I’m a chemist. Organic chemistry PhD, now a process chemist in the industry. I do this for a living. Do not distill isopropanol that’s been exposed to air for any meaningful length of time.
Isopropanol slowly reacts with oxygen in the air to generate peroxides that, when you concentrate them down, EXPLODE.Source. Sorry, not an open access journal. But please take my word for it.
Unless you have a way of confirming the peroxide levels in your isopropanol are near zero, do not concentrate it down by distillation. You’ll blow up your glassware, which will probably expose what you’re distilling to your heat source, which will generate a secondary fireball.
Ok, I’ll put I lid on this for now. However, what you did was get me extremely curious. Air exposure is minimal and the IPA is always sealed, that doesn’t negate what you are talking about, but it’s still obviously a concern.
There are commerical distillation machines for isopropyl that I have been able to find. How is the risk mitigated in those cases? These machines are in use with a couple of 3D printing farms that I have seen.
(Honestly, I have been curious about making peroxides too, but that is a subject for another day.)
Of course the full paper is paywalled. Sigh. Additional info on that subject:
The issue with isopropanol peroxide formation is that exposing it to air – even when just using it, like when you’re cleaning parts – starts the process. The air in the head space of your containers is also enough to form them over time. You don’t necessarily need to see solids in the containers for it to be dangerous, since they’ll crystallize out as you concentrate the solution during distillation.
It’s also a numbers game. It probably won’t explode the first time you do it. But there’s a chance each time. Do it enough, and you’ll have an incident.
There are chemical reductants that can clear peroxides. For industrial scale isopropanol distillation, I’m not sure what they use. It may be that they just never distill down to the point that peroxides concentrate to a dangerous level.
If this were a closed loop cycle for the IPA, I could see an issue. Between normal losses using the IPA in my projects, disposing of fairly diluted concentrates while also replenishing the IPA with fresh stock doesn’t seem like it would allow for for dangerous levels of peroxide buildup.
Testing the IPA is a good route to take though. If peroxides are coming across during distillation or if the dirty IPA contains measurable peroxides, that would be good data to have.
I am not above spending the cash to have an analysis done on the purity of my IPA either. It would be a hair expensive, but data is invaluable.
No no no no no.
I’m a chemist. Organic chemistry PhD, now a process chemist in the industry. I do this for a living. Do not distill isopropanol that’s been exposed to air for any meaningful length of time.
Isopropanol slowly reacts with oxygen in the air to generate peroxides that, when you concentrate them down, EXPLODE. Source. Sorry, not an open access journal. But please take my word for it.
Unless you have a way of confirming the peroxide levels in your isopropanol are near zero, do not concentrate it down by distillation. You’ll blow up your glassware, which will probably expose what you’re distilling to your heat source, which will generate a secondary fireball.
PLEASE do not do this.
Sounds like fun! Got to go get a still though.
Please, don’t do this thing.
Concentrated Hydrogen peroxide is scary AF!
I love EnF. But I assure you, organic peroxide formers are scarier.
This is the exact video I thought of and where I learned about them!
Ok, I’ll put I lid on this for now. However, what you did was get me extremely curious. Air exposure is minimal and the IPA is always sealed, that doesn’t negate what you are talking about, but it’s still obviously a concern.
There are commerical distillation machines for isopropyl that I have been able to find. How is the risk mitigated in those cases? These machines are in use with a couple of 3D printing farms that I have seen.
(Honestly, I have been curious about making peroxides too, but that is a subject for another day.)
Of course the full paper is paywalled. Sigh. Additional info on that subject:
https://cen.acs.org/articles/94/i31/Chemical-safety-peroxide-formation-isopropanol.html
The issue with isopropanol peroxide formation is that exposing it to air – even when just using it, like when you’re cleaning parts – starts the process. The air in the head space of your containers is also enough to form them over time. You don’t necessarily need to see solids in the containers for it to be dangerous, since they’ll crystallize out as you concentrate the solution during distillation.
It’s also a numbers game. It probably won’t explode the first time you do it. But there’s a chance each time. Do it enough, and you’ll have an incident.
There are chemical reductants that can clear peroxides. For industrial scale isopropanol distillation, I’m not sure what they use. It may be that they just never distill down to the point that peroxides concentrate to a dangerous level.
If this were a closed loop cycle for the IPA, I could see an issue. Between normal losses using the IPA in my projects, disposing of fairly diluted concentrates while also replenishing the IPA with fresh stock doesn’t seem like it would allow for for dangerous levels of peroxide buildup.
Testing the IPA is a good route to take though. If peroxides are coming across during distillation or if the dirty IPA contains measurable peroxides, that would be good data to have.
I am not above spending the cash to have an analysis done on the purity of my IPA either. It would be a hair expensive, but data is invaluable.