Catalytic Microwave Process for Upgrading of Pyrolysis Liquids from Ubiquitous Plastic Wastes

Plastics are ubiquitous in modern life, with global production of ~260 million tonnes per year and only 9 % recycled in 2019. 8.3 billion tonnes of plastic have been produced in total and predicted 12 billion tonnes in landfill or environment by 2050, taking 400 years to degrade naturally. In future, a strong growth in demand for and production of plastics is expected, whilst concerns for the greenhouse effect necessitate that carbon dioxide emissions and reliance on fossil fuels are decreased to meet legislation. Plastics can be recycled via a range of mechanical, thermal and chemical techniques, each route having advantages and disadvantages. Some chemical recycling techniques, such as glycolysis, are applicable only to particular types of polymer. Other routes, such as mechanical recycling, produce a lower grade product, whilst thermal techniques require a high energy input. Mixed waste, including halogenated polymers such as polyvinyl chloride presents a challenge, as the chlorine is a potential catalyst poison. A recycling and upgrading process is thus required that can process a range of different pyrolysis oils derived from polymers as part of a mixed waste stream, can deal with contaminants and produce a value-added product.

In Catawave we aim to address the above issues and develop a robust and energy efficient process to upgrade pyrolysis liquids derived from a range of plastic waste streams. To do this we bring together several novel requisite technologies, which will include the development of bespoke catalysts to effectively upgrade the pyrolysis oils. These will be formulated from industrial metal processing or mining waste by-products such as 'red mud' and known hydrocarbon cracking catalysts such as zeolite ZSM-5, and select samples will incorporate microwave susceptible carbon particles to aid their heating. We will assess whether microwave or induction heating in a flow reactor can deliver a more effective and energy efficient process compared with conventional resistive heating, in conjunction with the developed catalysts. The upgraded oil products will be characterised using a range of techniques, with aim of upgrading to increase the value of products, including upscaling to meet standards required for drop-in fuels. Fresh and spent catalyst will be characterised using a range of techniques to understand their catalytic behaviour and deactivation.

The results of the experimental studies will be applied to develop a kinetic model using lumped approach comprising component groups, which would be used to inform the design and scale-up of reactors for an industrialised process. Techno-economic modelling will be developed to inform the process scalability and profitability, for example the selection of tonnage throughput, distributed or centralised processing of waste.

We have engaged Project Partners from across the waste producing, recycling, fuels and process simulation sectors including Sabien Technology Plc, Halocycle, Severn Trent Green Power, Pressvess and Mitsubishi Chemical. They will provide samples of pyrolysis oil for upgrading, advise on catalyst formulations, assist with process design and economic evaluation, give technical consultation on the work plan and help setup routes to commercialisation and impact delivery as outlined in their letters of support.