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Author: Subject: Glass Batch Reactors vs RBFs
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[*] posted on 22-11-2024 at 13:29
Glass Batch Reactors vs RBFs


Hi everyone! Although the RBF is probably one of the most widely used pieces of glassware for the amateur, most of you probably have heard of glass batch reactor. They are used by almost everyone who can afford one - everyone from meth cooks to pilot scale production plants and laboratories finds a use for them, but why? What real advantages do the have? Yes they are available in larger sizes than RBFs, but not everyone requires that.

Jacketed glass reactor:

Cost: $3,000-$25,000+
Size: 1L-250L
It has many disadvantages compared to a RBF. The main one, of course, is cost. The cheapest Chinese reactors of a useful size (>10L) start at a few thousand dollars. The cheapest Chinese 200L ones cost over $10,000. There are also things such as the fact that the only way to heat the reactor is to use a liquid in the jacket, and that requires another machine that costs several thousand dollars. This thing is also just very big. How do you even clean it? You can't pick it up and wash it. What if you need higher temperatures than the liquid in the jacket can withstand? How do you repair the thing if it breaks (most of the parts are every expensive and proprietary). But the main question is, why? Just what advantages does the reactor provide compared to an RBF? It costs a few dozen times more and has many problems, so I don't see a reason to use it apart from the larger available size.

Single layer glass reactor:

Cost: $1,500-$5,000+
Size: 10L-250L
This has a few advantages over the previous one, most importantly cost. The cheapest Chinese reactors start at about a thousand dollars. The cheapest Chinese 200L ones cost about $5,000. These ones have build in heating, so a separate machine is not needed, but this means that it can't be cooled (if needed). This one is also a little smaller. But still, how do you clean it? You can't pick it up and wash it. These one usually have a slightly higher max temperature. But the question is still, why? What does the reactor provide to constitute the significantly higher cost than a RBF? It costs a much more and doesn't provide much advantages, besides the larger available size?

Round Bottom Flask:

Cost: $5-$500+
Size: 25ml-72L
The round bottom flask. What can't it do that a reactor can? A cheap Chinese 50L RBF costs under $300. It is "easy" to work with, can be lifted, moved, washed, and everything else. It can be heated with a heating mantle, or just an oil bath (which can also be heated by flame. A RBF can also withstand significantly higher temperatures than a reactor. It is easier and cheaper to repair. So, is there anything I'm missing? Why doesn't everyone use 50L RBFs?

Thanks.




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[*] posted on 22-11-2024 at 14:11


I have actually just been scaling up a reaction from a 10l flanged round bottom flask to a 50L jacketed reactor exactly like the one you showed, except American made. I cannot recommend these 50L reactors enough. I can't imagine scaling up to a 50L RBF without it being just a nightmare.

We heat the jacketed oil up to around 160C using Duratherm S. It works very well, the contents stay exactly 4 degrees cooler than the oil for the reaction we run. Since there is 10 gallons of oil in the system, the temperature is extremely consistent, it never changes by +- 2 degrees. With a closed loop heater I believe you can achieve temperatures of at least 220C. that covers 95% of all wet chemistry at this scale. and there are solutions for high temps.

One of the main advantages of these reactions is being able to do workup procedures in them without moving picking up or tipping the flask. Think about doing a liquid liquid extraction at 25L scale? with one of these reactors you can simply pump the fluid into the vessel stir, and drain out your bottom layer.

How do you even lift a 50L 100kg flask and safety pour it out when it's 160C? if you are running a business is it worth trusting 2 technicians to do this slightly dangerous task?

These reactors are costly, but not weighed against the contents. When full this reactor would contain roughly $10K worth of material for each individual run.

Happy to give you some more information later when I get more time. Obviously these are not for amateur chemistry, but make a lot more sense on a pharmaceutical scale.

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[*] posted on 22-11-2024 at 14:20


The main issue is that it is very difficult to work with round bottom flasks bigger than about 5L in almost any way. Once they have liquid in them, they get very heavy, they are fragile, and have to be handled often to move them to and from a heating mantle, pouring material from the flask to process it, they are hard to stir well, and you need a separate seporatory funnel.

Most reactors have valves and pumps to transfer materials in and out, and the reactor is fixed, generally in a sturdy frame. Heating via liquid gives very fast response, if you have a good chiller/heater, and the liquid helps buffer the temp, so temperatures stay more consisitant.

Most importantly, the various ways to remove liquids found in many reactors allow them to act as a separatory funnel, even for very large and heavy amounts of solvent. And once the reaction is over, often the entire workup is done in the reactor and the next step is done there, keeping out air and water in some cases between steps (not so relevant if you just did a water workup). Also, many of them can stir and heat the reactor while condensing vapors outside of the reactor, so they can act as a rotovap in many cases as well.

Often the product from one reaction is preciptated from the reaction after workup and then the solvent can be removed via a frit or such, then the next step redissolves the material for more work. Once the reaction(s) are done, the product is often transferred as a solution for final processing, or sometimes as a slurry into a filtration device. Then the reactor is usually cleaned by addig solvent and draining it, with stirring at each wash to agitate the whole thing.

I have never seen anyone use a single walled reactor (option B), it might be useful for something, but just not used in industrial uses in the US. I have used a few smaller reactors (and have a few small used ones for sale, plus one new 3L one.), but they are mostly used for larger scales, so small ones are mostly used to test processed to see if they will work in larger ones. In pilot plants, many of these systems are partly automated, so a process can be defined and then repeated over and over, with prompts to add some reagents, solvents are sometimes added by hoses or pumps.
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[*] posted on 22-11-2024 at 23:12


https://youtu.be/CdTsRa6ND1c

Nice video showing large scale reactor
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[*] posted on 23-11-2024 at 00:47


Based on the OP a 1 litre double wall reactor kit would cost about the same as my entire chemistry budget since I was born ;)

RBFs will have to suffice for me (and most members)
because chemistry as a hobby provides no income,
and I'm very unlikely to be working with $10k worth of pharmaceuticals per batch




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[*] posted on 23-11-2024 at 07:21


I used to work in kilo lab production and used 72 L RB flasks at the upper end. I loved working in big glassware. Other than having to have the pieces there was no added difficulty to working with a large flask. Mostly due to the fact that the chemicals we were working with were not just getting poured through the air. Everything was a nitrogen pressure or vacuum transfer so you were never picking up flasks or drums and pouring them that would be done in a home lab.

That being said I have also used jacketed reactors. Where they really shine is that quite a few reactions will involve running the actual reaction at low temp and then heating to reflux to finish or strip. In a regular flask that's going to involve running in a cold bath then swapping that out and switching to a mantle so it avoids that switch. Another area where they shine is anything where the reaction runs elevated but generates its own heat of reaction. In those cases you need to rely on reflux (if possible) to pull the heat out of the reaction but with a jacketed flask you can set it where you need it for temp and then charge at a more aggressive rate. The final case is with anything that has a 'runaway' temp or a hard to control exotherm at higher temps. In those cases a jacketed flasks is leagues better than trying to jam a nitrogen line in a heating mantle and praying. They are very cool to run but honestly I am too lazy most of the time to run the heating/cooling lines and setup the equipment so just go for a RB flask unless one of those previous scenarios are prevalent.

[Edited on 11/23/2024 by BromicAcid]




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[*] posted on 23-11-2024 at 19:52


Thank you all for the replies!

So, the main advantages I can see are:

1. Much easier and precise temperature control
2. Easier to work with/transfer liquids

Is this all?
Also, in this case, it seems like option B (which I originally (seemingly incorrectly) considered superior to the first option) is actually pretty much useless, as it's essentially just a severely overpriced RBF with a built in heating mantle?




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[*] posted on 24-11-2024 at 11:21


Yes, option B just looks like a large RBF with all the fixins for running a large-scale reaction included.

One benefit that hasn't been mentioned regarding the reactors is that the wide opening actually makes them much easier to clean than an RBF, especially if you're working with a heterogeneous mixture containing a lot of solids. Once you detach all of the accessories and remove it from the rack, it shouldn't be any harder to wash than a large, heavy stockpot.

Stirring them is also more effective since you can use a larger mechanical stirrer, not being limited by the diameter of the flask's central neck. At larger scales, mechanical stirring becomes a necessity as magnetic stirrers are simply not powerful enough to get 5+ liters into a good vortex, especially if it's heterogeneous or viscous. The sturdy, 4-bladed paddle shown in the one you posted wouldn't fit into an RBF, even if it had a 55/50 central joint. 2-bladed, rounded paddles that can rotate to fit into a flask do exist, but in my experience, these can be a bit cumbersome to get in and out and have an unfortunate tendency to scratch up your flasks.

But as others have noted, these are absolutely unnecessary for hobby chemists. They aren't even often seen in academic research labs. This is pilot-scale commercial synthesis stuff, and not designed with hobbyists or researchers in mind.




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[*] posted on 24-11-2024 at 15:26


Quote: Originally posted by Sulaiman  
Based on the OP a 1 litre double wall reactor kit would cost about the same as my entire chemistry budget since I was born ;)


But you can buy one used for a fraction of the new cost. But makes more sense if you are making a large amount of a valuable compound. If you are making something small or cheap, it is hard to justify.

Also, most pharmaceuticals have to be made via GLP rules, and they mostly require detailed protocols, and fixed reactors suit those well.
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[*] posted on 24-11-2024 at 15:39


The only time I have seen option 2 used was for the short path distillation of cannabinoids. Heating to ~200C at 50microns. This could maybe make sense if you are doing a reaction and distilling off solvent, then vacuum distillation of the product. Maybe useful for some decarboxylation?
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