Upgrading waste plastic pyrolysis oil via hydrotreating over sulfur-treated Ni-Mo/Al2O3 catalysts

The hydrotreating (HDT) reaction of waste plastic pyrolysis oil (WPPO) was investigated using the sulfide NiMo/Alumina catalysts with a fixed Ni loading of 5 wt% and varying Mo loadings (0, 5, 7, and 10 wt%). The catalysts exhibited an increasing presence of NiMoO4 as the Mo loading increased. The HDT results indicated that the NiMo/Alumina with the highest Mo loading demonstrated optimized reactivity for the HDT reaction. The analysis of WPPO and post-HDT products involved various techniques, including total nitrogen sulfur analyzer, X-ray fluorescence, simulated distillation, gas chromatography mass spectrometry, and nuclear magnetic spectroscopy (NMR). After HDT with the sulfide NiMo/Alumina catalyst, a significant reduction in nitrogen and chlorine content was observed in the WPPO. Furthermore, there was a notable decrease in the olefins portion of naphtha, accompanied by an increase in the paraffins portion. Characterization of the spent catalysts from the HDT reaction using X-ray diffraction and X-ray photoelectron spectroscopy analysis indicated the prevalence of sulfide species, including MoS2, NiMoS, and NixSy, on the catalyst surface. The prominence of these sulfide species correlated with an increase in Mo loading.