Technology in Action
Boasting multiple applications, pyrolytic oil can reduce dependence on fossil fuels, presenting a lower carbon solu- tion for hard-to-abate sectors, and diversifying energy mate- rials. In petroleum refineries, the oil can replace fossil-based naphtha as a more sustainable feedstock to produce fuels and chemicals. Industries that still rely heavily on crude oil and natural gas (such as shipping, construction, and manu- facturing) can use it as a fuel (once refined and blended with conventional fuels) to power vehicles and machinery. Diversifying energy materials is a necessity in today’s age. One only needs to look at the global turmoil experi - enced by the Russia-Ukraine war, which led to supply chain disruptions, energy security risks, and gas and energy price spikes, all on a global level. However, technical challenges still limit the wider adop- tion of pyrolytic oil as a raw feedstock – specifically, purity and compositional diversity. Mixed waste plastics are often a complex combination of polymers, and the final com - position of these products can differ due to regional and country-specific factors. Plastics such as polyethylene terephthalate (PET) and polyvinyl chloride (PVC) can yield oxygenated and chlorinated compounds. These factors can contribute to and result in the con- tamination of pyrolytic oil. With steam crackers featuring very tight specifications that need to be satisfied if the oil is added as a feedstock, removing these impurities in an economical and sustainable way is necessary. Starting point for a solution: catalysts Catalysts play a key role in the quality and quantity of recycled plastic waste products, with differing types used to improve the plastic pyrolysis process. With PVC as an example, where pyrolysis generates toxic and corrosive organochlorine compounds and hydrogen chloride (HCI), catalysts can be used to dechlorinate and condense these gases. To reduce HCI emissions, adsor- bents or additives (used in close contact with the plastic vapour in the reactor) assist with dichlorination through adsorption, a method also known as in situ upgrading.
Pyrolysis: Defossilation of the chemical industry with plastic waste – a case for collaboration
Plastics are ubiquitous in modern life. Ingrained in our everyday lives, it is no surprise that we are producing twice as much plastic globally as we did two decades ago. According to the UN Environment Programme (UNEP), 430 million tons of plastic are produced yearly, and production is expected to double yet again by 2050. Although the helpfulness of plastics cannot be denied, its downsides have been well-publicised. A third of plastics are single use, while the bulk, a significant 72%, end up in landfill, incinerated or leaking into the environment. Only 9% of plastics are reportedly successfully recycled, and the emissions from their production and disposal are expected to double by 2060. Reasons for low recycling rates vary, and complexity lies with the make-up of many individual plastic prod- ucts. Materials such as flexible films, multilayer materials, and coloured plastics cannot be recycled by conventional mechanical recycling, or at all. To see statistics improve, a more circular economy that involves the contribution of all entities in the process is required. With increasing public pressure for the greater collection, recycling, and reuse of plastics, pyrolysis – one method of chemical recycling – is seeing growing international inter- est. It offers a route to defossilating raw material streams into refineries. Next step in plastic recycling Pyrolysis is a process where plastics are collected at the end of their product life cycle and heated to high tempera- tures (300-900°C) in an inert atmosphere without oxygen. Thermal degradation causes plastic materials to break down into smaller molecules. From this, what once was plastic waste is transformed into pyrolysis (pyrolytic) oil or gas, which can be repurposed and utilised as reusable crude oils.
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Figure 1 Evonik’s specialised adsorbent for significant reduction of chlorides in light and heavy pyrolysis oil
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PTQ Q3 2024
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