PTQ Q1 2026 Issue

Boiling point reduction Hydrocarbon type improvement

Di-olen saturation

ReNewFine

Olen saturation

HDS/HDO/HDN

ReNewFine

Guard bed

ReNewFine

HYC Polishing

Silicon trap

Boiling point

Figure 5 The upgrading of WPO via subsequent hydroprocessing steps as followed by 2D chromatography

WPOs: feedstock characterisation and processing The composition of WPOs varies widely depending on the source plastic, conversion technology, and operating con- ditions. Accurate characterisation is essential for catalyst design and process optimisation for each use case. Figure 4 illustrates the proverbial ‘periodic table’ of inorganic impu- rities that have been found in WPO. The FCC process has a reputation for tolerance to impurities, largely based on many years of experience across a range of crude qualities. Steam crackers tend to operate with lower risk tolerance. Few publications define clear limits on impurities for steam There is a need for standardised characterisation protocols and benchmarking of catalyst performance across studies cracker operations. Table 1 gives a summary of values from a paper that is widely referenced in the industry, combined with Ketjen’s own intelligence. 5 For molecular impurities, Ketjen employs multi-dimen- sional chromatography and elemental analysis to profile WPOs, identifying key contaminants and their structures. This data informs the selection and design of catalysts for hydroprocessing, ensuring robust performance across a range of feedstocks. The use of 2D chromatography to follow the composition of the hydrocarbon stream during the different steps in the upgrading of WPOs via hydroprocessing is illustrated in Figure 5 . In the 2D chromatograms, each dot represents the concentration of a molecular compound with a certain

boiling point (horizontal position) and polarity (vertical posi- tion). When analysing the WPO before and after the olefin saturation step (left side of the figure), it can be observed that reactive dienes are selectively removed, which allows for deep hydroprocessing over more active catalysts with- out the risk of an extreme exotherm in downstream catalyst beds. During the hydrocracking step that concludes the upgrading of the WPO, the boiling point of the then-pure hydrocarbons is effectively reduced to yield a product that is suitable as steam cracker feed. There is a need for standardised characterisation pro- tocols and benchmarking of catalyst performance across studies. The complexity of WPOs, which contain additives, stabilisers, and degradation products, poses ongoing chal- lenges for both research and industrial implementation. Challenges and opportunities Despite significant progress, several challenges remain: • Feedstock variability: The wide range of waste plastics feedstocks and their contaminant profile complicate pro - cess design and catalyst selection. In theory, feedstock variability could be addressed by standardisation and clas- sification, similar to what is the current practice for varia - bility in crude oil qualities. Unlike crude that comes from reservoirs, waste plastics come from a range of disparate resources (such as municipal waste), and the current collec- tion and sorting techniques do not yield constant qualities. • There is a need for standardised characterisation pro- tocols and benchmarking of catalyst performance across studies. The complexity of WPOs containing additives, stabilisers, and degradation products poses ongoing chal- lenges for both research and industrial implementation. • Detailed analyses of the mechanisms underlying catalytic plastic recycling are key for future progress. For instance, it is clear that zeolites and silica-alumina catalysts promote

PTQ Q1 2026