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

•The hydro-liquefaction of plastic was conducted without solvent.•High initial H2 pressure was not conducive to the cracking of C17–C27.•The selectivity of aromatics reached 56.75% with Ni/HZSM-5 as a catalyst.•Liquid oil obtained by Ni/SAPO-11 can be used as jet-fuel additive.•Product distribution can be controlled by changing the catalyst support. 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 H2 pressure (1–4 MPa), and reaction time (2–6 h) on the product was investigated using Ni/Al2O3 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 H2 pressure (4 MPa) preferentially facilitated the production of C17–C27 hydrocarbons and improved alkene hydrogenation. The effect of catalyst support (Al2O3, SAPO-11, and HZSM-5) was also examined. Al2O3 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.