Catalytic Pyrolysis of Polyethylene for the Selective Production of Monocyclic Aromatics over the Zinc-Loaded ZSM-5 Catalyst.

ABSTRACT

The transformation of waste plastics into value-added aromatics could incentivize better waste plastic management. The reported studies had low selectivity for monocyclic aromatics because more polycyclic aromatic hydrocarbons and carbon residues were generated. The effects of temperature, pressure, and catalyst on monocyclic aromatic selectivity were explored using a central composite design (CCD) followed by the response surface methodology (RSM) at a high ramp rate of 15 °C/min. The liquid product yield and selectivity to aromatic hydrocarbons were enhanced by regulating the acidic properties of the catalyst and processing parameters. The proportion of monocyclic aromatics in the liquid product was up to 90%, and the yield of monocyclic aromatics based on the reactant mass was 51% at the optimized condition. The carbon deposit production was low (only approximately 1%), which allowed higher liquid yields. In addition, the coupling mechanism of multiple factors on the depolymerization/aromatization reactions was proposed. This conversion of polyethylene into high-yield monocyclic aromatics provides a viable plastic recycling approach.