Vaporizing Plastics Recycles Them Into Nothing But Gas, Researchers Find (arstechnica.com) 54
Polypropylene and polyethylene plastics "can be recycled," reports Ars Technica. But as "polyolefin" polymers, "the process can be difficult and often produces large quantities of the greenhouse gas methane.
"Now, researchers at the University of California, Berkeley have come up with a method of recycling these polymers that uses catalysts that easily break their bonds, converting them into propylene and isobutylene, which are gasses at room temperature. Those gasses can then be recycled into new plastics..." [T]he previous catalysts were expensive metals that did not remain pure long enough to convert all of the plastic into gas. Using sodium on alumina followed by tungsten oxide on silica proved much more economical and effective, even though the high temperatures required for the reaction added a bit to the cost. In both plastics, exposure to sodium on alumina broke each polymer chain into shorter polymer chains and created breakable carbon-carbon double bonds at the ends. The chains continued to break over and over.
Both then underwent a second process known as olefin metathesis. They were exposed to a stream of ethylene gas flowing into a reaction chamber while being introduced to tungsten oxide on silica, which resulted in the breakage of the carbon-carbon bonds. The reaction breaks all the carbon-carbon bonds in polyethylene and polypropylene, with the carbon atoms released during the breaking of these bonds ending up attached to molecules of ethylene... The entire chain is catalyzed until polyethylene is fully converted to propylene, and polypropylene is converted to a mixture of propylene and isobutylene. This method has high selectivity — meaning it produces a large amount of the desired product.
That means propylene derived from polyethylene, and both propylene and isobutylene derived from polypropylene. Both of these chemicals are in high demand, since propylene is an important raw material for the chemical industry, while isobutylene is a frequently used monomer in many different polymers, including synthetic rubber and a gasoline additive.
"Because plastics are often mixed at recycling centers, the researchers wanted to see what would happen if polypropylene and polyethylene underwent isomerizing ethenolysis together," the article adds. "The reaction was successful, converting the mixture into propylene and isobutylene, with slightly more propylene than isobutylene." The reaction worked, even if there were contaminants from other plastics. And "When the research team increased the scale of the experiment, it produced the same yield, which looks promising for the future...."
The researchers hope this some day could reduce the demand for chemicals derived from fossil fuels.
Thanks to Slashdot reader echo123 for sharing the article.
"Now, researchers at the University of California, Berkeley have come up with a method of recycling these polymers that uses catalysts that easily break their bonds, converting them into propylene and isobutylene, which are gasses at room temperature. Those gasses can then be recycled into new plastics..." [T]he previous catalysts were expensive metals that did not remain pure long enough to convert all of the plastic into gas. Using sodium on alumina followed by tungsten oxide on silica proved much more economical and effective, even though the high temperatures required for the reaction added a bit to the cost. In both plastics, exposure to sodium on alumina broke each polymer chain into shorter polymer chains and created breakable carbon-carbon double bonds at the ends. The chains continued to break over and over.
Both then underwent a second process known as olefin metathesis. They were exposed to a stream of ethylene gas flowing into a reaction chamber while being introduced to tungsten oxide on silica, which resulted in the breakage of the carbon-carbon bonds. The reaction breaks all the carbon-carbon bonds in polyethylene and polypropylene, with the carbon atoms released during the breaking of these bonds ending up attached to molecules of ethylene... The entire chain is catalyzed until polyethylene is fully converted to propylene, and polypropylene is converted to a mixture of propylene and isobutylene. This method has high selectivity — meaning it produces a large amount of the desired product.
That means propylene derived from polyethylene, and both propylene and isobutylene derived from polypropylene. Both of these chemicals are in high demand, since propylene is an important raw material for the chemical industry, while isobutylene is a frequently used monomer in many different polymers, including synthetic rubber and a gasoline additive.
"Because plastics are often mixed at recycling centers, the researchers wanted to see what would happen if polypropylene and polyethylene underwent isomerizing ethenolysis together," the article adds. "The reaction was successful, converting the mixture into propylene and isobutylene, with slightly more propylene than isobutylene." The reaction worked, even if there were contaminants from other plastics. And "When the research team increased the scale of the experiment, it produced the same yield, which looks promising for the future...."
The researchers hope this some day could reduce the demand for chemicals derived from fossil fuels.
Thanks to Slashdot reader echo123 for sharing the article.
That title (Score:5, Funny)
"Turning something into gas turns it into gas!"
Presumably what they really meant to say was that vaporizing plastics successfully breaks them down into non-plastic molecules.
It's not as short, but being brief is pointless if you sacrifice necessary accuracy.
Re: That title (Score:2)
How much energy do you need for it to be useful is also interesting.
Re: That title (Score:5, Interesting)
Plastics are very stable molecules, which is why when they 'break down' they tend to just break down into tinier bits that are still plastic. From that I infer that it takes a lot of energy to break them apart properly.
The cost of this recycling should be built into plastics as a tax at the point of manufacture, because externalizing the cost into ubiquitous global pollution is not the same as the cost actually going away.
Re: (Score:3, Insightful)
Cool story, bro. Are you new to the way the world works? Companies will just manufacture their plastics in some third world shithole that doesn't tax them because they want those sweet, sweeeeet jobs.
Not saying that you are wrong, but attitudes like yours are one reason for why we make less progress than we could.
Re: (Score:2)
There are more solutions than taxing that could be used, like stopping the oil company lobbying powers that probably push the government to purposefully make things less efficient in general.
Recycling local plastics is probably cheaper than drilling new oil, doing all the massive pipeline of chemical processing, shipping it overseas...
Re: (Score:1)
Granted, it's possible to take the paranoia too far and paralyze yourself with fear so that you never accomplish anything. But just because it's possible to take something too far, doesn't mean you should never do any of it at all. It's possible to eat too
Re: (Score:2)
How is that his attitude? When you state a fact, is that your attitude? That he stated it in the wording that he did, is reflective of how that fact makes him feel. Then you stepped in and tried to derail his point by strawmanning him into the whole 'bad attitude' bullshit. It's people like YOU, my friend, that are slowing progress.
If the US started charging extra to do business in the US (regardless WHAT it's for), then US companies WILL move overseas. They already do it in every single way that they
Re: That title (Score:3, Informative)
Re: (Score:2)
I can't tell from the summary if they really get rid of the plastic, or if there's a non-negligible amount of microplastics in the resulting gas.
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Re:That title (Score:5, Informative)
The summary says it turns the plastics into propylene and isobutylene -- the monomers from which we produce polypropylene and butyl rubber.
Polypropylene accounts for about 20% of all worldwide plastic production. Since it has many applications in common with polyethylene, it probably could be more. Polypropylene produced by this process would both be both recycled *and* from an engineering standpoint, virgin plastic. Butyl rubber is roughly 98% isobutylene. It's used for inner tubes, tires, gaskets, medical devices, sporting goods and so on. While not quite as common as styrene-butadiene synthetic rubber, it can replace it in numerous applications.
If this process can be economically scaled, it could take a lot of plastic out of the waste stream. If similar processes yielding ethylene could similarly be developed and scaled, then recycling could actually make a significant environmental difference -- at present it's largely greenwashing. Of course those are a lot of "ifs".
Re: That title (Score:3)
Re: That title (Score:1)
Re: (Score:1)
If you're going to be pedantic you should know intelligence and knowledge are two different things.
Re:That title (Score:5, Informative)
Using the correct terminology, vaporizing polymers successfully breaks them down into monomers.
The real news is finding better catalysts to do it. As TFA points out we always knew how to decompose polymers, but the catalysts kept fouling.
Making dog poo disappear (Score:2)
I was once asked the rhetorical question of if there was a product you could spray to make dog droppings disappear, would you use it?
If the dog poo disappeared, where did it go? Into the air? Yuk!
Re: (Score:2)
There is such a product. It's called "rain." Or "water." And, it doesn't disappear into the air, but into the closest storm drain output.
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Interesting (Score:4, Interesting)
I see that this is interesting, but I'm a bit concerned about chlorine and flourine that's common in some plastics as well as biological and metal contamination.
I can see that some biological contamination actually could contribute and be recycled and that metal probably separates relatively easy. But halogen gases can be tough to separate out.
Re:Interesting (Score:5, Informative)
Well, this process won't release elemental fluorine, but it may result in small molecules with fluorine attached. Probably the same for chlorine. Fluorine is too reactive to stick around, and chlorine if pretty reactive, to. I expect that chlorine would end up a HCl, but I suppose there might be an oxygen and maybe a carbon or so in there. (They don't seem to be doing this in a vacuum.) (OTOH, there's hot sodium in the first stage, so it might yield NaCl.)
Re: (Score:2)
I was thinking the same thing about the additives used to make the products more flexible, color them, etc.
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I do not call this "recycling" (Score:2)
Re:I do not call this "recycling" (Score:5, Insightful)
Implicit in the term recycling is an energy/effort/cost savings over just making a product from scratch. This "recycling" process requires more energy than simply making plastic from petrochemicals.
Citation Needed. Please show your full calculation for energy of both.
And when you're done I'll criticise you again. Your definition of recycling is arbitrary. At no point has recycling ever been defined as something that requires energy effort *OR* cost savings over making a product from scratch, to say nothing of the fact that your sentence implies you need all of them. Recycling is purely defined as turning waste into a usable product. The goal of recycling has always been to reduce the use an original raw material (doesn't need to be the same material the item is made from) and deal with waste.
There is no requirement for it to be energy positive, to say nothing of effort or cost positive.
It also requires the use of explosively dangerous chemicals at high temperatures
And? So does the creation of plastics - your ignorance of the process not withstanding. So does the creation of petroleum. And that's just oil and gas industry. If these scare you then you'd probably hide under your bed and never come out if you ever saw what the chemical industry was up to.
but the plant would require far more energy and use more dangerous processes that the polypropylene plant
Polypropylene plants don't operate in isolation. It's like comparing the effort of taking a road trip to the effort of just stopping at a petrol station. That is just one part of a road trip, and there are upwards of 5 different process plants upstream of polypropylene plants to provide it with various feedstocks because you don't just magic hydrogen, catalysts, diluents and pure propylene feed into existence.
Re: (Score:3, Informative)
Re:I do not call this "recycling" (Score:5, Insightful)
And a sanitation system takes more energy than just shitting in the street. But we rather prefer it. (There are lots of things in use that are more dangerous than ethylene at 320C.)
Parts of your argument are definitely correct. Every factual statement you made MAY be correct, as I'm no expert in that area. But your conclusions don't follow. This is part of a sanitation system, if it produces salable end products, that's a side benefit.
Re: (Score:2)
There is absolutely no way this can be done at less energy that simply making more plastic.
Irrelevant. We can't just keep making infinite amounts of plastic. We don't have infinite supplies of raw materials. We can't just go grab everything we need from another planet or something. Recycling will only get more and more necessary.
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"We don't have infinite supplies of raw materials."
The raw materials for plastic is mostly oil. While we don't have an infinite amount, Its probably better turning it into plastic than burning it in ICE's and putting CO2 in the air.
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No. It absolutely is not. It's cheaper. That's it. Exploitation always is.
Re:I do not call this "recycling" (Score:5, Informative)
Ethylene at 320C is way more dangerous than propylene at the typical 170C polypropylene production temperature.
LOL. Sorry but your view is very ignorant of chemical risks. Ethylene at 320C being "more dangerous" is like crossing the road without a traffic light being more dangerous than one with. It is meaningless in a larger context of risk. In this case it is nothing compared to significantly larger dangers the oil and gas and chemical industries deal with in processes in a generally accepted way. I guarantee to you that if you install this at a refinery it won't rank anywhere near the top risk, and we've accepted the risks for refining petroleum for over 100 years. If the process goes wrong what happens. It goes bang. Locally. Compare that to a large ammonia release from a storage facility, or better still compare it to a rupture of a hydrofluoric acid tank (Philadelphia is god damn fucking lucky they didn't join Union Carbide on top of the world's largest catastrophe's list when their local refinery had an explosion in their alkylation unit given their major risk scenario considered the fatalities of up to 80,000 people). Ethylene at 320C is not only not something anyone gives a shit about from a safety point of view, it's also several hundred degrees cooler than ethylene is during production with ethylene crackers typically running between 800-1100C and most petrochemical plants adjacent to a refinery having one. (Fun fact if you google the Philadelphia refinery accident I was talking about, the second link is about Shell and features a picture of Donald Trump looking over the construction of ... a new Ethylene cracker in Philadelphia. Ethylene at 320C is just not something to be scared of. It's boring from a risk point of view.
Just producing the required ethylene feed-stock for this process is almost as energy intensive as making polypropylene.
And the full working? I mean running a polypropylene plant doesn't just magic its raw ingredients into existence. Did you also take into account steam methane reforming (or electrolysis since that's all the rage) for the hydrogen source for polymerisation? Full working please of both processes. Want to see if you covered everything. Don't forget to include getting oil out of the ground, and to pro-rata that along with a portion of a typical oil refining process along with it.
Re: I do not call this "recycling" (Score:2)
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To ensure we have enough capacity at all times, we will have a lot of excess renewable generation most of the time. Gluts will be predictable 48 hours in advance with weather forecasting.
Technologies that can make use of energy when available, like electric heating to recycle plastics into gasses, will be a nice way of stabilizing energy prices by consuming energy when there is more than the rest of the grid needs. In exchange such operations will get preferential pricing, making stuff like recycling and de
Re: (Score:3)
>Implicit in the term recycling is an energy/effort/cost savings over just making a product from scratch.
I'm sure industry sees it that way, but that is because they've externalized the expense of dealing with the waste.
That's why we should be taxing them for the cost of the environmental cleanup at point of manufacture. If their products are still marketable at the required prices, recycling before the product is broken down and dispersed into the environment will be worth the rebate.
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OK, but you'll need import taxes on plastics imported from places that don't require externalities be included in the price.
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Absolutely. Level playing field.
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If you want to actually make people who use plastics pay for the cost of recycling them, you have to apply the tax not just at point of manufacture, but also at point of import, like an excise tax. Otherwise, the manufacturing will just all happen in another jurisdiction.
Also, we need to actually *have* the technology to recycle plastics, in order to know how much it costs to do that, before we can dec
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We have the technology. Heat. Lots of heat. With enough, it'll break down into component atoms.
It's difficult and expensive and we don't want to pay for it, so we poison our environment instead.
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Implicit in the term recycling is an energy/effort/cost savings over just making a product from scratch.
No. Recycling has never been about an energy, effort, or cost savings. Recycling only means "converting waste material into reusable materials". Just because most businesses only recycle if there is financial incentive to do so, doesn't mean recycling has to be that way. Recycling should be mandated and forced, regardless of whether or not it costs more. If the businesses can't handle it, they don't deserve to keep operating anyway.
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> Who would pay to build a money-losing, energy-hungry chemical plant like this?
Let the market handle it and then stupid money-losing schemes won't occur regularly.
Maybe Microsoft will have to excess power from Three Mile Island and they can recycle plastics during off hours.
Leave room for creative solutions.
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Unfortunately, in the real world, a lot of products can't be recycled that easily.
Some things can be. Metals are the most obvious, asphalt the most mundane. Glass is another.
Plastics, have not made their way onto this list at our current tech level. Even the easiest-to-recycle plastics, are cheaper to make new.
Today's title (Score:2)
brought to you by the department of redundancy department.
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Not necessarily. There are plenty of vaporization processes that leave behind solid by-products. More information is added to the context by saying "nothing but gas"
Acme (Score:3)
Where have I seen this tech before?
https://external-content.duckd... [duckduckgo.com]
Thermal depolymerization (Score:4, Interesting)
Re: (Score:2)
I'm by no means a chemist, but something like what you tagged, Thermal depolymerization, does seem like a more straightforward process. Perhaps coupled with some next gen plastic sorting to divert the really nasty stuff like PVC.
California basically throws away ("curtailment") anywhere from 1 GWH --12+ GWH daily in solar they can't use. Using that leftover solar for stuff like recycling, or generating hydrogen from water to be used later, seems like a valid test case of an admittedly variable supply of ult
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Is it really necessary to divert PVC from thermal depolymerization? From my understanding of it the halogens will just get reacted with other stuff and get turned into pretty inert slag in the end.
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Short version: it's too much hassle.
The thing is, there are bazillions of different kinds of plastic, each with their own properties, including things like what temperature and pressure you need to keep them at, and for how long, in order for them to depolymerize. (Also, you get different outputs, depending on the plastic.) Sorting all the waste plastic into hundreds of different bins, each of which has to be treated differently, is a lot
Once energy is free and plentiful (Score:3)
Why are we recycling plastic? (Score:2)
Re: (Score:2)
Plastic incinerators burn cleaner than coal plants.
Burning plastic instead of turning it into more plastic means releasing more CO2. Did you forget about AGW?
This has no effect on litter.
It doesn't have an effect on roadside litter. It does have an effect on trash dumping.
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Forget? No. But a lot of people don't GAF about it or at least don't think it's a huge emergency that requires trashing the whole planet's economy. This would still be an improvement, but instead of accepting a marginal improvement, some people want to insist on perfection, which doesn't exist. Thermal depolymerization is available now, works well enough, and outputs far less garbage to the environment. Even incinerators don't just spew the result out, they filter at least some of the junk. Given that we ca