Recycling breakthrough turns one common type of plastic into another
In a bid to reduce the environmental burden associated with both the manufacturing and disposal of plastics, scientists have demonstrated a new upcycling technique that turns one common form of it into another. The team says they also have the means to scale up and implement their technology, which they calculate could lead to massive reductions in global greenhouse emissions as a result.
Like many others in this field, the authors of the study were looking to make progress toward a circular economy for plastics. Rather than these materials making their way to landfill, better recycling technologies can see more of them repurposed into valuable new products, and this new work marks a promising step forward in this space.
The team started with the most widely produced plastic in the world, namely polyethylene (PE), which accounts for around 29% of the world’s plastic consumption. A catalyst was then used to remove hydrogen from the material and create a reactive location in the chain of molecules, and then another catalyst to split the molecules at this location and cap the exposed ends. A third catalyst then shifts this reactive location along the chain so the process can be repeated. This leaves behind molecules of propylene, which serve as the building blocks for the world’s second most widely used plastic, polypropylene (PP).
“Think of cutting a baguette in half, and then cutting precisely-sized pieces off the end of each half – where the speed at which you cut controls the size of each slice,” said co-lead author Damien Guironnet.
The scientists have also built a reactor that facilitates a continuous flow of propylene for a streamlined conversion into PP. They say this can be done with current technology and makes the process simple to scale up, but they hope to improve the efficiency further by designing faster, more productive catalysts.
“Our preliminary analysis suggests that if just 20% of the world’s PE could be recovered and converted via this route, it could represent a potential savings of [greenhouse gas] emissions comparable to taking 3 million cars off the road," said Garrett Strong, a graduate student associated with the project.
The research was published in the Journal of the American Chemical Society.