Photo-recycling: Molecular oxygen, aided by vanadium catalysts under purple-light irradiation mediates a high-yielding, selective cleavage of tertiary alkylbenzenes and polystyrenes into acetophenone and other ketone derivatives. The yield and selectivity achieved are not dependent on the molecular weight, polydispersity, or form of polystyrene produced (crystal, expanded, extruded).
Every year, thousands of tons of polystyrene are produced and discarded, filling landfills and polluting the marine environment. Although several degradation alternatives have been proposed, the need for an effective procedure for the chemical recycling of polystyrene still remains. Here, a vanadium-catalyzed reaction, assisted by visible light, promoted the direct, selective conversion of tertiary alkylbenzenes into acetophenone and other ketone derivatives. Likewise, standard polystyrene samples as well as polystyrenes from insulation and packaging waste could be chemically recycled into acetophenone in a scalable way regardless of their molecular weight, polydispersity, or form. Preliminary mechanistic investigations revealed the participation of singlet oxygen, superoxide, and hydroxyl radical species in this homogenously catalyzed process. Acetophenone could be used as an additive to accelerate the reaction and to increase the yields in some cases.Zum Volltext