American Association for the Advancement of Science
Using a unique catalyst to molecularly deconstruct polyethylene, the most commonly used form of plastic, researchers present a solvent-free way to transform it into higher-value, widely used chemical compounds.
"These developments will pave the way toward a circular plastics economy, in which plastic is not considered waste but rather a valuable raw material," writes Bert Weckhuysen in a related Perspective article.
Many plastic products are intended for single or short-term use, and most are not recycled. As a result, a vast amount of plastic waste ends up in landfills, or worse yet, steadily accumulates in the environment where it can persist for centuries. Efforts to improve the management and reuse of plastic waste have had limited success; many still face significant technical and economic challenges. For example, products created from recycled materials are often inferior to those made anew. And, while de-polymerization—also known as chemical or feedstock recycling—is capable of recovering a plastic's original chemical building blocks for use in other high-value chemicals, current strategies are complex, energy-intensive or require large amounts of co-reactants. Thus, the reclaimed products are unlikely to recoup the costs of processing.
Here, Zhang et al. present 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/aluminum catalyst, Zhang et al. show that various grades of polyethylene, including those used to make plastic bags and water-bottle caps, can efficiently be molecularly deconstructed into higher-value materials without the need for high temperatures or high-pressure hydrogen. While the results are promising, the authors note that catalyst improvements are needed to make the process economically viable.
"When this can be realized, 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," Weckhuysen writes.