A new type of catalyst breaks down polyolefin plastics into new, useful products. This project is part of a new strategy to reduce the amount of plastic waste and its impact on our environment, as well as recover value that is lost when plastics are thrown away. The catalyst was developed by a team from the Institute for Cooperative Upcycling of Plastic (iCOUP), a U.S. Department of Energy, Energy Frontier Research Center. The effort was led by Aaron Sadow, the director of iCOUP, scientist at Ames National Laboratory, and professor at Iowa State University; Andreas Heyden, professor at the University of South Carolina; and Wenyu Huang, scientist at Ames Lab and professor at Iowa State. The new catalyst is made only of earth-abundant materials, which they demonstrated can break carbon-carbon (CC) bonds in aliphatic hydrocarbons.
Cartoon representation of the zirconia catalyst. The teal shows the mesoporous silica plates, the red represents the zirconia nanoparticles between the two sheets. The polymer chains enter the pores, contact the zirconia nanoparticles, and are cut into shorter chains. Credit: U.S. Department of Energy Ames National Laboratory Aliphatic hydrocarbons are organic compounds made up of only hydrogen and carbon. Polyolefin plastics are aliphatic hydrocarbon materials composed of long chains of carbon atoms linked together to form strong materials. These materials are a big part of the plastic waste crisis. Wenyu Huang said, "More than half of produced plastics so far are polyolefin based." Polyolefin plastics are used everywhere in the modern world, including in shrink wrap and other packaging products, containers for liquids such as detergents or milk, fibers in waterproof clothing, dental floss, and electronics. Yet, as Andreas Heyden explained, polyolefins are some of the most difficult plastics to recycle and new approaches are needed. One such promising alternative to recycling is known as upcycling. This approach involves chemical transformation of the materials into higher value products. One way to upcycle polyolefins is a chemical process called hydrogenolysis. During this process, a catalyst splits chains of molecules by cutting CC bonds and adding hydrogen. According to Aaron Sadow, catalysts that are used for hydrogenolysis are typically based on precious metals, such as platinum. Platinum is expensive because of its low abundance in the earth's crust, and due to its effectiveness, it is used in many types of catalytic transformations. To address both challenges of sustainability and economy, Heyden said, "We thought we'd…