[HackOfAllTrades]

Why do people keep falling for this? This same fraud used to pop up only every 10 years. Now it's 5 or less.

I'm a PhD chemist. Please consider this: While plastics and oil are both hydrocarbons they have this important difference. Liquid hydrocarbons have short carbon chains and lots of hydrogen. Plastics have very LONG carbon chains, usually with many double bonds, and very little hydrogen.

That is why, when you heat plastic it decomposes into char -- as in charcoal. It is IMPOSSIBLE to produce oil, even theoretically, without adding a source of hydrogen.

A few centuries ago these same fraudsters would be selling you a way to change Iron into Gold.

[userbinator]

Plastics have very LONG carbon chains, usually with many double bonds, and very little hydrogen.

Which plastics? The most common ones, polyethylene and polypropylene, which this method is designed to process, are entirely hydrogen and carbon, with no double bonds. I don't dispute that additional hydrogen is necessary to crack the polymers into shorter ones, but your description of plastics does not seem to be completely correct.

[perilunar]

> I don't dispute that additional hydrogen is necessary to crack the polymers into shorter ones

polyethelelene -> cycloalkanes doesn't require any additional hydrogen.

[cal85]

Interesting, thanks. As someone with little understanding of chemistry, can you clarify why "adding a source of hydrogen" is not possible/practical?

[chii]

Free elemental hydrogen isn't common. Most are stuck as water, or inside hydrocarbons in the first place (see natural gas), and using those sources basically defeats the purpose.

So therefore, it would take more energy to free that hydrogen from water than the recovered output would give you - which is fine, as oil is a dense storage of energy, and current technology is geared towards using it. However, it makes more sense to directly utilize the electricity that is expended freeing hydrogen in the first place.

[para_parolu]

There are still usages where it can be useful like planes and ships. And some small portion of cars. Right?

[godelski]

Is it hard to add a source of hydrogen? In the images they have here it looks like there is a vat of water and it explicitly says it produces H2O and CO2 gas waste (though calls the CO2 harmless). That would imply there is a source of hydrogen here. (Not an expert, just legitimately curious so I can better spot snake oil)

[didericis]

https://youtu.be/Zmtc22uPLd4

I’m not a chemist/someone else can offer a more detailed explanation (just love the excuse to post that song), but with most of these kinds of things the energy and advanced equipment required to go in a theoretically plausible direction for a minuscule amount of yield is usually absurd. Including turning iron into gold. (I think it might theoretically be possible to do that at this point as well, but if it is possible I’m sure it’d be astronomically energy intensive and wasteful to manipulate matter to that degree)

[otikik]

The way to turn iron to gold is ancient: smelt the iron, make a weapon with it, and use that to steal the gold from someone else.

[agumonkey]

teleochemistry

[outworlder]

Turning iron to gold is not possible as a chemical reaction. They are elements. You need a nuclear reaction.

[40yearoldman]

Ahh! So it is possible, just need a nuclear reaction!

[trompetenaccoun]

It's quite simple: Gather a sufficient amount of iron (4 million times earth's mass will probably do). Bring it all in one place, it will naturally compact. Wait for the resulting supernova - you do want to keep your distance for this step. Lastly collect gold and other heavy elements.

[outworlder]

Yeah. It's even better since you are starting with iron, don't have to wait billions of years for everything to burn first.

[didericis]

I have a vague memory of someone or some article saying there’s a way to get from lead to gold if you really wanted to with some combination of available nuclear tech, but it’d be completely absurd/ludicrously expensive (I think the context was somebody humoring what would be needed for atomic level assembly/star trek replicator stuff). I assume the same would apply to iron.

[andrewflnr]

Yeah, but even worse. You need to add a lot of nucleons to iron just to get to (impure, radioactive) lead, and then from there to gold.

[cowpig]

Iron (26) -> Lead (82) -> Gold (79)

How does that work?

[throwaway5959]

At that point, why not just use hydrogen as a fuel? Or better yet, just use batteries.

[mananaysiempre]

Hydrogen is extraordinarily annoying to store and transport. Oil is kind of annoying, but not “heavy cans of pressurized gas that leaks through metal walls anyway and is explosive in a wide range of air concentrations” annoying. Nobody has figured out a workable way to deal with this, though they might at some point.

It’s also not an accident electric cars are so heavy—gasoline or diesel fuel are fantastically energy-dense compared to almost anything else you might want to use, even accounting for the intricate engine you need to haul around to take advantage of them. Not to say that you shouldn’t try and use something else, just that it’s a very real problem.

[whatshisface]

Hydrogen leaks through metals because it can diffuse through the lattice, and attaching it to carbon stops it from doing that.

[arbitrage]

I can't fuel my car with hydrogen.

[LarryMullins]

You could, the technology exists. The reason hydrogen fuel cells never caught on is because the production of hydrogen doesn't make economic and environmental sense. Which gets back to the root of problem with the OP claims.

[SketchySeaBeast]

And there we have it, the solution we've needed all along - dirigibles.

[_hypx]

You can steam reform plastic and get hydrogen for that purpose. It will imply that you have to lose a percentage of your plastic input, but if it is just plastic waste then that is not a huge problem.

[TeMPOraL]

Was going to ask about that - I mean, hydrocarbon chains, by definition, contain hydrogen, so surely you should be able to use part of the input as hydrogen source (leaving concerns of practicality, efficiency and price aside).

[aliswe]

I'm not calling you out, but please check these clips and comment.

I dont know anything about this so I appreciate the opportunity to learn.

https://youtu.be/njIYHtFmcSs https://youtu.be/TFuTCpCVSbM https://youtu.be/1STaZYZ-P1w etc

[etaioinshrdlu]

My understanding is that polyethylene, one of the most common plastics, has no double bonds, and the exact same ratio of carbon:hydrogen as shorter carbon chains. Simply breaking the polymer into short chains should literally give you oil. Why not?

[jcranmer]

Polyethylene is (CH2)n, where n is in the thousands or so, or 2.00 H per C. An octane (e.g., for gasoline) would be C8H18, or 2.25 H per C. Smaller-chain molecules are even higher H/C ratio.

So even polyethylene is short about .25 H per C.

[micropresident]

What are you talking about? This works: https://en.wikipedia.org/wiki/Thermal_depolymerization

The carbon without hydrogen produced CO, and it is burned to produce CO2, and that is used to actually heat the mixture.

[overboard2]

Could you potentially do it with steam and the right catalyst?

[lvxferre]

>I'm a PhD chemist.

This sort of "chrust me, I have kwalifikashuns" is rather fitting the overall poor quality of your comment.

There are a thousand things wrong with this application. Viability of the process is NOT one of them, as already attested in the literature. Refer for example to

https://www.sciencedirect.com/science/article/pii/S016523701...

https://www.sciencedirect.com/science/article/abs/pii/S09213...

https://pubmed.ncbi.nlm.nih.gov/31917892/

The reaction boils down to R'-CH₂-CH₂-R" → R'-CH=CH₂ + H-R". It's practically the reversal of the polymerisation that created the plastic on first place. It's specially obvious by the third paper that I've listed as example, since they're generating butadiene and olefins from polyethylene.

It is by no means on the same level as "selling you a way to change Iron into Gold".

>Plastics have very LONG carbon chains, usually with many double bonds, and very little hydrogen

General purpose polymers like polyethylene and polypropylene do not usually have double bonds. Specially not in the main chain (that you need to cleave to get smaller molecules). You'll only get double bonds in the main chain if your monomers had a triple bond in its place, as one of the bonds is broken in the polymerisation. Most monomers however start with a double bond and the resulting polymers have single bonds. Here, let me show it to you:

(...) + R'=R" + R'=R" + (...) → (...) + [·R'-R"·] + [·R'-R"·] + (...) → (...)-R'-R"-R'-R"-(...)

This is common knowledge among chemists.

>That is why, when you heat plastic it decomposes into char -- as in charcoal.

Yeah, because the hydrogens magically disappear. The presence of nearby oxidants (specially one that you, QuackOfAllTrades, should stop consuming, for a better humankind) is totally unrelated.

_____________________

For actual criticism of the application:

You'll get nasty junk oil as output. That oil will have ONE purpose: to be burned down. If you're burning down the oil might as well burn the plastic directly.

This could be solved by fractional distillation... yeah good luck doing it at home.

What happens if some clueless individual tries to recycle PAN? Or even PVC, given how nasty organochlorines are. So there is both health and environmental concerns.

What's the catalyst being used? Plenty catalysts are environmentally nasty.

1KWh/kg is a lot of energy, and it will have an environmental footprint.

It is not trying to sell you a magical device that transforms iron into gold. Instead it is trying to sell you a device that converts good iron into crappy iron, and marketing the crappy iron as if it was more useful than it is.

[frinko]

Thank you for shedding light on this.

[aeroblade]

You know, before tossing around your "PhD" in Chemistry maybe it'd be good to be sure you know what you're talking about first...

https://www.frontiersin.org/articles/10.3389/fenrg.2019.0002...)

https://cen.acs.org/environment/recycling/Amid-controversy-i...

https://www.sciencedirect.com/science/article/abs/pii/S01652...

[zwkrt]

I don't know if you meant to, but all three of those links are hilarious if you read them. The first one has `moving toward` in the title, which is academic speak for "it doesn't work and we don't know how to make it work". Otherwise it would be arrived at. Very similar to Betteridge's Law of Headlines for academia.

The second link is a news article that is very critical about the motivations, projected success, and sneaky language used by companies to justify pyrolisys. And this is coming from what is ostensibly a pro-chemical news source.

The third article is paywalled and I'm guessing 99% of us can't read it. However, the `Opportunities and Challenges` is again academic talk for "we looked into it and it's really really hard".

[trompetenaccoun]

https://sci-hub.st/https://doi.org/10.1016/j.jaap.2020.10480...

I found this link while searching the DOI of the third article. Sci-Hub seems to be a site that lets you access all sorts of scientific papers, because they believe everyone rich or poor should have free access to science. It was created by Alexandra Elbakyan, a modern day Robin Hood.

Or so they say, I'd never endorse you reading the paper without giving more money to the multi-billion dollar private publisher Elsevier.