Research Results

Establishing a New Transformation Method for Plastics!
─ Successful Development of a Heterogeneous Catalyst System Effective for Synthesizing Useful Chemical Products from Polyolefinic Plastics at Low Temperatures ─

This research announcement has been featured in the following media outlets:

• January 14, 2021: The Chemical Daily
• February 8, 2021: The Chemical Daily

Key Points of This Research

• Successful development of a solid catalyst that transforms polyolefinic plastics into useful chemical products such as lubricants under low-temperature conditions.
• Expected to emerge as a new solid catalyst technology for plastic transformation.

Summary

A research group led by Masazumi Tamura (Associate Professor, Research Center for Artificial Photosynthesis, Osaka City University) and Keiichi Tomishige (Professor, Department of Applied Chemistry, Graduate School of Engineering, Tohoku University) has successfully developed a solid catalyst system effective for decomposing polyolefinic plastics, which account for the majority of plastic waste. The group has demonstrated that useful chemical products, such as lubricants and liquid chemicals, can be synthesized in high yields under low-temperature conditions.

While technologies such as liquefaction and gasification are known as chemical recycling methods for polyolefinic plastics, they face various problems. Therefore, establishing a technology to transform plastics under low-temperature conditions, along with a catalyst technology that enables direct and selective conversion into valuable chemical raw materials, has been highly demanded. The ruthenium catalyst supported on cerium oxide (Ru/CeO₂ catalyst) developed in this research successfully lowers the reaction temperature by more than 100 degrees Celsius compared to conventional technologies. It is the world's first solid catalyst system applicable to commercially available trash bags and waste plastics, successfully obtaining useful chemical products in high yields.

These research results were published online in Applied Catalysis B: Environmental (IF=16.68) on Thursday, December 10, 2020.

Research Background

In recent years, plastic waste has become a global issue, impacting marine environments and ecosystems. Under these circumstances, reducing plastic consumption and establishing appropriate disposal methods are required, and plastic recycling and reuse technologies are also becoming important from the perspective of resource circulation. Polyolefinic plastics account for the majority of plastic waste, making the development of its recycling technology an urgent matter. Among recycling technologies, chemical recycling is expected to be a process that enables lower carbon emissions, waste reduction, and the supply of raw materials and chemicals. While technologies such as liquefaction and gasification are known as chemical recycling methods for polyolefinic plastics, they generally require high temperatures of 400 degrees Celsius or higher and have suffered from issues such as the generation of low-value gas, large amounts of byproducts, and catalyst deactivation. From the perspective of improving energy utilization efficiency and reducing carbon dioxide emissions, it has been requested to establish a technology that enables plastic transformation under low-temperature conditions, as well as a catalyst technology that enables direct and selective conversion into high-value-added chemical raw materials.

Research Details

As a result of catalyst development using polyethylene as a model substrate, we found that a ruthenium catalyst supported on cerium oxide (Ru/CeO₂ catalyst) exhibits higher activity than other metal-supported catalysts. This enabled the transformation of polyolefins under conditions as low as 200 degrees Celsius and low hydrogen pressures of 2 MPa, and also revealed that useful chemical products such as lubricants and liquid chemicals can be obtained in high yields of 90% or more. Compared to previously reported solid catalysts, this catalyst can lower the reaction temperature required for decomposing polyolefinic plastics by more than 100 degrees Celsius, making it an extremely highly active solid catalyst. Furthermore, this solid catalyst system is applicable to commercially available trash bags and waste plastics, successfully obtaining useful chemical products in high yields.

Expected Impact

This technology will enable a resource circulation cycle for plastics and is expected to contribute to solving the plastic waste issue. Furthermore, by replacing chemical processes that have been synthesized from petrochemical resources, carbon dioxide, energy, and costs will be reduced, which is expected to lead to the construction of a low-carbon society.

Future Development

Toward practical application, we will work on developing catalyst processes using actual waste plastics.

Funding Information

This research was conducted with the support of the Environment Research and Technology Development Fund (JPMEERF20183R03) of the Environmental Restoration and Conservation Agency.

Publication Information

⇒All Press Release (PDF:1069KB)

Published on: Osaka City University website