Vaporizing Plastics Recycles Them Into Nothing But Gas, Researchers Find (arstechnica.com)
- Reference: 0175101807
- News link: https://science.slashdot.org/story/24/09/22/047204/vaporizing-plastics-recycles-them-into-nothing-but-gas-researchers-find
- Source link: https://arstechnica.com/science/2024/09/vaporizing-plastics-recycles-them-into-nothing-but-gas/
"Now, [2]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.
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> 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 [3]echo123 for sharing the article.
[1] https://arstechnica.com/science/2024/09/vaporizing-plastics-recycles-them-into-nothing-but-gas/
[2] https://www.science.org/doi/10.1126/science.adq7316
[3] https://www.slashdot.org/~echo123
Interesting (Score:2)
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.
I do not call this "recycling" (Score:2)
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. It also requires the use of explosively dangerous chemicals at high temperatures that are not required when making plastics in the first place. You would need something that looks like a polypropylene plant to perform this process at scale, but the plant would require far more energy and use more dangerous pr
Re: (Score:2)
> 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 r
Re: I do not call this "recycling" (Score:2)
Who would pay? That's what government subsidies are for.
Today's title (Score:2)
brought to you by the department of redundancy department.
Re: (Score:2)
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"
That title (Score:2)
"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: (Score:2)
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: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.
Re: (Score:3)
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, medi