New process gives recycling boost to plastics

Developed by researchers at Washington State University, the process converted 90 per cent of plastic within an hour at moderate temperatures. The effort was led by graduate student Chuhua Jia and Hongfei Lin, associate professor in the Gene and Linda Voiland School of Chemical Engineering and Bioengineering. Their work is detailed in Chem Catalysis.

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"In the recycling industry, the cost of recycling is key," Lin said in a statement. "This work is a milestone for us to advance this new technology to commercialisation."

According to WSU, the most common mechanical recycling methods melt the plastic and re-mould it, a process that lowers its economic value and quality for use in other products. Chemical recycling can produce higher quality products, but it has required high reaction temperatures and a long processing time, making it too expensive and cumbersome for industries to adopt. Consequently, around nine per cent of plastic in the US is recycled every year.

The WSU researchers developed a catalytic process to convert polyethylene - the most commonly used plastic - to jet fuel and high-value lubricants.

The researchers used a ruthenium on carbon catalyst and a commonly used solvent. They were able to convert about 90 per cent of the plastic to jet fuel components or other hydrocarbon products within an hour at a temperature of 220^oCelsius, which is more efficient and lower than temperatures typically used.

"Before the experiment, we only speculated but didn't know if it would work," Jia said. "The result was so good."

Adjusting processing conditions, such as the temperature, time or amount of catalyst used, provided the critically important step of being able to fine-tune the process to create desirable products, 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 are now scaling up the process for future commercialisation. They also believe their process could work effectively with other types of plastics.