Converting waste plastics back to their constituent monomers

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Plastic materials are very widely used throughout the world and the trend is that many forms of plastic materials will be more extensively used in the future. However, it is well known that many plastic materials, due to their stability in use, are not bio-degradable and that significant problems exist in the disposal of such materials.

Pyrolysis for the conversion of waste plastics to make synthetic crude oil mixture and mixed distillates have drawn great commercial interest due to increasing oil prices. However, the stability and quality of these oil products are low and thus subsequent treatment is required to obtain valuable products.

Researchers at Oxford have developed a novel and sustainable catalytic system and process for the depolymerisation of waste plastics to produce very high-value constituent monomers of thermoplastic polymers. Consequently, this could achieve a truly circular economy of plastic usage.

The problem of plastic waste

Between 1950 and 2015, cumulative waste generation of primary and secondary (recycled) plastic waste amounted to 6300 Mt and of this approximately 800 Mt (12%) has been incinerated and 600Mt (9%) has been recycled; less than 10% of which has been recycled more than once. Around 4900 Mt — 60% of all plastics ever produced — has been discarded and is accumulating in landfill or in the natural environment. Accordingly, if current production and waste management trends continue, roughly 12,000 Mt of plastic waste will be in landfill or in the natural environment by 2050.

Processes for the conversion of waste plastics and other solid hydrocarbon materials to other useful products are known. For instance, plastic depolymerisation techniques were developed actively during the 1980s and 1990s, but none was adopted commercially as mechanical recycling methods developed rapidly.

Over the past 10 years, there has been an increase in the amount of research into the conversion of plastic into hydrocarbon fuels as oil prices have increased and waste collection and sorting methods have improved. However, the stability, ease of handling and quality of these oil products is low and further processing is required to give a fuel product.

A novel process for depolymerisation of plastic waste

Researchers at Oxford University have developed a novel and more effective method for converting the waste plastic back into its constituent monomers with very high selectivity. The process had been tested for real-world waste and can tolerate various contaminations such as oil and dust etc.

The process is rapid, effective and suitable for both stationary waste disposal and on-board disposal for mobilities.

The technology opens a new era of application in waste plastic in which the thermoplastic polymers in waste plastic could be converted back to their original monomers, thus creating a circular economy for the plastic industry.


Oxford University Innovation Ltd. has filed a priority patent application on the technology and welcomes discussions with companies interested in licensing it for commercial development.

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