One-step reconstruction of plastic waste back to its constituent monomers (ONESTEP)

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A truly circular plastic economy in which waste plastics do not find their way into landfill, or the environment is only achievable by developing new, efficient processes that can avoid the major limitations of the current methods used in the recycling industry. The processes we rely upon at the moment require a number of costly and energy intensive steps, can produce greenhouse gases, and cannot treat many different types of plastic waste, particularly single-use plastics due to their low economic value of recycling.By using a method that can efficiently break down waste plastics into their original molecular components, then using them to remake, new reusable plastics, the catastrophic effects upon the environment caused by waste plastics can be removed.This programme of research brings together international experts in catalysis and electromagnetism with the goal of developing a one step process to turn a range of polymers into their constituent monomers thereby realising a fully circular plastic economy. Using the energy efficient heating characteristics of and control afforded by the microwave spectrum it is possible to obtain yields unachievable by current recycling methods. Conventional thermochemical recovery of monomers from polyolefins in one or multiple steps is challenging due to the chemical inertness of plastics. Existing single step methods can only yield about 20-30% of the desired monomers, and multiple step processes are highly energy intensive, requiring high catalyst loading and temperatures above 700 C. The unique properties of microwaves offer a greener, faster, one-step process in which it is possible to enhance yields of valuable, constituent monomers to higher than 70% from a range of waste plastics at milder reaction conditions, impacting the entire life cycle and value chain of the plastics and related industries. This research will directly address plastic waste pollution by offering a truly sustainable, circular plastic economy.Here, working closely with industrial partners, and partners from Welsh Government and public campaign group no2plastics, we target scaled-up (pilot scale, 6kW) production of virgin-quality depolymerised monomers, in a single step, and with no greenhouse gas emissions. This will be followed by efficient synthesis of new high-quality polymers from the recovered molecular components. Key to this research is delivery of (i) catalysts and microwave protocols capable of the depolymerisation of a wide range of different polymers into constituent monomers, with targeted and controllable selective scission of C-C and C-H bonds not accessible by other routes, and (ii) a sustainable, low-energy, zero emission route to a circular plastic economy, which will contribute significantly to reduction of energy usage, wastage and emissions, impacting the entire life cycle and value chain.