The accumulation of plastic waste in the oceans, on the soil and even inside our bodies is one of the major pollution problems our planet is facing. More than 5,000 million tonnes currently abandoned in the natural environment, both marine and terrestrial. Despite great efforts to efficiently recycle plastic products, the reality is that Recovery of this heterogeneous mixture of materials remains a problem. Now American scientists have found a way to better reuse plastic waste.
A major problem is that there are many different types of plastics, and the chemical processes to break them down into a form that can be reused tend to be very specific to each type of plastic. The messy sorting of waste materials, from soda bottles to detergent containers to plastic toys, is impractical on a large scale. That’s why today most plastic materials collected through recycling programs end up in landfills around the planet.
convert to propane
It looks like there may be a much more efficient way to recycle, according to new research from the Massachusetts Institute of Technology (MIT) and other think tanks. A chemical process using a cobalt-based catalyst has been found to be highly effective in separating various plastics into a single product, propane, including the two most commonly produced plastic forms, polyethylene (PET) and polypropylene (PP). .
This propane can then be used as fuel for stoves, heaters and vehicles, or as a raw material for the manufacture of a wide variety of products, including new plastics that could provide at least a partial closed-loop recycling system.
The finding is published in the open access journal JACS Au in a paper by MIT chemical engineering professor Yuriy Román-Leshkov, postdoctoral fellow Guido Zichitella, and seven other scientists from MIT, SLAC National Accelerator Laboratory and SLAC Laboratory. Renewable energy.
Román-Leshkov explains that plastic recycling is a challenging problem, because The long chain molecules in plastics are held together by carbon bonds that are “very stable and hard to break.”
Current techniques for breaking these bonds tend to produce a random mix of different molecules; this would require sophisticated purification methods to then separate them into specific usable compounds. “The problem,” he says, “is no way to control where the molecule breaks in the carbon chain.”
But to the surprise of researchers, A catalyst made of a microporous material called zeolite containing cobalt nanoparticles can selectively break down several plastic polymer molecules and convert more than 80 percent of them to propane.
Although zeolites are riddled with pores smaller than one nanometer wide (corresponding to the width of the polymer chains), the logical assumption is that there will be little interaction between the zeolite and the polymers. But surprisingly the opposite turned out: not only do the polymer chains enter the pores, but the synergistic working between the cobalt and acid sites on the zeolite can break the chain at the same point. It turns out that this cleavage site corresponds exactly to the cleavage of one propane molecule without producing unwanted methane, leaving the rest of the longer hydrocarbons ready for repeated processing.
“When you have this compound, propane, it reduces the load on downstream separations,” says Román-Leshkov. “That is the essence of why we think this is pretty important. We are not just breaking ties, we are essentially producing a single product.” It can be used for many different products and processes.
The materials required for the process, zeolites and cobalt, are “quite cheap” and widely available. Most of the cobalt today comes from the troubled areas of the Democratic Republic of the Congo.
A new production is under development in Canada, Cuba and elsewhere. The other material needed for the process is hydrogen, which is now primarily produced from fossil fuels, but can also be easily produced by other means, including the electrolysis of water using carbon-free electricity such as solar or wind power.
Tested on a real sample
The researchers tested their system on a real sample of mixed recycled plastics and showed promising results. However, further testing will be required on a wider variety of mixed waste streams to determine how much of the contamination is from various contaminants in the material, such as inks, adhesives and labels attached to plastic containers or other non-plastic materials mixed in. with waste and how this affects the long-term stability of the process.
Alongside collaborators at NREL, the MIT team continues to examine the economics of the system and how it fits into existing systems for managing plastic and mixed waste streams. “We don’t have all the answers yet,” admits Roman-Leshkov, but the preliminary analysis looks promising.
The research team included Amani Ebrahim and Simone Bare of the SLAC National Accelerator Laboratory; Jie Zhu, Anna Brenner, Griffin Drake, and Julie Rorrer at MIT; and Greg Beckham from the National Renewable Energy Laboratory. The work was supported by the US Department of Energy (DoE), the Swiss National Science Foundation and the Office of Energy Efficiency and Renewable Energy, the Office of Advanced Manufacturing (AMO), and the Department of Bioenergy Technologies (BETO). Energy of Energy as part of the Biooptimized Technologies to Keep Thermoplastics Away from Landfills and the Environment (BOTTLE) Consortium.
Reference work: https://pubs.acs.org/doi/10.1021/jacsau.2c00402?cookieSet=1
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Environment department contact address:crisclimatica@prensaiberica.es
Source: Informacion
Anika Rood is an author at “Social Bites”. She is an automobile enthusiast who writes about the latest developments and news in the automobile industry. With a deep understanding of the latest technologies and a passion for writing, Anika provides insightful and engaging articles that keep her readers informed and up-to-date on the latest happenings in the world of automobiles.