Epoxy resins, utilized as coatings and adhesives, have a wide array of applications in construction, engineering, and manufacturing. Nevertheless, recycling or disposing of them responsibly can be challenging. Recently, a research team, including members from the University of Tokyo, has created a new method to effectively recover materials from various epoxy products for reuse, employing an innovative solid catalyst.
You are likely in the presence of epoxy compounds right now. They are found in electronic devices because of their insulating features, as well as in footwear due to their strong bonding and durability. They are also used in construction for similar reasons and even in manufacturing components for aircraft and wind turbines, where they help bind tough materials like carbon and glass fibers. The significance of epoxy products in today’s society cannot be overstated. However, these compounds carry a drawback—being synthetic plastics, they are difficult to manage post-use or at the end of their lifecycle in products that include them.
“For instance, to break down fiber-reinforced plastics, like those used in aircraft, you need temperatures above 500 degrees Celsius or extreme acidic or basic conditions. These processes have a substantial energy cost and can damage the fibers and other valuable materials intended for recovery,” explained Associate Professor Xiongjie Jin from the University of Tokyo. “To address this issue, a relatively new technique called catalytic hydrogenolysis shows potential, but the current catalysts dissolve in the solvent used for epoxy breakdown, making them non-reusable. Thus, we developed a novel solid catalyst that can be easily recovered and reused.”
Jin, along with Professor Kyoko Nozaki from the Department of Chemistry and Biotechnology and their research team, formulated an efficient and resilient catalyst that breaks down epoxy compounds into carbon fibers, glass fibers, and phenolic compounds—critical raw materials for the chemical sector. This catalyst is termed bimetallic because it combines two metals, nickel and palladium, supported on cerium oxide, and works together to facilitate reactions between epoxy resins and hydrogen gas. While the reaction requires a temperature of around 180 degrees Celsius, this energy demand is much lower than that of the previous 500-degree methods, allowing for the reuse of the extracted materials.
“We were excited to see that the experimental outcomes closely aligned with our expectations of how the process would function, but even more pleasantly surprised to find that the catalyst could be reused at least five times without losing effectiveness,” noted Jin. “Given that our catalyst is proficient at breaking carbon-oxygen bonds, with some modifications, it could potentially be applicable to other plastics, which also contain these bonds.”
The team is eager to investigate ways to refine their techniques and materials, as further development may be necessary to enhance commercial viability.
“While our catalyst operates at lower temperatures, there remains scope for improving the environmental impact of the solvent we are currently using,” said Nozaki. “We also aim to reduce costs by identifying a catalyst that doesn’t include precious metals like palladium. Additionally, it may be possible to expand the types of materials that can be reclaimed from diverse epoxy compounds, thereby decreasing the environmental burden of these highly versatile and beneficial plastics.”
