Pyrolysis of waste polyethylene under vacuum using zinc oxide

Innovative approaches in pyrolysis process to recover energy from plastic wastes in a sustainable manner are being explored progressively. Present study reports the effect of vacuum on pyrolysis of polyethylene waste in the presence of zinc oxide as a catalyst. Firstly, the effect of vacuum on the pyrolysis of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) wastes was investigated by conducting the pyrolysis at various applied vacuums of 101.325 kPa, 88 kPa, 73 kPa, 60 kPa, and 47 kPa in the absence of catalyst. Vacuum was observed to have positive effect on the pyrolysis in terms of increase in the yield of liquid product. Further, the effect of zinc oxide on the pyrolysis was studied by performing the pyrolysis at various catalyst feed ratios of 3:100, 5:100, 10:100 and 15:100 under the applied vacuum of 50 kPa. The maximum yield of liquid product obtained was 74.58% and 78.65% for the waste LDPE and HDPE, respectively, for the catalyst feed ratio of 15:100 and at applied vacuum of 50 kPa. GC-MS analysis of the liquid products demonstrated that the major fraction of hydrocarbons present is in a sufficiently narrow range. The fuel properties of the obtained liquid product were also determined.