Catalysis 2025 Issue

600

Light Pyrolysis oil

Heavy Pyrolysis oil

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Untreated Pyoil

Treated Pyoil w/ Evonik

Untreated Pyoil

Treated Pyoil w/ Evonik

Untreated pyrolysis oil with 485 ppm Cl, fractionated into light and heavy pyoil (cuto 205˚C)

Figure 1 Treating light and heavy pyrolysis oil with Evonik’s specialised adsorbent resulted in significant reduction of chlorides

Catalyst solution Recent technological advancements, notably new and improved catalysts, have increased pyrolysis efficiency and output quality. Catalysts play a key role in both the quality and quantity of recycled plastic waste processing. Part of this movement includes catalytic pyrolysis, a process that combines pyrolysis and vapour-phase catalytic upgrading, offering lower temperature and energy requirements, higher yields, and optimised product distribution and selectivity. For PVC, pyrolysis produces toxic, corrosive organochlo- rine compounds and hydrogen chloride (HCI). However, the right catalysts can be used to dechlorinate and con- dense these gases. To minimise HCI emissions, adsorbents or additives introduced in close contact with the plastic vapour in the reactor can assist with dichlorination through adsorption, a technique also known as in situ upgrading. Evonik’s chloride and fluoride adsorbents and hydro - processing catalysts allow for the separation of impurities and the reduction of contamination during production. Researchers are taking industrially proven processes and adsorbents used elsewhere in the industry and applying

and adapting them to plastic waste recycling processes to introduce new brands of products for purification. Hydroprocessing catalysts are an important tool for con- tributing to refineries’ sustainability goals because they can be regenerated and reused. As well as catching unwanted elements and removing contaminants, hydroprocessing also reduces olefins and aromatics, decreasing heater foul - ing in steam crackers, increasing yields, and helping make pyrolysis oil suitable for steam cracking. Case study The recent development of a new specialised adsorbent for removing organic chlorides from plastic pyrolysis oil is shown in Figure 1 , demonstrating significant chloride reduction across the treatment of both light and heavy pyrolysis oil. In this case study, industrially produced pyrolysis oil was distilled into a naphtha (light) and residual (heavy) fraction with a cut-off point of 400°F (200°C). Chloride concentra- tion decreased by 300 parts per million (ppm) across both oils, with removal efficiency higher for the naphtha fraction. These specialised adsorbents have also demonstrated three times higher chloride removal than conventional organic chloride sorbents (see Figure 2 ). The brand’s alkoxide catalysts and process technologies also enable the recycling of PET and coloured PET plastics, which are not suitable for mechanical recycling, at the end of their lifecycle. Partnership and circular economy success The management of plastic waste is clearly siloed, with mandates of usage and recycling differing between regions and countries. Businesses and industries are also having to adhere to stricter, although not uniform, emission rules, cre- ating more confusion. Simultaneously, downstream brands and retailers are finding themselves increasingly subject to consumer pressure for more sustainable products; eco- friendly producers are growing more rapidly in the market- place than other incumbents. Part of the reason the management of this problem is so varied internationally is due to the high economic cost of plastic waste and the complexity that collecting, sorting, and cleaning said waste presents. According to McKinsey, $50 billion may be needed by 2030 to support the scale-up

100%

3x improvement

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New pyoil chloride sorbent

Conventional organic chloride sorbent

Figure 2 Evonik’s specialised adsorbent demonstrates significant improvements over existing sorbents

Catalysis 2025