Upcycling Waste Plastics with a C–C Backbone by Heterogeneous Catalysis

Abstract

Plastics with an inert carbon−carbon (C−C) backbone, such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC), are the most widely used types of plastic in human activities. However, many of these polymers were directly discarded in nature after use, and few were appropriately recycled. This not only threatens the natural environment but also leads to the waste of carbon resources. Conventional chemical recycling of these plastics, including pyrolysis and catalytic cracking, requires a high energy input due to the chemical inertness of C−C bonds and C−H bonds and leads to complex product distribution. In recent years, significant progress has been made in the development of catalysts and the introduction of small molecules as additional coreactants, which could potentially overcome these challenges. In this Review, we summarize and highlight catalytic strategies that address these issues in upcycling C−C backbone plastics with small molecules, particularly in heterogeneous catalysis. We believe that this review will inspire the development of upcycling methods for C−C backbone plastics using small molecules and heterogeneous catalysis.

Recent advances in oxidative degradation of plastics

“…Chemical upcycling, a conversion of discarded plastics to higher-value materials or feedstocks, is another approach to resolve plastic pollution. 18–24 One specific example is oxidative degradation, which uses thermally induced radicals and a cheap oxidant, molecular oxygen (O 2 ), to cleave polymer chains and produce small molecule oxidized compounds. 25,26 In the environment, plastics slowly degrade in air under sunlight due to photooxidative degradation, meaning light is involved in the oxidative degradation of plastics.…”