Good Day gentlemen.

There are two choices of materials to use here. 
1. Stainless Steel
2. Pyrex Glass

The only hold-back which I see with Stainless Steel, is that it may react with certain substances.  Research has led to believe that it is suitable for use with acid solutions, yet upon furthing reading it shows that Stainless corrodes with Formic Acid, and Acetic Acid.  While this is used in Various reactions on larger scale such as Epoxidation, Hydrolysis, and so on with no (seemingly) issues.

The only hold-back with Pyrex is that is can shatter easily with heat, depending on the size of the vessel.  While it is indeed pyrex, the literature for such size vessels say do not heat or use on a hotplate.  This makes no sense, as rbf's are pyrex and can be heated all day long.

The other benefit with stainless is that it can be welded easily, and outfitted with all sorts of goodies and extras needed.  One easy benefit noted is welding on a bearing for easy stir shaft integration.  Using glass, this is more difficult and subject to breaking once again.

If yall can chime in with notes on either side of the discussion that would be cool. 
For better reference, think Stainless 5 gallon pot with lid, or Pyrex 5 gallon carboy.

Epoxidation using Performic.
Amination.

Simply for reading purposes...

Epoxidation using Performic.
Amination.

Simply for reading purposes...

So over 20 liters, you´ll need a big separation funnel too. 50 liters and of course you have to transfer the whole shebang.

Hey, look at the performic write up and scale it linear up. Don´t forget to take into account this being a exothermic reaction and the problem of volume rising exponentiell, surface area only linear. The heat produced gets not away think heat transfer, there are physical limits to this. Thats the eason why such big glass reactors are actually almost solely used for biological processes, fermentations for example and even in a fermentation over 500 liters the generated heat gets a serious problem which can not really solved by cooling the vessels jacket. Coils inside are needed.
Ok there is stuff which can be done this way but not the performic I guess.

Scaling rections massivly up is not trivial as there always barriers of  handable volume with a certain setup and breaking through this barrier usually means a complete rethinking and redesigning the process. The books on industrial chemistry will tell you the same.

The most practical solution is often to run several identical setups at same time for not having to invent the wheel again but working with known parameters and not having to fear that one failure (human or technical) can cause tremendeous damage.

Either this or you start reading about how industry does or has done peroxidations in large batches or small continious setups and try to find a solution from this point.

/ORG

PS: A hint: There are no seperation funnels so big as with amounts of 5l or more in the reaction a necessary extraction is always done as a continous extractions. It would be a good idea with 2l already but in clandestine chemistry  it seems to be a matter of honor to employ insane amounts of highflammable solvents for no reason but not having read Vogel´s 3rd.

Actually in this size borosilikate has not so much advantages over sodalime anymore. So big boro cannot stand thermal shock anymore (Duran thick walled rection vessels are rated to temperature differences of maximum 30°C) but soda playsnow the card of elasticity being able to twist a bit when boro just breaks.

Back on topic:
The solution is as obvious as easy, though not simple. To get the best of two worlds you may use them both. A glasslined, enameled vessel. Thats perfect but probably a bit too expensive. PTFE coating? Honestly forget it people should think more and listen less to advertisements. PTFE aka Teflon is chemical resistant but not mechanical tough, not at all. In special it is prone to abrasion. You dont want ultrafine fluorocarbon particles in your reaction and product, trust me on this.

There is one possibility which is in reach and affordable. Glasscoating in a Sol-Gel process. From a Sol-Gel real glass can is precipated tetraorthosilane is the main reagent needed, this is not expensive in the small amounts needed for a micrometer coating.
The problem is that curing is done at 450°C. Or by time, several months in the worst case. Otherwise the coating will crack. There are compositions curing at lower temperatures too, lots of possibilities....

A very good procedure absolutely in reach for you and me giving an outstanding resistant coating is described in the attached document.

As the main problem is the curing it would be unfair not to provide a cure  :
A perfect crack free coating is achieved by treating the deposited (sprayed, painted, etc.) with a cold discharge. Works for synthetic polymeres too.
Uh? Ah! Think: Cold discharge = ozone generation = ozone generator/china/Ebay = 20$ 
(The referring article I would have to dig up in my piles of unsorted stuff, so only on request for need not curiosity)


Again an excellent solution nobody will use,
at least I tried.

/ORG
 

ok, but if the trouble is the thermal shock of the glass. It would be external coated with a few millimeters ( one centimeter is better) of Polyester Resin. And heat it in a water bath (ok, just reactions  100ºC around)...  If the glass broke the reaction mixture will still inside the flask.
I had check "polyester chemical resistance", and is  enough for the most part of chemistry discussed here.

Lousy temperature resistance and makes heating/cooling a pain in the ass.
Glass, in special high quality glass is just fine, Büchi sells glass reactors rated up to 12atm pressure and they cost you just a signature (yes, parchment and blood. Own blood  )
The quest for the universal, cheap ghetto reaction vessel is as old as boards like this older since, it was already on ADC...

In reality at this large it is considered a production setup, parts choosen to fit for the demands of a special synthesis. And a reaction vessel being only part of a bigger setup, lab, plant as you may call it and this demands a much more holistic point of view anyways.

Personally I find the Sol-Gel and related techniques of glasslike coating so interesting for this might be used not just on metal but virtually any surface. Giving now that - lts take pulp, impregnated paper wood pulp takes far higher temperatures then your plastic and with some hemp fibers reinforcement its structurally more stable too, and it can be formed freely by hand by anybody, taking this into account and add a chemically resistant layer of glasslike properties, then we would have an instant disposable kilo-lab, not buildt for eternity but for six months not even a joint to leak.

That would be real fun.

/ORG