Plastics pervade almost every aspect of modern life, but once they have served their purpose, it’s tough to get rid of them. That’s because the polymers degrade very slowly in landfills or the environment, and recycling is inefficient.
Now researchers reporting in ACS Central Science have developed a catalyst that can transform polyethylene –– the type of plastic used to make grocery bags and another packaging –– into high-quality liquid products, such as motor oils and waxes.
Hundreds of millions of tons of plastic are produced worldwide each year, and the majority of these materials are discarded after a single-use. Most end up in landfills or the environment. Because of technical challenges, even the plastic that does get recycled typically generates materials that are of lower quality and value than the original polymer.
Kenneth Poeppelmeier, Aaron Sadow, Massimiliano Delferro and colleagues wanted to develop a catalyst that could be used to selectively upcycle polyethylene into high-quality, value-added products.
The researchers deposited platinum nanoparticles onto a strontium titanate support. At moderate pressure and temperature, this catalyst cleaved carbon-carbon bonds in the polyethylene to produce high-quality liquid hydrocarbons. These liquids could be used as motor oil, lubricants or waxes, or further processed to make ingredients for detergents and cosmetics.
The new catalyst preferentially bound and cleaved longer hydrocarbon chains, so that the products were all of a similar, intermediate size. In contrast, a commercially available catalyst generated lower-quality products with a broader size range and many short hydrocarbons, limiting the products’ usefulness.