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

Mechanical recycling of plastic waste is not sustainable and inefficient in terms of the resources needed to accomplish the process, and the quality of the materials obtained from this technique is substandard. Chemical recycling of waste polymers appears to be preferable because this technology allows for the production of new materials. This review compiles the most recent research in which selected transition metals are used as catalysts for the hydrogenolytic depolymerization of waste polyolefins as a polymer upcycling process. Hydrogenolysis is an emerging chemical recycling method that uses transition-metal complexes as catalysts in the presence of hydrogen to cleave the C–C bonds of polymer substances into shorter hydrocarbons. Transition metals such as Ruthenium (Ru), Platinum (Pt), Nickel (Ni), Cobalt (Co), Zirconium (Zr), Tantalum (Ta), and Rhodium (Rh) have been utilized most recently for this type of reaction. This hydrogenolysis technique can produce valuable hydrocarbon products, such as gas/liquid fuels and lubricating oils, under relatively milder operational conditions and with less environmental impact. The review focused on the supported metal and organometal catalytic system and their mechanism for the polyolefin hydrogenolysis pathways and detailed investigation of the impact of reaction parameters on the production of high quality fuels such as gasoline, diesel, and light lubricants.