Space Velocities comparison in catalytic Methylation of Phenol 1

[byte20]

Hi all!

May I first apologise for linguistic mistakes. I'm italian and I recently discovered this useful Forum!
I'm dealing with gas phase methylation of phenol for 2,6 xylenol production. In scientific literature there are several works about this topic, and each work suggests to carry out the reaction with a specific Weigh Hourly Space Velocity (WHSV) or, alternatively, Liquid Hourly Space Velocity (LHSV). In this reaction a liquid mixture of phenol, methanol and water is tipically fed in a multitubular reactor. However, in some cases no water is fed with reactant.
Now I'm comparing the different WHSV (or LHSV) but I have the doubt that could be incorrect to compare WHSV of stream with water with ones of stream without water.
Could the Phenol Based WHSV (kg/h of phenol/kg cat. )comparison be more correct?
What do you think about this? What is your suggestion?

Thanks to all

 

[byte20]

Is there anybody who can help me?
Perhaps the question is not clear...
Please tell me what you think on this issue, I need an exchange of opinions about it.

Thank you in advance.

 

[cloa]

Probably too specialised to find a suitable audience here.
Try this forum.

http://www.cheresources.com/invision/forum/12-general-chemical-engineering-forum/

Maybe at least they can suggest an academic to give you some suggestions.

 

[byte20]

Thank you cloa

in fact I've already posted the question in the suggested forum 2 weeks ago, but unfortunately still no answer!

Actually, I don't think that this question is so specialised. This is more an idea for discussion than just a question.
I thought that different processes should be compared each other based on the phenol WHSV, which is the limiting reactant. The water isn't a reactant but only (in this case) an inert carrier, so my doubt is that could be incorrect to compare a stream with an inert carrier to a different stream without inert carrier. In my opinion two different streams (and consequently two different processes for the same reaction) should be compared with each other based on the limiting reactant, which is phenol in my case.

Thanks anyway for the answer and the suggestion and I hope that someone else will leave his opinion...

Thanks in advance

byte20

 

[moltenmetal]

byte20: this is elementary reaction engineering and kinetics. Get yourself a copy of Levenspiel and read the applicable section.

To answer your question: it is doubtful that you can compare liquid phase and gas phase kinetics for this reaction or for any other catalyzed reaction in any meaningful way. You need kinetic data obtained by experiment under the conditions you intend to operate in before you can design a reactor.

An hourly space velocity is a proxy for residence time, which is only meaningful in certain kinds of reactors, and under certain kinetic regimes.

If water is a diluent in this reaction rather than a participant or co-catalyst or solvent (I know nothing about your reactioni or catalyst in particular), it will have an influence as a diluent which depends on the kinetics. The presence of a diluent can NEVER be ignored when working in space time units, even if the reaction is zero order in limiting reagent- and that itself is unlikely.

Note that most catalytic reactors are sized based on catalyst deactivation rather than straight kinetics, and only give the minimum required conversion at the end of the life cycle of the catalyst. The space-time required for that is determined based on the catalyst activity in the fully deactivated (replacement) condition.