Evaluation of process parameters on high-density polyethylene hydro-liquefaction products

Abstract The hydro-liquefaction of high-density polyethylene (HDPE) was studied in the absence of a solvent. The influence of reaction temperature (400–440 °C), initial H 2 pressure (1–4 MPa), and reaction time (2–6 h) on the product was investigated using Ni/Al 2 O 3 as a catalyst. Results showed that increased reaction temperature and time promoted hydrocarbon cracking, thereby favoring the enhancement of C7–C16 selectivity, whereas the high initial H 2 pressure (4 MPa) preferentially facilitated the production of C17–C27 hydrocarbons and improved alkene hydrogenation. The effect of catalyst support (Al 2 O 3 , SAPO-11, and HZSM-5) was also examined. Al 2 O 3 presented the highest liquid yield because of its weak acidity, with the liquid product dominated by n -alkanes (78.88%), whereas the yield of the liquid obtained from HZSM-5 as a catalyst support was the lowest, and aromatics was the major component (56.75%). SAPO-11 exhibited excellent selectivity for iso-alkanes, which improved the quality of the liquid oil. Meanwhile, liquid oil obtained using SAPO-11 was compliant with commercial jet-fuel standards and can be directly used as a jet-fuel additive. From this perspective, the hydro-liquefaction is a technology with potential for energy recovery from waste plastic.