From waste to fuel: catalytic conversion of waste cooking oil in batch and continuous modes

In this work, a bimetallic Co-Mo catalyst supported on carbon nanotubes (CNT) was synthesised and evaluated for the hydrotreating of waste cooking oil (WCO) in both batch and continuous flow reactors. Zeolite HZSM-5 was also tested alone and physically mixed with Co-Mo/CNT to assess its effect on product distribution. The results showed that the catalytic properties control the balance between hydrodeoxygenation (HDO) and cracking, allowing tuneable product distributions through catalyst selection and temperature control. Continuous flow operation resulted in near complete HDO (93-100 %) for all catalyst systems and enhanced n-alkane selectivity and more efficient removal of oxygenated intermediates. Product distribution was tuneable: ∼50 % in the diesel-range (C₁₇-C₂₂) over Co-Mo/CNT, ∼50 % in the jet-range (C₈-C₁₆) over HZSM-5, and ∼ 60 % in the gasoline-range (C₅-C₇) over the mixture in continuous flow at 325 °C, based on carbon number distribution. These results demonstrate a cost-effective, efficient pathway for producing tailored biofuels from WCO via continuous catalytic processing.