September 25, 2021, 02:42:09 PM
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Topic: Aspirin - Designing a Process for large scale production (Ideas/Alternative)  (Read 27902 times)

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Offline discodermolide

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The use of water as a solvent will cause a reverse reaction.
Areas of high pressure, will it affect where using glass piping is appropriate?

We are planning to use fractional distillation to seperate:
-water
-unreacted materials (acetic-anhydride, salicylic acid)
-Catalyst(sulfuric acid)
-by-product(acetic acid, in the sense that it's not going to be used for 'this' process)

Will there be any problems to the seperation such as difficulty maintaining a specific chemical compound after it is condensed?
(I'm not sure hot to say it)
Will any compounds have trouble condensing back after evaporation?


Glass should be ok because you only make the transfers with this material. Pressure is applied afterwards.
Fractional distillation of these materials will not work, compare boiling points, you will ned a good vacuum and an efficient column, the lower the BPt. the worse the fractionation.
An extractive work-up is better. If you use toluene, for example, as the reaction solvent you can add water and wash out the acids with bicarbonate (lots of CO2.  produced). Separate the layers and evaporate the toluene, azeotropic drying will take place, hopefully the product will crystallise.
I have no idea if this works in toluene, lets assume it does.
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Offline amir885

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Have you  got any idea about the material selection for equipments of Aspirin production ? I'm looking for it.

Use enamelled reactors, as you have conc. sulphuric acid as well as other corrosive materials. Transfers with glass or hasteloy piping.
You can filter the product with a pressure filter or use a centrifuge. Drying in a standard oven under vacuum.
Watch out for electrostatic solids.
That's about it really, pretty standard equipment.


It makes sense ! Could you please introduce me a reference or website so I can do more research ? Let me know if you have anything and I will give you my email or you may find it in my profile.
Cheers,

Offline discodermolide

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Have you  got any idea about the material selection for equipments of Aspirin production ? I'm looking for it.

Use enamelled reactors, as you have conc. sulphuric acid as well as other corrosive materials. Transfers with glass or hasteloy piping.
You can filter the product with a pressure filter or use a centrifuge. Drying in a standard oven under vacuum.
Watch out for electrostatic solids.
That's about it really, pretty standard equipment.


It makes sense ! Could you please introduce me a reference or website so I can do more research ? Let me know if you have anything and I will give you my email or you may find it in my profile.
Cheers,

I think you have enough ideas here to start doing your own research on this topic.
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Offline curious stackhouse

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The use of water as a solvent will cause a reverse reaction.
Areas of high pressure, will it affect where using glass piping is appropriate?

We are planning to use fractional distillation to seperate:
-water
-unreacted materials (acetic-anhydride, salicylic acid)
-Catalyst(sulfuric acid)
-by-product(acetic acid, in the sense that it's not going to be used for 'this' process)

Will there be any problems to the seperation such as difficulty maintaining a specific chemical compound after it is condensed?
(I'm not sure hot to say it)
Will any compounds have trouble condensing back after evaporation?

Before you fraction distillate you should know that probably all the acetic anhydride will have been turned into acetic acid by the water.
Salicylic acid will be in solid form at temperatures below 150°c
The relevance of recovering your catalyst H2SO4 will depend on your Basis.Hope this can be helpful in determining a suitable separation process :)

Offline discodermolide

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The use of water as a solvent will cause a reverse reaction.
Areas of high pressure, will it affect where using glass piping is appropriate?

We are planning to use fractional distillation to seperate:
-water
-unreacted materials (acetic-anhydride, salicylic acid)
-Catalyst(sulfuric acid)
-by-product(acetic acid, in the sense that it's not going to be used for 'this' process)

Will there be any problems to the seperation such as difficulty maintaining a specific chemical compound after it is condensed?
(I'm not sure hot to say it)
Will any compounds have trouble condensing back after evaporation?

Before you fraction distillate you should know that probably all the acetic anhydride will have been turned into acetic acid by the water.
Salicylic acid will be in solid form at temperatures below 150°c
The relevance of recovering your catalyst H2SO4 will depend on your Basis.Hope this can be helpful in determining a suitable separation process :)


As I said above fractional distillation will not work in this case. The best way is an extractive work-up Followed by a crystallisation.
These starting materials are cheap it it more expensive to recover them. Anyway how do you hope to recover conc. sulphuric acid?
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Offline curious stackhouse

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You are right, an extractive work up using an organic solvent would be the only way out, atleast for the salicylic acid and acetic acid.The rest could be treated as effluent seeing that it would be more expensive to try and recover than recharge, especially the small amount of conc. sulfuric acid.

Offline discodermolide

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You are right, an extractive work up using an organic solvent would be the only way out, atleast for the salicylic acid and acetic acid.The rest could be treated as effluent seeing that it would be more expensive to try and recover than recharge, especially the small amount of conc. sulfuric acid.

I am glad you agree! Any work-up that removes acetic acid will also remove sulühuric acid.
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Offline ProdigyLee

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Side Note: Wow guys, thanks for taking the time to read this thread, I didn't expect it to get so big. I do appreciate the discussion though but if you can, please start your own thread if asking side questions as I'm having trouble reading through and finding the information I need.


So:
*Fractional  Fractional Distillation alone is not an ideal option because:
-Recycling is much more expensive than buying new materials.
-The acids will not reform perfectly to original material (unreacted acetic anhydride, sulfuric acid going in)

Will this work:
-Nuetralize Acids by 'washing out with bicarbonate'
-Then Distil with objective to recover pure solvent (Toluene), this will be reused.
-Unreacted material and biproducts will be considered waste material.
(Acetic anhydride and acetic acid[Neutralized], water, catalyst).

About piping and reactor components:
-Some reacting materials are corrosive to metals
-glass or enamelled material is best to contain/transfer material.
RMIT Australia - 3st Year Undergraduate 'Bachelor of Engineering - Chem'.
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Offline discodermolide

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Side Note: Wow guys, thanks for taking the time to read this thread, I didn't expect it to get so big. I do appreciate the discussion though but if you can, please start your own thread if asking side questions as I'm having trouble reading through and finding the information I need.


So:
*Fractional  Fractional Distillation alone is not an ideal option because:
-Recycling is much more expensive than buying new materials.
-The acids will not reform perfectly to original material (unreacted acetic anhydride, sulfuric acid going in)

Will this work:
-Nuetralize Acids by 'washing out with bicarbonate'
-Then Distil with objective to recover pure solvent (Toluene), this will be reused.
-Unreacted material and biproducts will be considered waste material.
(Acetic anhydride and acetic acid[Neutralized], water, catalyst).

About piping and reactor components:
-Some reacting materials are corrosive to metals
-glass or enamelled material is best to contain/transfer material.


That about sums up what I said, yes.
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Offline ProdigyLee

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That about sums up what I said, yes.

I really want to thank you, you have provided us with a great backbone to our design. I'll let you know how it goes.
RMIT Australia - 3st Year Undergraduate 'Bachelor of Engineering - Chem'.
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Offline discodermolide

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That about sums up what I said, yes.

I really want to thank you, you have provided us with a great backbone to our design. I'll let you know how it goes.

Good luck. I would be interested to know how you get on with it.
Development Chemists do it on Scale, Research Chemists just do it!
My Research History

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