Coprocessing of polymeric waste with coal: Reaction of polyethylene and coal model compounds

Environmental and economical concerns over diminishing landfill space and the growing abundance of mixed plastic waste mandate development of viable strategies for recovering highvalued resources from waste polymers. Co-processing of waste polymer mixtures with coal allows for the simultaneous conversion of coal and plastics into high-valued fuels. However, there is limited information about the underlying reaction pathways, kinetics, and mechanisms controlling coal liquefaction in the presence of polymeric materials. A series of model compound experiments has been conducted, providing a starting point for unraveling the complex, underlying chemistry. Neat pyrolysis studies of model compounds of polyethylene and coal were conducted in batch reactors. Tetradecane (C₁₄H₃₀) was used as a polyethylene mimic, and 4-(naphthylmethyl)bibenzyl was used as a coal model compound. Reaction temperatures were 420 and 500°C, and batch reaction times ranged from 5-150 minutes. Detailed product analysis using gas chromatography and mass spectrometry enabled the reactant conversion and product selecuvities to be determined. Reaction of single components and binary mixtures allowed the kinetic coupling between feedstocks to be examined.