Chemical Upcycling of Polyethylene to Value-Added alpha,omega-Divinyl-Functionalized Oligomers

Today, only 9% of plastic waste is recycled worldwide, with polyethylene being one of the most frequently discarded plastics. In this work, a new route to chemically recycle polyethylene is demonstrated. Polyethylenes of two different molecular weights (M-n = 1.5 kg/mol and M-n = 6.6 kg/mol) were upgraded to value-added alpha,omega-divinyl-functionalized oligomers with shorter, tunable chain lengths via a sequence of bromination, dehydrobromination, and olefin metathesis reactions. Brominated polyethylene (BPE) was isolated in good yields (up to 86 wt %, based on PE) by direct bromination of polyethylene in air, without oxidative cleavage side-reactions. Elimination of bromide resulted in complete conversion of BPE to vinylene polyethylene (VPE) in high yields (up to 91 wt %, based on BPE). Ethenolysis of VPE afforded alpha,omega-divinyl-functionalized oligomers, also in high yields (up to 97 wt %, based on VPE), with carbon numbers significantly lower than those of the starting PE. Preliminary techno-economic assessments demonstrate that this three-step process could be economically viable on an industrial scale for upcycling PE into value-added chemicals that can be used in the synthesis of lubricants, as well as transformed into new commodity polymers such as polyolefins, polyethers, polyesters, and polyamides.