Size of catalyst

[cherry123]

Does the size of the reactor (catalyst weight) needs to be changed if we want to change the feed.
Initially only fresh reactants were charged but now since the products forms not only the desired product but also undesired products as well, so I want to recycle back the undesired products but the feed rate of fresh reactants is same as before. Actually its amination of Methanol. It produces MMA DMA and TMA in the presence of zeolite catalyst. I want DMA not MMA and TMA so they are recycled back.

Please advice.

 

[dcasto]

typically, the space velocity, which also gives residence time is a criteria for the design of reactors.

Between your company and the catalyst vendor, you should be able to quantify an answer.

 

[cherry123]

Yes I know the space velocity of methanol in WHSV.
But since I am recycling now so would it make any difference? or same size of catalyst can be used?

 

[dcasto]

As for size, the size of the catalyst can be adjusted to keep pressure drop reasonable and still keep the residence time in range.

 

[epoisses]

Another question would be if a bigger reactor or a more active catalyst would take away the need for recycling.
An alternative solution would be a separate reactor for the undesired byproducts only i.e. instead of blending them back into the feed.
I think you won't find the optimum solution by thinking in qualitative terms only. Get a good simulation model of your unit and see what happens in quantative terms in the different scenarios.

 

[cherry123]

MMA DMA and TMA all are reversable reactions, it is impossible to have only DMA. They are all parellel reactions, it is possible to supress the formation of MMA and TMA by keeping there concentration high in the reactor, so that DMA formation is favoured that is why after separation of DMA using distillation, the side products MMA and TMA are recycled back. But now they are recycled back, will it make any difference on catalyst mass?