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Researchers at Washington State University developed the method, which they said makes it easier and more cost-effective to reuse plastics.
The researchers converted 90% of plastic to jet fuel and other valuable hydrocarbons at ‘moderate’ temperatures. The process can reportedly be fine-tuned to provide different products.
The work was led by graduate student Chuhua Jia and associate professor Hongfei Lin. “In the recycling industry, the cost of recycling is key,” Lin said. “This work is a milestone for us, to advance this new technology to commercialisation.”
The most common mechanical recycling methods melt plastic and remould it, but that lowers its value and quality for use in other products. Chemical recycling can produce higher quality products, but it normally requires high reaction temperatures and a long processing time, making it too expensive and inconvenient for industries to adopt. Only about 9% of plastic in the US is recycled every year as a result of the limitations, the Washington State researchers said.
The team developed a catalytic process to efficiently convert polyethylene to jet fuel and high-value lubricants. Polyethylene is the most commonly used plastic, used in a huge variety of products – from bags, milk bottles and shampoo bottles to corrosion-resistant piping, wood-plastic composite lumber and furniture.
To enable the process, the researchers used a ruthenium on carbon catalyst and a commonly used solvent. They were able to convert about 90% of the plastic within an hour at a temperature of 220ºC, lower than typical temperatures in other recycling processes.
Jia was ‘surprised’ to see how well the solvent and catalyst worked. “Before the experiment, we only speculated but didn't know if it would work,” he said. “The result was so good.”
Adjusting processing conditions – such as the temperature, time or amount of catalyst – allowed ‘critically important’ fine-tuning, Lin said. “Depending on the market, they can tune to what product they want to generate,” he said. “They have flexibility. The application of this efficient process may provide a promising approach for selectively producing high-value products from waste polyethylene.”
The researchers hope to scale up the process for future commercialisation, with support from the Washington Research Foundation. They believe the process could work effectively with other types of plastics.
The work was published in Chem Catalysis.
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