Lubricant Base Oils From Polyethylene via Pyrolysis and Catalytic Upgrading

The escalating proliferation of plastic waste necessitates transformative and sustainable valorization pathways. Herein, we report an efficient two-step process for converting virgin and postconsumer high-density polyethylene (HDPE) into high-value lubricant base oils. The approach integrates thermal pyrolysis in a conical spouted bed reactor with subsequent catalytic oligomerization of olefin-rich pyrolyzates. This methodology optimizes wax and liquid hydrocarbon yields while suppressing undesirable by-products. Following wax separation, the liquid fractions underwent oligomerization over solid acid catalysts to generate branched hydrocarbons predominantly in the base oil range (≥C₂₀). Among the tested catalysts, MCM-22, owing to its unique pore structure, exhibited superior performance, achieving ≥C₂₀ yields of 65 and 49 wt% in the oligomerization of the virgin and postconsumer waste HDPE pyrolysis liquids, respectively. Moreover, the zeolite proved reusable and largely regenerable, with a simple calcination restoring the majority of its initial activity. The oligomeric products displayed compositional and physicochemical characteristics analogous to Group III base oils, with minimal aromatic content. Post hydrofinishing and distillation, the final products exhibited favorable viscosity and cold-flow properties, underscoring their potential as sustainable lubricant base stocks.