Polyethylene terephthalate conversion into liquid fuel by its co-pyrolysis with low- and high-density polyethylene employing scrape aluminium as catalyst

Abstract

ABSTRACT The co-pyrolysis of polyethylene terephthalate (PET) with low-density polyethylene (LDPE) and high-density polyethylene (HDPE) was carried out in a batch steel pyrolyzer in order to convert the PET into pyrolysis oil as its pyrolysis alone resulted in wax and gases. The study also aimed to increase the aromatic content of pyrolysis oil by the interaction of degradation fragments of linear chains of LDPE and HDPE with the benzene ring of PET during the pyrolysis. The reaction conditions were optimized for a higher yield of pyrolysis oil which were found to be 500 °C pyrolysis temperature with a heating rate of 0.5 °Cs−1, 1 h reaction time and 20 g of the initial mass of polymer mixture having 20% PET, 40% LDPE and 40% HDPE. Waste aluminium particles were applied as an economical catalyst in the process. The thermal co-pyrolysis yielded 8% pyrolysis oil, 32.3 wax, 39.7 wt% gases and 20% coke while the catalytic co-pyrolysis produced 30.2% pyrolysis oil, 4.2% wax, 53.6 wt% gases and 12% coke. The fractional distillation of catalytic oil resulted in 46% gasoline range oil, 31% kerosene range oil and 23% diesel range oil. These fractions resembled the standard fuels in terms of their fuel properties as well as FT-IR spectra. The GC-MS analysis revealed that the catalytic co-pyrolysis favoured the formation of relatively short-chain hydrocarbons with olefins and isoparaffins as major components while the thermal co-pyrolysis formed long-chain paraffins. The naphthenes and aromatics were also found in higher amounts in the catalytic oil compared with the thermal oil.