Benzene from PET

Ok, I think I missed this... http://www.sciencemadness.org/talk/viewthread.php?tid=14200#...
Should have read that first

Still, does anyone think this one-pot method could work?

Quote: Originally posted by ScienceSquirrel

I doubt it will work. Might be worth a try with a small amount.

Ok, I've just tried it

20g of chopped PET bottle and 30g NaOH prills (way too much for a first try on hindsight) were put in a 100ml conical flask and a makeshift condenser attached. Heated strongly for 10-20 mins. The distillate was about 3ml of an orange, semi opaque liquid that floats on water with a strong and sickening smell which I suppose I would describe as alkene like (I don't know what pure benzene smells like). I've attatched a pic of the distillate on water in a little bottle.

I could have heated it for longer and got a bit more, but it was starting to get all blackened in the flask. The residue broke my flask on cooling, but I was half expecting that.

Well, this does sound fairly similar to the results of the well documented heating of sodium benzoate with NaOH in the old PDF: orange liquid distillate, etc. I know the yield was awful, but I think it could be well improved- lots of the PET had barely even melted in the flask.

So, what do you all reckon? Could my crude distillate be high in benzene? It sounds promising to me, but I haven't really got enough to distill or check boiling point, not with my equipment anyway.

That looks pretty good See if you can find a can to do it in next time, seeing as you're using copper tubing you could just have a fitting through a hole in the lid and clamp the lid of the can between the male and female threading on one of those things that makes a flange and seals off copper tube (don't know what they're called ) I did the same to seal up the can for my benzene still except I wedged a 24/40 still head into the opening from the fitting instead.
Jeez benzene smelling sweet? To me it smells sharp and awful, quite different to toluene. Perhaps mine is still impure :/

Thanks for the replies all! I will try it in a metal can with copper pipe next time, if I can construct such a thing, after a week in sunny Cornwall , then hopefully I will have enough to redistill, check boiling point, etc.

As for the smell of benzene, maybe it could be highly subjective? But I'm sure there's loads of crap in my crude orange oil.

And Picric-A, when you say about removing the ethylene glycol, you mean just wash it out by shaking with water, yes? Looking at that pdf on PET pyrolysis though, (which seems to have just dissapeared from the net, but you can still get on Google's HTML cache), it indicates that most of the ethylene glycol gets decomposed in the pyrolysis, but maybe the NaOH will change this.

This seems like a more accessible route to small amounts of benzene for some of us, good work. I might try it soon if I have the time

Quote: Originally posted by MagicJigPipe

Not like alkenes (or worse, 6 membered cycloalkenes). I'd say like toluene except ... sweeter and "heavier".

Tell me about it....I was using cyclohexene (from a 500ml bottle) in the school lab a few weeks ago, running numerous test-tube scale reactions. I was nearly sick.

I do like the smell of toluene, and ethyl acetate too for that matter

Benzene

Quote: Originally posted by mowsala

Like so many others, I want to make some benzene. I have read the benzene production pdf at http://www.sciencemadness.org/member_publications/benzene_pr... , and I have been thinking that maybe I could generate the benzoates in situ from bits of PET soda bottle. Reading the article on PET pyrolysis at http://www.pm-kbase.com/articles/PETsdarticle(21).pdf, I see that pyrolysis of PET can yield nearly 50% benzoic acid, terephthalitic acid, and derivatives, with most of the rest going to worthless gases. So my idea is to heat hard a mixture of ground PET and sodium hydroxide, which might generate benzoic acid, which reacts with the NaOH to make sodium benzoate, approximating straight heating of sodium benzoate and sodium hydroxide, as discussed in the old pdf. Then I can just distill off the benzene. I'm gussing that disodium terepthalate will act pretty similar to sodium benzoate when formed in terms of breakdown to benzene and sodium carbonate. What do you reckon, will it work? I'm not expecting great yield, but since empty soda bottles are free and sodium benzoate is not, I think it could be quite worthwile. [Edited on 21-10-2010 by mowsala]

Quote: Originally posted by mowsala

Thanks for the replies all! I will try it in a metal can with copper pipe next time, if I can construct such a thing, after a week in sunny Cornwall , then hopefully I will have enough to redistill, check boiling point, etc. As for the smell of benzene, maybe it could be highly subjective? But I'm sure there's loads of crap in my crude orange oil. And Picric-A, when you say about removing the ethylene glycol, you mean just wash it out by shaking with water, yes? Looking at that pdf on PET pyrolysis though, (which seems to have just dissapeared from the net, but you can still get on Google's HTML cache), it indicates that most of the ethylene glycol gets decomposed in the pyrolysis, but maybe the NaOH will change this.

Quote: Originally posted by Palladium

I'm very sceptic to gain any profit of producing benzene from PET where those are 30-50 US-cent worth in deposit. The weight of one kind of our 2L PET-flasks here in Europe is 40 grams, and 1 kg of those flaskes are 25 pieces, which is 8,60 USD. I can imagine that for produce 1 kg benzene, it takes at least 10 times the weight of PET - which is very roughly at least 86 USD. This is expensive benzene.