PTQ Q3 2023 Issue

Purifying and upgrading of waste plastics pyrolysis oils

Closing the plastics production disposal loop requires the ability to recycle at scale by combining chemical recycling with pyrolysis technology

Artem Vityuk and Sanaz Norouzi BASF Corporation

P lastics as materials feature unique benefits that have proven indispensable for modern society. As their use areas span building materials and mobility to consumer goods and machinery, low costs and wide avail - ability make plastics a universal solution. However, they are also extremely difficult to replace. Production volumes have also been impressive. Global production of thermoplastic resins (PE, PP, PS, PET, PVC) reached 300 MMt/yr in 20221 and continues posting growth rates above global GDP. While industry has been able to supply much-needed plastics volumes to support economic growth, the issue of plastics waste has never been truly resolved. Plastics are among the least recycled materials, with an average global recycling rate of only 9%, compared to steel at 85%, aluminium at 75%, paper at 60%, and glass at 50%.2 Fundamentally, the problem of waste plastics is not only an environmental or pollution problem but also a resource efficiency issue. As industries look to transition from linear to circular economy models to reduce associ - ated GHG emissions, the reuse of materials and specifically plastics is crucial. Looking at recycling methods that are used commercially, mechanical recycling plays an important role. However, they only apply to specific polymer grades and are not uti - lised for hard-to-recycle plastics, limiting their impact on a global scale.1 While there are alternative methods in devel - opment and commercialisation, the only feasible option for recycling waste plastics at scale is chemical recycling, where pyrolysis technology has been proven instrumental.3 There are certain unique benefits associated with pyroly - sis. However, the key features include scalability (pyrolysis As industries look to transition from linear to circular economy models to reduce associated GHG emissions, the reuse of materials and specifically plastics is crucial

and its modifications have been known to industry for decades) and ease of integration into existing olefin pro - duction assets (steam crackers). Waste plastics pyrolysis facilities produce pyrolysis oil (pyoil), which can be used as a feedstock for naphtha crackers towards ethylene and propylene production, the core monomer building blocks of most plastics.4 , ⁵ Ideally, it is possible to divert hard-to-recycle waste plas - tics from landfill and dumps (unsuitable for mechanical recycling) to pyrolysis sites supplying polyolefin complexes producing brand-new plastics and in essence close the plastics production disposal loop. That exciting recycling solution is gaining momentum in chemical and petrochemi - cal companies engaged in olefins value chains. There are challenges; pyrolysis of waste plastics at a com - mercial scale is not mature. The most pronounced technical challenge limiting the wider use of waste plastics-derived pyoils in downstream petrochemical assets includes purity and compositional diversity. For example, steam cracker feedstocks feature very tight specifications that need to be satisfied if pyoil is added as a feedstock. High contamination of pyoils is not surprising as mixed waste plastics are normally a very complex combination of polymers that often contain electronics waste, multilayer films, plastics composites, and other side components con - tributing to contamination of the resulting pyoils. Regional and country-specific factors also influence the composition of mixed waste plastics. Thus, the purification of waste plastics pyoils is an abso - lute must if industry aims to reach large industrial use of this technology and reduce plastics waste by chemical recycling. Alternatives are to apply extensive presorting or modify the pyrolysis process by reducing useful liquids yields – cost-prohibitive measures that would limit wide industrial usage. Solving the pyoil purification challenge Solving these bespoke challenges and building a more circular economy for plastics requires innovation and joint efforts across the value chain. To enable more efficient plas - tics recycling, the proprietary PuriCycle line of high-per - formance products has been developed. They use novel catalysts and adsorbents to purify most of the investigated

PTQ Q3 2023