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The developers of the new system, from Osaka City University and Tohoku University in Japan, hope it could help tackle the world’s growing plastic waste problem while providing useful materials for other uses.
“Plastics are essential materials for our life because they bring safety and hygiene to our society,” said paper co-authors Masazumi Tamura from Osaka City and Keiichi Tomishige from Tohoku. “However, the growth of the global plastic production and the rapid penetration of plastics into our society brought mismanagement of waste plastics, causing serious environmental and biological issues such as ocean pollution.”
Polyolefinic plastics – the most common type – have physical properties that make it difficult for catalysts to interact directly with molecular elements and cause change. Current recycling efforts require temperatures of 300-800ºC.
The researchers investigated heterogeneous catalysts in an effort to find a reaction that might require a lower temperature to activate. By using a catalyst in a different state of matter than the plastics, they hypothesised that the reaction would be stronger at a lower temperature.
The team combined ruthenium, a metal in the platinum family, with cerium dioxide, used to polish glass among other applications, to produce a catalyst that caused the plastics to react at 200ºC. While the temperature might still seem high, the team said it requires “significantly less” energy input compared to other catalyst systems.
“Our approach acted as an effective and reusable heterogeneous catalyst, showing much higher activity than other metal-supported catalysts, working even under mild reaction conditions,” the researchers said.
“Furthermore, a plastic bag and waste plastics could be transformed to valuable chemicals in high yields.”
The team processed a plastic bag and waste plastics with the catalyst, reportedly producing a 92% yield of useful materials, including a 77% yield of liquid fuel and a 15% yield of wax.
“This catalyst system is expected to contribute to not only suppression of plastic waste but also to utilisation of plastic waste as raw materials for production of chemicals,” the researchers said.
The work was published in Applied Catalysis B: Environmental.
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