Researchers have discovered an improved method of upcycling used plastic waste into valuable products. A team from Pacific Northwest National Laboratory (PNNL), says their findings have produced a more cost-efficient, fast-acting catalyst for the breakdown of polymers into usable chemicals.
Presented to the American Chemical Society (ACS) yesterday and published in ACS Catalysis, the results are also being touted for their ability to reduce greenhouse gas (GHG) emissions, like methane, a typical byproduct of the conversion process in other methods.
“It was very interesting to us that there had been nothing previously published showing this result,” says postdoctoral research scientist Linxiao Chen, who presented the research at ACS. “This research shows the opportunity to develop effective, selective and versatile catalysts for plastic upcycling.”
Less is more
Petroleum-based plastic waste presents an untapped source of carbon-based chemicals that can serve to create useful materials and fuels. Very little plastic is currently recycled, mainly due to a lack of infrastructure and investment.
Adding hydrogen to difficult-to-recycle plastics like PP and PE, a reaction known as hydrogenolysis, is a strategy that converts plastic waste into small value-added hydrocarbons. This process requires efficient and selective catalysts to make it economically feasible.
“The key discovery we report is the very low metal load,” remarks PNNL chemist Janos Szanyi, who led the research team. “This makes the catalyst much cheaper.”
The study authors found that reducing the amount of the precious metal ruthenium actually improved the polymer upcycling efficiency and selectivity.
Their findings show that the improvement in efficiency happened because the low ratio of metal to support structure caused the structure to shift from an orderly array of particles to disordered rafts of atoms.
The researchers observed the transition to disorder on the molecular level and then used established theory to show that single atoms are actually more effective catalysts in this experimental work.
“There has been a lot of effort from a material perspective to try to understand how single atoms or very small clusters can make effective catalysts,” says chemist Oliver Gutiérrez, an expert in industrial applications for catalysis.
At ACS, Chen also described new work that explores the support material’s role in improving the system’s efficiency.
“We have investigated cheaper and more easily available support materials to replace cerium oxide,” said Chen. “We found that a chemically modified titanium oxide may enable a more effective and selective pathway for polypropylene upcycling.”
To make the method practical for use with mixed plastic recycling streams, the research team is now exploring how chlorine’s presence affects the chemical conversion efficiency.
“We are looking into more demanding extraction conditions,” said chemist Oliver Y. Gutiérrez, an expert in industrial applications for catalysis.
“When you don’t have a clear plastic source, in an industrial upcycling process, you have chlorine from polyvinylchloride and other sources. Chlorine can contaminate the plastic upcycling reaction. We want to understand what effect chlorine has on our system.”
That fundamental understanding may help convert waste plastic that usually ends up as environmental pollution into useful products.
By Louis Gore-Langton
France has launched an offshore green hydrogen production platform at the country’s Port of Saint-Nazaire this week, along with its first offshore wind farm. The hydrogen plant, which its operators say is the world’s first facility of its type, coincides with the launch of another “first of its kind” facility in Sweden dedicated to storing hydrogen in an underground lined rock cavern (LRC).
The project sets up the Hydrogen Valley in Rome, the first industrial-scale technological hub for the development of the national supply chain for the production, transport, storage and use of hydrogen for the decarbonization of industrial processes and for sustainable mobility.
At first glance, hydrogen seems to be the perfect solution to our energy needs. It doesn’t produce any carbon dioxide when used. It can store energy for long periods of time. It doesn’t leave behind hazardous waste materials, like nuclear does. And it doesn’t require large swathes of land to be flooded, like hydroelectricity. Seems too good to be true. So…what’s the catch?