Polyethylene: new catalyst breaks it down to boost value

A new method to molecularly deconstruct polyethylene could see the most commonly used form of plastic transformed it into higher-value, widely used chemical compounds.

Many plastic products are intended for single or short-term use — most are not recycled. Efforts to improve the management and reuse of plastic waste have had limited success. Due to significant technical and economic challenges, products created from recycled materials are often inferior in quality to those that are newly made.

De-polymerisation — also known as chemical or feedstock recycling — is capable of recovering the original chemical building blocks of plastic for use in other high-value chemicals, but current strategies are complex and energy-intensive or require large amounts of co-reactants. For this reason, reclaimed products are unlikely to recoup the costs of processing.

Publishing results in Science, lead author and University of California Santa Barbara postdoctoral scholar Fan Zhang and his team have developed a ‘one-pot’, low-temperature method for transforming waste polyethylene into long-chain alkylaromatic compounds, which are an important ingredient in the production of detergents, lubricants and refrigeration fluids.

Using a platinum–aluminium catalyst, the research team found that various grades of polyethylene — including those used to make plastic bags and water-bottle caps — can be efficiently molecularly deconstructed into higher-value materials without the need for high temperatures or high-pressure hydrogen.

In a related perspective piece, also published in Science, Professor Bert Weckhuysen from Utrecht University in the Netherlands said, “These developments will pave the way toward a circular plastics economy, in which plastic is not considered waste but rather a valuable raw material.”

He commented that, when catalyst improvements are realised to make the process economically viable, “non-fossil-based plastics may become more economically attractive as carbon atoms can be recycled and chemical functionality can be reintroduced in a high-value product”.

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