Dielectric Barrier Discharge Plasma Synergistic Catalytic Pyrolysis of Waste Polyethylene into Aromatics-Enriched Oil

The dielectric barrier discharge (DBD) plasma synergistic catalytic pyrolysis scheme was developed for upgrading polyethylene (PE) pyrolysis volatiles to obtain aromatics-enriched oil. The effects of the PE/HZSM-5 ratio, discharge power, and discharge time interval on the product yield, oil composition, and carbon deposition were studied by the experiment. When the PE/HZSM-5 ratio shifted from 5:1 to 1:5, the oil yield decreased first and then ramped to 51.32%. The selectivity for aromatics in oil increased from 69.93 to 98.43%. In the discharge power range of 0–15 W, increasing the power increased the aromatic content with the maximum of 98.14%, consequently decreasing the alkane and alkene contents of the product oils. The further addition of the power resulted in a small decrease in the selectivity for the aromatics. The coke showed a decrease in yield with increasing discharge power when the power did not exceed 20 W. The maximum selectivities for aromatics (97.69%) and the minimum coke yield (2.82%) were obtained at the discharge time intervals of 2.5 and 5 ms, respectively. In general, both of the free radicals excited by the plasma and the specific surface area, acidity, and strength of HZSM-5 changed by the plasma favored the aromatization reaction.