Sulphated zirconia catalysed conversion of high density polyethylene to value-added products using a fixed-bed reactor

A sulphated zirconia catalyst (SZ) was investigated for catalytic conversion of high density polyethylene (HDPE) to liquid and gaseous hydrocarbons using a fixed-bed reactor. The SZ catalyst reduced the onset of degradation from 337 °C for HDPE alone to 187 °C with 10 wt% SZ added. At 450 °C a complete weight loss was obtained with the SZ addition against only 4 wt% loss for HDPE only. Fixed-bed reactor experiments using 2 g of HDPE with 10 wt% SZ catalyst with a 30 min residence time showed a 98.0 wt% conversion at temperature as low as 380 °C. The liquid yield obtained was 39.0 wt% with a composition of 16 wt% paraffins, 21 wt% olefins, 5 wt% naphthenes and 58 wt% aromatics. The carbon number distribution of the liquid was C7–C12, which is within the gasoline range. Equally, gaseous products ranging from methane up to different isomers of pentane which contained more paraffinic and naphthenic hydrocarbon were obtained. The sulphated zirconia catalyst was found to have high ammonia desorption (337.0 μmol NH₃ g⁻¹), BET surface area (116.0 m² g⁻¹), external surface area (112.0 m² g⁻¹) and mesoporous structure. The overall results indicate that sulphated zirconia had excellent properties for catalytic conversion at temperature as low as 380 °C with significant liquid yield which could offer a solution to plastic waste problem by converting the waste back into value-added chemicals and fuel.