
Flow Chemistry - mindcrime
https://en.wikipedia.org/wiki/Flow_chemistry
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refurb
Flow chemistry is super useful in some situations and can actually be quite
"green" as well as you avoid a lot of solvent usage.

However, it can be really changing as well. If something crashed out in your
typical reaction vessel, no big deal. If it crashed out in a flow system,
everything grinds to a halt and it can be a huge pain getting the blockage
cleared.

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neltnerb
Agreed. I designed supercritical CO2 flow reactors. There are a lot of
advantages, and agree the main disadvantage is that a clog has the potential
to cause serious damage to your system. I still think it's superior because
the product consistency can be much higher when you can control exactly how
long a reaction takes place (vs batch processing).

I'm kind of confused why this is an article on HN, but I used to have a
startup doing microreactor based flow chemistry. It's pretty great for purely
liquid based processes.

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burfog
Flow reactors always struck me as the distinction between chemistry and
chemical engineering. Chemists mix up little batches in borosilicate glass.
Chemical engineers use stainless steel pipes big enough to crawl through.

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neltnerb
You might be surprised, though I think you're broadly right about this.

Think about it like this -- if you have a molecule flowing through a tube
along with the molecules it reacts with, you can flow it at a controlled flow
rate through a hot zone or catalyst bed and largely the "plug" will flow
through as a unit and so the total time the mixture is at a particular
condition is very consistent.

Whereas for a batch reactor, you basically have a giant cooking pot with a
stirrer agitating the molecules together. But nothing is typically removing
the product, so some of the product can get destroyed or be less efficiently
made because the time of reaction for different molecules varies.

That said, a company I used to work for was doing batch chemistry at hundreds
of liter scale reactor size. Some of these batch reactors are enormous. And
they make sense for situations where you need to do something like slurry
processing or super high pressures (sometimes) or are not at a big enough
scale to justify building a flow system. For instance, if one 200L batch meets
your production needs for a year there's absolutely no economical incentive to
switch to a flow reactor at such a small production rate.

But in my experience, yes, I can make a flow reactor with yields of 99% for
somewhat tricky chemistry. With a batch system I might hit 95%. That isn't a
big deal for a high value product, but is a huge problem for a commodity
chemical.

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kazinator
Application of certain coatings is effectively flow chemistry, like
polyurethane foam where you have two components flowing into the nozzle from
separate containers.

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jjtheblunt
epoxies?

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photojosh
I haven't done chemistry since high school, but was a curious as to what a
simple setup would look like. This 'gentle introduction to flow chemistry' [0]
article seems to do a good job.

[0]:
[https://pubs.rsc.org/en/content/articlehtml/2014/mh/c4mh0005...](https://pubs.rsc.org/en/content/articlehtml/2014/mh/c4mh00054d)

