The massive amount of plastics discarded each year requires new sustainable end-of-life solutions. Current technologies are insufficient to deal with the crisis in its entirety. New methods involving chemical upcycling, by catalytic conversion of the used materials into higher value products, could provide new useful chemicals. In addition, few existing catalytic methods can break C–C bonds in aliphatic hydrocarbons lacking directing groups and introduce new heteroatom functionality. We will report the development of a new, mild catalytic conversion of polyolefins in which carbon–carbon bonds are broken and new aluminum–carbon bonds are formed, providing moderate length fatty aluminum intermediates.

Surface-supported single-site zirconium species, from Zr(CH₂CMe₃)₄ grafted onto partially-dehydroxylated silica-alumina, heated with high density polyethylene and AlⁱBu₃, affords an oil after quenching with O₂, CO₂, I₂, or MeOH. These oil products contain fatty alcohols, carboxylic acids, alkyl iodides, or alkanes, respective, as determined by infrared and ¹H and ¹³C NMR spectroscopy. MALDI-TOF-MS confirms the oils are ~C₃₅-centered distributions of hydrocarbon chains containing a single functional group.

Independent reactions of surface-grafted neopentylzirconium and AlⁱBu₃ generate isobutylene, detected by ¹H NMR spectroscopy. Isobutylene is also detected in catalytic experiments. Analysis of the catalytic solid by DRIFT spectroscopy indicate that hydridozirconium surface sites are plausible under the reaction conditions. Remarkably, air-exposed neopentylzirconium is also active under (air-free) catalytic conditions, indicating that the aluminum reagents react with Zr–OR bonds to generate reactive hydridozirconium. Moreover, the fatty alcohol or fatty acid catalytic products are useful in range of current commercial applications and are biodegradable. Thus, this catalytic approach could lead to new end-of-life applications for single-use polyolefins.

Frederic Perras

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