(47c) From Unfit to on-Spec Steam Cracker Feedstock: Hydroprocessing of Waste Plastic Pyrolysis Oil

The need for a circular plastic economy has highlighted the importance of effective chemical recycling of mixed plastic waste into high quality products suitable for contact-sensitive packaging amongst other applications. The diverse composition and properties of plastic waste, along with various liquefaction technologies, pose challenges that demand an upgrading step that can provide not only drop in naphtha quality for steam crackers but also absorb all the fluctuations in the feedstock quality. The contribution introduces the TOPSOE research and development efforts to tailor make a technology that offers the required flexibility and robustness.

This hydroprocessing technology, PureStep™, is based on results from more than 60 continuous flow pilot plant tests with different plastic pyrolysis oils. These tests, along with ongoing testing efforts, were conducted with the purpose of producing on-spec naphtha or heavier cut steam cracker feedstock. A process has been developed that addresses the complexities of chemical recycling by coupling knowledge from in-house analyses and testing with decades of experience from hydroprocessing and technology development within fossil and bio-based feedstocks.

Analyses techniques have been developed for speciation of selected contaminants, and fractionation studies have been performed showing that major contaminants do not occur in predetermined boiling point fractions across different mixed waste plastic derived oils. Understanding of specific impurities inherent to plastic derived oils gives valuable insights into the required hydroprocessing. The focus on guard catalyst development, for example for silicon uptake, further enhanced the effectiveness of the process, enabling the removal of key contaminants.

One of the key advantages of PureStep™ is its ability to adapt to different plastic liquefaction technologies, ensuring solutions for variable oil compositions and targeting steam cracker feedstock properties.

In 2024, the technology is being commissioned in two commercial plants. This contribution includes some of the first learnings from these plants.