Heavy polyethylene catalytic pyrolysis with 15% HZSM-5 catalyst was performed at 500 ° C in a semi-continuous stirrer reactor under nitrogen gas. In the first experiment, about 46.7% of the liquid product, 29.2% of the gas product and 4.5% of coke was produced. In the second experiment, with the changes made on the reactor and condenser, the liquid product output increased by about 8%. In a similar study, the effect of HZSM-5 zeolite catalyst acidity on the catalytic degradation of heavy polyethylene was evaluated. To have HZSM-5 with different acidities, sodium nitrate solution with different concentrations was used. Displacement of protons in the original sample by sodium cations (at room temperature for 4 hours) reduces the acidity of the samples. By adding sodium to HZSM-5 and ion transfer, the acidity of the catalyst decreased and the degradation temperature increased from 390 °C to 555 °C. The gases released from pyrolysis were also analyzed by gas chromatography and it was concluded that the selectivity of volatile products changes with catalytic acidity.