The application of spent catalysts from catalytic pyrolysis of plastic waste as solid functional materials

Plastic consumption has surged due to population growth and shifts in consumer behavior. Upcycling aims to address plastic waste by finding innovative reuse strategies. By integrating waste plastic into new products and materials, upcycling supports a more sustainable and environmentally friendly economic model. This reduces the overall environmental footprint, including CO₂ emissions, associated with plastic consumption. Moreover, converting plastic waste into carbon nanotubes, can effectively sequester carbon. This means that carbon is captured and stored in a stable form, preventing its release into the atmosphere as CO₂. This contributes directly to reducing net emissions. Recent interest in upcycling strategies includes producing target-oriented catalysts to reform plastic waste into carbon nanotubes embedded spent catalysts, offering potential for various applications. However, research in this area is scattered and lacks comprehensive conclusions. This review critically examines the use of spent catalysts from plastic waste pyrolysis and identifies their suitability for practical applications. It suggests focusing on the catalytic pyrolysis of plastic waste for target-oriented catalysts, as they offer good hydrogen yield and post-pyrolysis use in targeted applications. The unique structure of these catalysts enhances performance compared to commercial alternatives, but post-treatment is crucial to remove impurities for optimal performance. The upcycling of plastic waste into CNTs-metal composites substantially contributes to Sustainable Development Goals 7, 9, 12 and 13, by taking action to combat climate change and by guaranteeing access to affordable, clean, and sustainable energy. This review aims to be helpful for researchers who are currently new to the topic and want to continue research in this domain.