deploying catalysts in at least one stage, are under develop- ment to improve olefin yields for downstream integration with steam crackers. Feedstock challenges The composition of plastic waste critically influences the proper - ties, yield, and quality of pyroly - sis oil. It is possible to predict the pyrolysis product by knowing something about the polymers. Key considerations include: • Polyolefins including polyeth - ylene (PE) and polypropylene (PP): Mixed polyolefins provide the highest liquid yields and pro- duce oils low in aromatics, mak- ing them ideal feedstocks.
the inherent variability in plastic waste streams. Commercialisation status Chemical recycling pathways are gaining traction as demand for recycled polymers increases. Pyrolysis-derived WPO cur- rently represents a small frac - tion of total recycling capacity (<0.1 million tonnes annually in the EU, compared to ~9 million tonnes for mechanical recy - cling).² However, industry fore - casts project significant growth, with chemical recycling capacity expected to exceed 17 million tonnes annually by 2035. First-generation pyrolysis plants typically have input capac- ities of 10-50 kilo tonnes per year (kt/year), much smaller than
Figure 1 Unprocessed and contaminated PPO (left) and its upgraded counterpart (right). Processed using PureStep technology
• Polystyrene (PS): Yields sty- rene monomers upon pyrolysis, allowing for polymerisation as the only other step away from new plastic. It is best processed when sorted. • Polyester plastic, such as PET: High oxygen content leads to low oil yields and significant production of organic acids and char. Unsuitable for steam cracker feedstock. • Chlorinated plastics, such as polyvinylchloride (PVC): Resembles polyethylene to a large extent, but it has chlo- rine in the backbone. Releases large amounts of hydrogen chloride (HCl) during pyrolysis at relatively low tempera- tures. Will give a low oil yield and leave the oil with a lot of unsaturated components, aromatics, and chlorinated hydrocarbons from secondary reactions. High char for - mation and corrosive byproducts. Not recommended for pyrolysis. • Other plastics, such as acrylonitrile-butadiene-styrene (ABS), polyamide (PA), polycarbonate (PC), and more: Similar attributes, and introduces aromatics and heteroa- toms (nitrogen and oxygen) to the pyrolysis oil. The most suitable polymers for pyrolysis are therefore PE, PP, and PS or a mixture of these polyolefins. A small amount of the less suitable polymers can be allowed in the mixture. However, keep in mind that if the goal is to obtain a pyrolysis oil with low aromatic content, PS should be avoided. To improve the predictability and consistency of pyrolysis oil properties, significant research is focused on feedstock preparation and predictive modelling. Proprietary methods and artificial intelligence (AI) tools are being developed to optimise feedstock blends, minimise contamination risks, and ensure consistent WPO output quality. While equipment and process steps, such as washing, are behind feedstock preparation techniques, strong pre - dictive models based on data and experience combined with AI, are the key to the prediction of oil properties. They can help identify optimal feedstock blends, reduce contamination risks, and ensure consistent WPO output quality. These advancements are essential for managing
conventional petrochemical steam crackers (500-1,000 kt/ year). Some of these smaller-sized pyrolysis plants/chemical recycling plants have entered commercial operations, while others are in pilot or demo stages. Fixed costs in chemical recycling of WPO depend on factors such as scale, location, technology, and integration with existing infrastructure. These costs remain constant regardless of output and are largely tied to capital-intensive assets like reactor systems (such as hydroprocessing units, steam crackers) and specialised hydrotreating units used to remove contaminants, such as chlorine, oxygen, nitrogen, and sulphur. Additional investments are required for stor - age, pipelines, catalysts, hydrogen handling, wastewater treatment, and gas clean-up systems, particularly when processing contaminated feedstocks. Co-locating recycling facilities with refineries or petro - chemical plants can lower costs through shared infrastruc - ture, though supply chain logistics remain a key challenge. Post-consumer plastic waste is often collected far from industrial centres, requiring either long-distance transport of pyrolysis oil or development of regional production hubs. Some regions benefit from existing refinery and steam cracker assets that can be repurposed and integrated into waste-to-plastics production units. Achieving circular plastics production will require large volumes of recycled feedstock from both mechanical and chemical recycling. According to Plastics Europe,2 member companies plan to invest €8 billion in chemical recycling by 2030, targeting production of 3.4 million metric tons of recycled plastics annually. Scaling up: upgrading pyrolysis oil Due to the high level of contaminants, plastic pyrolysis oils (PPOs) can only be fed directly into fluid catalytic cracker (FCC) units or steam crackers at very high dilution rates. To achieve higher recycling rates, which are essential for creating a robust market for recycled plastics and reducing
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Catalysis 2026
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