100th Anniversary of Macromolecular Science Viewpoint: Toward Catalytic Chemical Recycling of Waste (and Future) Plastics

Abstract

The current global materials economy has long been inefficient due to unproductive reuse and recycling efforts. Within the wider materials portfolio, plastics have been revolutionary to many industries but they have been treated as disposable commodities leading to their increasing accumulation in the environment as waste. The field of chemistry has had significant bearing in ushering in the current plastics industry and will undoubtedly have a hand in transforming it to become more sustainable. Existing approaches include the development of synthetic biodegradable plastics and turning to renewable raw materials in order to produce plastics similar to our current petrol-based materials or to create new polymers. Additionally, chemists are confronting the environmental crisis by developing alternative recycling methods to deal with the legacy of plastic waste. Important emergent technologies, such as catalytic chemical recycling or upcycling, have the potential to alleviate numerous issues related to our current and future refuse and, in doing so, help pivot our materials economy from linearity to circularity.

Heterodinuclear catalysts Zn(ii)/M and Mg(ii)/M, where M = Na(i), Ca(ii) or Cd(ii), for phthalic anhydride/cyclohexene oxide ring opening copolymerisation

“…The two additional ether donors appear important in regulating epoxide coordination, at the other Zn(II) centre, and in preventing the formation of ether linkages. 27 The two complexes with Cd(II) coordination, (6) and (11) show equivalent activity values (TOF = 65 h −1 , k obs = 230 × Fig. 4 a) Linear fit plot of [PA] vs. time (s) for PA/CHO ROCOP using catalyst (4).…”

On the use of catalysis to bias reaction pathways in out-of-equilibrium systems

“…Expanding nature's toolbox by using articial catalysts, such as transition metals, simpler small molecule organocatalysts or even acid/base catalysis could signicantly boost the application potential of this eld. Especially organocatalysts can be easily modied and applied in so materials or bulk polymer materials, 42,43 although they do oen suffer from low activity and high background reactivity. Transition metal catalysts generally outperform organocatalysts when it comes to activity and on/off-ratios.…”

Recent Advancements in Photocatalytic Valorization of Plastic Waste to Chemicals and Fuels

“…The approach collects and reprocesses the plastic polymer as raw material for new plastic manufacturing by sorting, shredding, melting, and re-extrusion (Al-Salem et al, 2009;Kumar et al, 2011;Mark et al, 2020;Schyns and Shaver, 2021;Zhang K et al, 2021). It is favored by environmental friendliness, but commonly suffers from property deterioration of the products due to the chain scission, branching, and oxidation of the plastic polymer caused by the reprocess treatment (Mark et al, 2020;Worch and Dove, 2020). In addition, the application of the approach is limited by the type of the plastic.…”

“…In contrast, chemical recycling is a more promising plastic valorization strategy that now sparkle in both academic and industrial arenas. The process focuses on transformation of plastic waste into small molecules, ranging from starting monomers to constituent hydrocarbons (Worch and Dove, 2020). The products not only can be re-polymerized into virgin plastic, but also can be upcycled into alternative chemicals and fuels, thus enabling the materials reusing in a closed loop.…”