PTQ Q3 2023 Issue

Chloroalkanes

Chloroalkenes

Chlorooxygenates

Chloronaphthenes

Chloroaromatics

( )

n = 3-12

Increased diculty to remove Cl

Figure 2 Exemplary chloride species in commercial waste plastics pyrolysis pyoils

these results are exemplary and only applicable to specific pyoil used, the data underline the importance of proper cat- alysts selection. Dehalogenation (dechlorination) Removal of halogens and, most importantly, chlorides are among the most difficult purification tasks. While the chlorides level is highly dependent on the composition of mixed waste plastics feed and pyrolysis process design, it is extremely challenging to eliminate chlorides from pyoils fully without on-purpose purification. It is important to emphasise that dechlorination guards are known and used in refining; a good example would be the chloride removal section in reforming plants, where reformate or recycle hydrogen is often purified from chlo - rides However, there is a fundamental difference in spe- ciation and properties of chloride compounds normally found in reforming streams and the chlorides often seen in waste plastics pyoils. Most chloride compounds in pyrolysis naphtha are organic chlorides with complicated structures, where removal of these species using conventional adsor- bents is often impossible ( Figure 2 ). For these challenges, PuriCycle H serves as a guard with a formulation designed for the dechlorination of waste plastics pyoils. An example shown in Figure 3 highlights the performance of PuriCycle H compared to conventional

chloride guards. A sample of the pyoil from a commercial waste plastics pyrolysis site was used at a chloride level of 80 ppmw. As seen from the plot, even though conventional alkali-pro - moted alumina and metal oxide-based guards initially exhibit high removal efficiency, performance rapidly degrades even at consistently increasing temperatures, pointing to the low efficiency of these formulations in tackling organic chlo - rides in pyoils. In another example, performance in chlorides removal was measured at a constant temperature and com- pared to mixed metal oxide guards widely used for chlorides removal in reforming plants. Chlorides pick-up is profoundly deteriorating over metal oxide adsorbents, with removal effi - ciency dropping to 50-60% within just 250 hours on stream, while PuriCycle H shows a steady and complete chlorides removal performance. Chemical recycling of waste plastics: industry perspective Even though chemical recycling of waste plastics using pyrolysis is widely seen as an important pillar in build- ing more circular value chains in plastics, and industry is actively investing in it, implementation challenges exist. Most commercial pyrolysis plants are well below through- puts that would allow feedstock supply to a world-scale steam cracker in quantities covering 40-50% of its demand.

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PuriCycle H Guard A (AlOx) Guard B (MMO)

PuriCycle H Guard B (MMO) Guard C (MMO + prom)

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Figure 4 Chlorides removal from waste plastics PyOil by PuriCycle H compared to conventional metal oxide guards. Conditions: chlorides inlet ~ 150 ppmw, temperature 250°C, 50 barg argon

Figure 3 Chlorides removal from waste plastics PyOil by PuriCycle H compared to conventional guards (alumina and mixed metal oxide based). Conditions: chlorides inlet ~ 80 ppmw, temperature 200-330°C, 50 barg argon

PTQ Q3 2023