Biologically bound nickel accelerated de-polymerization of polyethylene to high value hydrocarbons and hydrogen

Abstract

The goal of a carbon-neutral society can be realized by utilizing a circular carbon pathway, which combines recycling, biomass utilization, carbon capture and utilization. Inspired by the potential of metal-contaminated biomass and plastic waste as valuable feed-stocks, we have developed a biologically-bound nickel catalyst (Ni-phytocat) to accelerate de-polymerization of polyethylene into high value chemicals. The synergistic effect of microwaves, together with Ni-phytocat as microwave absorbers, accelerate the catalytic de-polymerization process at low temperature (250 °C). The single step process typically takes up to 70 s to transform a sample of low-density polyethylene into liquid hydrocarbons (40–60% oil yield), hydrogen (11–30% gas yield) and filamentous carbon (25–37% solid yield), depending on varying catalyst to polymer weight ratios. The Ni-phytocat enhanced the production of C₆–C₁₂ aliphatics (up to 56% selectivity) and favored the aromatization of linear alkanes to form monocyclic aromatics (up to 33% selectivity), thereby releasing more H₂ (up to 74% selectivity) as gaseous fractions. The enhancement of (de)hydrogenation, de-carboxylation and cyclization, utilizing Ni-phytocat can be established as a proof of concept to advance and enable selective transformation of polymeric consumer products, paving the way to harness complete circular chemical potential of these future feed-stocks.