Abstract: Catalytic pyrolysis of high density polyethylene (HDPE) on HZSM-5 catalyst and an iron-alumina pillared montmorillonite, prepared in laboratory (FAMO), was performed by means of a conical spouted bed reactor. This type of reactor is a suitable technology for plastic pyrolysis due to its high heat and mass transfer rates and excellent performance in the handling of sticky solid materials. The pyrolytic process carried out on HZSM-5 catalyst gave significant yield of gaseous products (above 74 wt%), while FAMO catalyst gave high yields of waxes, particularly rich in diesel hydrocarbon range (C11–C21). Waxes obtained by subjecting HDPE to thermal pyrolysis had a higher range of molecular weight. Waxes have been characterised using different techniques, such as gel permeation chromatography (GPC), polidispersity (PD), Fourier transform infrared (FTIR) spectroscopy, Simulated Distillation, and TDP.