the results reported the ones about the Ni trilobe catalyst? Please clarify

L 298 The design paradigm here reported is really interesting, however can the authors provide more justification for their choices. Moreover, in typical design paradigm catalyst deactivation is accounted for. What of the author choices may be influenced by this? Typically some margin on the operative temperature or on the catalyst mass is considered

L 334. Did the authors made some considerations on the pellet diameter, in tems of gas/liquid transport and pressure drops in the reactor?

L 335 333K is the inlet temperature? It could be not clear as it is written

L 374 Please report the motivation of the required increase of the catalyst volume while larger reactor columns are employed.

Author Response

We thank the Reviewer for the kind comments on the overall quality of the paper.  We give below our actions in response to the specific questions and queries:

L64 – We have added the word as suggested for clarity.

L162 – The packing density has been added to Table 1

L218 – the specification of the catalyst as Ni/Al₂O₃ is already given in both the text and in the figure caption.  We have altered the text to clearly say Ni₂O₃ trilobe

L298 – the comment on the impact of deactivation is a very good point.  As noted later (4.4) we do not have specific data for deactivation at this juncture.  We have added text at this point and in Section 4.4 for clarification.  In essence we applied an experiential 20% design margin. 

L334 – This is also a very good question.  It is indeed true that in this operating regime a smaller extrudate will almost certainly be beneficial.  This study was however constrained to commercially available catalysts.  We have added a discussion of this very important observation.

L335 – We have added the requested clarification.

L337 – The change in catalyst volume with diameter is a result of the rate dependence on liquid velocity.  We have added a sentence to this effect as it was evidently not clear

Reviewer 2 Report

The use of trickle bed or fixed bed system could replace a batch autoclave typically used for hydrogenation reactions. This study, using the production of 1,3 cyclohexanedione from catalytic hydrogenation of resorcinol as a case study demonstrates how the laboratory-scale recycle trickle bed can be used for catalyst screening and selection.

My understanding this work is more or less like a technical report or an assessment of the performance of this fixed bed catalyst.

Comments:

1.        The most important thing is the novelty and scientific value of this manuscript. Research status on this topic should be reviewed and the novelty of this scientific work should be addressed. In introduction part, the engineering part review is good. The trickle beds and many not relevant studies are also reviewed. The research novelty of 3-Cyclohexanedione Formation, hydrogenation of resorcinol over commercial Ni/Al2O3 catalyst may be paid more attention. The references are rare in this study.

2.        This study lab experiment results seems to be interesting. In experiment part, the measurement method of conversion of catalyst was not given.

3.        The results in Figure 6 is generic for hydrogenation reactions demonstrate zero order kinetics. However, in some other figures, for example figure 1, the pseudo first order kinetics are found. How to evaluate the results and link to the trickle bed system design?

4.        Would a system design by Aspen works? This will be a good design tool.

5.        Please remove citations in conclusion part. Otherwise you can set a discussion section.

Author Response

We thank the Reviewer for the kind comments on the overall quality of the paper.  We give below our actions in response to the specific questions and queries:

1)  Section on hydrogenation of resorcinol added to the introduction

2) The analytical method for substrate / product is given in Section 2 .6.  We have added a sentence that the conversion was evaluated by mass balance closure

3) The process does indeed transition from pseudo-zero to 1^st order at high (>85% or so) conversion.  As noted in Section 4.4., there is presently insufficient data to apply the same numerical approach to the 1^st order regime: rather this will be required for a more detailed design.  Given Reviewer 1 makes a related comment this clearly needs more emphasis.  We have accordingly  added a discussion of this feature at the bottom of Section 3.2

4) This may indeed be true for a more complex flowsheet, but this one is easily done using more manual methods.  An additional consideration is that with organics that are not commonplace and aqueous solutions the physical and chemical properties may not be readily available in the database associated with a commercial or open course flowsheeting package. 
We have not made any modification to the manuscript.

5) Citations removed as suggested.

Reviewer 3 Report

The manuscript entitled “Batch To Continuous: From Laboratory Recycle Trickle Bed Test Reactor Data to Full Scale Plant Preliminary Design. A Case Study based on the Hydrogenation of Resorcinol” is a well-prepared paper. However, the following deficiencies ought to be addressed prior to any potential publication:

-          Title: An attempt to make the title short would be greatly appreciated. Highlights and abstract cover the rest. No need for full stop in the end.

-          Abstract: Explain what EHS stands for. Do the same for every abbreviation used at first appearance.

-          Keywords: The word “continuous” is inappropriate as a single word.

-          Introduction: A recent research on M&S in hydrogenation for scaling-up would be good to be cited (e.g. 10.1016/j.ijhydene.2020.09.082).

-          Section 2: A process flow diagram of the experimental reactor would be helpful to understand the instrumentation.

-          Section 2.4 and 2.5: Please cite references that mention the experimental protocol used as well as the catalytic activation process.

-          Section 3, line 285: Explain the equation and its symbols.

-          Section 3.2: Replace “>” symbol with words to avoid misunderstanding.

-          Figure 4: What do the red and purple arrows show?

-          Section 4.3: Do the authors believe that the cost estimate is adequate and precise in function with the given data?

-          Do not use caps without reason (e.g. in page 21, 23, 320, 321, 400, and many others). Check and fix the entire manuscript.

Author Response

We thank the Reviewer for the kind comments on the overall quality of the paper.  We give below our actions in response to the specific questions and queries:

• Title:  We gave the title considerable thought.  There are shorter and longer examples in the literature.  I’ll leave this to the Journal editor.  We will modify if requested by the Editor
• Abstract: We have removed the EHS acronym, which is actually unnecessary in this context
• Keywords : We have modified this accordingly to “continuous reactors”
• Introduction: Added a comments regarding modelling and simulation studies and reference as suggested.
• Section 2: We have refrained from including the PFD of the experimental rig as this has been published in various papers by the authors, including significantly those that have used this set up for trickle bed work.  The relevant papers are cited in the experimental methods section.  We have some sympathy with the reviewer, but we have equally been criticized in a previous paper review for including a PFD that is readily already available. We will happily include this if so requested by the Editor
• Section 2.4 and 2.5: Sections modified
• Section 3, Equation nomenclature added This was an omission on our part.
• Section 3.2: We have replaced replace “>” symbol
• Figure 4: What do the red and purple arrows show?   The formatting of this Fig 9 (Fig 4 has no arrows – Fig 9 does) is inconsistent with the others.    We have replaced this with a new version that replaces the arrows with a legend.
• Section 4.3: For a Preliminary Estimate – yes, we do believe this is adequate This is discussed in Section 4.4, but some clarification has been added
• “Do not use caps without reason (e.g. in page 21, 23, 320, 321, 400, and many others).” This is a moot point.  The instances highlighted are, with one exception, where we are denoting a proper noun and as such the use of capitals is correct.  For example “Preliminary Estimate” (in the abstract) refers to a specific document prepared as part of a design project and is, as such, a proper noun.  We have checked through the document for instances where we have used capitals where is does not infer a proper noun and removed.

Round 2

Reviewer 3 Report

Authors took into consideration reviewer's comments-suggestions and a couple of them left them to Editor's final decision.