New catalyst process could reduce plastic waste

Polyolefinic plastics - the most common type found in everything from food packaging to toys, electronics and liquid fuels - has physical properties that make it difficult for a catalyst to interact directly with the molecular elements. 

Current efforts to recycle these plastics require temperatures of at least 573 degrees Kelvin, and up to 1,173 degrees Kelvin. The researchers aimed to find a reaction that required a lower temperature to activate, looking to heterogenous catalysts.

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According to the team, they combined ruthenium, a metal in the platinum family, with cerium dioxide to produce a catalyst causing the plastics to react at 473 degrees Kelvin. While still high for human sensibilities, it requires significantly less energy input compared to other catalyst systems, researchers explained.

“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,” said paper co-authors Masazumi Tamura and Keiichi Tomishige. 

Researchers said they processed a plastic bag and waste plastics with the catalyst, producing a 92 per cent yield of useful materials including a 77 per cent yield of liquid fuel and a 15 per cent yield of wax.

“Plastics are essential materials for our life because they bring safety and hygiene to our society,” the paper co-authors added. “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.”

Tamura and Tomishige explained that they expect the system to contribute toward suppression of plastic wastes as well as utilisation of raw materials for production of chemicals. 

Results were published in Applied Catalysis B: Environmental on 10 December 2020.