Recent Advances in Catalytic Chemical Recycling of Polyolefins

Abstract

Scheme 1. Mechanism of polyolefin hydrocracking, during which CÀ C bonds are dehydrogenated, cracked via carbocation chemistry, and re-hydrogenated over a bifunctional metal-acid catalyst.

Quantifying synergy for mixed end-scission and random-scission catalysts in polymer upcycling

“…Chemical recycling processes, especially with catalysts to guide selectivity, have the potential to create high value chemicals from plastic waste. 4–17 Different catalysts for polymer upcycling operate in different ways: end scission or random scission, heterogeneous or homogeneous, processive or non-processive, etc. Processes that use a mixture of catalysts may even exploit synergies between different catalyst modalities.…”

Review on Catalytic Depolymerization of Polyolefin Waste by Hydrogenolysis: State-of-the-Art and Outlook

“…Some of the methods used for upcycling of plastic wastes include pyrolysis, − solvolysis, − hydrogenolysis, , cracking, − combustion (incineration), − hydrothermal liquefaction, , and gasification . Even though chemical recycling is more expensive compared to mechanical recycling, it still has advantages over the latter and is more suitable for many commercial and industrial applications. ,− Even the rate of the depolymerization as an upcycling techniques is also investigated today . The chemical recycling process is applicable to a mixture of plastic waste and does not generate greenhouse gases.…”

“…The chemical recycling process is applicable to a mixture of plastic waste and does not generate greenhouse gases. The chemical recycling technique is employed in the manufacture of hydrocarbon fuels, waxes, diesel oil, and lubricants, that serve as feedstocks for the manufacture of new plastic materials and other petrochemicals . Furthermore, the controlled incineration of plastic wastes in reactors is used for electricity generation from the heat energy produced during the burning process .…”

“…The chemical recycling technique is employed in the manufacture of hydrocarbon fuels, waxes, diesel oil, and lubricants, that serve as feedstocks for the manufacture of new plastic materials and other petrochemicals. 36 Furthermore, the controlled incineration of plastic wastes in reactors is used for electricity generation from the heat energy produced during the burning process. 67 Hydrogenolysis is one of the potential processes for chemical recycling of waste plastics.…”

“…Only about 8.53 billion metric tons (equivalent of 25.7%) of the world plastic population is recycled, and about 12.39 billion metric tons (equivalent of 37.3%) are incinerated, while the rest of the plastic volume (37.0%) is either buried in landfills or deposited in dumpsites (Figure ). Chemical recycling, or depolymerization on the other hand, is a technology for transforming waste plastics into more useful starting feedstocks by breaking them down into their monomer units (building blocks) and other lower molecular weight hydrocarbons-fragments by selective fragmentation of the long polymer chain. − …”