Organocatalytic Aerobic Oxidative Degradation of Polystyrene to Aromatic Acids

Abstract

Polystyrenes are among the most prevalent commercial plastics produced worldwide, but their end-of-life treatment remains highly suboptimal today. Although currently only in their infancy, chemical upcycling of polystyrenes into functional chemicals have emerged as a potential solution to the growing waste plastic problem. Herein, we describe the first thermal organocatalytic method to oxidatively degrade commercial waste polystyrenes to benzoic acid and 4-nitrobenzoic acid, both of which are important chemicals in demand across multiple industries. Using N-hydroxyl catalysts such as N,N′,N″-trihydroxyisocyanuric acid and N-hydroxyphthalimide derivatives, our operationally simple method affords substantial yields of these aromatic acids in the presence of a suitable nitrate source in air at atmospheric pressure. Furthermore, our method can degrade commercial polystyrene products containing additives such as dyes on gram-scales as well as different polystyrene derivatives (e.g., polystyrene sulfonic acid) into other industrially relevant aromatic acids. Our findings not only redefine the currently overlooked potential of organocatalysis in chemical upcycling of recalcitrant plastics containing inert, non-cleavable polymer backbone structures but also complement other emerging catalytic methods for chemical degradation of plastic waste.

Pioneering Aromatic Generation from Plastic Waste via Catalytic Thermolysis: A Minireview

“…To catalyze the reaction, they used an organic compound called N , N , N -trihydroxy isocyanuric acid, with a mass ratio of PS/catalyst of 5.9. The reaction was carried out at 120 °C for 24 h, resulting in benzoic acid (30%) and nitrobenzoic acid (13%) as the major products Table presents a brief summary of the development of catalytic pyrolysis using stirred-tank reactors.…”

Enhancing the photocatalytic upcycling of polystyrene to benzoic acid: a combined computational-experimental approach for acridinium catalyst design

“…5 Instead of disposal, upcycling end-of-life plastics into financially more-valuable chemicals and materials is of great interest, 6–10 with PS being especially valued as a possible source of industrially-relevant aromatics. 11,12 Amongst them, benzoic acid (BA) is of particular importance, with annual demand exceeding 500 000 metric tons 13 across multiple industrial applications, such as food preservatives, antimicrobial agents and chemical precursors. However, PS oxidative degradation is hindered by the chemical inertness of its saturated C–C backbone, which traditionally necessitates harsh oxidation conditions involving high temperatures and pressures.…”

The global burden of plastics in oral health: prospects for circularity, sustainable materials development and practice

“…Chemical upcycling of plastic waste transforms these post-use polymers into new products of higher value, thus placing this low-cost and readily-abundant waste material at the beginning of the value chain instead of at the end. 50–53 This approach can reduce our reliance on petroleum sources to produce these essential chemicals, whose industrial demand may prove financially viable to sustain a possible post-use plastics industry. Alternatively, several classes of polymers in current use ( e.g.…”