Polyolefins comprise a major fraction of single-use plastics, yet their catalytic deconstruction/recycling has proven challenging due to their inert hydrocarbon connectivities. While several precious metal catalysts have been recently investigated for such transformations, they generally require forcing conditions. Here an electrophilic earth-abundant single-site organozirconium catalyst chemisorbed on a highly Brønsted acidic support is characterized via EXAFS, solid state 1H MAS and 13C CP-MAS NMR, DRIFTS and DFT computation is show. The catalyst is shown to mediate the rapid hydrogenolytic cleavage of molecular and macromolecular saturated hydrocarbons under mild conditions, with catalysis onset occurring as low as room temperature at ambient H2 pressure. Kinetic analyses were performed using n-hexadecane hydrogenolysis batch reactions and in-situ gas-phase 1H NMR hydrogenolysis of propane, which also shows an initial TOF of 50.7 mol C3H8 mol(Zr)-1h-1 at 70°C. The mechanism for C-C bond cleavage is proposed to proceed via a turnover-limiting C-C scission pathway involving ß-alkyl transfer, with experimental results agreeing closely with the computed barrier for this process. For polyethylene, quantitative hydrogenolysis to light hydrocarbons proceeds within 48 min with an activity of &gt; 4000 mol(CH2 units) mol(Zr)-1 h-1 at 200°C/2 atm H2 pressure at 0.06 mol% Zr loading. Under similar solventless conditions, polyethylene-co-1-octene, isotactic polypropylene and post-consumer polyolefins containing antioxidant and processing additives are rapidly hydrogenolyzed to low molecular mass hydrocarbons.

Facile polyolefins hydrogenolysis facilitated by a heterogeneous electrophilic d0 Zr catalyst

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ACS Fall 2022

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