Sciencemadness Discussion Board - 1,4-Dioxane from Ethelene Glycol and H2SO4

1,4-Dioxane from Ethelene Glycol and H2SO4

MrMario - 12-2-2016 at 06:27

Hello,

I want to make 1,4-Dioxane from EG and Sulphuric Acid (catalyst) by Dehydrogenation. The reaction forms 1,4-Dioxane (Bp. 101), H2O (Bp. 100) and 2-methyl-1,3-dioxolane (Bp. 75) in smaller quantities. I want to use fractional distillation to separate the 2-methyl-1,3-dioxolane from the water and 1,4-Dioxane and than salt the Dioxane out of solution.

What kind of salt can I use for this? On youtube someone uses K2CO3, but does this also work with NaCl, Na2SO4 or Na2CO3 (all anhydrous ofcourse)?

PHILOU Zrealone - 18-2-2016 at 08:05

Should work, the only aim of the salting out effect is to take care of the water activity sothat it is less available for the organic molecule that is then kicked off solution...salting out effect also works by a density change favorizing the segregation of the organic phase vs the aqueous one.

UC235 - 18-2-2016 at 11:56

I've done this before. Workup is complicated by:

1) There is a fair amount of free acetaldehyde in the crude distillate.

2) 2-methyl-1,3-dioxolane is completely immune to base, including molten sodium metal.

3) 1,4-dioxane forms an azeotrope with water boiling at 88C and containing 18% water.

My suggestion is to take the crude distillate and add in solid NaOH in small portions with shaking. This salts water out and polymerizes free acetaldehyde. You're going to need a lot of it. The liquid will turn dark brown and tarry matter will settle out on standing. Decant the liquid and discard the lower layer. Allow to stand for more time over solid NaOH prills/pellets. A large column will be able to separate the two components in the absence of water but it is a very difficult fractionation.

Alternately add a portion of ~50% aq sulfuric acid and stir overnight. Carefully neutralize with conc. NaOH solution (it gets very hot. you will need to stop and let it cool). Add more solid NaOH to salt out water and polymerize the acetaldehyde you produced by destroying 2-methyl-1,3-dioxolane. Dry again over solid NaOH. I do not know if this is sufficient to destroy all the dioxolane but it will probabl make the fractionation easier.

DJF90 - 18-2-2016 at 14:52

Quote: Originally posted by UC235

I've done this before. Workup is complicated by:

1) There is a fair amount of free acetaldehyde in the crude distillate.

2) 2-methyl-1,3-dioxolane is completely immune to base, including molten sodium metal.

3) 1,4-dioxane forms an azeotrope with water boiling at 88C and containing 18% water.

My suggestion is to take the crude distillate and add in solid NaOH in small portions with shaking. This salts water out and polymerizes free acetaldehyde. You're going to need a lot of it. The liquid will turn dark brown and tarry matter will settle out on standing. Decant the liquid and discard the lower layer. Allow to stand for more time over solid NaOH prills/pellets. A large column will be able to separate the two components in the absence of water but it is a very difficult fractionation.

Alternately add a portion of ~50% aq sulfuric acid and stir overnight. Carefully neutralize with conc. NaOH solution (it gets very hot. you will need to stop and let it cool). Add more solid NaOH to salt out water and polymerize the acetaldehyde you produced by destroying 2-methyl-1,3-dioxolane. Dry again over solid NaOH. I do not know if this is sufficient to destroy all the dioxolane but it will probabl make the fractionation easier.

That second method looks much better than the first UC but I still feel it is lacking... lets think through this rationally...

In the reaction two molecules of ethylene glycol are condensed to produce one mole of dioxane and two moles of water. Acetaldehyde, 2-methyl-1,3-dioxolane and more water are formed as side products from competing reactions. Addition of concentrated sulfuric acid (theres enough water already present) to the crude mixture and arranging for distillation at e.g. 50 *C should hydrolyse the 2-methyl-1,3-dioxolane and remove acetaldehyde as an overhead product (bp 20.2 *C). With any luck any ethylene glycol formed in this hydrolysis will either form more dioxane, or undergo pinacol rearrangement to give acetaldehyde which is removed during distillation.

As such, the mixture at this point should consist only of dioxane, water and sulfuric acid. Fractionation of this mixture should give the dioxane-water azeotrope as an overhead at 87.8 *C, which has the composition of 18 %w/w (52 mol%) water, i.e. half of the water formed in the original condensation reaction (see stoichiometry) will remain as bottoms with the sulfuric acid which was added for hydrolysis of the side product 2-methyl-1,3-dioxolane.

The dioxane-water azeotrope so obtained could be further processed by salting out. Potassium carbonate is a good candidate as it has good solubility in water (52 %w/w at 20 *C). 100 g of azeotropic distillate contains 18 g water and so should be treated with ca 18 g potassium carbonate. The dioxane phase should be separated, dried over further potassium carbonate (or other dessicant) if necessary and purified by fractional distillation - any residual water passes over first as the azeotrope (saved for reprocessing with a future batch) and subsequently anhydrous dioxane should be obtained as an overhead product.

Thats how I would approach it anyway.

[Edited on 18-2-2016 by DJF90]

AvBaeyer - 18-2-2016 at 19:56

If you can get access to Elderfield's "Heterocyclic Compounds" Vol 6 there is a chapter on dioxane. Of interest is a list of references which describe solid addition complexes of dioxane which can be used for purification via crystallization. For example the complexes with sulfuric and phosphoric acids and elemental bromine are recrystalizable solids. The chapter also points out the extreme difficulty of purifying dioaxane by distillation.

AvB

DJF90 - 19-2-2016 at 03:36

Quote: Originally posted by AvBaeyer

If you can get access to Elderfield's "Heterocyclic Compounds" Vol 6 there is a chapter on dioxane. Of interest is a list of references which describe solid addition complexes of dioxane which can be used for purification via crystallization. For example the complexes with sulfuric and phosphoric acids and elemental bromine are recrystalizable solids. The chapter also points out the extreme difficulty of purifying dioaxane by distillation.
AvB

Cheers for the reference Av, I've requested it at the library and will provide photocopies of the relevant section when I get round to looking at it. I was aware of adducts with bromine and SO3, but neither are particularly efficient/useful for the purification of dioxane (as the value of the other reagents involved is quite high). The adducts with sulfuric and phosphoric acids are new to me. A quick SciFinder search revealed very little on these species, and I found two references which I have attached. I'm not sure either of the acid-adducts will be particularly useful in the purification of dioxane. I think the best method would be fractional crystallisation of the solvent but it preferably needs to be dry to avoid melting point depression (in order to facilitate good recovery).

What I suggested in my previous post was a means of obtaining dioxane from the initial crude distillate without using large quantities of other reagents. The main contaminants (acetaldehyde, 2-methyl-1,3-dioxolane, water) that make separation difficult by fractional distillation are removed first to facilitate purification. It was intended to be a suggestion/starting point for a lean process. I've attached the pages from Armarego and Perrin on what they say about 1,4-Dioxane purification.

Attachment: Crystal structure of the molecular compound 1,4-dioxane-sulfuric acid.pdf (672kB)
This file has been downloaded 363 times

Attachment: Dioxane-2H3PO4.pdf (222kB)
This file has been downloaded 353 times

Attachment: 1,4-Dioxane purification (Armarego and Perrin 6th Ed.).pdf (78kB)
This file has been downloaded 561 times

BromicAcid - 19-2-2016 at 04:32

Here's a procedure from one of my favorite members we don't see anymore.

http://web.archive.org/web/20080424022257/http://www.frogfot...

MrMario - 19-2-2016 at 08:34

I feel really sorry for all those moles who always get used in chemical reactions, kind of animal abuse

But jokes aside, many thanks for the detailed comments. This will surely will help me and other people out a lot.

DJF90 - 19-2-2016 at 13:04

Quote: Originally posted by DJF90

Cheers for the reference Av, I've requested it at the library and will provide photocopies of the relevant section when I get round to looking at it.

The book was retrieved from the stacks quicker than anticipated, so I've been down and scanned the relevant pages. Please find attached. Sorry for the large file size (not sure how to get it smaller) and wonky pages.

Attachment: Dioxane excerpt from Elderfield's Heterocyclic Compounds volume 6.pdf (3.1MB)
This file has been downloaded 463 times

Quote: Originally posted by BromicAcid

Here's a procedure from one of my favorite members we don't see anymore.

http://web.archive.org/web/20080424022257/http://www.frogfot...

I remember seeing Frogfot's site when it was still online, but I don't think he was active on the forum when I joined up on SM. Thanks for that blast from the past Bromic. Theres some other nice syntheses on his site too.

[Edited on 19-2-2016 by DJF90]

Boffis - 19-2-2016 at 14:42

Quote: Originally posted by Magpie

Here's a video of a guy making dioxane from ethylene glycol anti-freeze. He's using NaOH for drying but does not quantify his purity.

I'm amazed that he was doing this with the garage door open for all to see. One comment addresses that.

https://www.youtube.com/watch?v=RfQGwleIA8E

At 2:53 he gives a quick shot of his large flasks sitting out on the driveway!

This was posted some time back, has anyone ever tried NaOH as the cyclitizing reagent? It looks cleaner than sulphuric acid.

MrMario - 30-3-2016 at 02:45

So I tried to make 1,4-Dioxane from EG and Sulphuric acid and got similar results to Doug's Lab.
My ethylene glycol was pre-distilled under vacuum to ensure that there were no impurities. After I obtained the mixture of 1,4-Dioxane and the side products I added some K2CO3 and NaOH (~20g for 300mls of crude yield) and let it sit for 3 days. It turned to a red mixture with two layers, but the lower layer was not extremely black like oil like in Doug's video but pretty similar. When I started the distillation of the crude separated dioxane layer most came over in the 84-88 range and only 25mls were left which I did not distill because of peroxides.

My question is, did any Dioxane even form or is it possibly destroyed by prolonged storing over NaOH or side reactions? I used a good Vigreux Column to get a decent separation.
I can re-distill it with two Vigreux columns (700mm in total) if needed. Any thoughts on this?

UC235 - 30-3-2016 at 03:48

Quote: Originally posted by MrMario

So I tried to make 1,4-Dioxane from EG and Sulphuric acid and got similar results to Doug's Lab.
My ethylene glycol was pre-distilled under vacuum to ensure that there were no impurities. After I obtained the mixture of 1,4-Dioxane and the side products I added some K2CO3 and NaOH (~20g for 300mls of crude yield) and let it sit for 3 days. It turned to a red mixture with two layers, but the lower layer was not extremely black like oil like in Doug's video but pretty similar. When I started the distillation of the crude separated dioxane layer most came over in the 84-88 range and only 25mls were left which I did not distill because of peroxides.

My question is, did any Dioxane even form or is it possibly destroyed by prolonged storing over NaOH or side reactions? I used a good Vigreux Column to get a decent separation.
I can re-distill it with two Vigreux columns (700mm in total) if needed. Any thoughts on this?

Sounds like you distilled a mixture of 1,4-dioxane-water azeotrope (b.p. 88C) and 2-methyl-1,3-dioxolane (b.p. 82-83C).

See if adding more solid NaOH forms more of an aqueous layer. 20g seems like not nearly enough for 300ml of distillate. Peroxides don't form in a couple days in the stuff so I think you're being overly-cautious in discarding the last 25ml.

I have some crude dioxane (post H2SO4 treatment as described upthread). It's sitting over NaOH for months now and freezes almost solid on cold days. It does not react.

Vigreux colums are terribly inefficient. A packed column with copper or stainless steel scrubby should be excellent here.

MrMario - 14-5-2016 at 10:37

I read the added pages and tried today to reflux 200ml of crude Dioxane (I froze it twice and decanted the remaining liquid) with 20ml H2O with 8ml HCl (32% aq.)
The freezing was anhydrous and did not have any water nor HCl.
In the paper they had it sit over Ferric Chloride and I did not. Will this have effect on the reflux (without the ferric chloride) or will refluxing with just aq. HCl be fine?
It has also stand for several weeks now over solid NaOH (minimal amount of water) and the redish colored mixture was distilled to remove the impurities.

[Edited on 14-5-2016 by MrMario]

PirateDocBrown - 10-2-2018 at 05:43

I just turned out a batch.

300 mLs of the cheapest antifreeze concentrate Wal-Mart had, with 30 mLs of Rooto, in a 1000 mL RBF in simple distillation, to get a crude product.

Next, to work up this product to a pure state.

Shout out to Doug and Nurdrage, for the videos.

[Edited on 2/10/18 by PirateDocBrown]

j_sum1 - 10-2-2018 at 13:08

Brilliant work. Including the antigravity thumbnail.

PirateDocBrown - 10-2-2018 at 13:25

Not sure why it does that. It's right side up, when you click on it.

PirateDocBrown - 13-2-2018 at 00:55

After about 200 mL of crude product came over, I added another 200 mL of antifreeze to the cooled reaction flask, and continued.

Got about 400 mL crude product.

I think I wanna do hydrolysis first, before drying. Nurdrage and Doug went with base catalysis, but Allchemystery used more acid.

I have smelled none of the sour-apple smell of acetaldehyde during any of this, so I am guessing that it all has reacted to make methyl dioxolane (or polymers left in the residuum), and came over with the product. Hydrolysis should break this up, and heat should drive off what acetaldehyde does not polymerize via aldol reaction in situ.

In short, it calls for fractional distillation, but following acid, or base catalyzed hydrolysis? Nurdrage indicates that if base is chosen, KOH is preferable to NaOH, due to higher solubility.

All questions for another day.

Chemateur80 - 23-3-2018 at 11:43

I had a go at this synthesis. For now I plan to use the dioxane to extract sodium metal Nurdrage style.

The purification steps are not completed yet.

For the synthesis I used:
Pure ethylene glycol
Pure sulfuric acid (96-98%)
Pure potassium hydroxide

I ran two batches in a 500ml RB-flask in a heating mantle. One batch with 250ml ethylene glycol and one with 200ml. I added 20-25ml sulfuric acid to each.
I then set up for simple distillation.
I had some problems with temp control in both batches, but finally got a steady drip rate of around 2 drops/sec at 102-106C.
When the foaming started I increased stirring, but finally it was too much and the heat was turned off. No black tarry foam escaped the reaction vessle.

I collected around 200-250ml of distillate after each batch. The distillate was pale yellow and had a kind of weird sweet and sharp smell, something like liquorice/vanilla. Hard to describe.

Purification
I combined the two batches and added 20ml of conc. sulfuric acid to hydrolyze 2-methyl-1,3-dioxolane.
The mixture turned orange.

I set up for fractional distillation. At first acetaldehyde came over at 20-30C, then the temp increased with a slower dripping rate.
At 84C I switched the receiver and the distillate that came over between 84C and 97C was collected.
The two fractions collected were:
47ml between 20C and 84C (mostly acetaldehyde)
ca 370-400ml between 84C and 97C

In the distillation flask I was left with around 150ml of orange liquid with some tarry pieces sticking to the magnet. I suppose this was mostly sulfuric acid and water.

To the dioxane mix I then added 40g of KOH and let it stir. The solution turned dark orange/red. When the KOH dissolved I added another 50g.
This also dissolved and when I stopped stirring I had two phases.
The bottom water phase was around 150-200ml and quite clear.
The top dioxane phase was around 200-250ml and cloudy.
I've left the two phases standing like this.

Some questions:
Any ways to improve the synthesis? Better temp control? Larger reaction vessle to control foam longer? Adding water to begin with, instead of using conc acid/glycol-mix? Better to run one big batch if possible?

I feel that the yield will be a bit low from 450ml of ethylene glycol.
Theoretical yield should be around 350ml of 1,4-dioxane and I only have maybe 200-250ml of crude product.

How fast should the drip rate be during fractional distillation? I had several drops a second. Any risk of overpowering the condensor?

Why not collect the fraction from 84 all the way up to 102C? Should all the dioxane/water-azeotrope be boiled of by around 94-97C?
If there's an excess of water I suppose so, but why not collect all the way up to 102C since pure dioxane boils at 101C?
Would I only be collecting water around 100C?

I had around 180ml left in the distillation flask after fractional distillation. It seems like a lot. Is this normal from a batch my size? Is it mostly water and/or high boiling side products?

Is the dioxane layer supposed to be cloudy after adding and stirring with KOH? Should I add more KOH when it all dissolves?

Any ideas of how to remove tarry gunk from my magnets? I've tried a mix of hexane/acetone and also quite konc NaOH solution. It's still there.
Maybe heating the NaOH solution?
I'd like to avoid things like dichromates and piranha solution if possible.

Any help would be appreciated!

Vosoryx - 23-3-2018 at 12:40

I tried this, DCM works wonders for removing the tar from flasks. Don't see why it wouldn't do the same for magnets.

DraconicAcid - 23-3-2018 at 12:48

I find that boiling nitric acid cleans magnets very well.

Chemateur80 - 4-4-2018 at 13:14

A little DCM worked very well for cleaning the magnets. Thanks for the tip Vosoryx.

So I'm kind of disappointed with the experiment so far.
For details in the synthesis, see my post earlier.

After drying with KOH for a week I collected the upper dioxane layer (ca 150ml), which had an intense yellow colour.
To this I added some Na/MgO-aggregate to further dry it. This caused a lot of bubbling.
The next day I filtered the mix and added some more Na/MgO to the dioxane to see if I could isolate some sodium metal.
I set up for simple distillation, and the temp quickly reached ca 100-101C, which is the boiling point of 1,4-dioxane. The distillate was clear.

After a while I could see some tiny spheres (<1mm diam) of molten sodium dancing around on the surface. I distilled to near dryness, but the spheres never grew bigger. Probably too much Na/MgO with too little dioxane.
I used an RBF so I also think the magnet had a hard time stirring the mix to coalesce the sodium.

I collected 100ml of sweet-smelling 1,4-dioxane, which seems very low from two batches of 200/250ml ethylene glycol.

I collected some of the small spheres of sodium and put them in the dioxane to prevent peroxides from forming during storage.

Since I got so little dioxane I dumped the rest of the Na/MgO in a bucket of water. Vigorous reaction with flames, especially with the aggregate closer to the bottom of my reaction container.
With a bit more solvent I think I definitely could have isolated more sodium metal.

So, has anyone else tried the dioxane-synth with better yields?
Any improvements that I could make when I try to make more?

Maybe I could have added more KOH to the KOH/water mix to see I there was more dioxane to salt out, but I doubt that there was any.

greenlight - 4-4-2018 at 19:33

I just made some 1,4-dioxane myself using antifreeze and successfully made elemental sodium yesterday with it.
Some things I did differently:

● After the second distillation (fractional), I placed 35g KOH in and stirred for 15 mins. I only let it sit overnight and then seperated the top organic layer the next morning. A week seems a little long and adding more KOH makes the top layer darker and darker the more you add. My colour was medium dark orange.

● I added a generous amount of cooled potassium/magnesium oxide and let it stir for the whole day. When added, there was noticeable fizzing.

● I then distilled this and collected about 250ml crystal clear 1,4-dioxane from the initial 800ml antifreeze.

When you go again, use a big flask for the initial distill do you get a decent amount of product because you lose some with every distillation. I started out with 400ml from the first distillation.

The first time I tried the sodium synthesis it failed. There was a lit of fizzing and the dioxane got very warm upon addition of the aggregate prior to distillation. I got no product and I am convinced there was residual water in the dioxane still which killed the sodium.
The second time I got 8g of elemental Na from it probably due to the fact that the previous run had taken all the water out of the dioxane. Am going to run it again as I need a decent amount of sodium

[Edited on 5-4-2018 by greenlight]

Vosoryx - 4-4-2018 at 20:52

Figured i'd add in my experience to help anyone else out there.

I made 1,4-dioxane and then successfully made Sodium metal from it (though not a lot) for a science fair project a few months ago.
Everything for me worked fine on the first run. I don't have my lab journal with me right now, so I don't have the exact yields/starting amounts. However, i'm fairly sure I used, in total, 600 mLs of EG, and got about 115 mLs of dioxane. After I used it to make some sodium metal, this number was reduced even more. (Due to some being lost to the vent, dead space in the apparatus, left in the remaining slag, etc)

I just used concentrated antifreeze, and straight sulphuric acid drain cleaner - not even boiled down, and certainly not my precious 98%. I used 40 mLs for ever 300 mLs of antifreeze. For the first part of my project, I didn't have access to a magnetic stirrer. (Though I borrowed the school's for the actual sodium extraction) Thus, I couldn't use the stirring to regulate the tar produced - which ended up plaguing me intensely. The first time, I turned off heating as soon as I noticed a tar forming. However, due to the fact that my heating source was not a proper hot-plate, the reaction mixture continued to be heated lightly. The tar, fortunately, didn't reach OVER the still head (though it did reach the still head, calling for a week-long NaOH bath.) The second time however, even with me turning off the heating as soon as I saw tar, the tar ended up almost instantaneously boiling into the receiver. This proved not to be a problem, once I fractionated everything.
For each run, I placed in a bunch of NaOH. At the time, I had no KOH to use instead. I left it for a few weeks (while I was away from my lab) and decanted and fractionated the remaining liquid, to get the ethanal and other bi-products out.

From the amount of Na-MgO I had, I ended up not having enough dioxane to coalesce all the sodium, it was left in really small balls. So after I distilled off all the dioxane, I took the distillate and added it back into the boiling flask and re-distilled. This was needed in order to make the beads large enough so that i could reasonably take them out with a small pair of pliers.
Interestingly, I noticed that some of the vapour this time came off much below the dioxane BP or even the azeotrope. (It was approximately in the 60-70 degree range.) What this is I have no idea, and i'm starting to suspect it might be an error on the part of the thermometer because it is, for all tests I can run, indistinguishable from dioxane. It was dry, same freezing point, and after I tested it in these ways the boiling point had gone up to exactly that of dioxane. However, if it was a thermometer problem, I have never experienced it at any other point.

Once I had distilled down the second time, I took it off before it was completely dry (for some reason - I dunno, it was late at night) and dumped the contents onto a piece of dry paper in a plastic bin. I then spent some time with a set of jewelry pliers picking everything out. Because there was probably more sodium left in the slag, I put the slag back into a container, so that I could remove more of it at a later date should I feel so inclined, and I might do so now that I have my own hotplate.

Vosoryx - 4-4-2018 at 20:54

Quote: Originally posted by Chemateur80

A little DCM worked very well for cleaning the magnets. Thanks for the tip Vosoryx.

Glad I could help!

Chemateur80 - 9-4-2018 at 05:13

Thanks for your input greenlight and Vosoryx. Very interesting.
I will definitely use a larger flask and do one distillation the next time.

It's a messy reaction, so maybe the yields won't get better than 25-40% anyway.
My theoretical yield should have been around 350ml of dioxane, and I got 100ml, which is a 25% yield.

Would be nice to find ways to increase the yield in the starting reaction between EG and sulphuric acid. Temp control and the tarry crap seem to be the biggest problems.

I notice that neither of you used sulphuric acid to hydrolyse the 2-methyl-1,3-dioxolane formed in the initial reaction. How come?
I think I saw a thread here on SM saying that it could be as much as 10-20% of the yield.
It hydrolyses into acetaldehyde and EG when mixed with sulfuric acid, and the dioxane can then be fractionally distilled without this impurity.

The KOH was left for about a week because I didn't have time to experiment more at the time. I wonder if it makes any difference in yield.
Could the KOH and the dioxane react?

Congrats on your 8g of sodium metal greenlight! Must have been nice to see those shiny spheres.

I will make more dioxane soon.
I'm also thinking about improvements in the thermite-like reaction between NaOH and Mg, but maybe that's for another thread.
I used freshly crushed NaOH and 200um Mg-powder.

greenlight - 9-4-2018 at 05:30

I did use a small amount of 98% sulfuric acid in the fractional distillation, I just forgot to mention it haha. I used 60ml H2SO4 for every 500ml of antifreeze in the first distillation and about 16-17ml in the fractional distillation to hydrolyse impurities.

I am not sure sure if the week wait would actually affect the dioxane yield but maybe next time try it the other way and see if it makes a difference.

Also I have re-weighed the sodium yield and it is only 6 grams. Something wrong with my scale and it is fines simce I replaced the batteries. Still a decent yield though I think..
It is very exciting to see blobs of molten Na as the solvent level gets low. I plan to run the reaction quite a few more times as I need something like 50g elemental sodium.

I wonder if the reaction can be scaled up?

[Edited on 9-4-2018 by greenlight]

MöbiusMan - 15-7-2018 at 00:12

https://www.sciencemadness.org/whisper/viewthread.php?tid=84...

[Edited on 15-7-2018 by MöbiusMan]

Fery - 31-8-2022 at 06:14

Pitty that there are 2 threads with the same topics 1,4-dioxane, here another one:
https://www.sciencemadness.org/whisper/viewthread.php?tid=84...

I did not want to do this reaction after seeing the nasty sticky black residue foaming into condenser in youtube, but later I changed my mind. I did some adjustments and luckily no problems with foaming from the flask into condenser, also stir bar as well glass stayed clean. I did only the reaction, not the workup yet. My ideas and improvements:

1.
according the 3 MB attachment by DJF90 the amount of H2SO4 should be 4% (but I do not know whether it is vol% or wt%) and not 10 vol% as used everywhere in youtube videos as well all experiments here in the forum
I performed the reaction by using third of the sulfuric acid, 11 ml 96% H2SO4 (Lach-Ner) for 300 ml of pure commercial ethylene glycol (fichema.cz) which is 3,7 vol% of the catalyst. If the 4% should not be volume but weight then only about 6 ml would be enough for 300 ml of ethylene glycol.
Moreover after distilling out some product, I added fresh ethylene glycol to the flask and continued.
I did 4 cycles, the remainder in the flask before adding fresh ethylene glycol was always approx 100 ml or even more. In the last round when I distilled out more, there stayed about 50 ml of black viscous liquid in the flask which was easy to pour out.
I processed that way approx 900 grams = 800 ml of ethylene glycol in 4 cycles (distilling out 200 ml of product and then adding 200 ml of ethylene glycol).
The H2SO4 is only catalyst, not reactant...

2.
I used large 1 L flask for the 300 ml liquid with plenty of empty space to be safe and avoid foaming into condenser (the dead volume and distance from surface of boiling liquid to the level of condenser also reduces droplets carried into condensate by vapor).

3.
I did not distill too far during the last cycle, for the 11 ml of H2SO4 the remainder in the flask was about 50 ml and no foaming / bumping observed. I used heater with integrated magnetic stirring.

4.
??? maybe ethylene glycol could be dripped from additional funnel during the reaction at the same drop rate as the volume of condensate ???

5.
??? could be 75% or 85% H3PO4 used too ??? as a legal and maybe more available alternative than H2SO4 for home chemistry???

Lionel Spanner - 31-8-2022 at 07:07

Something which may be of interest is this Dow Chemical patent from 1985, which involves using diethylene glycol as a starting material, and running the reaction under reduced pressure - hence, the reaction occurs at a lower temperature, resulting in less foaming and sludge.

I've not tried it myself, so I can't comment on its feasibility.

Attachment: 1,4-dioxane (1985 patent).pdf (511kB)
This file has been downloaded 11 times

Fery - 1-9-2022 at 07:53

Hi Lionel Spanner, interesting, my friend Bedlasky brought me diethylene glycol which are they producing. But it is not so available to home chemists as ethylene glycol.
To prevent foaming and sludge: use less H2SO4, only approx. 4 %, it is only a catalyst. Temperature during the reaction is approx 140-150 C thanks to high boiling point of ethylene glycol and this temperature is similar as used in production of diethylether where you drip ethanol into 140-145 C hot mixture of conc. H2SO4 and ethanol. Do not distill too far, e.g. in my case for 11 ml of conc. H2SO4 I let about 50 ml residue in the flask and did not distill further. Use big flask and fill it to 1/4-1/3, not more, e.g. for 11 ml of H2SO4 + 300 ml of ethylene glycol I used 1 L flask. My ethylene glycol was also pure (commercial) as well H2SO4. Moreover I managed to perform 4 cycles with the above amount of catalyst so I processed approx. 900 g = 850 ml of ethylene glycol. I collected approx. 800 ml of condensate. Maybe the ethylene glycol could be added from dropping funnel during the distillation.
I added 10 ml of conc. H2SO4 to the 800 ml of condensate and let to stay overnight. After half a day I performed simple distillation - I collected everything upto 98 C which gave 500 ml of distillate and later I collected 100 ml of distillate in range 99-108 C. I added excess of K2CO3 to that 100 ml fraction and 25 ml of organic upper phase separated which I tested in small flask with inserted thermometer and on boiling the thermometer read 85 C which is close to azeotrope of 1,4 dioxane with water (88 C).
I will treat also that 500 ml fraction with K2CO3 and then KOH and distill on Hempel column (packed with Raschig rings) and variable ratio distillation head (that's why I did not yet fractionate it more precisive, I will do that as the final step, until now I hydrolyzed 2-methyl-1,3-dioxolane = acetaldehyde ethylene acetal and now I have to remove all water present).
There stayed about 200 ml residue in the distillation flask so that 10 ml of H2SO4 and the rest could be H2O and some ethylene glycol or maybe 3-hydroxybutanal from acid catalyzed aldol condensation of acetaldehyde.

[Edited on 1-9-2022 by Fery]

Fery - 5-9-2022 at 04:34

I processed the distillate with K2CO3 . 1,5 H2O and totally 130 g was necessary, only then it did not dissolve anymore (100 g should be enough if used anhydrous K2CO3). I kept upper organic layer circa 400-450 ml and I distilled the bottom aqueous layer circa 150-200 ml from which I collected fraction in range 85-98 C of volume 15 ml of distillate which after salting out with K2CO3 gave 9 ml of dioxane which was added to the main portion.
To the 400-450 + 9 ml ml was added 10 g freshly fused anhydrous K2CO3 (heated in nickel melting pot for 30 minutes at 300 C) which clumped immediately so then KOH was added incrementally, totally 25 g of KOH was necessary and was let to stay for 2 days at room temperature. Then upper layer separated (circa 350-400 ml) and bottom layer discarded (circa 50 ml). The upper layer was then let to stay with fresh solid 10 g KOH for half a day, no more water separated, so the dioxane was then distilled, collected fraction 95-101 C which weighed 350 g and the remainders from distillation (forerun + residuum in flask) had 20 ml.
I did not dry it with Na as I do not plane any experiment with dioxane soon. It will be dried and redistilled before possible experiment in the future.
I processed various remainders to increase yield as much as possible. I got 350 g of 1,4 dioxane (not completely dry) from 900 g of ethylene glycol.