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acetone
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pyrolysis of plastic and plastic products
What would be the result if plastic is heated strongly in absence of air?
The measure of a man is what he does with power.
-Plato
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AndersHoveland
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It depends what type of plastic, but usually the plastic initially just melts.
For polyethylene, various hydrocarbons are produced, with wax, liquid, and gas fractions.
[Edited on 18-6-2013 by AndersHoveland]
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Random
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There is a method to obtain styrene from polystyrene by thermal depolymerization on Versuchschemie. Product needs to be purified and stabilized with
polymerization inhibitor.
Other plastics produce more mess IIRC.
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eidolonicaurum
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It really depends on the type of plastic you have in mind.
Polystyrene -> styrene
Polyethene -> various hydrocarbons
PVC -> various chlorocarbons, HCl,
http://www3.ntu.edu.sg/r3c/PDF/News/R3C_International_Sympos...
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testimento
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PS produces styrene and other aromatics and some hydrocarbons, and it can be mixed with polyethene for improved results. Just heating it up to
300-400C is sufficient to pyrolyse it. This can be performed to any plastic or rubber for similar results, except chlorine and fluorine compositions.
PE, PP and these will produce mostly hydrocarbons. Improved results can be obtained by mixing it with zeolite catalysts, ZSM-5 if I remember right.
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Oxirane
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Styrene does not need stabilizers based on my observations. I've had a bottle of once distilled pyrolysis distillate from styrofoam sitting on a shelf
for over a year now and only some very small amounts of polymerization can be detected. It has not been protected from light specifically, being on an
open shelf in a room that has a small window. My laziness has prevented me to fractionate it but I'm gonna do something about it.
But I have another project on my mind on plastics. This document states that a significant portion of pvc pyrolysis product is hydrogen chloride,
based on the fact that common PVC has about 50% in weight chlorine:
http://fire.nist.gov/bfrlpubs/fire87/PDF/f87015.pdf
This made me very interested on the possibility of actually distilling significant amounts of HCl gas from common waste PVC and dissolving them to
make hydrochloric acid.
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Bert
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| Quote: |
This made me very interested on the possibility of actually distilling significant amounts of HCl gas from common waste PVC and dissolving them to
make hydrochloric acid.
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In pyrotechnics, PVC is used as a "chlorine donor". Added to colored fireworks stars, most particularly blue, purple and green, it helps to assure the
Copper and Barium species in the flame envelope are the mono chlorides- These are believed best capable of producing the desired spectra.
Yes, PVC has a LOT of HCl generation capability, and is often chosen due to low cost and adding at least a moderate fuel value to pyrotechnic
mixtures. Never tried to pyrolize it on the ground and collect HCl though.
Chlorine donors for pyrotechnic compositions
See table at the bottom of this page for % information- Chlorinated rubbers (Parlon, Pergut) or Saran resin can be a higher Cl % yet, but likely will
be more expensive.
There are even "double chlorinated" grades of PVC offered occasionally on the pyrotechnic materials market, once again, not as cheap as scrap PVC.
[Edited on 25-9-2014 by Bert]
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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Oxirane
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Well honestly I am not expecting to PAY to get pvc scrap. When its used almost everywhere, there must be some on the waste bins too. Its a shame my
country has extremely strict environment policy and PVC is almost restricted nowadays and believe it or not, waste bins and dumps are locked so
heavily that most thieves wont even look what's behind the doors, they steal the locks.. 
Any ideas on what stuff is made of pvc that could be encountered around? PVC pipes are of course, but one may expect to find them only around
construction yards. Something that could be found from municipal wastes..
[Edited on 25-9-2014 by Oxirane]
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Bert
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PVC is used for WATER PIPES, SIDINGS of houses, plastic trim moulding of buildings, interior & exterior, FLOORING, disposable MEDICAL DEVICES...
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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blogfast25
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Quote: Originally posted by Bert  | | PVC is used for WATER PIPES, SIDINGS of houses, plastic trim moulding of buildings, interior & exterior, FLOORING, disposable MEDICAL DEVICES...
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uPVC window frames. All kinds of bottles and flacons (should be easy to find in domestic waste streams):
https://www.google.co.uk/search?q=pvc+bottles&tbm=isch&a...
Shower curtains. PVC gloves. Garden hose (all plasticised PVC).
A simple flame test can also tell you with some likelihood whether a given plastic is PVC or not. Strike it with a very hot piece of copper wire,
making sure a bit of the object sticks to it. Then insert into Bunsen flame (or similar): green flame is due to CuCl2 and points to PVC...
[Edited on 25-9-2014 by blogfast25]
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aga
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[Edited on 27-9-2014 by aga]
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Oxirane
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So it's essentially an effective and OTC source of benzene and HCl.
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aga
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*If* you got a metal pot and some copper pipe.
I think metal pots are List II, copper pipe List I.
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Oxirane
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Dont worry, I've got mine.
I just tested this thing. I cut up some pvc tubing into steel pot, lead a distill bridge into receiver flask and gas tube to water trap. After the
tube got hot, receiver filled with chlorine coloured gas and bubbles came through the water trap. The gas production came more intense when heat built
up, so I had to relieve it a little, and the liter of cold water got hot and I got to make own cold bath for it. Eventually more HCl was released what
the water could handle, so I had to stop the reaction. pH paper gave very dark red. The whole reaction took no more than half an hour. The downside is
that the HCl solution in this setup got greenish tint and some solid impurities in it. I think this could be avoided by cooling the receiver and
installing a reflux column to it to condense all the solids.
The reaction also releases a lot of noxious and thick fumes and one may need to build two water traps back to back and make sure that all connections
and threads etc. are thightly closed. I made my reaction outside and yet there was quite a stench.
So it can be said that PVC is very efficient OTC source of HCl, but some special equipment is needed to utilize it. I still got to open the pot and
see how grimy it has become and if there is any corrosion. I believe it's quite a view.
[Edited on 28-9-2014 by Oxirane]
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blogfast25
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Oxirane:
If I recall well (note caveat) concerns have been raised about the pyrolysis of PVC yielding dioxins. You may want to research that before going much
further.
| Quote: Originally posted by Oxirane | Eventually more HCl was released what the water could handle, so I had to stop the reaction. pH paper gave very dark red.
[Edited on 28-9-2014 by Oxirane] |
With a maximum attainable concentration of 37 w% the amount of water needed to absorb the 'theoretical amount' of HCl should be easy to estimate.
[Edited on 28-9-2014 by blogfast25]
The generation of dioxins is related to the combustion (incineration) of PVC bearing household waste.
http://en.wikipedia.org/wiki/Polyvinyl_chloride#Dioxins
[Edited on 28-9-2014 by blogfast25]
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Oxirane
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Oh well thanks, now I'm sitting here shit scared and waiting for the symptoms of dioxin poisoning to show up...
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Oxirane
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http://rua.ua.es/dspace/bitstream/10045/12199/1/articulo%20c...
It seems that dioxins generally need oxygen at 400-700C to form. My reactor was closed from oxygen and the temperature decreased very quickly far
below 400 before facing oxygenic environment. Even the distilling bridge was cool to hand touch.
On the page 6, if you mind to see the results, pyrolysis of PVC results only very little or no PCDD:s.
Think if Im going to continue pyrolysis tests I'll have to make an ejector chimney to blow all the remaining exhaust fumes up to the sky, make a
larger condenser to condense all solids and wear complete safety gear when cleaning the parts.
This issue must be solved dead clear, because this sounds very good source of HCl. There must be way to complete it safely and cleanly.
[Edited on 28-9-2014 by Oxirane]
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aga
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Oxirane ! You Pioneering wonder !
I haven't even got my rig set up, and you got HCl !
Any Benzene apparent anywhere ?
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Oxirane
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Still alive, though dioxine will take 1-6 weeks to kill. Doh..
I only got very thick, heavy fuel oil - type residue, which I believe is a mixture of additives and benzene. Part of this residue came out and mixed
to the HCl solution, which is because there was no actual condenser in use, only submerged receiver. HCl came out from the nozzle as a white, thick
fume with extremely irritating smell, and mixed with it was greenish-brown gunk.
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phlogiston
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Pyrolysing rubber will yield Limonene in significant quantities:
http://www.sciencedirect.com/science/article/pii/S0165237000...
Full text available here
I doubt it'll smell as good as limonene made via other routes.
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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blogfast25
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From the structures it's clear oxygen would be needed to get dioxins from PVC. Anaerobic pyrolysis will yield a witches' brew (possibly with its own
toxicity issues) without dioxins.
[Edited on 29-9-2014 by blogfast25]
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Oxirane
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That means there should be insignificant amounts of dioxins. I've got to clean the parts yet, gonna wear chemical industry grade respirator mask,
gloves and maybe even protective suit. Bought those well ahead. 
It would be good to make a topic for overall pyrolysis product, because many OTC stuff and even things considered garbage may yield some very
interesting chemicals.
Polystyrene - styrene (and some toluene and benzene)
PVC - hydrogen chloride
Rubber - limonene
And so on.
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TheChemiKid
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UC has a good video on the pyrolysis of polystyrene: https://www.youtube.com/watch?v=6tEs7P6UUVQ
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aga
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Spurred on by Oxirane's attempt, i had a go at PVC pyrolysis today, using a 1L paint thinners tin, a rocket stove, and some copper pipe.
37.8g of PVC-B was cut from a PVC drainpipe coupler and put in the tin.
The outlet of the tin was taken via about 1m of 15mm dia copper pipe into exactly 1L of distilled water. The end of the pipe was underwater.
After 20mins, bubbles were seen leaving the pipe.
It was allowed to run for 1hr 30 mins.
The water is now rather acidic, turning UI paper red instantly.
A quick distillation of 200ml of the water gave a distillate at 95.5 C for 10 minutes.
The liquid left in the pot is still acidic, the distillate is neutral.
The distillate smells slightly sweet, but does not burn.
I was expecting gaseous HCl to be present, so had some damp UI paper in front of the vac adapter, but it remained neutral.
Allowing +/- 1 C around 95.5, that gives two azeotropes most likely:-
anisole / water (95.5 C) however insoluble in water ...
chloral / water (95.0 C)
Mightliy confusled.
[Edited on 29-9-2014 by aga]
The Acidity is around 0.08 [M] after a rough titration, and an even rougher Mohr's shows chlorides present.
[Edited on 29-9-2014 by aga]
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blogfast25
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Aga:
Careful about suck back with that set up: water sucked back into the pyrolyser retort (the paint can, LOL) could be nasty (steam explosion). At a very
minimum always get the tube out of the water before switching off the heat!
Assuming the 0.08 M to be correct, calculate how much of the PVC's chlorine ended up in the water as HCl. Did the water smell of anything?
If the pyrolyser is hot enough, organics should also come over and form a two layer system (but some will be gaseous). But if temperature is too low
you might not be depolymerising the PVC just yet. The higher the temperature the jollier, within reason.
What does the PVC look like now?
Any idea of temperature inside the pyrolyser pot?
'Cracking' the backbone of this polymer requires fairly high temperatures, if you want it to proceed reasonably fast. The backbone is after all
-C-C-C-C-C-C-, so highly stable. All these stable C-C covalent bonds...
[Edited on 29-9-2014 by blogfast25]
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