lollerskatez
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Pyrolysis Oil via Ozonide Decomposition?
Preface: I understand that playing around with ozone is extremely unwise.
With that out of the way, I ozonated some vegetable oil, then heated it to ~93C, and then a (somewhat violent) chain reaction occurred. The end
products were a mixture of gases—which unfortunately I wasn't able to capture—and a viscous, tar-like, dark-amber/brown substance. The tar-like
substance appears to resemble pine tar/tall oil, and is in fact miscible with pine tar. It's only partially soluble in denatured alcohol and acetone,
but has better solubility in, strangely enough, gum turpentine (not to be confused with mineral spirits).
The substance does saponify, but it's saponfication value is incredibly low. So low, in fact, that given my experimental error, the value was
0. Acid value (using NaOH) is roughly 35.6. If my math is right, converting this to KOH Acid Value, it's 49.9. I had to use gum turpentine as a
solvent, not sure if this would throw off the acid value (it's the only thing that would dissolve the tar best).
Now, the weird thing is that the explosive reaction (and resulting tar-like substance) does not occur if heat is applied during the vegetable
oil ozonation. Instead, it produces a different type compound, one that I have absolutely no clue about. The only thing I can determine about it is
that it's denser than propylene glycol but less dense than glycerol (additionally, some of the reaction products are possibly miscible with glycerol).
It too is only partially soluble in denatured alcohol and acetone. I have yet to see if it's saponifiable, and if so, what its saponification value
and acid value are.
From my (very) tenuous knowledge of organic chemistry and ozonolysis, ozonation of fatty acids/triglycerides essentially results in semi-stable
ozonide (after going through Crigee intermediates). Based on what I've read in the literature and from seeing the reaction occur, it appears that
thermally decomposing ozonides formed from the triglycerides generates organic peroxides. These organic peroxides then react with whatever was left
over from the decomposed ozonides, producing a variety of gases and something resembling a pyrolysis oil. Again, I don't have a good knowledge of
organic chemistry theory, so this is mostly speculation; I'm really out of my depth here.
I have yet to perform a fractional distillation of the compound, which I'm hoping to avoid (would need all the appropriate equipment for it). So far,
I haven't been able to find a lab that can analyze the reaction product(s) to determine if it actually is a pyrolysis oil.
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Ubya
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well vegetable oil is not a defined mixture of oils. To be more specific with any determination you should start with only one kind of oil to begin
with(oleic acid trigliceride for example)
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feel free to correct my grammar, or any mistakes i make
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Tsjerk
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I would expect any double bound to be cleaved and oxidized to carboxylic acids. I expect the ester bonds to be preserved.
Please be careful, ozonides can be very explosive.
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lollerskatez
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Quote: Originally posted by Ubya  | | well vegetable oil is not a defined mixture of oils. To be more specific with any determination you should start with only one kind of oil to begin
with(oleic acid trigliceride for example) |
Oh, yes, good point, one that I forgot to address. I've tested this on multiple different types of oils already (sunflower, canola, peanut, olive, and
vegetable shortening), and the end reaction is still the same. There are differences in the reaction products directly after ozonation (e.g., the
vegetable shortening & olive oil turned into a white, cream/paste-like ozonide mixture, while the canola turned into a viscous, pale yellow
liquid/"sludge"), but this does not seem to affect the thermal decomposition reaction. It always ends with an exothermic, peroxide-like reaction that
leaves behind a dark brown/amber, tar-like product.
Now, the specific make of the tar most likely differs (in fact, I'm sure it does; the saponification value of the sunflower oil tar was ~0.02) based
on the vegetable used, but they're so similar otherwise that I aggregated them together.
| Quote: Originally posted by Tsjerk | | I would expect any double bound to be cleaved and oxidized to carboxylic acids. I expect the ester bonds to be preserved. |
Well, that's the puzzle, since I'm not getting just carboxylic acids, but an explosive reaction that results in something else. According to one lab
that was only able to partial analyze the aggregated tars before giving up, there were ketones, aldehydes, and heavy hydrocarbons—which I'm
supposing are polymerized chains of carboxylic acids.
I know the results of ozonolysis of alkanes/alkenes/alkynes are supposed to give certain end procuts, but what I can't find much about is the
ozonolysis of triglycerides: what happens to the glycerol molecule? The ozonated vegetable oil also appears to be supersaturated with ozone: when the
residual ozone decomposes, would this generate atomic oxygen? Would this oxygen atom only attack double-bonds, or could it cleave single C–C and
C–H bonds as well?
[Edited on 6/12/2020 by lollerskatez]
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Dr.Bob
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Your ozonalide may be degrading to the epoxide or other similar compounds. Those would still be quite unstable. You also may generate some odd
peroxyketals, peroxides, peresters, and who knows what else. if you quenches them with dimethylsulfide while cold, you would generate the aldehyde
fragments (maybe some ketones, but side chains are rare in plant oils) which would be more stable. But that is why you normally either reduce or
oxidize the ozonilide while cold, as otherwise they turn to crap. Symettrical olefins are easier to deal with, as they provide only one product, but
polyunsat'd oil will provide a mixture of many things. Most (fuel type) pyrolosis is designed to be reductive, to saturate the double bonds and
remove heterocyclic atoms in order to make a less complex and more burnable mixture.
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lollerskatez
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That's a definite possibility. During the lead up to the more violent reaction (I hesitate to call it "explosive"), it does appear that there's
another reaction occurring first and producing a different compound. What I'm unsure about is whether the violent reaction occurs due to 1. two
competing reactions, and after the more favorable reaction has run out of reactants the second reaction occurs or 2. one reaction occurs, which
generates the reactant mass for the second reaction once enough has been produced.
I have video of it, actually, if anyone's interested. I can share a Google Drive link for it.
| Quote: Originally posted by Dr.Bob | | Most (fuel type) pyrolosis is designed to be reductive, to saturate the double bonds and remove heterocyclic atoms in order to make a less complex and
more burnable mixture. |
Is there any way to test for saturated double-bonds/presence of heterocyclic compounds? Whatever remains is highly resistant to oxidation and yet
still a carboxylic acid. Any idea of what carboxylic acids are highly resistant to oxidation?
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Dr.Bob
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bromine is used to test for double bonds in oils. Google it.
most carboxylic acids are very stable to further oxidation, they are already oxidized to a stable state. Short of burning them, they are stable to
most things.
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lollerskatez
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Thanks for pointing that out, I didn't know about that. What about using potassium permagnate? Would it be worth it to find out the iodine value?
| Quote: Originally posted by Dr.Bob | | most carboxylic acids are very stable to further oxidation, they are already oxidized to a stable state. |
Although I haven't confirmed this yet, I'm assuming the tar substance is highly resistant (possibly unaffected) by ozone. It's non-drying, staying
"sticky" on surfaces much like pine tar does. Would it be possible that that carboxylic acids with different structures than fatty acid chains could
form, e.g. terpenes?
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