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Author: Subject: Distillation of paraffin wax (or its thermal decomposition)
xfusion44
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[*] posted on 16-11-2022 at 14:16
Distillation of paraffin wax (or its thermal decomposition)


Hello!

For a long time I've been wanting to try to distill paraffin wax, just to see what I get. I've been searching online but wasn't able to find anything useful on this topic. I'm just an amateur with no chemistry background, except for the things I've learned online, so I didn't know what to expect. Somehow I thought that paraffin was product of distillation of crude oil and that if it's a mixture of compounds that I should be able to separate those compounds. (it's actually crystallized out of a mixture of oil and wax, industrially, not distilled).

Long story short:

I tried distilling the wax, the wax started turning more and more yellow, I got the first drops through and something started stinking like burnt rubber. At first I thought it was the melting rubber on the clamp that was holding everything together but after turning off the heat (due to melting rubber) I noticed it was actually the distilled stuff that was giving off the smell. In receiving beaker there was only a drop of clear and a drop of dark (haven't noticed that before) liquid. I carefully smelled the product from a few inches away from the beaker and was almost catapulted away from it! The product was something, apparently super acidic - it really burned my nose and liquid started forming in my nose to regulate the pH back to normal.
Upon cooling, the wax in boiling flask turned from dark yellow to brown/almost black and with strong light, the surface of the mass inside the flask had a greenish reflection to it. After the wax solidified, It had a dirty orange/yellow tint. Anyways, the product never solidified, it's still liquid at r.t. and is kind black-ish looking, bad smelling (like burnt rubber or something) and it even burns eyes if you get as close as 1ft to the beaker.

My question is; what happened? What did I make? It' obviously some thermal decomp. product but what? Nothing too healthy, I assume... All of this kinda reminds me of thermal cracking/pyrolysis of plastic, except the smell is even worse and even more irritating.

Thanks!

Best regards!




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Rainwater
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[*] posted on 16-11-2022 at 16:43


Recommended reading
The Chemical History of a Candle
Edit:
https://youtu.be/RrHnLXMTOWM

So commercial paraffin has additives that change its melting point, texture, and hardness for the purpose it will be used for.

Pure paraffin melts over 40~70C.(from vegetable oils)
And boils at over 350c if I remember right.

You probably distilled off some additives. Can you measure what temperature the6 distilled over at?
Or the distillates freezing point

[Edited on 17-11-2022 by Rainwater]




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xfusion44
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[*] posted on 17-11-2022 at 06:04


@Rainwater

Unfortunately I wasn't measuring anything here and I already got rid of the two drops of distillate as it was just too nasty to keep it stored.

Anyway, I think I know what happened. I was using 3 way distillation adapter and at the top of it (although the temps are a little bit lower there) was that thermometer cap, with a hole in it and a black rubber seal, but the temps were obviously still way too high. I think it was actually that rubber decomposing which created that burnt rubber smell.

Is it possible? And if so, what the hell could that super irritating compound be?

Also, does that mean I should still be able to distill wax normally if I use glass only, instead of that plastic and rubber at the top?

Thanks for the help!




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Rainwater
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[*] posted on 17-11-2022 at 08:43


Ya. At the temp needed it will decompose some. And your passed the flashpoint, so any oxygen can create an explosion or flame.
Synthetic paraffin is made from distilling crude oil.
Wiki says 370c to boil it.
That's hard on glassware, a soup can would work well. Metal pipe coming out of the top wet rag draped over it as a condenser. Good luck.




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[*] posted on 17-11-2022 at 11:48


Why not to distill it using vacuum?
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[*] posted on 17-11-2022 at 12:30


Yes, you could distill paraffin under vacuum, but it is mostly a mixture of CH3(CH2)xCH3, so just a short chain polymer version of polyethylene, but x is likely 10 to 1000 times smaller in paraffin. It could also be considered the higher boiling cousin of diesel.

Some candles are made of biologically lipids like beeswax or saturated fats, but most commercial ones are likely made of pure hydrocarbons distilled from crude oil. I understand the cost of beeswax and the like is much higher than petrochemicals.
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Rainwater
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[*] posted on 17-11-2022 at 12:36


I just seen the coolest looking apparatus now i want it Page 3. Them old timers, wow. I bet that thing was beautiful
Sorry. Hope this is helpful

VAPOR PRESSURES AND BOILING POINTS OF SOME
PARAFFIN,ALKYLCYCLOPENTANE, ALKYLCYCLOHEX"
ANE, AND ALKYLBENZENE HYDROCARBONSI

https://nvlpubs.nist.gov/nistpubs/jres/35/jresv35n3p219_A1b....




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xfusion44
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[*] posted on 18-11-2022 at 06:41


@Rainwater

Yes, I am aware of the flash point thing. As soon as the rbf breaks, you're in trouble, especially when using open flame, I guess.

It's hard on glassware indeed, I have to give some respect to the chinese rbf producers from ebay (gg17 branded) for withstanding that test, but I did start and progress very gently. I started with smallest flame, barely reaching the bottom of the rbf, waited for temperature inside flask to reach equilibrium and then carefully increased the flame, little by little. I did that for about five times, before the flame was powerful enough to lift the vapor all the way up.

Glass can withstand around 800°C before it becomes too soft but it's the thermal shock that is the most problematic. Correct me if I'm wrong, but I think it would be even worse if some low b.p. liquid was boiled, using bunsen burner, than boiling wax, because water, for example, won't let the inside get over about 100°C, but the flame temp can be up to 1800°C, so the outer part of the glass gets very hot, while the inner part stays at "cool-ish" 100°C.

The only problem with reaching higher temps, as far as I can tell, is the more substantial expansion at the bottom of the rbf, while the top (at least untill you get proper vapor) is not expanded as much and counters the expansion of the bottom part, which in turn can cause high internal forces that can break the flask.

I do have a vacuum pump, but it requires some work before it can be used and I do admit I'm a bit lazy and try to avoid "complicated" setups if not necessary.

Yeah, that apparatus is quite extreme, indeed :)

Thank you all!




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[*] posted on 20-11-2022 at 11:09


Put a bit in an iron... plate, apply heat under plate and smell it... but what you expected from this shit? smell of roses?

[Edited on 20-11-2022 by pneumatician]
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xfusion44
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[*] posted on 22-11-2022 at 00:09


Quote: Originally posted by pneumatician  
Put a bit in an iron... plate, apply heat under plate and smell it... but what you expected from this shit? smell of roses?

[Edited on 20-11-2022 by pneumatician]


I wasn't expecting the smell off roses. I don't mind some hot plastic/petroleum smell, but that burnt rubber thing is on a whole different level and as it turns out, it was due to rubber seal, not the paraffin wax. ;)




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