Microwave-assisted catalytic co-pyrolysis of waste edible oil and low-density polyethylene: Synergistic enhancement of co-melt feeding

In this study, a new delayed feeding process for blending waste edible oil (WEO) as cosolvent with molten low-density polyethylene (LDPE) applied in microwave-assisted fixed bed pyrolysis was proposed. The experiment was carried out at the melting temperature of 250 ℃, the pyrolysis temperature of 550 ℃, and the catalytic temperature of 450 ℃. The co-feeding of the WEO and molten LDPE effectively promoted the formation of light aromatics, with the content of monocyclic aromatic hydrocarbons as high as 82.69 % (LDPE/WEO = 1:3) and the relative content of BTEX (benzene, toluene, ethylbenzene, xylenes) as high as 65.96 %. The proportion of feedstocks affects the distribution of pyrolysis products by adjusting the content of hydrogen radicals in the pyrolysis system. Hydrogen radicals derived from LDPE can combine with oxygen-containing intermediate from triglycerides, to promote the removal of oxygen in the form of H₂O, and inhibit the decarboxylation and decarbonylation reactions. Compared with the pre-feeding process, the relative content of BTEX increased by 14.43 % and the relative content of PAHs decreased by 10.86 %. The application of downdraft reactors further improved the relative content of BTEX in pyrolysis oil. When the mass of SiC was 500 g, the peak relative content of BTEX was 69.79 %. This study provides a new process for the effective production of light aromatic hydrocarbons.