The accumulation of plastic waste in oceans, soils, and even within living organisms remains a critical pollution challenge for the planet. Currently, more than 5,000 million tonnes have been left behind in natural environments, spanning both marine and terrestrial ecosystems. Despite concerted efforts to recycle plastic products, recovering this heterogeneous mix of materials remains difficult. Yet researchers in the United States have identified a path to reuse plastic waste more effectively.
A key hurdle is the variety of plastics in use. Each type often requires a different chemical process to break it down into reusable forms. Sorting waste from soda bottles to detergent bottles and plastic toys is laborious and costly at scale, making large‑scale recycling programs prone to ending up in landfills. That situation has driven ongoing exploration of more efficient recycling strategies.
convert to propane
New findings from the Massachusetts Institute of Technology and several partner institutions point to a potentially more efficient recycling approach. A cobalt‑based catalyst has shown the ability to separate multiple plastics into a single product: propane. This includes the two most common plastics, polyethylene terephthalate (PET) and polypropylene (PP).
The propane produced through this method can serve as fuel for stoves, heaters, and even vehicles, or act as a feedstock for manufacturing a broad spectrum of products. It could enable a partial closed‑loop recycling cycle by supplying raw materials for new plastics.
The open access study appears in JACS Au, detailing work led by MIT chemical engineering professor Yuriy Román‑Leshkov, with contribution from postdoctoral fellow Guido Zichitella and seven other scientists from MIT, SLAC National Accelerator Laboratory, and related institutions. Renewable energy.
Román‑Leshkov notes that plastic recycling is challenging because long chain molecules are held together by carbon bonds that are unusually stable and hard to break.
Traditional methods to fracture these bonds tend to yield a random mix of molecules, necessitating expensive purification to extract usable compounds. He explains that there has been little control over where a molecule breaks along the carbon chain.
In a surprising development, a catalyst built from a microporous zeolite framework containing cobalt nanoparticles can selectively dismantle several polymer chains and convert more than 80 percent of them into propane.
Despite the small pore size of zeolites, researchers observed that polymer chains can enter the pores. The cobalt and acid sites on the zeolite work together to break the chain at a precise point. This cleavage aligns with producing propane while avoiding the generation of unwanted methane, leaving the remaining hydrocarbons ready for reprocessing.
When propane is formed, it reduces the burden on downstream separations. This is a central reason researchers see potential value in the method. It is possible to produce a versatile product that can feed many different applications.
The materials required for the process, zeolites and cobalt, are described as affordable and widely available. Much of the cobalt currently comes from regions facing economic or political challenges.
A new production pathway is under development in Canada, Cuba, and other locations. The other essential input is hydrogen, which today is largely produced from fossil fuels but can also be generated through clean methods, such as water electrolysis powered by renewable energy sources like solar or wind.
Tested on a real sample
Researchers tested the system on a real sample of mixed recycled plastics and observed encouraging results. Additional validation across a wider range of waste streams will help determine how contaminants such as inks, adhesives, and labels affect long‑term stability and performance.
In collaboration with the National Renewable Energy Laboratory and other partners, the MIT team continues to evaluate the economics of the approach and how it could integrate with existing plastic and mixed‑waste management systems. Román‑Leshkov acknowledges that more work is needed, yet the early analysis suggests promise.
The research team included Amani Ebrahim and Simone Bare from 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 effort is connected to energy initiatives and the BOTTLE Consortium that focuses on keeping thermoplastics out of landfills and the environment.
Reference work: https://pubs.acs.org/doi/10.1021/jacsau.2c00402?cookieSet=1
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