A photo of a plastic bag underwater.
Aaron Sadow, an Ames National Laboratory researcher, Professor of Chemistry at Iowa State University, and Director of the Institute for Cooperative Upcycling of Plastic (iCOUP), has developed a new catalyst that transforms hydrocarbons into more environmentally friendly chemicals and materials.
Because of their lack of functional groups, aliphatic hydrocarbons are usually not mixed with water and form separate layers. The properties of the materials may be significantly altered and become more recyclable.
"Methane in natural gas is the simplest of hydrocarbons, with nothing but carbon-hydrogen (CH) bonds." Oils and polymers have chains of carbon atoms linked by carbon-carbon (CC) bonds, according to Sadow.
Several petroleum and refined petroleum products are made from these non-functional elements, such as plastics and motor oils, according to Sadow. "These materials are not easy to biodegrade, which means they are difficult to take from them," said the author.
The conventional method of forming hydrocarbon chains requires significant energy inputs. First, petroleum is “cracked” with heat and pressure into small building blocks. Next, these small building blocks are used to build chains. The desired atoms are added at the end of the chains.
Sadow's team had previously used a catalyst to break the CC bonds in these hydrocarbon chains, and then attached aluminum to the ends of the smaller chains. Next, they added oxygen or other components to introduce functional groups. "We might, in principle, simply transfer the chains from the catalyst to aluminum, and then add air to install the functional group," Sadow said.
Sadow explained that the catalyst is synthesized by attaching a commercially available zirconium compound to commercially available silica-alumina. All components are earth-abundant and inexpensive, which is beneficial for future commercial applications.
The catalyst and the reactant are advantageous in terms of sustainability and cost. Aluminum is the most abundant metal on earth, and the aluminum reactant used is air-stable, readily available, and activated in the reactor, according to Sadow.
This chemistry is a step towards becoming able to modify a wide variety of plastics' physical properties, such as making them stronger and easier to color, according to Sadow.
iCOUP's collaborative nature allows for collaborative research. Perras' group at Ames National Laboratory studied catalyst structures using Nuclear Magnetic Resonance (NMR) spectroscopy. Coates', LaPointe's and Delferro's groups at Cornell University studied polymer structure and physical properties. Peters' group at the University of Illinois statistically modelled polymer functionalization.
Uddhav Kanbur, Alexander L. Paterson, Jessica Rodriguez, Yi-Yu Wang, Massimiliano Delferro, Anne M. LaPointe, Frédéric A. Perras, and Aaron D. Sadow, in Journal of the American Chemical Society, 25 January 2023. DOI: 10.1021/jacs.2c11056
The project has also been highlighted in JACS Spotlight, "A Versatile New Tool for Making Commodity Chemicals."
The Institute for Cooperative Upcycling of Plastics (iCOUP) is a research facility based at Ames National Laboratory. iCOUP is a collaboration between Ames National Laboratory, UC Santa Barbara, University of South Carolina, Cornell University, and the University of Illinois Urbana-Champaign.