Effect of temperature and type of catalyst on the composition of pyrolysis oil obtained from oil sludge

Oil sludge is composed of both inorganic and organic compounds, poses a serious threat to the environment. This research aimed to examine the impact of temperature (200–600 °C), N₂ flow rate (100–800 mL/min), and HZSM-5, KOH, TiO₂, and Al₂O₃ catalysts on pyrolysis oil. Each catalyst had a unique effect on the process, generally increasing the heating value and producing lighter hydrocarbons. In addition, increasing temperature increased pyrolysis oil and increasing N₂ flow increased biochar production. The optimal temperature and gas flow rate for pyrolysis oil production yield were determined to be 531 °C and 202 mL/min. TiO₂ exhibited the best performance, resulting in a 25% increase in heat value, a 15% increase in H/C, and a 60% decrease in O/C compared to the non-catalytic process, due to its high activity on promoting secondary cracking phenomena. Furthermore, the use of catalysts led to the production of 80–520 wt% more aliphatic compounds in the pyrolysis oil while simultaneously reducing the presence of aromatics by 18–81 wt%. The Al₂O₃ catalyst produced the highest percentage of light hydrocarbons at 48.13 wt%, while the KOH catalyst had the lowest amount of SNO compounds at a rate of 89.62 wt%.